U.S. patent application number 11/746931 was filed with the patent office on 2007-11-15 for core drill assembly with adjustable total flow area and restricted flow between outer and inner barrel assemblies.
This patent application is currently assigned to Baker Hughes Incorporated. Invention is credited to Thorsten Regener, Bob T. Wilson.
Application Number | 20070261886 11/746931 |
Document ID | / |
Family ID | 38684052 |
Filed Date | 2007-11-15 |
United States Patent
Application |
20070261886 |
Kind Code |
A1 |
Wilson; Bob T. ; et
al. |
November 15, 2007 |
CORE DRILL ASSEMBLY WITH ADJUSTABLE TOTAL FLOW AREA AND RESTRICTED
FLOW BETWEEN OUTER AND INNER BARREL ASSEMBLIES
Abstract
A core drill assembly with replaceable fluid nozzles permitting
effective total flow area adjustment (TFA), substantial
optimization of hydraulic force at the cutting face to improve rate
of penetration (ROP) and core quality. At least one seal assembly
to restrict drilling fluid flow while permitting mutual rotation
between the core head ID and the lower shoe is disposed in an
annulus defined therebetween.
Inventors: |
Wilson; Bob T.; (Dubai,
AE) ; Regener; Thorsten; (Niedersachsen, DE) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Assignee: |
Baker Hughes Incorporated
Houston
TX
|
Family ID: |
38684052 |
Appl. No.: |
11/746931 |
Filed: |
May 10, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60800620 |
May 15, 2006 |
|
|
|
Current U.S.
Class: |
175/58 ;
175/249 |
Current CPC
Class: |
E21B 10/02 20130101;
E21B 25/00 20130101; E21B 10/605 20130101 |
Class at
Publication: |
175/58 ;
175/249 |
International
Class: |
E21B 49/02 20060101
E21B049/02 |
Claims
1. A core drill assembly comprising: a core head including an
inside diameter, a face, and at least one fluid course having an
outlet on the face; a lower shoe; at least one replaceable nozzle
disposed in the at least one fluid course proximate the outlet; and
at least one seal structure, configured to permit rotation between
the core head and lower shoe assembly, disposed between the core
head inside diameter and an exterior surface of the lower shoe.
2. The assembly of claim 1, wherein the at least one replaceable
nozzle is replaceable with another replaceable nozzle having a
different inner diameter.
3. The assembly of claim 1, wherein the at least one seal structure
comprises a seal assembly and includes at least one groove formed
on at least one of the inside diameter of the core head and the
exterior surface of the lower shoe.
4. The assembly of claim 3, wherein the at least one seal assembly
includes at least one seal element carried in the at least one
groove.
5. The assembly of claim 4, wherein the at least one seal element
is at least one of an o-ring seal, a wiper seal, a split-ring seal,
a chevron seal or a packer cup.
6. The assembly of claim 4, wherein the at least one seal element
is made of at least one of a nylon, a Teflon.RTM., a polyethylene,
a rubber or a neoprene material.
7. The assembly of claim 1, wherein the at least one seal structure
comprises a labyrinth seal.
8. The assembly of claim 1, wherein the at least one seal structure
comprises a restrictor sleeve disposed within the core head
laterally adjacent an exterior surface of the lower shoe.
9. The assembly of claim 8, wherein the restrictor sleeve rests on
an annular shoulder on the ID of the core head.
10. The assembly of claim 8, wherein an ID of the restrictor sleeve
and the laterally adjacent exterior surface of the lower shoe are
mutually spaced by about 1 mm.
11. A method for substantially controlling the total flow area
(TFA) of a core drill assembly comprising: providing a core head
including at least one fluid course having an outlet on the face
thereof; installing a replaceable nozzle having a selected inner
diameter in the fluid course proximate the outlet; disposing a
lower shoe at least partially within the core head; and rotating
the core head about the lower shoe while substantially preventing a
flow of drilling fluid between the core head and the lower shoe and
directing flow through the at least one replaceable nozzle.
12. The method of claim 11, further including replacing the at
least one replaceable nozzle with another replaceable nozzle having
a different inner diameter.
13. The method of claim 11, further comprising providing an
absolute fluid seal between the core head and the lower shoe.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/800,620, filed May 15, 2006, the
entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] Embodiments of the present invention are related to a core
drill assembly with adjustable drill fluid total flow area and,
more particularly, to a core drill assembly which includes
replaceable cutting fluid nozzles and a seal assembly disposed
between adjacent portions of the outer barrel assembly and the
inner barrel assembly, as well as to methods of coring.
