U.S. patent application number 12/120763 was filed with the patent office on 2008-09-04 for impact excavation system and method with particle separation.
This patent application is currently assigned to Particle Drilling Technologies, Inc.. Invention is credited to Gordon A. Tibbitts.
Application Number | 20080210472 12/120763 |
Document ID | / |
Family ID | 46322457 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080210472 |
Kind Code |
A1 |
Tibbitts; Gordon A. |
September 4, 2008 |
Impact Excavation System And Method With Particle Separation
Abstract
A system and method for excavating a subterranean formation,
according to which a suspension of liquid and a plurality of
impactors are introduced into at least one cavity formed in a body
member and are discharging from the cavity so that the impactors
remove a portion of the formation. The impactors are separated from
at least a portion of the fluid, and are passed to a conduit so
that the impactors accumulate in the conduit before being removed
from the conduit.
Inventors: |
Tibbitts; Gordon A.;
(Murray, UT) |
Correspondence
Address: |
BRACEWELL & GIULIANI LLP
P.O. BOX 61389
HOUSTON
TX
77208-1389
US
|
Assignee: |
Particle Drilling Technologies,
Inc.
Houston
TX
|
Family ID: |
46322457 |
Appl. No.: |
12/120763 |
Filed: |
May 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11204722 |
Aug 16, 2005 |
7383896 |
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12120763 |
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10897196 |
Jul 22, 2004 |
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11204722 |
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10825338 |
Apr 15, 2004 |
7258176 |
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10897196 |
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60463903 |
Apr 16, 2003 |
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Current U.S.
Class: |
175/54 |
Current CPC
Class: |
E21B 10/602 20130101;
E21B 21/10 20130101; E21B 10/42 20130101; E21B 7/18 20130101 |
Class at
Publication: |
175/54 |
International
Class: |
E21B 7/16 20060101
E21B007/16 |
Claims
1. A system for excavating a subterranean formation, the system
comprising: a body member for receiving a suspension of liquid and
a plurality of impactors and discharging the suspension so that the
impactors remove a portion of the formation; a first conduit for
receiving the suspension after the removal; a separator in the
first conduit for separating the impactors from at least a portion
of the fluid; a second conduit for receiving the separated
impactors from the separator; and at least one controller to
control the flow of impactors into the second conduit so that a
substantial portion of the impactors can accumulate in the second
conduit.
2. A system of claim 1, further comprising at least one controller
to control the flow of the impactors from the second conduit.
3. A system of claim 1, wherein the first-mentioned controller
comprises a first valve, and the second-mentioned controller
comprises a second valve, the impactors accumulating the second
conduit when the first valve is open and the second valve is
closed, and the impactors discharge from the second conduit when
the second valve is open.
4. A system of claim 1, further comprising a pressure relief
portion associated with the second conduit.
5. A system of claim 4, wherein the pressure relief includes a
third conduit registering the second conduit and at least one valve
disposed in the third conduit to control the relief of the pressure
in the second conduit.
6. A system of claim 5, further comprising at least one valve
positioned to prevent the flow of the impactors into the third
conduit.
7. A system of claim 1, further comprising a nozzle disposed in the
body member to discharge the suspension therefrom.
8. A method for excavating a subterranean formation, the system
comprising: introducing a suspension of liquid and a plurality of
impactors into at least one cavity formed in a body member;
discharging the suspension from the cavity so that the impactors
remove a portion of the formation; separating the impactors from at
least a portion of the fluid; and passing the impactors to a
conduit so that a substantial portion of the impactors accumulate
in the conduit.
9. A method of claim 8, further comprising discharging the
accumulated impactors from the conduit.
10. A method of claim 8, further comprising relieving the pressure
in the conduit.
11. A method of claim 9, wherein the step of relieving comprises
connecting another conduit to the first-mentioned conduit and
adjusting a valve in the other conduit.
12. A method of claim 11, wherein another portion of the fluid is
received in the first-mentioned conduit with the impactors and is
relieved from the first-mentioned conduit by flowing into the other
conduit under the control of the valve.
13. A method of claim 12, further comprising blocking the flow of
the impactors into the other conduit.
14. A system for excavating a subterranean formation, the system
comprising: a body member; at least one receiver portion disposed
in the body member to receive a suspension of liquid and a
plurality of impactors and discharging the suspension so that the
impactors remove a portion of the formation; a first conduit for
receiving the suspension after the removal; a separator positioned
in the first conduit to separate the impactors from at least a
portion of the fluid; a second conduit for receiving the separated
impactors from the separator; and at least a first valve positioned
to control the flow of impactors to the second conduit so that a
substantial portion of the impactors can accumulate in the second
conduit.
15. A system of claim 14, further comprising at least a second
valve positioned to control the flow of the impactors from the
second conduit.
16. A system of claim 15, wherein the impactors accumulate in the
second conduit when the first valve is open and the second valve is
closed; and wherein the impactors discharge from the second conduit
when the second valve is open.
17. A system of claim 14, further comprising a pressure relief
portion positioned to relieve the pressure in the second
conduit.
18. A system of claim 17, wherein the pressure relief portion
includes a third conduit registering with the second conduit and a
third valve disposed in the third conduit to control the relief of
the pressure.
19. A system of claim 18, further comprising at least one valve
positioned to prevent the flow of the impactors into the third
conduit.
20. A system of claim 18, wherein another portion of the fluid is
received in the second conduit with the impactors and flows out of
the second conduit and through third conduit when the second valve
is in its closed position and the third valve is at least partially
open.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of pending application
Ser. No. 11/204,722, filed Aug. 16, 2005 which, in turn is a
continuation-in-part of pending application Ser. No. 10/897,196,
filed Jul. 22, 2004 which, in turn is a continuation-in-part of
pending application Ser. No. 10/825,338, filed Apr. 15, 2004,
which, in turn claims the benefit of 35 U.S.C. 111 (b) provisional
application Ser. No. 60/463,903, filed Apr. 16, 2003, the
disclosures of which are incorporated herein by reference.
BACKGROUND
[0002] This disclosure relates to a system and method of excavating
a formation, such as to form a well bore for the purpose of oil and
gas recovery, to construct a tunnel, or to form other excavations
in which the formation is cut, milled, pulverized, scaped, sheared,
indented, and/or fractured, (hereinafter referred to collectively
as "cutting"). The cutting process is a very interdependent process
that preferably integrates and considers many variables to ensure
that a usable bore is constructed. As is commonly known in the art,
many variables have an interactive and cumulative effect of
increasing cutting costs. These variables may include formation
hardness, abrasiveness, pore pressures, and formation elastic
properties. In drilling wellbores, formation hardness and a
corresponding degree of drilling difficulty may increase
exponentially as a function of increasing depth. A high percentage
of the costs to drill a well are derived from interdependent
operations that are time sensitive, i.e., the longer it takes to
penetrate the formation being drilled, the more it costs. One of
the most important factors affecting the cost of drilling a
wellbore is the rate at which the formation can be penetrated by
the drill bit, which typically decreases with harder and tougher
formation materials and formation depth.
[0003] There are generally two categories of modern drill bits that
have evolved from over a hundred years of development and untold
amounts of dollars spent on the research, testing and iterative
development. These are the commonly known as the fixed cutter drill
bit and the roller cone drill bit. Within these two primary
categories, there are a wide variety of variations, with each
variation designed to drill a formation having a general range of
formation properties. These two categories of drill bits generally
constitute the bulk of the drill bits employed to drill oil and gas
wells around the world.
[0004] Each type of drill bit is commonly used where its drilling
economics are superior to the other. Roller cone drill bits can
drill the entire hardness spectrum of rock formations. Thus, roller
cone drill bits are generally run when encountering harder rocks
where long bit life and reasonable penetration rates are important
factors on the drilling economics. Fixed cutter drill bits, on the
other hand, are used to drill a wide variety of formations ranging
from unconsolidated and weak rocks to medium hard rocks.
[0005] In the case of creating a borehole with a roller cone type
drill bit, several actions effecting rate of penetration (ROP) and
bit efficiency may be occurring. The roller cone bit teeth may be
cutting, milling, pulverizing, scraping, shearing, sliding over,
indenting, and fracturing the formation the bit is encountering.
The desired result is that formation cuttings or chips are
generated and circulated to the surface by the drilling fluid.
Other factors may also affect ROP, including formation structural
or rock properties, pore pressure, temperature, and drilling fluid
density. When a typical roller cone rock bit tooth presses upon a
very hard, dense, deep formation, the tooth point may only
penetrate into the rock a very small distance, while also at least
partially, plastically "working" the rock surface.
[0006] One attempt to increase the effective rate of penetration
(ROP) involved high-pressure circulation of a drilling fluid as a
foundation for potentially increasing ROP. It is common knowledge
that hydraulic power available at the rig site vastly outweighs the
power available to be employed mechanically at the drill bit. For
example, modern drilling rigs capable of drilling a deep well
typically have in excess of 3000 hydraulic horsepower available and
can have in excess of 6000 hydraulic horsepower available while
less than one-tenth of that hydraulic horsepower may be available
at the drill bit. Mechanically, there may be less than 100
horsepower available at the bit/rock interface with which to
mechanically drill the formation.
[0007] An additional attempt to increase ROP involved incorporating
entrained abrasives in conjunction with high pressure drilling
fluid ("mud"). This resulted in an abrasive laden, high velocity
jet assisted drilling process. Work done by Gulf Research and
Development disclosed the use of abrasive laden jet streams to cut
concentric grooves in the bottom of the hole leaving concentric
ridges that are then broken by the mechanical contact of the drill
bit. Use of entrained abrasives in conjunction with high drilling
fluid pressures caused accelerated erosion of surface equipment and
an inability to control drilling mud density, among other issues.
