U.S. patent application number 11/444966 was filed with the patent office on 2007-12-06 for apparatus for separating solids from liquids.
Invention is credited to Donald Roy Smith.
Application Number | 20070278012 11/444966 |
Document ID | / |
Family ID | 38788797 |
Filed Date | 2007-12-06 |
United States Patent
Application |
20070278012 |
Kind Code |
A1 |
Smith; Donald Roy |
December 6, 2007 |
Apparatus for separating solids from liquids
Abstract
In a drilling operation, where used drilling fluid is screened
into a substantially solid portion and a substantially liquid
drilling fluid and the drilling fluid is thereafter stored in a
storage tank. A method and apparatus for of separating solids from
liquids. The apparatus comprises a recirculation tank having a
second liquid for receiving the solid portion, and a first
rotational particle separator for separating the solid portion from
the second liquid. The apparatus further includes a pump for
pumping the solid portion and the second liquid from the
recirculation tank to the first rotational particle separator and a
bin region to receive and retain the separated solids from the
first rotational particle separator, wherein the separated second
liquid is returned to the recirculation tank.
Inventors: |
Smith; Donald Roy;
(Strathmore, CA) |
Correspondence
Address: |
FULWIDER PATTON LLP
HOWARD HUGHES CENTER, 6060 CENTER DRIVE, TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
38788797 |
Appl. No.: |
11/444966 |
Filed: |
May 31, 2006 |
Current U.S.
Class: |
175/66 ; 175/206;
175/207 |
Current CPC
Class: |
E21B 21/065
20130101 |
Class at
Publication: |
175/66 ; 175/206;
175/207 |
International
Class: |
E21B 21/06 20060101
E21B021/06 |
Claims
1. An apparatus for separating solids from liquids in a drilling
operation wherein used drilling fluid is screened into a
substantially solid portion and a substantially liquid drilling
fluid, the drilling fluid being stored in a storage tank, the
apparatus comprising: a recirculation tank having a second liquid
for receiving said solid portion; a first rotational particle
separator for separating said solid portion from said second
liquid; a pump for pumping said solid portion and said second
liquid from said recirculation tank to said first rotational
particle separator; and a bin region to receive and retain said
separated solids from said first rotational particle separator,
wherein said separated second liquid is returned to said
recirculation tank.
2. The apparatus of claim 1 wherein said rotational particle
separator comprises a centrifuge.
3. The apparatus of claim 1 wherein said rotational particle
separator comprises a cyclonic separator.
4. The apparatus of claim 1 wherein said apparatus is mounted on a
field transportable skid.
5. The apparatus of claim 4 wherein said skid includes a raised
platform for mounting said rotational particle separator.
6. The apparatus of claim 1 further comprising a second rotational
particle separator for removing particles from the drilling fluid
supplied from the storage tank, said particles being deposited in
said bin region wherein said drilling fluid is returned to the
storage tank.
7. The apparatus of claim 1 wherein said recirculation tank
includes an angled bottom having a high end and a low end relative
to each other.
8. The apparatus of claim 7 wherein said pump draws said solid
portion and said second liquid proximate to said low end.
9. The apparatus of claim 8 wherein said recirculation tank
includes a closable top
10. The apparatus of claim 9 wherein when said drilling fluid is a
water based drilling fluid, said top may be closed such that said
solid portion slide across said top to be deposited into said bin
and when said drilling fluid is an oil based drilling fluid, said
top may be opened such that said solid portion is deposited in said
recirculation tank.
11. The apparatus of claim 1 wherein said second liquid is drilling
fluid.
12. The apparatus of claim 1 further comprising at least one tank
for supplying a particle separation assisting agent to the input of
said second rotational particle separator when said drilling fluid
is a water based drilling fluid.
13. The apparatus of claim 12 wherein said particle separation
assisting agent is a calcium water solution.
14. The apparatus of claim 13 wherein said calcium water solution
is stored in a stripping tank.
15. The apparatus of claim 14 wherein said apparatus includes two
stripping tanks.
16. The apparatus of claim 12 wherein said particle separation
assisting agent is a polymer flocculating agent.