BACKGROUND
[0003] Current core head designs use a fixed total flow area (TFA)
to circulate drilling fluid through the core head, also known as a
core bit, during down-hole coring operations. The TFA is a
calculated discharge area for the drilling fluid which may include
an annulus ID gauge fluid course between the core head ID and the
exterior of the lower shoe, carried by the inner barrel assembly,
or core head face discharge ports, or a combination of the two.
Drilling fluid is circulated through the ID fluid courses and the
face discharge ports to cool and clean cutting structure carried on
the face of the core head, and to remove cuttings generated when
the cutting head penetrates the formation being cored. The
hydraulic force, or the ability of the drilling fluid to removing
material cuttings from the cutting head face, is measured in
hydraulic horsepower/in.sup.2 (HSI) and is an indicator of drilling
fluid cleaning efficiency. If the hydraulic force is too low, there
will be poor cleaning of the cutting structure and cuttings will
interfere with the rate of penetration (ROP) in forming the bore
hole. If the hydraulic force is too high, there may be erosion of
the bole hole, which can result in a stuck drill string, and the
drilling fluid may contaminate the core sample. By using HSI and
ROP measurements, the optimum amount of hydraulic force can be
designed into a core drill assembly.
[0004] FIG. 1 is a cross-section of a conventional core drill
assembly 10, with a non-adjustable TFA or drilling fluid flow area
defined by the areas of the annulus 50 and the discharge ports 30.
The annulus 50 is the gap between the ID of core head 14 and the
outside of the lower shoe 18. With this arrangement, drilling fluid
is pumped down the drill string, to core drill assembly 10, where a
portion of the drilling fluid will travel through the annulus 50
and exit the core drill assembly 10 proximate the leading edge of
the lower shoe 18, while the remaining drilling fluid enters the
fluid course 20 within core head 14, and exits the discharge ports
30 located on the face 16 of core head 14, as respectively shown by
the arrows in FIG. 1l The drilling fluid is used to cool the
cutters 60 and flush cuttings away from the face 16 of core head
14. However, since the TFA is non-adjustable, the operator cannot
optimize the amount of drilling fluid at the drill face 16 of core
head 14 and the HSI.
[0005] With the non-adjustable TFA of current core head designs,
the only variable is the circulation rate of the drilling fluid,
and therefore, the HSI cannot be optimized. Also, in current core
heads there is always some drilling fluid flow through the annular
space between the core head ID and the lower shoe. In core heads
using ID fluid courses only, all of the flow travels through the
annulus whereas, when core head face discharge ports are used in
combination with the annulus, it is difficult to determine amount
of drilling fluid "split" between the discharge ports and the
annulus. The difficulty arises because the actual annulus gap
spacing between the core head ID and the lower shoe is not known
when the core head is down hole. The annulus gap is nominally 3/8
inch to 1/2 inch ; however, when using an aluminum or fiberglass
inner tube, in the inner barrel assembly, gaps up to 51/2 inches
may be required in order to compensate for the different rates of
thermal expansion attributed to the materials of the inner tube and
the core head. Under bottom-hole temperature, the gap may decrease
to the estimated desirable gap of 3/8 inch to 1/2 inch, but
uncertainty about the actual and estimated bottom-hole temperature,
can result in a significant error in spacing adjustment. As the
area of the annulus gap is added directly into the TFA calculation,
the uncertainty of the gap size makes accurately calculating TFA
difficult. The split of flow between the annulus between the OD of
the inner tube shoe and the ID of the core head, and the face
discharge ports is dependent upon their relative TFA. Depending
upon actual spacing down hole, the annular TFA could be higher than
the TFA of the face discharge ports, with the result that most of
the flow of drilling fluid will pass through the ID annulus. This
significantly reduces the effectiveness of the face discharge
ports, and reduces further the HSI delivered to the cutting
structure of the core head. Adjusting the TFA of the face discharge
ports in this case would not increase HSI, since the bypass flow
would simply be increased through the ID annulus. To increase HSI,
the bypass flow through the ID annulus must be sealed off, or
severely restricted, to divert as much of the flow as possible to
the face discharge ports, or nozzles.
[0006] For a conventional drill bit with replaceable nozzles, the
TFA can be optimized by utilizing different diameter nozzles in the
discharge ports. However, in a conventional core drill assembly,
since at least some of the drilling fluid flow travels through the
annulus, a change of discharge port size will change the resistance
at the nozzles and will proportionally change the amount of
drilling fluid bypassing through the annulus. This problem is
highlighted when looking at the performance of the drill bit versus
a core drill. A drill bit will normally operate in the range of 4-8
HSI, whereas an 81/2 inch by 4 inch core drill may operate as low
as 0.2 HSI.