Generally, the use of entrained abrasives was considered
practically and economically unfeasible. This work was summarized
in the last published article titled "Development of High Pressure
Abrasive-Jet Drilling," authored by John C. Fair, Gulf Research and
Development. It was published in the Journal of Petroleum
Technology in the May 1981 issue, pages 1379 to 1388.
[0008] Another effort to utilize the hydraulic horsepower available
at the bit incorporated the use of ultra-high pressure jet assisted
drilling. A group known as FlowDril Corporation was formed to
develop an ultra-high-pressure liquid jet drilling system in an
attempt to increase the rate of penetration. The work was based
upon U.S. Pat. No. 4,624,327 and is documented in the published
article titled "Laboratory and Field Testing of an Ultra-High
Pressure, Jet-Assisted Drilling System" authored by J. J. Kolle,
Quest Integrated Inc., and R. Otta and D. L. Stang, FlowDril
Corporation; published by SPE/IADC Drilling Conference publications
paper number 22000. The cited publication disclosed that the
complications of pumping and delivering ultrahigh-pressure fluid
from surface pumping equipment to the drill bit proved both
operationally and economically unfeasible.
[0009] Another effort at increasing rates of penetration by taking
advantage of hydraulic horsepower available at the bit is disclosed
in U.S. Pat. No. 5,862,871. This development employed the use of a
specialized nozzle to excite normally pressured drilling mud at the
drill bit. The purpose of this nozzle system was to develop local
pressure fluctuations and a high speed, dual jet form of hydraulic
jet streams to more effectively scavenge and clean both the drill
bit and the formation being drilled. It is believed that these
hydraulic jets were able to penetrate the fracture plane generated
by the mechanical action of the drill bit in a much more effective
manner than conventional jets were able to do. ROP increases from
50% to 400% were field demonstrated and documented in the field
reports titled "DualJet Nozzle Field Test Report-Security DBS/Swift
Energy Company," and "DualJet Nozzle Equipped M-1 LRG Drill Bit
Run". The ability of the dual jet ("DualJet") nozzle system to
enhance the effectiveness of the drill bit action to increase the
ROP required that the drill bits first initiate formation
indentations, fractures, or both. These features could then be
exploited by the hydraulic action of the DualJet nozzle system.
[0010] Due at least partially to the effects of overburden
pressure, formations at deeper depths may be inherently tougher to
drill due to changes in formation pressures and rock properties,
including hardness and abrasiveness. Associated in-situ forces,
rock properties, and increased drilling fluid density effects may
set up a threshold point at which the drill bit drilling mechanics
decrease the drilling efficiency.
[0011] Another factor adversely effecting ROP in formation
drilling, especially in plastic type rock drilling, such as shale
or permeable formations, is a build-up of hydraulically isolated
crushed rock material, that can become either mass of reconstituted
drill cuttings or a "dynamic filtercake", on the surface being
drilled, depending on the formation permeability. In the case of
low permeability formations, this occurrence is predominantly a
result of repeated impacting and re-compacting of previously
drilled particulate material on the bottom of the hole by the bit
teeth, thereby forming a false bottom. The substantially continuous
process of drilling, re-compacting, removing, re-depositing and
re-compacting, and drilling new material may significantly
adversely effect drill bit efficiency and ROP. The re-compacted
material is at least partially removed by mechanical displacement
due to the cone skew of the roller cone type drill bits and
partially removed by hydraulics, again emphasizing the importance
of good hydraulic action and hydraulic horsepower at the bit. For
hard rock bits, build-up removal by cone skew is typically reduced
to near zero, which may make build-up removal substantially a
function of hydraulics. In permeable formations the continuous
deposition and removal of the fine cuttings forms a dynamic
filtercake that can reduce the spurt loss and therefore the pore
pressure in the working area of the bit. Because the pore pressure
is reduced and mechanical load is increased from the pressure drop
across the dynamic filtercake, drilling efficiency can be
reduced.
[0012] There are many variables to consider to ensure a usable well
bore is constructed when using cutting systems and processes for
the drilling of well bores or the cutting of formations for the
construction of tunnels and other subterranean earthen excavations.
Many variables, such as formation hardness, abrasiveness, pore
pressures, and formation elastic properties affect the
effectiveness of a particular drill bit in drilling a well bore.
Additionally, in drilling well bores, formation hardness and a
corresponding degree of drilling difficulty may increase
exponentially as a function of increasing depth. The rate at which
a drill bit may penetrate the formation typically decreases with
harder and tougher formation materials and formation depth.
[0013] When the formation is relatively soft, as with shale,
material removed by the drill bit will have a tendency to
reconstitute onto the teeth of the drill bit. Build-up of the
reconstituted formation on the drill bit is typically referred to
as "bit balling" and reduces the depth that the teeth of the drill
bit will penetrate the bottom surface of the well bore, thereby
reducing the efficiency of the drill bit. Particles of a shale
formation also tend to reconstitute back onto the bottom surface of
the bore hole. The reconstitution of a formation back onto the
bottom surface of the bore hole is typically referred to as "bottom
balling". Bottom balling prevents the teeth of a drill bit from
engaging virgin formation and spreads the impact of a tooth over a
wider area, thereby also reducing the efficiency of a drill bit.
Additionally, higher density drilling muds that are required to
maintain well bore stability or well bore pressure control
exacerbate bit balling and the bottom balling problems.
[0014] When the drill bit engages a formation of a harder rock, the
teeth of the drill bit press against the formation and densify a
small area under the teeth to cause a crack in the formation. When
the porosity of the formation is collapsed, or densified, in a hard
rock formation below a tooth, conventional drill bit nozzles
ejecting drilling fluid are used to remove the crushed material
from below the drill bit. As a result, a cushion, or densification
pad, of densified material is left on the bottom surface by the
prior art drill bits. If the densification pad is left on the
bottom surface, force by a tooth of the drill bit will be
distributed over a larger area and reduce the effectiveness of a
drill bit.
[0015] There are generally two main categories of modern drill bits
that have evolved over time. These are the commonly known fixed
cutter drill bit and the roller cone drill bit. Additional
categories of drilling include percussion drilling and mud hammers.
However, these methods are not as widely used as the fixed cutter
and roller cone drill bits. Within these two primary categories
(fixed cutter and roller cone), there are a wide variety of
variations, with each variation designed to drill a formation
having a general range of formation properties.
[0016] The fixed cutter drill bit and the roller cone type drill
bit generally constitute the bulk of the drill bits employed to
drill oil and gas wells around the world. When a typical roller
cone rock bit tooth presses upon a very hard, dense, deep
formation, the tooth point may only penetrate into the rock a very
small distance, while also at least partially, plastically
"working" the rock surface. Under conventional drilling techniques,
such working the rock surface may result in the densification as
noted above in hard rock formations.
[0017] With roller cone type drilling bits, a relationship exists
between the number of teeth that impact upon the formation and the
drilling RPM of the drill bit. A description of this relationship
and an approach to improved drilling technology is set forth and
described in U.S. Pat. No. 6,386,300 issued May 14, 2002. The '300
patent discloses the use of solid material impactors introduced
into drilling fluid and pumped though a drill string and drill bit
to contact the rock formation ahead of the drill bit. The kinetic
energy of the impactors leaving the drill bit is given by the
following equation: E.sub.k=1/2Mass(Velocity).sup.2. The mass
and/or velocity of the impactors may be chosen to satisfy the
mass-velocity relationship in order to structurally alter the rock
formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an isometric view of an excavation system as used
in a preferred embodiment;
[0019] FIG. 2 illustrates an impactor impacted with a
formation;
[0020] FIG. 3 illustrates an impactor embedded into the formation
at an angle to a normalized surface plane of the target formation;
and
[0021] FIG. 4 illustrates an impactor impacting a formation with a
plurality of fractures induced by the impact.
[0022] FIG. 5 is a side elevational view of a drilling system
utilizing a first embodiment of a drill bit;
[0023] FIG. 6 is a top plan view of the bottom surface of a well
bore formed by the drill bit of FIG. 5;
[0024] FIG. 7 is an end elevational view of the drill bit of FIG.
5;
[0025] FIG. 8 is an enlarged end elevational view of the drill bit
of FIG. 5;
[0026] FIG. 9 is a perspective view of the drill bit of FIG. 5;
[0027] FIG. 10 is a perspective view of the drill bit of FIG. 5
illustrating a breaker and junk slot of a drill bit;
[0028] FIG. 11 is a side elevational view of the drill bit of FIG.
5 illustrating a flow of solid material impactors;
[0029] FIG. 12 is a top elevational view of the drill bit of FIG. 5
illustrating side and center cavities;
[0030] FIG. 13 is a canted top elevational view of the drill bit of
FIG. 5;
[0031] FIG. 14 is a cutaway view of the drill bit of FIG. 5 engaged
in a well bore;
[0032] FIG. 15 is a schematic diagram of the orientation of the
nozzles of a second embodiment of a drill bit;
[0033] FIG. 16 is a side cross-sectional view of the rock formation
created by the drill bit of FIG. 5 represented by the schematic of
the drill bit of FIG. 5 inserted therein;
[0034] FIG. 17 is a side cross-sectional view of the rock formation
created by drill bit of FIG. 5 represented by the schematic of the
drill bit of FIG. 5 inserted therein;
[0035] FIG. 18 is a perspective view of an alternate embodiment of
a drill bit;
[0036] FIG. 19 is a perspective view of the drill bit of FIG. 18;
and
[0037] FIG. 20 illustrates an end elevational view of the drill bit
of FIG. 18.
[0038] FIG. 21 is a schematic diagram of a particle trap system for
use in the system of FIG. 1.
[0039] FIG. 22 is a graph depicting the performance of the
excavation system according to one or more embodiments of the
present invention as compared to two other systems.