17. The apparatus of claim 16 wherein said flocculating agent is
stored in at least one polymer tank.
18. The apparatus of claim 17 wherein said apparatus includes two
polymer tanks.
19. A method for separating solids from liquids in a drilling
operation wherein used drilling fluid is screened into a
substantially solid portion and a substantially liquid drilling
fluid, the drilling fluid being stored in a storage tank, the
method comprising: depositing said solid portion in a recirculation
tank having a second liquid; drawing off said solid portion and
said second liquid from said recirculation tank for delivery to a
first rotational particle separator; separating said solid portion
from said second liquid in a first rotational particle separator;
and collecting said separated solids in a bin region and deposing
said second liquid back in said recirculation tank.
20. The method of claim 19 further comprising removing solid
particles from a portion of screened drilling fluid in a second
rotational particle separator and returning the liquid portion to a
collection tank, wherein said solids are deposited in said bin
region.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a method and apparatus for
separating solids from liquids in general and in particular to a
method and apparatus for separating solids from liquids in an oil
well drilling operation.
[0003] 2. Description of Related Art
[0004] Wells for recovering oil, gas and the like are typically
created by drilling into an underground source using a hollow drill
string supported by a drilling rig. The drill string includes a
drill bit at the lower end that is rotated into the ground to
create a well bore. As the drill bit is rotated, drilling fluid is
pumped down through the interior of the drill string to pass
through the bit and return to the surface in the well bore external
to the drill string. The drilling fluid acts to lubricate the drill
bit and carries the loose solids or cuttings created by the drill
bit to the surface. At the surface, the used drilling fluid is
collected and recycled by removing some or all of the cuttings. The
composition of the cuttings content in the drilling fluid can be
varied depending on the state of the drilling process and the
location of the drill bit below the surface.
[0005] Presently, a mud storage tank to hold drilling fluid and a
shale shaker to perform screening of larger cuttings tend to be
standard equipment for a drilling rig. In normal well site
operation, drilling fluid is circulated out of the borehole and
passed over a shale shaker which is a screen to separate large
solid particles from the drilling fluid. The shale shaker is
generally positioned directly above the mud storage tank and the
large particles are collected in a shale bin. The resulting
collected large particles typically still have at least some
drilling fluid on them after being deposited in the shale bin and
are typically in the form of a slurry. A rotational particle
separator such as for example a centrifuge or cyclonic separator is
typically used to remove the smaller particles remaining in the
drilling fluid in the storage tank.
[0006] Drilling fluids are typically either water based or oil
based. Regulations in many countries require that when an oil based
drilling fluid is used, the cuttings in the shale bin be hauled
away for disposal or blended with sawdust and canola for land
spreading. This is because the remaining drilling fluid on the
cuttings discussed above would contaminate any site at which the
cuttings were disposed unless the drilling fluid was removed
beforehand. Blending of the cuttings prior to land spreading
increases the cost to dispose of cuttings as compared to the cost
of disposal of dry cuttings alone. In addition, the resulting wet
cuttings composition is greater in volume and weight than dry
cuttings alone. This increased weight and volume of the wet
cuttings further increases transportation and disposal costs.
[0007] While the smaller particles in the drilling fluid are
typically separated from the drilling fluid by a centrifuge, the
larger particles removed by the shale shaker are not. The wet
cuttings resulting from not centrifuging the larger particles
results in the aforementioned problems with disposal of such wet
cuttings. Previous attempts to pass all of the cuttings through a
centrifuge have not been successful.
[0008] Heretofore, it has been impractical to pass all of the solid
materials removed by the shale shaker through a centrifuge to
further remove any drilling fluid from the solid material. The
larger particles removed by the shale shaker would constitute too
dry of a composition to properly pass through a centrifuge or
cyclonic separator without plugging the same.
[0009] In addition, it has not been practical to pass all of the
used drilling fluid through a centrifuge without first separating
the drilling fluid from the larger particles with a shale shaker.