[0007] In view of the shortcomings in the art, it would be
advantageous to provide a core drill with adjustable TFA, by
fitting the core head with replaceable nozzles and sealing off the
annulus between the core head ID and the lower shoe. This will
allow an operator to apply the same drilling optimization concepts
to coring as used with conventional drilling, and allow the HSI to
be improved over conventional core head designs, with corresponding
improvements in coring performance, ROP and core quality.
BRIEF SUMMARY OF THE INVENTION
[0008] Embodiments of the invention include replaceable nozzles
fitted in at least some of the drilling fluid outlet ports,
proximate the face of the core head. The nozzle design will
compensate for the smaller surface area of the typical core drill
face and new nozzle locations and jet directions are contemplated
to take advantage of the improved HSI at the cutting face,
including directing nozzles towards interior cutters of the core
head in order to clear cuttings and provide cooling.
[0009] In one embodiment of the present invention, the annulus
between the cutting head and the lower shoe is substantially sealed
with a seal structure, which may be broadly characterized as a seal
assembly or a seal element, without substantial rotational
interference between the core head and the lower shoe, which would
cause the lower shoe and inner tube to turn with the outer barrel
assembly and core head.
[0010] One embodiment includes one or more grooves formed into the
ID of the core head to accommodate an annular seal similar to an
O-ring in each of the grooves. The design of the O-ring or other
annular seal allows some drilling fluid flow to bypass under
reduced pressure, but under normal operating circumstances the
O-ring or other annular seal seals substantially completely.
[0011] In a second embodiment of the present invention, the annulus
between the core head and the lower shoe is substantially sealed
using split rings made from a material such as nylon or
Teflon.RTM.. This embodiment includes one or more grooves formed in
the ID of the core head where split rings of the appropriate size
are installed to seal the annulus. The seals will fit somewhat
loosely in the grooves and may rotate during coring operations, but
will provide a sufficient seal to enable effective TFA adjustments
by installing different sizes of drilling fluid nozzles. The loose
fit will reduce friction between the core head ID and the lower
shoe, to eliminate any tendency for the lower shoe and inner tube
to rotate.
[0012] Other embodiments of the present invention employ one or
more of a wiper seal, a chevron seal, a packer cup or a restrictor
sleeve disposed between the core head and the lower shoe to
substantially restrict fluid flow therebetween while permitting
rotational movement of the core head about the lower shoe.
[0013] Embodiments of the present invention also include methods of
using a core drill assembly.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] The foregoing and other advantages of the invention will
become apparent upon reading the following detailed description and
upon reference to the drawings in which:
[0015] FIG. 1 is a cross-section of a conventional core drill
assembly with an non-adjustable TFA defined by the area of the
annulus between the core head and the lower shoe, and the area of
the drilling fluid ports.
[0016] FIG. 2 is a cross-section of a core drill assembly with a
seal structure between the core head and the lower shoe and
replaceable nozzles;
[0017] FIG. 3 is a partial cross-section of a core drill assembly
including an O-ring or wiper seal type seal assembly;
[0018] FIG. 4 is a partial cross-section of a core drill assembly
including a split-ring type seal assembly;
[0019] FIG. 5 is a partial cross-section of a core drill assembly
including a labyrinth seal assembly; and
[0020] FIG. 6 is a partial cross-section of a core drill assembly
including a restrictor sleeve.
DETAILED DESCRIPTION
[0021] FIG. 2 schematically depicts a core drill assembly 10 of the
present invention including replaceable nozzles 36 at the discharge
ends of fluid courses 20, and at least one seal assembly 40
disposed between the core head 14 and the lower shoe 18. These
features allow the operator to change the TFA of the core drill
assembly 10 and optimize the HSI. The operator can select
replaceable nozzles 36 having a discharge opening 34 of an
appropriate diameter to adjust TFA. Thus, if a volume of drilling
fluid is pumped under pressure, at a substantially constant flow
rate, down the drill string, seal assembly 40 will divert
substantially all of the drilling fluid volume away from the
annulus 50 and into the fluid courses 20 where the drilling fluid
will exit through discharge opening 34 of replaceable nozzles 36.