DETAILED DESCRIPTION
[0040] In the drawings and description that follows, like parts are
marked throughout the specification and drawings with the same
reference numerals, respectively. The drawings are not necessarily
to scale. Certain features of the invention may be shown
exaggerated in scale or in somewhat schematic form and some details
of conventional elements may not be shown in the interest of
clarity and conciseness. The present invention is susceptible to
embodiments of different forms. Specific embodiments are described
in detail and are shown in the drawings, with the understanding
that the present disclosure is to be considered an exemplification
of the principles of the invention, and is not intended to limit
the invention to that illustrated and described herein. It is to be
fully recognized that the different teachings of the embodiments
discussed below may be employed separately or in any suitable
combination to produce desired results. The various characteristics
mentioned above, as well as other features and characteristics
described in more detail below, will be readily apparent to those
skilled in the art upon reading the following detailed description
of the embodiments, and by referring to the accompanying
drawings.
[0041] FIGS. 1 and 2 illustrate an embodiment of an excavation
system 1 comprising the use of solid material particles, or
impactors, 100 to engage and excavate a subterranean formation 52
to create a wellbore 70. The excavation system 1 may comprise a
pipe string 55 comprised of collars 58, pipe 56, and a kelly 50. An
upper end of the kelly 50 may interconnect with a lower end of a
swivel quill 26. An upper end of the swivel quill 26 may be
rotatably interconnected with a swivel 28. The swivel 28 may
include a top drive assembly (not shown) to rotate the pipe string
55. Alternatively, the excavation system 1 may further comprise a
drill bit 60 to cut the formation 52 in cooperation with the solid
material impactors 100. The drill bit 60 may be attached to the
lower end 55B of the pipe string 55 and may engage a bottom surface
66 of the wellbore 70. The drill bit 60 may be a roller cone bit, a
fixed cutter bit, an impact bit, a spade bit, a mill, an
impregnated bit, a natural diamond bit, or other suitable implement
for cutting rock or earthen formation. Referring to FIG. 1, the
pipe string 55 may include a feed, or upper, end 55A located
substantially near the excavation rig 5 and a lower end 55B
including a nozzle 64 supported thereon. The lower end 55B of the
string 55 may include the drill bit 60 supported thereon. The
excavation system 1 is not limited to excavating a wellbore 70. The
excavation system and method may also be applicable to excavating a
tunnel, a pipe chase, a mining operation, or other excavation
operation wherein earthen material or formation may be removed.
[0042] To excavate the wellbore 70, the swivel 28, the swivel quill
26, the kelly 50, the pipe string 55, and a portion of the drill
bit 60, if used, may each include an interior passage that allows
circulation fluid to circulate through each of the aforementioned
components. The circulation fluid may be withdrawn from a tank 6,
pumped by a pump 2, through a through medium pressure capacity line
8, through a medium pressure capacity flexible hose 42, through a
gooseneck 36, through the swivel 28, through the swivel quill 26,
through the kelly 50, through the pipe string 55, and through the
bit 60.
[0043] The excavation system 1 further comprises at least one
nozzle 64 on the lower 55B of the pipe string 55 for accelerating
at least one solid material impactor 100 as they exit the pipe
string 100. The nozzle 64 is designed to accommodate the impactors
100, such as an especially hardened nozzle, a shaped nozzle, or an
"impactor" nozzle, which may be particularly adapted to a
particular application. The nozzle 64 may be a type that is known
and commonly available. The nozzle 64 may further be selected to
accommodate the impactors 100 in a selected size range or of a
selected material composition. Nozzle size, type, material, and
quantity may be a function of the formation being cut, fluid
properties, impactor properties, and/or desired hydraulic energy
expenditure at the nozzle 64. If a drill bit 60 is used, the nozzle
or nozzles 64 may be located in the drill bit 60.
[0044] The nozzle 64 may alternatively be a conventional
dual-discharge nozzle. Such dual discharge nozzles may generate:
(1) a radially outer circulation fluid jet substantially encircling
a jet axis, and/or (2) an axial circulation fluid jet substantially
aligned with and coaxial with the jet axis, with the dual discharge
nozzle directing a majority by weight of the plurality of solid
material impactors into the axial circulation fluid jet. A dual
discharge nozzle 64 may separate a first portion of the circulation
fluid flowing through the nozzle 64 into a first circulation fluid
stream having a first circulation fluid exit nozzle velocity, and a
second portion of the circulation fluid flowing through the nozzle
64 into a second circulation fluid stream having a second
circulation fluid exit nozzle velocity lower than the first
circulation fluid exit nozzle velocity. The plurality of solid
material impactors 100 may be directed into the first circulation
fluid stream such that a velocity of the plurality of solid
material impactors 100 while exiting the nozzle 64 is substantially
greater than a velocity of the circulation fluid while passing
through a nominal diameter flow path in the lower end 55B of the
pipe string 55, to accelerate the solid material impactors 100.
[0045] Each of the individual impactors 100 is structurally
independent from the other impactors. For brevity, the plurality of
solid material impactors 100 may be interchangeably referred to as
simply the impactors 100. The plurality of solid material impactors
100 may be substantially rounded and have either a substantially
non-uniform outer diameter or a substantially uniform outer
diameter. The solid material impactors 100 may be substantially
spherically shaped, non-hollow, formed of rigid metallic material,
and having high compressive strength and crush resistance, such as
steel shot, ceramics, depleted uranium, and multiple component
materials. Although the solid material impactors 100 may be
substantially a nonhollow sphere, alternative embodiments may
provide for other types of solid material impactors, which may
include impactors 100 with a hollow interior. The impactors may be
substantially rigid and may possess relatively high compressive
strength and resistance to crushing or deformation as compared to
physical properties or rock properties of a particular formation or
group of formations being penetrated by the wellbore 70.
[0046] The impactors may be of a substantially uniform mass,
grading, or size. The solid material impactors 100 may have any
suitable density for use in the excavation system 1. For example,
the solid material impactors 100 may have an average density of at
least 470 pounds per cubic foot.
[0047] Alternatively, the solid material impactors 100 may include
other metallic materials, including tungsten carbide, copper, iron,
or various combinations or alloys of these and other metallic
compounds. The impactors 100 may also be composed of non-metallic
materials, such as ceramics, or other man-made or substantially
naturally occurring non-metallic materials. Also, the impactors 100
may be crystalline shaped, angular shaped, sub-angular shaped,
selectively shaped, such as like a torpedo, dart, rectangular, or
otherwise generally non-spherically shaped.
[0048] The impactors 100 may be selectively introduced into a fluid
circulation system, such as illustrated in FIG. 1, near an
excavation rig 5, circulated with the circulation fluid (or "mud"),
and accelerated through at least one nozzle 64. "At the excavation
rig" or "near an excavation rig" may also include substantially
remote separation, such as a separation process that may be at
least partially carried out on the sea floor.
[0049] Introducing the impactors 100 into the circulation fluid may
be accomplished by any of several known techniques. For example,
the impactors 100 may be provided in an impactor storage tank 94
near the rig 5 or in a storage bin 82. A screw elevator 14 may then
transfer a portion of the impactors at a selected rate from the
storage tank 94, into a slurrification tank 98. A pump 10, such as
a progressive cavity pump may transfer a selected portion of the
circulation fluid from a mud tank 6, into the slurrification tank
98 to be mixed with the impactors 100 in the tank 98 to form an
impactor concentrated slurry. An impactor introducer 96 may be
included to pump or introduce a plurality of solid material
impactors 100 into the circulation fluid before circulating a
plurality of impactors 100 and the circulation fluid to the nozzle
64. The impactor introducer 96 may be a progressive cavity pump
capable of pumping the impactor concentrated slurry at a selected
rate and pressure through a slurry line 88, through a slurry hose
38, through an impactor slurry injector head 34, and through an
injector port 30 located on the gooseneck 36, which may be located
atop the swivel 28. The swivel 36, including the through bore for
conducting circulation fluid therein, may be substantially
supported on the feed, or upper, end of the pipe string 55 for
conducting circulation fluid from the gooseneck 36 into the latter
end 55a. The upper end 55A of the pipe string 55 may also include
the kelly 50 to connect the pipe 56 with the swivel quill 26 and/or
the swivel 28. The circulation fluid may also be provided with
rheological properties sufficient to adequately transport and/or
suspend the plurality of solid material impactors 100 within the
circulation fluid.
[0050] The solid material impactors 100 may also be introduced into
the circulation fluid by withdrawing the plurality of solid
material impactors 100 from a low pressure impactor source 98 into
a high velocity stream of circulation fluid, such as by venturi
effect. For example, when introducing impactors 100 into the
circulation fluid, the rate of circulation fluid pumped by the mud
pump 2 may be reduced to a rate lower than the mud pump 2 is
capable of efficiently pumping. In such event, a lower volume mud
pump 4 may pump the circulation fluid through a medium pressure
capacity line 24 and through the medium pressure capacity flexible
hose 40.
[0051] The circulation fluid may be circulated from the fluid pump
2 and/or 4, such as a positive displacement type fluid pump,
through one or more fluid conduits 8, 24, 40, 42, into the pipe
string 55. The circulation fluid may then be circulated through the
pipe string 55 and through the nozzle 64. The circulation fluid may
be pumped at a selected circulation rate and/or a selected pump
pressure to achieve a desired impactor and/or fluid energy at the
nozzle 64.
[0052] The pump 4 may also serve as a supply pump to drive the
introduction of the impactors 100 entrained within an impactor
slurry, into the high pressure circulation fluid stream pumped by
mud pumps 2 and 4. Pump 4 may pump a percentage of the total rate
of fluid being pumped by both pumps 2 and 4, such that the
circulation fluid pumped by pump 4 may create a venturi effect
and/or vortex within the injector head 34 that inducts the impactor
slurry being conducted through the line 42, through the injector
head 34, and then into the high pressure circulation fluid
stream.