Because of the relatively large volume of the mud storage tank, the
velocity and agitation of the drilling fluid in this tank is
relatively low. The lack of agitation of the mud storage tank
allows the small and large particles to accumulate on the bottom of
the tank. Because of the settling of the particles on the bottom of
the tank, the larger particles would accumulate in the tank and
thereby would not be removed quickly enough from the mud storage
tank by the centrifuge. This allows for solids carry over between
chambers of the mud storage tank and eventually allows for
recirculation of the solids in the mud storage tank down the drill
string which is undesirable.
[0010] What is desirable is a solid separation system that produces
a drier solid product that does not require blending prior to
disposal. Specifically, a method and apparatus that enables all of
the solid material to be passed through a centrifuge or cyclonic
separator so as to produce a drier solid is desirable.
SUMMARY OF THE INVENTION
[0011] The present invention provides a method and apparatus that
enables all of the solid material in a drilling fluid to be passed
through a centrifuge or cyclonic separator to remove all excess
drilling fluid from the solid material. Specifically, the present
invention permits the solid material removed from the drilling
fluid by a shale shaker or screen to be passed through a centrifuge
or cyclonic separator to further remove any drilling fluid from the
solid material.
[0012] According to a first embodiment of the present invention,
there is provided an apparatus for separating solids from liquids
in a drilling operation. In the drilling operation, used drilling
fluid is screened into a substantially solid portion and a
substantially liquid drilling fluid whereby the drilling fluid is
stored in a storage tank. The apparatus comprises a recirculation
tank having a second liquid for receiving the solid portion, and a
first rotational particle separator for separating the solid
portion from the second liquid. The apparatus further includes a
pump for pumping the solid portion and the second liquid from the
recirculation tank to the first rotational particle separator and a
bin region to receive and retain the separated solids from the
first rotational particle separator, wherein the separated second
liquid is returned to the recirculation tank.
[0013] The rotational particle separator may comprise a centrifuge.
The rotational particle separator may comprise a cyclonic
separator. The apparatus may be further mounted on a field
transportable skid. The skid may include a raised platform for
mounting the rotational particle separator. The apparatus may
further comprise a second rotational particle separator for
removing particles from the drilling fluid supplied from the
storage tank wherein the particles are deposited in the bin region
wherein the drilling fluid is returned to the storage tank.
[0014] The recirculation tank may include an angled bottom having a
high end and a low end relative to each other. The pump may draw
the solid portion and the second liquid proximate to the low end.
The recirculation tank may further include a closable top. The
second liquid may comprise drilling fluid. The apparatus may
further include at least one tank for supplying a particle
separation assisting agent to the input of the second rotational
particle separator when said drilling fluid is a water based
drilling fluid.
[0015] According to a further embodiment of the present invention,
there is provided a method for separating solids from liquids in a
drilling operation. In the drilling operation, used drilling fluid
is screened into a substantially solid portion and a substantially
liquid drilling fluid, wherein the drilling fluid is stored in a
storage tank. The method comprises depositing the solid portion in
a recirculation tank having a second liquid and drawing off the
solid portion and the second liquid from the recirculation tank for
delivery to a first rotational particle separator. The method
further comprises separating the solid portion from the second
liquid in a first rotational particle separator and collecting the
separated solids in a bin region and deposing the second liquid
back in the recirculation tank. The method may further include
removing solid particles from a portion of the screened drilling
fluid in a second rotational particle separator and returning the
liquid portion to a collection tank, wherein the solids are
deposited in a bin region.
[0016] Other aspects and features of the present invention will
become apparent to those ordinarily skilled in the art upon review
of the following description of specific embodiments of the
invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In drawings which illustrate embodiments of the
invention,
[0018] FIG. 1 is a schematic view of a drilling system
incorporating the drilling fluid cleaning system of the present
invention.
[0019] FIG. 2 is a perspective view of a preferred embodiment of
the drilling fluid cleaning system according to the present
invention.
[0020] FIG. 3 is a top plan view of the drilling fluid cleaning
system of FIG. 2.
[0021] FIG. 4 is cross sectional view of the recirculation tank of
FIG. 2 taken along the line 4-4 of FIG. 3.
[0022] FIG. 5 is cross sectional view of the shale bin and two
polymer tanks of FIG. 2 as taken along the line 5-5 of FIG. 3.