The diameters of discharge openings 34 will affect both the rate of
discharge and the velocity of the escaping drilling fluid. Under
optimized conditions, as provided by the present invention, the
drilling fluid, emanating from the discharge openings 34, will
effectively clear cuttings away from the face 16 and of core head
14 and properly cool cutters 60. The optimum diameter of discharge
openings 34 for a specific material or formation, and core head or
core size, can be determined or predicted by the use of historical
data, including ROP measurements. As shown at the left-hand side of
FIG. 2, the seal assembly 40 may be partially received in a groove
in ID of the core head 14 or, as shown at the right-hand side of
FIG. 2, the seal assembly 40 may be partially received in a groove
in the exterior of the lower shoe 18. As core head 14 rotates about
lower shoe 18 during a coring operation, fluid flow therebetween
will be substantially restricted by seal assembly 40, as indicated
by the smaller size of the arrows below annulus 50 in comparison to
those in fluid courses 20.
[0022] FIGS. 3 and 4, are partial cross-section views of core drill
assembly 10 provided, to show additional detail of several
embodiments of the at least one seal assembly 40. The at least one
seal assembly 40 is positioned in the annulus 50, or the gap
defined between the ID of core head 14 and the outside of the lower
shoe 18. The seals 42 and 44 are installed in grooves 46 formed in
the ID of core head 14. The seals 44 shown in FIG. 3 may comprise
an O-ring or other continuous ring type that may have a round or
oval cross-section, or may include lips which function as "wipers,"
as shown. The material of seals 44 may include, but is not limited
to, rubber, neoprene, or polyethylene or a combination thereof. The
seals 42 shown in FIG. 4 are of a split-ring design which rides
loosely in the grooves 46. Examples of suitable materials for the
split-ring seals 42 are nylon and Teflon.RTM. polymers. The at
least one seal assembly 40 will substantially restrict the flow of
the drilling fluid pumped down the drill string, forcing the
drilling fluid to bypass the annulus 50 and into the fluid courses
20, traveling in the direction of flow arrows 26.
[0023] FIG. 5 is a partial cross-section view of a core drill
assembly 10 including a labyrinth seal 48 having a plurality of
radially projecting, axially spaced annular elements separated by
labyrinth slots 56. The labyrinth seal 48 is formed into the
structure of one of the core head 14 ID or the exterior surface of
the lower shoe 18. However, a labyrinth seal 48 with mating,
interdigitated elements or components as shown in broken lines at E
can be formed with the cooperating parts disposed on both the core
head 14 ID and the lower shoe 18. The total number of labyrinth
slots 56 is not specified, and will vary depending on the expected
pressure differential between the pumped drilling fluid and drill
work face. The labyrinth seal 48 must have sufficient length and
number of labyrinth slots 56 to effectively seal annulus 50. With
annulus 50 sealed, the drilling fluid will enter fluid courses 20,
flowing in the direction indicated by flow arrows 26.
[0024] It is also contemplated that the seals may be carried on the
exterior of the lower shoe 18 instead of on core head 14, or may be
carried on both components. It is also contemplated that a seal
comprising an upwardly facing packer cup with a frustoconical
elastomeric skirt may be utilized in addition to, or in lieu of,
other seal configurations. Chevron-type seals, as well as metallic
or elastomeric seal back-up components, may also be employed.
[0025] FIG. 6 depicts yet another embodiment of the present
invention, wherein a seal element in the form of restrictor sleeve
64 is disposed on an annular shoulder 62 machined or otherwise
formed on the ID of the core head 14, and retained therein through
the use of an appropriate bonding agent, such as BAKERLOK.RTM.
compound, available from various operating units of Baker Hughes
Incorporated, assignee of the present invention. As with the
previous embodiments, discharge openings 34 of replaceable nozzles
36 may be selected for optimum TFA. A conventional lower shoe 18 is
run inside of core head 14, and extends longitudinally
therethrough. The outer surface (shown in broken lines for clarity)
of lower shoe 18 is in close proximity to the ID of restrictor
sleeve 64, so that a very small clearance radial clearance C, for
example about 1 mm, is achieved This small, annular clearance C
between lower shoe 18 and restrictor sleeve 64, while permitting
rotation of lower shoe 18 and restrictor sleeve 64 about lower shoe
18, will substantially restrict the flow of the drilling fluid
pumped down the drill string, forcing the drilling fluid to bypass
the annulus 50 and into the fluid courses 20 to exit through
discharge openings 34 of replaceable nozzles 36.
[0026] While the present invention has been depicted and described
with reference to certain embodiments, the invention is not so
limited. Additions and modifications to, and deletions from, the
described embodiments will be readily apparent to those of ordinary
skill in the art. The present invention is, thus, limited only by
the claims which follow, and equivalents thereof.
* * * * *