[0053] From the swivel 28, the slurry of circulation fluid and
impactors may circulate through the interior passage in the pipe
string 55 and through the nozzle 64. As described above, the nozzle
64 may alternatively be at least partially located in the drill bit
60. Each nozzle 64 may include a reduced inner diameter as compared
to an inner diameter of the interior passage in the pipe string 55
immediately above the nozzle 64. Thereby, each nozzle 64 may
accelerate the velocity of the slurry as the slurry passes through
the nozzle 64. The nozzle 64 may also direct the slurry into
engagement with a selected portion of the bottom surface 66 of
wellbore 70. The nozzle 64 may also be rotated relative to the
formation 52 depending on the excavation parameters. To rotate the
nozzle 64, the entire pipe string 55 may be rotated or only the
nozzle 64 on the end of the pipe string 55 may be rotated while the
pipe string 55 is not rotated. Rotating the nozzle 64 may also
include oscillating the nozzle 64 rotationally back and forth as
well as vertically, and may further include rotating the nozzle 64
in discrete increments. The nozzle 64 may also be maintained
rotationally substantially stationary.
[0054] The circulation fluid may be substantially continuously
circulated during excavation operations to circulate at least some
of the plurality of solid material impactors 100 and the formation
cuttings away from the nozzle 64. The impactors 100 and fluid
circulated away from the nozzle 64 may be circulated substantially
back to the excavation rig 5, or circulated to a substantially
intermediate position between the excavation rig 5 and the nozzle
64.
[0055] If a drill bit 60 is used, the drill bit 60 may be rotated
relative to the formation 52 and engaged therewith by an axial
force (WOB) acting at least partially along the wellbore axis 75
near the drill bit 60. The bit 60 may also comprise a plurality of
bit cones 62, which also may rotate relative to the bit 60 to cause
bit teeth secured to a respective cone to engage the formation 52,
which may generate formation cuttings substantially by crushing,
cutting, or pulverizing a portion of the formation 52. The bit 60
may also be comprised of a fixed cutting structure that may be
substantially continuously engaged with the formation 52 and create
cuttings primarily by shearing and/or axial force concentration to
fail the formation, or create cuttings from the formation 52. To
rotate the bit 60, the entire pipe string 55 may be rotated or only
the bit 60 on the end of the pipe string 55 may be rotated while
the pipe string 55 is not rotated. Rotating the drill bit 60 may
also include oscillating the drill bit 60 rotationally back and
forth as well as vertically, and may further include rotating the
drill bit 60 in discrete increments.
[0056] Also alternatively, the excavation system 1 may comprise a
pump, such as a centrifugal pump, having a resilient lining that is
compatible for pumping a solid-material laden slurry. The pump may
pressurize the slurry to a pressure greater than the selected mud
pump pressure to pump the plurality of solid material impactors 100
into the circulation fluid. The impactors 100 may be introduced
through an impactor injection port, such as port 30. Other
alternative embodiments for the system 1 may include an impactor
injector for introducing the plurality of solid material impactors
100 into the circulation fluid.
[0057] As the slurry is pumped through the pipe string 55 and out
the nozzles 64, the impactors 100 may engage the formation with
sufficient energy to enhance the rate of formation removal or
penetration (ROP). The removed portions of the formation may be
circulated from within the wellbore 70 near the nozzle 64, and
carried suspended in the fluid with at least a portion of the
impactors 100, through a wellbore annulus between the OD of the
pipe string 55 and the ID of the wellbore 70.
[0058] At the excavation rig 5, the returning slurry of circulation
fluid; formation fluids (if any), cuttings, and impactors 100 may
be diverted at a nipple 76, which may be positioned on a BOP stack
74. The returning slurry may flow from the nipple 76, into a return
flow line 15, which maybe comprised of tubes 48, 45, 16, 12 and
flanges 46, 47. The return line 15 may include an impactor
reclamation tube assembly 44, as illustrated in FIG. 1, which may
preliminarily separate a majority of the returning impactors 100
from the remaining components of the returning slurry to salvage
the circulation fluid for recirculation into the present wellbore
70 or another wellbore. At least a portion of the impactors 100 may
be separated from a portion of the cuttings by a series of
screening devices, such as the vibrating classifiers 84, to salvage
a reusable portion of the impactors 100 for reuse to re-engage the
formation 52. A majority of the cuttings and a majority of
non-reusable impactors 100 may also be discarded.
[0059] The reclamation tube assembly 44 may operate by rotating
tube 45 relative to tube 16. An electric motor assembly 22 may
rotate tube 44. The reclamation tube assembly 44 comprises an
enlarged tubular 45 section to reduce the return flow slurry
velocity and allow the slurry to drop below a terminal velocity of
the impactors 100, such that the impactors 100 can no longer be
suspended in the circulation fluid and may gravitate to a bottom
portion of the tube 45. This separation function may be enhanced by
placement of magnets near and along a lower side of the tube 45.
The impactors 100 and some of the larger or heavier cuttings may be
discharged through discharge port 20. The separated and discharged
impactors 100 and solids discharged through discharge port 20 may
be gravitationally diverted into a vibrating classifier 84 or may
be pumped into the classifier 84. A pump (not shown) capable of
handling impactors and solids, such as a progressive cavity pump
may be situated in communication with the flow line discharge port
20 to conduct the separated impactors 100 selectively into the
vibrating separator 84 or elsewhere in the circulation fluid
circulation system.
[0060] The vibrating classifier 84 may comprise a three-screen
section classifier of which screen section 18 may remove the
coarsest grade material. The removed coarsest grade material may be
selectively directed by outlet 78 to one of storage bin 82 or
pumped back into the flow line 15 downstream of discharge port 20.
A second screen section 92 may remove a re-usable grade of
impactors 100, which in turn may be directed by outlet 90 to the
impactor storage tank 94. A third screen section 86 may remove the
finest grade material from the circulation fluid. The removed
finest grade material may be selectively directed by outlet 80 to
storage bin 82, or pumped back into the flow line 15 at a point
downstream of discharge port 20. Circulation fluid collected in a
lower portion of the classified 84 may be returned to a mud tank 6
for re-use.
[0061] The circulation fluid may be recovered for recirculation in
a wellbore or the circulation fluid may be a fluid that is
substantially not recovered. The circulation fluid may be a liquid,
gas, foam, mist, or other substantially continuous or multiphase
fluid. For recovery, the circulation fluid and other components
entrained within the circulation fluid may be directed across a
shale shaker (not shown) or into a mud tank 6, whereby the
circulation fluid may be further processed for re-circulation into
a wellbore.
[0062] The excavation system 1 creates a mass-velocity relationship
in a plurality of the solid material impactors 100, such that an
impactor 100 may have sufficient energy to structurally alter the
formation 52 in a zone of a point of impact. The mass-velocity
relationship may be satisfied as sufficient when a substantial
portion by weight of the solid material impactors 100 may by virtue
of their mass and velocity at the exit of the nozzle 64, create a
structural alteration as claimed or disclosed herein. Impactor
velocity to achieve a desired effect upon a given formation may
vary as a function of formation compressive strength, hardness, or
other rock properties, and as a function of impactor size and
circulation fluid rheological properties. A substantial portion
means at least five percent by weight of the plurality of solid
material impactors that are introduced into the circulation
fluid.
[0063] The impactors 100 for a given velocity and mass of a
substantial portion by weight of the impactors 100 are subject to
the following mass-velocity relationship. The resulting kinetic
energy of at least one impactor 100 exiting a nozzle 64 is at least
0.075 Ft.Lbs or has a minimum momentum of 0.0003 Lbf.Sec.
[0064] Kinetic energy is quantified by the relationship of an
objects mass and its velocity. The quantity of kinetic energy
associated with an object is calculated by multiplying its mass
times its velocity squared. To reach a minimum value of kinetic
energy in the mass-velocity relationship as defined, small
particles such as those found in abrasives and grits, must have a
significantly high velocity due to the small mass of the particle.
A large particle, however, needs only moderate velocity to reach an
equivalent kinetic energy of the small particle because its mass
may be several orders of magnitude larger.
[0065] The velocity of a substantial portion by weight of the
plurality of solid material impactors 100 immediately exiting a
nozzle 64 may be as slow as 100 feet per second and as fast as 1000
feet per second, immediately upon exiting the nozzle 64.
[0066] The velocity of a majority by weight of the impactors 100
may be substantially the same, or only slightly reduced, at the
point of impact of an impactor 100 at the formation surface 66 as
compared to when leaving the nozzle 64. Thus, it may be appreciated
by those skilled in the art that due to the close proximity of a
nozzle 64 to the formation being impacted, the velocity of a
majority of impactors 100 exiting a nozzle 64 may be substantially
the same as a velocity of an impactor 100 at a point of impact with
the formation 52. Therefore, in many practical applications, the
above velocity values may be determined or measured at
substantially any point along the path between near an exit end of
a nozzle 64 and the point of impact, without material deviation
from the scope of this invention.
[0067] In addition to the impactors 100 satisfying the
mass-velocity relationship described above, a substantial portion
by weight of the solid material impactors 100 have an average mean
diameter of between approximately 0.050 to 0.500 of an inch.
[0068] To excavate a formation 52, the excavation implement, such
as a drill bit 60 or impactor 100, must overcome minimum, in-situ
stress levels or toughness of the formation 52. These minimum
stress levels are known to typically range from a few thousand
pounds per square inch, to in excess of 65,000 pounds per square
inch. To fracture, cut, or plastically deform a portion of
formation 52, force exerted on that portion of the formation 52
typically should exceed the minimum, in-situ stress threshold of
the formation 52. When an impactor 100 first initiates contact with
a formation, the unit stress exerted upon the initial contact point
may be much higher than 10,000 pounds per square inch, and may be
well in excess of one million pounds per square inch. The stress
applied to the formation 52 during contact is governed by the force
the impactor 100 contacts the formation with and the area of
contact of the impactor with the formation. The stress is the force
divided by the area of contact. The force is governed by Impulse
Momentum theory whereby the time at which the contact occurs
determines the magnitude of the force applied to the area of
contact. In cases where the particle is contacting a relatively
hard surface at an elevated velocity, the force of the particle
when in contact with the surface is not constant, but is better
described as a spike. However, the force need not be limited to any
specific amplitude or duration. The magnitude of the spike load can
be very large and occur in just a small fraction of the total
impact time. If the area of contact is small the unit stress can
reach values many times in excess of the in situ failure stress of
the rock, thus guaranteeing fracture initiation and propagation and
structurally altering the formation 52.
[0069] A substantial portion by weight of the solid material
impactors 100 may apply at least 5000 pounds per square inch of
unit stress to a formation 52 to create the structurally altered
zone Z in the formation. The structurally altered zone Z is not
limited to any specific shape or size, including depth or width.
Further, a substantial portion by weight of the impactors 100 may
apply in excess of 20,000 pounds per square inch of unit stress to
the formation 52 to create the structurally altered zone Z in the
formation. The mass-velocity relationship of a substantial portion
by weight of the plurality of solid material impactors 100 may also
provide at least 30,000 pounds per square inch of unit stress.
[0070] A substantial portion by weight of the solid material
impactors 100 may have any appropriate velocity to satisfy the
mass-velocity relationship. For example, a substantial portion by
weight of the solid material impactors may have a velocity of at
least 100 feet per second when exiting the nozzle 64. A substantial
portion by weight of the solid material impactors 100 may also have
a velocity of at least 100 feet per second and as great as 1200
feet per second when exiting the nozzle 64. A substantial portion
by weight of the solid material impactors 100 may also have a
velocity of at least 100 feet per second and as great as 750 feet
per second when exiting the nozzle 64. A substantial portion by
weight of the solid material impactors 100 may also have a velocity
of at least 350 feet per second and as great as 500 feet per second
when exiting the nozzle 64.
[0071] Impactors 100 may be selected based upon physical factors
such as size, projected velocity, impactor strength, formation 52
properties and desired impactor concentration in the circulation
fluid. Such factors may also include; (a) an expenditure of a
selected range of hydraulic horsepower across the one or more
nozzles, (b) a selected range of circulation fluid velocities
exiting the one or more nozzles or impacting the formation, and (c)
a selected range of solid material impactor velocities exiting the
one or more nozzles or impacting the formation, (d) one or more
rock properties of the formation being excavated, or (e), any
combination thereof.
[0072] If an impactor 100 is of a specific shape such as that of a
dart, a tapered conic, a rhombic, an octahedral, or similar oblong
shape, a reduced impact area to impactor mass ratio may be
achieved. The shape of a substantial portion by weight of the
impactors 100 may be altered, so long as the mass-velocity
relationship remains sufficient to create a claimed structural
alteration in the formation and an impactor 100 does not have any
one length or diameter dimension greater than approximately 0.100
inches. Thereby, a velocity required to achieve a specific
structural alteration may be reduced as compared to achieving a
similar structural alteration by impactor shapes having a higher
impact area to mass ratio. Shaped impactors 100 may be formed to
substantially align themselves along a flow path, which may reduce
variations in the angle of incidence between the impactor 100 and
the formation 52. Such impactor shapes may also reduce impactor
contact with the flow structures such those in the pipe string 55
and the excavation rig 5 and may thereby minimize abrasive erosion
of flow conduits.
[0073] Referring to FIGS. 1-4, a substantial portion by weight of
the impactors 100 may engage the formation 52 with sufficient
energy to enhance creation of a wellbore 70 through the formation
52 by any or a combination of different impact mechanisms. First,
an impactor 100 may directly remove a larger portion of the
formation 52 than may be removed by abrasive-type particles. In
another mechanism, an impactor 100 may penetrate into the formation
52 without removing formation material from the formation 52. A
plurality of such formation penetrations, such as near and along an
outer perimeter of the wellbore 70 may relieve a portion of the
stresses on a portion of formation being excavated, which may
thereby enhance the excavation action of other impactors 100 or the
drill bit 60. Third, an impactor 100 may alter one or more physical
properties of the formation 52. Such physical alterations may
include creation of micro-fractures and increased brittleness in a
portion of the formation 52T which may thereby enhance
effectiveness the impactors 100 in excavating the formation 52. The
constant scouring of the bottom of the borehole also prevents the
build up of dynamic filtercake, which can significantly increase
the apparent toughness of the formation 52.
[0074] FIG. 2 illustrates an impactor 100 that has been impaled
into a formation 52, such as a lower surface 66 in a wellbore 70.
For illustration purposes, the surface 66 is illustrated as
substantially planar and transverse to the direction of impactor
travel 100a. The impactors 100 circulated through a nozzle 64 may
engage the formation 52 with sufficient energy to effect one or
more properties of the formation 52.
[0075] A portion of the formation 52 ahead of the impactor 100
substantially in the direction of impactor travel T may be altered
such as by micro-fracturing and/or thermal alteration due to the
impact energy. In such occurrence, the structurally altered zone Z
may include an altered zone depth D. An example of a structurally
altered zone Z is a compressive zone Z1, which may be a zone in the
formation 52 compressed by the impactor 100. The compressive zone
Z1 may have a length L1, but is not limited to any specific shape
or size. The compressive zone Z1 may be thermally altered due to
impact energy.
[0076] An additional example of a structurally altered zone 102
near a point of impaction may be a zone of micro-fractures Z2. The
structurally altered zone Z may be broken or otherwise altered due
to the impactor 100 and/or a drill bit 60, such as by crushing,
fracturing, or micro-fracturing.
[0077] FIG. 2 also illustrates an impactor 100 implanted into a
formation 52 and having created an excavation E wherein material
has been ejected from or crushed beneath the impactor 100. Thereby
the excavation E may be created, which as illustrated in FIG. 3 may
generally conform to the shape of the impactor 100.
[0078] FIGS. 3 and 4 illustrate excavations E where the size of the
excavation may be larger than the size of the impactor 100. In FIG.
2, the impactor 100 is shown as impacted into the formation 52
yielding an excavation depth D.
[0079] An additional theory for impaction mechanics in cutting a
formation 52 may postulate that certain formations 52 may be highly
fractured or broken up by impactor energy. FIG. 4 illustrates an
interaction between an impactor 100 and a formation 52. A plurality
of fractures F and micro-fractures MF may be created in the
formation 52 by impact energy.
[0080] An impactor 100 may penetrate a small distance into the
formation 52 and cause the displaced or structurally altered
formation 52 to "splay out" or be reduced to small enough particles
for the particles to be removed or washed away by hydraulic action.
Hydraulic particle removal may depend at least partially upon
available hydraulic horsepower and at least partially upon particle
wet-ability and viscosity. Such formation deformation may be a
basis for fatigue failure of a portion of the formation by
"impactor contact," as the plurality of solid material impactors
100 may displace formation material back and forth.
[0081] Each nozzle 64 may be selected to provide a desired
circulation fluid circulation rate, hydraulic horsepower
substantially at the nozzle 64, and/or impactor energy or velocity
when exiting the nozzle 64. Each nozzle 64 may be selected as a
function of at least one of (a) an expenditure of a selected range
of hydraulic horsepower across the one or more nozzles 64, (b) a
selected range of circulation fluid velocities exiting the one or
more nozzles 64, and (c) a selected range of solid material
impactor 100 velocities exiting the one or more nozzles 64.
[0082] To optimize ROP, it may be desirable to determine, such as
by monitoring, observing, calculating, knowing, or assuming one or
more excavation parameters such that adjustments may be made in one
or more controllable variables as a function of the determined or
monitored excavation parameter. The one or more excavation
parameters may be selected from a group comprising: (a) a rate of
penetration into the formation 52, (b) a depth of penetration into
the formation 52, (c) a formation excavation factor, and (d) the
number of solid material impactors 100 introduced into the
circulation fluid per unit of time. Monitoring or observing may
include monitoring or observing one or more excavation parameters
of a group of excavation parameters comprising: (a) rate of nozzle
rotation, (b) rate of penetration into the formation 52, (c) depth
of penetration into the formation 52, (d) formation excavation
factor, (e) axial force applied to the drill bit 60, (f) rotational
force applied to the bit 60, (g) the selected circulation rate, (h)
the selected pump pressure, and/or (i) wellbore fluid dynamics,
including pore pressure.
[0083] One or more controllable variables or parameters may be
altered, including at least one of (a) rate of impactor 100
introduction into the circulation fluid, (b) impactor 100 size, (c)
impactor 100 velocity, (d) drill bit nozzle 64 selection, (e) the
selected circulation rate of the circulation fluid, (f) the
selected pump pressure, and (g) any of the monitored excavation
parameters.
[0084] To alter the rate of impactors 100 engaging the formation
52, the rate of impactor 100 introduction into the circulation
fluid may be altered. The circulation fluid circulation rate may
also be altered independent from the rate of impactor 100
introduction. Thereby, the concentration of impactors 100 in the
circulation fluid may be adjusted separate from the fluid
circulation rate. Introducing a plurality of solid material
impactors 100 into the circulation fluid may be a function of
impactor 100 size, circulation fluid rate, nozzle rotational speed,
wellbore 70 size, and a selected impactor 100 engagement rate with
the formation 52. The impactors 100 may also be introduced into the
circulation fluid intermittently during the excavation operation.
The rate of impactor 100 introduction relative to the rate of
circulation fluid circulation may also be adjusted or interrupted
as desired.
[0085] The plurality of solid material impactors 100 may be
introduced into the circulation fluid at a selected introduction
rate and/or concentration to circulate the plurality of solid
material impactors 100 with the circulation fluid through the
nozzle 64. The selected circulation rate and/or pump pressure, and
nozzle selection may be sufficient to expend a desired portion of
energy or hydraulic horsepower in each of the circulation fluid and
the impactors 100.
[0086] An example of an operative excavation system 1 may comprise
a bit 60 with an 81/2 inch bit diameter. The solid material
impactors 100 may be introduced into the circulation fluid at a
rate of 12 gallons per minute. The circulation fluid containing the
solid material impactors may be circulated through the bit 60 at a
rate of 462 gallons per minute. A substantial portion by weight of
the solid material impactors may have an average mean diameter of
0.100''. The following parameters will result in approximately a 27
feet per hour penetration rate into Sierra White Granite. In this
example, the excavation system may produce 1413 solid material
impactors 100 per cubic inch with approximately 3.9 million impacts
per minute against the formation 52. On average, 0.00007822 cubic
inches of the formation 52 are removed per impactor 100 impact. The
resulting exit velocity of a substantial portion of the impactors
100 from each of the nozzles 64 would average 495.5 feet per
second. The kinetic energy of a substantial portion by weight of
the solid material impacts 100 would be approximately 1.14 Ft Lbs.,
thus satisfying the mass-velocity relationship described above.
[0087] Another example of an operative excavation system 1 may
comprise a bit 60 with an 81/2'' bit diameter. The solid material
impactors 100 may be introduced into the circulation fluid at a
rate of 12 gallons per minute. The circulation fluid containing the
solid material impactors may be circulated through the nozzle 64 at
a rate of 462 gallons per minute. A substantial portion by weight
of the solid material impactors may have an average mean diameter
of 0.075''. The following parameters will result in approximately a
35 feet per hour penetration rate into Sierra White Granite. In
this example, the excavation system 1 may produce 3350 solid
material impactors 100 per cubic inch with approximately 9.3
million impacts per minute against the formation 52. On average,
0.0000428 cubic inches of the formation 52 are removed per impactor
100 impact. The resulting exit velocity of a substantial portion of
the impactors 100 from each of the nozzles 64 would average 495.5
feet per second. The kinetic energy of a substantial portion by
weight of the solid material impacts 100 would be approximately
0.240 Ft Lbs., thus satisfying the mass-velocity relationship
described above.
[0088] In addition to impacting the formation with the impactors
100, the bit 60 may be rotated while circulating the circulation
fluid and engaging the plurality of solid material impactors 100
substantially continuously or selectively intermittently. The
nozzle 64 may also be oriented to cause the solid material
impactors 100 to engage the formation 52 with a radially outer
portion of the bottom hole surface 66. Thereby, as the drill bit 60
is rotated, the impactors 100, in the bottom hole surface 66 ahead
of the bit 60, may create one or more circumferential kerfs. The
drill bit 60 may thereby generate formation cuttings more
efficiently due to reduced stress in the surface 66 being
excavated, due to the one or more substantially circumferential
kerfs in the surface 66.
[0089] The excavation system 1 may also include inputting pulses of
energy in the fluid system sufficient to impart a portion of the
input energy in an impactor 100. The impactor 100 may thereby
engage the formation 52 with sufficient energy to achieve a
structurally altered zone Z. Pulsing of the pressure of the
circulation fluid in the pipe string 55, near the nozzle 64 also
may enhance the ability of the circulation fluid to generate
cuttings subsequent to impactor 100 engagement with the formation
52.
[0090] Each combination of formation type, bore hole size, bore
hole depth, available weight on bit, bit rotational speed, pump
rate, hydrostatic balance, circulation fluid rheology, bit type,
and tooth/cutter dimensions may create many combinations of optimum
impactor presence or concentration, and impactor energy
requirements. The methods and systems of this invention facilitate
adjusting impactor size, mass, introduction rate, circulation fluid
rate and/or pump pressure, and other adjustable or controllable
variables to determine and maintain an optimum combination of
variables. The methods and systems of this invention also may be
coupled with select bit nozzles, downhole tools, and fluid
circulating and processing equipment to effect many variations in
which to optimize rate of penetration.
[0091] FIG. 5 shows an alternate embodiment of the drill bit 60
(FIG. 1) and is referred to, in general, by the reference numeral
110 and which is located at the bottom of a well bore 120 and
attached to a drill string 130. The drill bit 110 acts upon a
bottom surface 122 of the well bore 120. The drill string 130 has a
central passage 132 that supplies drilling fluids to the drill bit
110 as shown by the arrow A1. The drill bit 110 uses the drilling
fluids and solid material impactors 100 when acting upon the bottom
surface 122 of the well bore 120. The drilling fluids then exit the
well bore 120 through a well bore annulus 124 between the drill
string 130 and the inner wall 126 of the well bore 120. Particles
of the bottom surface 122 removed by the drill bit 110 exit the
well bore 120 with the drilling fluid through the well bore annulus
124 as shown by the arrow A2. The drill bit 110 creates a rock ring
142 at the bottom surface 122 of the well bore 120.
[0092] Referring now to FIG. 6, a top view of the rock ring 124
formed by the drill bit 110 is illustrated. An excavated interior
cavity 144 is worn away by an interior portion of the drill bit 110
and the exterior cavity 146 and inner wall 126 of the well bore 120
are worn away by an exterior portion of the drill bit 110. The rock
ring 142 possesses hoop strength, which holds the rock ring 142
together and resists breakage. The hoop strength of the rock ring
142 is typically much less than the strength of the bottom surface
122 or the inner wall 126 of the well bore 120, thereby making the
drilling of the bottom surface 122 less demanding on the drill bit
110. By applying a compressive load and a side load, shown with
arrows 141, on the rock ring 142, the drill bit 110 causes the rock
ring 142 to fracture. The drilling fluid 140 then washes the
residual pieces of the rock ring 142 back up to the surface through
the well bore annulus 124.
[0093] The mechanical cutters, utilized on many of the surfaces of
the drill bit 110, may be any type of protrusion or surface used to
abrade the rock formation by contact of the mechanical cutters with
the rock formation. The mechanical cutters may be Polycrystalline
Diamond Coated (PDC), or any other suitable type mechanical cutter
such as tungsten carbide cutters. The mechanical cutters may be
formed in a variety of shapes, for example, hemispherically shaped,
cone shaped, etc. Several sizes of mechanical cutters are also
available, depending on the size of drill bit used and the hardness
of the rock formation being cut.
[0094] Referring now to FIG. 7, an end elevational view of the
drill bit 110 of FIG. 5 is illustrated. The drill bit 110 comprises
two side nozzles 200A, 200B and a center nozzle 202. The side and
center nozzles 200A, 200B, 202 discharge drilling fluid and solid
material impactors (not shown) into the rock formation or other
surface being excavated. The solid material impactors may comprise
steel shot ranging in diameter from about 0.010 to about 0.500 of
an inch. However, various diameters and materials such as ceramics,
etc. may be utilized in combination with the drill bit 120. The
solid material impactors contact the bottom surface 122 of the well
bore 120 and are circulated through the annulus 124 to the surface.
The solid material impactors may also make up any suitable
percentage of the drilling fluid for drilling through a particular
formation.
[0095] Still referring to FIG. 7 the center nozzle 202 is located
in a center portion 203 of the drill bit 110. The center nozzle 202
may be angled to the longitudinal axis of the drill bit 110 to
create an excavated interior cavity 244 and also cause the
rebounding solid material impactors to flow into the major junk
slot, or passage, 204A. The side nozzle 200A located on a side arm
214A of the drill bit 110 may also be oriented to allow the solid
material impactors to contact the bottom surface 122 of the well
bore 120 and then rebound into the major junk slot, or passage,
204A. The second side nozzle 200B is located on a second side arm
2148. The second side nozzle 200B may be oriented to allow the
solid material impactors to contact the bottom surface 122 of the
well bore 120 and then rebound into a minor junk slot, or passage,
204B. The orientation of the side nozzles 200A, 200B may be used to
facilitate the drilling of the large exterior cavity 46. The side
nozzles 200A, 200B may be oriented to cut different portions of the
bottom surface 122. For example, the side nozzle 200B may be angled
to cut the outer portion of the excavated exterior cavity 146 and
the side nozzle 200A may be angled to cut the inner portion of the
excavated exterior cavity 146. The major and minor junk slots, or
passages, 204A, 204B allow the solid material impactors, cuttings,
and drilling fluid 240 to flow up through the well bore annulus 124
back to the surface. The major and minor junk slots, or passages,
204A, 204B are oriented to allow the solid material impactors and
cuttings to freely flow from the bottom surface 122 to the annulus
124.
[0096] As described earlier, the drill bit 110 may also comprise
mechanical cutters and gauge cutters. Various mechanical cutters
are shown along the surface of the drill bit 110. Hemispherical PDC
cutters are interspersed along the bottom face and the side walls
of the drill bit 110. These hemispherical cutters along the bottom
face break down the large portions of the rock ring 142 and also
abrade the bottom surface 122 of the well bore 120. Another type of
mechanical cutter along the side arms 214A, 214B are gauge cutters
230. The gauge cutters 230 form the final diameter of the well bore
120. The gauge cutters 230 trim a small portion of the well bore
120 not removed by other means. Gauge bearing surfaces 206 are
interspersed throughout the side walls of the drill bit 110. The
gauge bearing surfaces 206 ride in the well bore 120 already
trimmed by the gauge cutters 230. The gauge bearing surfaces 206
may also stabilize the drill bit 110 within the well bore 120 and
aid in preventing vibration.
[0097] Still referring to FIG. 7 the center portion 203 comprises a
breaker surface, located near the center nozzle 202, comprising
mechanical cutters 208 for loading the rock ring 142. The
mechanical cutters 208 abrade and deliver load to the lower stress
rock ring 142. The mechanical cutters 208 may comprise PDC cutters,
or any other suitable mechanical cutters. The breaker surface is a
conical surface that creates the compressive and side loads for
fracturing the rock ring 142. The breaker surface and the
mechanical cutters 208 apply force against the inner boundary of
the rock ring 142 and fracture the rock ring 142. Once fractured,
the pieces of the rock ring 142 are circulated to the surface
through the major and minor junk slots, or passages, 204A,
204B.
[0098] Referring now to FIG. 8, an enlarged end elevational view of
the drill bit 110 is shown. As shown more clearly in FIG. 8, the
gauge bearing surfaces 206 and mechanical cutters 208 are
interspersed on the outer side walls of the drill bit 110. The
mechanical cutters 208 along the side walls may also aid in the
process of creating drill bit 110 stability and also may perform
the function of the gauge bearing surfaces 206 if they fail. The
mechanical cutters 208 are oriented in various directions to reduce
the wear of the gauge bearing surface 206 and also maintain the
correct well bore 120 diameter. As noted with the mechanical
cutters 208 of the breaker surface, the solid material impactors
fracture the bottom surface 122 of the well bore 120 and, as such,
the mechanical cutters 208 remove remaining ridges of rock and
assist in the cutting of the bottom hole. However, the drill bit
110 need not necessarily comprise the mechanical cutters 208 on the
side wall of the drill bit 110.
[0099] Referring now to FIG. 9, a side elevational view of the
drill bit 110 is illustrated. FIG. 9 shows the gauge cutters 230
included along the side arms 214A, 214B of the drill bit 110. The
gauge cutters 230 are oriented so that a cutting face of the gauge
cutter 230 contacts the inner wall 126 of the well bore 120. The
gauge cutters 230 may contact the inner wall 126 of the well bore
at any suitable backrake, for example a backrake of 15.degree. to
45.degree.. Typically, the outer edge of the cutting face scrapes
along the inner wall 126 to refine the diameter of the well bore
120.
[0100] Still referring to FIG. 9 one side nozzle 200A is disposed
on an interior portion of the side arm 214A and the second side
nozzle 200B is disposed on an exterior portion of the opposite side
arm 214B. Although the side nozzles 200A, 200B are shown located on
separate side arms 214A, 214B of the drill bit 110, the side
nozzles 200A, 200B may also be disposed on the same side arm 214A
or 214B. Also, there may only be one side nozzle, 200A or 200B.
Also, there may only be one side arm, 214A or 214B.
[0101] Each side arm 214A, 214B fits in the excavated exterior
cavity 146 formed by the side nozzles 200A, 200B and the mechanical
cutters 208 on the face 212 of each side arm 214A, 214B. The solid
material impactors from one side nozzle 200A rebound from the rock
formation and combine with the drilling fluid and cuttings flow to
the major junk slot 204A and up to the annulus 124. The flow of the
solid material impactors, shown by arrows 205, from the center
nozzle 202 also rebound from the rock formation up through the
major junk slot 204A.
[0102] Referring now to FIGS. 10 and 11, the minor junk slot 204B,
breaker surface, and the second side nozzle 200B are shown in
greater detail. The breaker surface is conically shaped, tapering
to the center nozzle 202. The second side nozzle 200B is oriented
at an angle to allow the outer portion of the excavated exterior
cavity 146 to be contacted with solid material impactors. The solid
material impactors then rebound up through the minor junk slot
204B, shown by arrows 205, along with any cuttings and drilling
fluid 240 associated therewith.
[0103] Referring now to FIGS. 12 and 13, top elevational views of
the drill bit 110 are shown. Each nozzle 200A, 200B, 202 receives
drilling fluid 240 and solid material impactors from a common
plenum feeding separate cavities 250, 251, and 252. Since the
common plenum has a diameter, or cross section, greater than the
diameter of each cavity 250, 251, and 252, the mixture, or
suspension of drilling fluid and impactors is accelerated as it
passes from the plenum to each cavity. The center cavity 250 feeds
a suspension of drilling fluid 240 and solid material impactors to
the center nozzle 202 for contact with the rock formation. The side
cavities 251, 252 are formed in the interior of the side arms 214A,
214B of the drill bit 110, respectively. The side cavities 251, 252
provide drilling fluid 240 and solid material impactors to the side
nozzles 200A, 200B for contact with the rock formation. By
utilizing separate cavities 250, 251, 252 for each nozzle 202,
200A, 200B, the percentages of solid material impactors in the
drilling fluid 240 and the hydraulic pressure delivered through the
nozzles 200A, 200B, 202 can be specifically tailored for each
nozzle 200A, 200B, 202. Solid material impactor distribution can
also be adjusted by changing the nozzle diameters of the side and
center nozzles 200A, 200B, and 202 by changing the diameters of the
nozzles. However, in alternate embodiments, other arrangements of
the cavities 250, 251, 252, or the utilization of a single cavity,
are possible.
[0104] Referring now to FIG. 14, the drill bit 110 in engagement
with the rock formation 270 is shown. As previously discussed, the
solid material impactors 272 flow from the nozzles 200A, 200B, 202
and make contact with the rock formation 270 to create the rock
ring 142 between the side arms 214A, 214B of the drill bit 110 and
the center nozzle 202 of the drill bit 110. The solid material
impactors 272 from the center nozzle 202 create the excavated
interior cavity 244 while the side nozzles 200A, 200B create the
excavated exterior cavity 146 to form the outer boundary of the
rock ring 142. The gauge cutters 230 refine the more crude well
bore 120 cut by the solid material impactors 272 into a well bore
120 with a more smooth inner wall 126 of the correct diameter.
[0105] Still referring to FIG. 14 the solid material impactors 272
flow from the first side nozzle 200A between the outer surface of
the rock ring 142 and the interior wall 216 in order to move up
through the major junk slot 204A to the surface. The second side
nozzle 200B (not shown) emits solid material impactors 272 that
rebound toward the outer surface of the rock ring 142 and to the
minor junk slot 204B (not shown). The solid material impactors 272
from the side nozzles 200A, 200B may contact the outer surface of
the rock ring 142 causing abrasion to further weaken the stability
of the rock ring 142. Recesses 274 around the breaker surface of
the drill bit 110 may provide a void to allow the broken portions
of the rock ring 142 to flow from the bottom surface 122 of the
well bore 120 to the major or minor junk slot 204A, 204B.
[0106] Referring now to FIG. 15, an example orientation of the
nozzles 200A, 200B, 202 are illustrated. The center nozzle 202 is
disposed left of the center line of the drill bit 110 and angled on
the order of around 20.degree. left of vertical. Alternatively,
both of the side nozzles 200A, 200B may be disposed on the same
side arm 214 of the drill bit 110 as shown in FIG. 15. In this
embodiment, the first side nozzle 200A, oriented to cut the inner
portion of the excavated exterior cavity 146, is angled on the
order of around 10.degree. left of vertical. The second side nozzle
200B is oriented at an angle on the order of around 14.degree.
right of vertical. This particular orientation of the nozzles
allows for a large interior excavated cavity 244 to be created by
the center nozzle 202. The side nozzles 200A, 200B create a large
enough excavated exterior cavity 146 in order to allow the side
arms 214A, 214B to fit in the excavated exterior cavity 146 without
incurring a substantial amount of resistance from uncut portions of
the rock formation 270. By varying the orientation of the center
nozzle 202, the excavated interior cavity 244 may be substantially
larger or smaller than the excavated interior cavity 244
illustrated in FIG. 14. The side nozzles 200A, 200B may be varied
in orientation in order to create a larger excavated exterior
cavity 146, thereby decreasing the size of the rock ring 142 and
increasing the amount of mechanical cutting required to drill
through the bottom surface 122 of the well bore 120. Alternatively,
the side nozzles 200A, 200B may be oriented to decrease the amount
of the inner wall 126 contacted by the solid material impactors
272. By orienting the side nozzles 200A, 200B at, for example, a
vertical orientation, only a center portion of the excavated
exterior cavity 146 would be cut by the solid material impactors
and the mechanical cutters would then be required to cut a large
portion of the inner wall 126 of the well bore 120.
[0107] Referring now to FIGS. 16 and 17, side cross-sectional views
of the bottom surface 122 of the well bore 120 drilled by the drill
bit 110 are shown. With the center nozzle angled on the order of
around 20.degree. left of vertical and the side nozzles 200A, 200B
angled on the order of around 10.degree. left of vertical and
around 14.degree. right of vertical, respectively, the rock ring
142 is formed. By increasing the angle of the side nozzle 200A,
200B orientation, an alternate rock ring 142 shape and bottom
surface 122 is cut as shown in FIG. 17. The excavated interior
cavity 244 and rock ring 142 are much more shallow as compared with
the rock ring 142 in FIG. 16. It is understood that various
different bottom hole patterns can be generated by different nozzle
configurations.
[0108] Although the drill bit 110 is described comprising
orientations of nozzles and mechanical cutters, any orientation of
either nozzles, mechanical cutters, or both may be utilized. The
drill bit 110 need not comprise a center portion 203. The drill bit
110 also need not even create the rock ring 142. For example, the
drill bit may only comprise a single nozzle and a single junk slot.
Furthermore, although the description of the drill bit 110
describes types and orientations of mechanical cutters, the
mechanical cutters may be formed of a variety of substances, and
formed in a variety of shapes.
[0109] Referring now to FIGS. 18-19, a drill bit 150 in accordance
with a second embodiment is illustrated. As previously noted, the
mechanical cutters, such as the gauge cutters 230, mechanical
cutters 208, and gauge bearing surfaces 206 may not be necessary in
conjunction with the nozzles 200A, 200B, 202 in order to drill the
required well bore 120. The side wall of the drill bit 150 may or
may not be interspersed with mechanical cutters. The side nozzles
200A, 200B and the center nozzle 202 are oriented in the same
manner as in the drill bit 150, however, the face 212 of the side
arms 214A, 214B comprises angled (PDCs) 280 as the mechanical
cutters.
[0110] Still referring to FIGS. 18-20 each row of PDCs 280 is
angled to cut a specific area of the bottom surface 122 of the well
bore 120. A first row of PDCs 280A is oriented to cut the bottom
surface 122 and also cut the inner wall 126 of the well bore 120 to
the proper diameter. A groove 282 is disposed between the cutting
faces of the PDCs 280 and the face 212 of the drill bit 150. The
grooves 282 receive cuttings, drilling fluid 240, and solid
material impactors and direct them toward the center nozzle 202 to
flow through the major and minor junk slots, or passages, 204A,
204B toward the surface. The grooves 282 may also direct some
cuttings, drilling fluid 240, and solid material impactors toward
the inner wall 126 to be received by the annulus 124 and also flow
to the surface. Each subsequent row of PDCs 280B, 280C may be
oriented in the same or different position than the first row of
PDCs 280A. For example, the subsequent rows of PDCs 280B, 280C may
be oriented to cut the exterior face of the rock ring 142 as
opposed to the inner wall 126 of the well bore 120. The grooves 282
on one side arm 214A may also be oriented to direct the cuttings
and drilling fluid 240 toward the center nozzle 202 and to the
annulus 124 via the major junk slot 204A. The second side arm 214B
may have grooves 282 oriented to direct the cuttings and drilling
fluid 240 to the inner wall 126 of the well bore 120 and to the
annulus 124 via the minor junk slot 204B.
[0111] The PDCs 280 located on the face 212 of each side arm 214A,
214B are sufficient to cut the inner wall 126 to the correct size.
However, mechanical cutters may be placed throughout the side wall
of the drill bit 150 to further enhance the stabilization and
cutting ability of the drill bit 150.
[0112] Referring to FIG. 21, an embodiment of a particle separation
system is shown, in general, by the reference numeral 300 for use
in the excavation system 1 of FIG. 1. The system 300 is designed to
separate the particles from the drilling fluid after the suspension
has discharged from the nozzles 200, 200A and 200B (FIG. 7) in the
drill bit 110 and removed a portion of the well bore 120 (FIG. 5),
as described above.
[0113] The system 300 includes a conduit 302, one end of which is
coupled to the return flow line 15 (FIG. 1) of the reclamation tube
assembly 44, which is otherwise replaced by the system 300. The
other end of the conduit 302 is coupled to the input of a choke
304, and a return line 306 is coupled to the output of the choke.
Although not shown in the drawing, it is understood that a
conventional choke valve is provided in the choke 304 to control
the volume of flow through the choke under conditions to be
described. The above couplings can be done in any manner such as by
providing flanges on the corresponding ends of the members to be
coupled, as shown, and using bolts, other fasteners, weldments,
brazing, or other metal-to-metal joining techniques.
[0114] One end of a conduit 308 registers with an opening in the
conduit 302, and a screen separator 310 is disposed in the conduit
302 at its junction with the conduit 308. The screen separator 306
extends across the interior of the conduit 302 and at an angle to
the longitudinal axis of the conduit.
[0115] The other end of the conduit 308 is coupled, via an elbow
312, to the inlet side of a valve 314, and one end of a conduit 316
extends from the outlet side of the latter valve. The valve 314 may
be conventional and, as such, includes a closure device 314a, such
as a disc, flap, or the like, that moves in the valve housing
between two positions shown by the solid lines and the dashed lines
to open or close the valve, respectively.
[0116] The other end of the conduit 316 registers with an inlet of
another valve 320, and a discharge elbow 322 is coupled to the
outlet of the latter valve. The valve 320 is includes a closure
device 320a, such as a disc, flap, or the like, that moves in the
valve housing between two positions shown by the solid lines and
the dashed lines to open or close the valve, respectively. In this
closed position of the valve 320, the impactors 100 in the
suspension will be blocked from flowing through the valve 320 and
will settle in the lower portion of the conduit 316 under the force
of gravity.
[0117] A pressure relief conduit 326 communicates with an opening
in the conduit 316 between the valves 314 and 320, and a screen
separator 328 is disposed at the junction of the conduits 316 and
326. A valve 330 is disposed in the conduit 326 for controlling the
relief of the pressure in the latter conduit to atmosphere, under
conditions to be described.
[0118] In operation, the valve 314 is fully opened, the valves 320
and 330 are closed. The suspension of the fluid and impactors 100
from the bottom of the well bore 124 (FIG. 5) flows into and
through the return flow line 15 (FIG. 1), into the conduit 302, and
to the screen 310. The screen 310 is sized so as to permit passage
of the fluid therethrough but to prevent passage of the impactors
100.
[0119] The choke 304 is adjusted as needed to provide the desired
flow characteristics, and the separated fluid passes from the
screen 310 through the conduit 302 and discharges from the conduit
306 after which it can be recycled or discarded.
[0120] The separated impactors 100, carrying a small volume of
fluid with them, pass through the conduit 308 and the elbow 312,
through the open valve 314, through the conduit 316, and to the
closed valve 320. Thus, a mixture of the separators 100 and a
relatively small volume of the fluid accumulates in the conduit 316
and the valve 330 is opened as necessary to provide adequate
pressure relief to the atmosphere. The screen 328 blocks any flow
of the impactors 100 into the conduit 326, and the impactors settle
to the bottom of the conduit 316 under the force of gravity. When a
sufficient volume of the impactors 100 have accumulated in the
conduit 316 in the above manner, the valve 320 is then opened and
the impactors flow out the conduit 316, through the open valve 320
and through the discharge elbow 322. The impactors 100 can be
transported to a holding tank, or the like for reuse.
[0121] It is understood that other solids, such as cuttings, fines,
dirt, etc. might be also present in the suspension that passes into
the system 300 from the flow line 15. In this case, the size of the
screen can be selected to let these solid pass through with the
fluid or to block their passage. In the former case the solids
would pass through the choke 304 and discharge with the fluid from
the conduit 306. In the latter case, the solids would pass through
the conduit 308, the open valve 314 and into the conduit 316 with
the impactors 100 and settle in the conduit 316 with the impactors,
as described above.
[0122] Other variations may be made in the embodiment of FIG. 21.
For example, the valves can be disposed in their corresponding
conduits or in a separate housing attached to the conduits. Also,
the elbows and/or the choke may be eliminated, and the type of
screen and the type of valves may be varied. Further, the various
conduits can be coupled together in any conventional manner.
[0123] FIG. 22 depicts a graph showing a comparison of the results
of the impact excavation utilizing one or more of the above
embodiments (labeled "PDTI in the drawing) as compared to
excavations using two strictly mechanical drilling bits--a
conventional PDC bit and a "Roller Cone" bit--while drilling
through the same stratigraphic intervals. The drilling took place
through a formation at the GTI (Gas Technology Institute of
Chicago, Ill.) test site at Catoosa, Okla.
[0124] The PDC (Polycrystalline Diamond Compact) bit is a
relatively fast conventional drilling bit in soft-to-medium
formations but has a tendency to break or wear when encountering
harder formations. The Roller Cone is a conventional bit involving
two or more revolving cones having cutting elements embedded on
each of the cones.
[0125] The overall graph of FIG. 22 details the performance of the
three bits though 800 feet of the formation consisting of shales,
sandstones, limestones, and other materials. For example, the upper
portion of the curve (approximately 306 to 336 feet) depicts the
drilling results in a hard limestone formation that has compressive
strengths of up to 40,000 psi.
[0126] Note that the PDTI bit performance in this area was
significantly better than that of the other two bits--the PDTI bit
took only 0.42 hours to drill the 30 feet where the PDC bit took 1
hour and the roller cone took about 1.5 hours. The total time to
drill the approximately 800 foot interval took a little over 7
hours with the PDTI bit, whereas the Roller cone bit took 7.5 hours
and the PDC bit took almost 10 hours.
[0127] The graph demonstrates that the PDTI system has the ability
to not only drill the very hard formations at higher rates, but can
drill faster that the conventional bits through a wide variety of
rock types.
[0128] The table below shows actual drilling data points that make
up the PDTI bit drilling curve of FIG. 22. The data points shown
are random points taken on various days and times. For example, the
first series of data points represents about one minute of drilling
data taken at 2:38 pm on Jul. 22.sup.nd, 2005, while the bit was
running at 111 RPM, with 5.9 thousand pounds of bit weight ("WOB"),
and with a total drill string and bit torque of 1,972 Ft Lbs. The
bit was drilling at a total depth of 323.83 feet and its
penetration rate for that minute was 136.8 Feet per Hour. The
impactors were delivered at approximately 14 GPM (gallons per
minute) and the impactors had a mean diameter of approximately
0.100'' and were suspended in approximately 450 GPM of drilling
mud.
TABLE-US-00001 TORQUE WOB DEPTH PENETRATION PENETRATION DATE TIME
RPM Ft. Lbs. Lbs. Ft. FT/MIN FT/HR Jul. 22, 2005 2:38 PM 111 1,972
5.9 323.83 2.28 136.8 Jul. 22, 2005 4:24 PM 103 2,218 9.1 352.43
2.85 171.0 Jul. 25, 2005 9:36 AM 101 2,385 9.5 406.54 3.71 222.6
Jul. 25, 2005 10:17 AM 99 2.658 10.9 441.88 3.37 202.2 Jul. 25,
2005 11:29 AM 96 2.646 10.1 478.23 2.94 176.4 Jul. 25, 2005 4:41 PM
97 2,768 12.2 524.44 2.31 138.6 Jul. 25, 2005 4:54 PM 96 2,870 10.6
556.82 3.48 208.8
[0129] While specific embodiments have been shown and described,
modifications can be made by one skilled in the art without
departing from the spirit or teaching of this invention. The
embodiments as described are exemplary only and are not limiting.
Many variations and modifications are possible and are within the
scope of the invention. Accordingly, the scope of protection is not
limited to the embodiments described, but is only limited by the
claims that follow, the scope of which shall include all
equivalents of the subject matter of the claims.
* * * * *