[0023] FIG. 6 is cross sectional view of the shale bin of FIG. 2 as
taken along the line 6-6 of FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Referring to FIG. 1, there is shown a schematic view of a
well drilling system 10, which includes a drill rig 12, and a
transportable drilling fluid cleaning system 40. The drilling rig
includes a drill derrick 14 supporting a drill string 16, which is
rotated to drill a well bore into the ground. A mud storage tank 20
is associated with the drilling rig and stores drilling fluid 18.
The composition of the drilling fluid 18 can be adjusted depending
on the stage to which the well bore is drilled. The apparatus of
the present invention can be used to remove undesirable solids from
the drilling mud and to recycle the drilling fluid to the tank 20
at a desired viscosity.
[0025] The drilling fluid is pumped in a conventional manner from
the tank 20 through a conduit 22 into drill string 16. Drilling
fluid 18 flows downwardly through the drill string to exit from the
lower end of the string at bit 17. The drilling fluid 18 acts to
lubricate the drill bit and collect cuttings created by the
drilling action of the bit. The drilling fluid with additional
solids flows upwardly in the well bore externally to the drill
string to be collected near the surface. The collected drilling
fluids/solids mixture passes through conduit 24 to be delivered to
a shale shaker 26. Shale shaker is a vibrating screen positioned
above the tank 20 that removes larger solids from the drilling
fluid and delivers cleaned drilling fluid back to the tank 20. The
larger solids are delivered to the apparatus for further removal of
drilling fluid for collection. Drilling fluid from the tank 20 may
also be pumped by conventional means to the cleaning system 40 for
further removal of smaller particles via conduit 28 wherein cleaned
drilling fluid is returned to the tank 20 via conduit 30.
[0026] FIG. 2 shows a side elevation view of a preferred embodiment
of the drilling fluid cleaning system 40. The system includes a
recirculation tank 50, a shale bin 70, a first centrifuge 92 and a
pump house 100. The system may also include a second centrifuge 94
and a plurality of strip tanks and polymer tanks 102 and 104
respectively. The above components may be arranged on a platform,
preferably in the form of a skid 42, to permit loading of the
system onto a trailer towable by a truck for transport of all of
the components as a unit in a single trip by roads between drilling
sites. In the province of Alberta, Canada, where the inventors are
based, skid 42 can be dimensioned to a maximum size of 63 feet
long, 12.5 feet wide and 17.5 feet high in order to be
transportable on roads and highways as a non-divisible load. A skid
of this size requires a special permit for oil field hauling,
however, a pilot vehicle to lead the truck is not required. Skids
of different sizes may be permitted in other jurisdictions.
[0027] The centrifuges 92 and 94 may be located on a secondary
platform 96 above the shale bin and recirculation tank. The
secondary platform 96 may also be moveable between a stored
position during transportation and an operating position. The
secondary be located above the shale bin 70 and recirculation tank
50 by means of telescoping arms 98 wherein the telescoping arms
facilitate movement between the stored and operating positions. It
will be appreciated that other means of moving the secondary
platform between the stored and operating positions, such as, for
example, by means of supporting the secondary platform on rotatable
arms, will also be acceptable.
[0028] FIG. 3 shows a plan view of the fluid cleaning system 40
with the centrifuges removed showing details primarily of
recirculation tank 50, shale bin 70 and strip tanks and polymer
tanks 102 and 104, respectively. The recirculation tank and shale
bin are located at a first end 44 of the skid 42. The pump house
100 is located at a second end 46 of the skid 42 and includes
various pumps and ancillary equipment for use in the fluid cleaning
operation including pump 48. The strip tanks and polymer tanks 102
and 104, respectively, are located intermediate the pump house 100
and the shale bin 70 and recirculation tank 50.
[0029] In the preferred embodiment shown in FIG. 3, the
recirculation tank 50 is located longitudinally along the skid 42
adjacent to the first end 44 of the skid. The shale bin 70 is
located adjacent to the recirculation tank 50 and is substantially
coterminous along the longitudinal length of the skid 42. The
recirculation tank 50 comprises a substantially rectangular
container region defined by first and second longitudinal walls 52
and 54 respectively, first and second end walls 56 and 58,
respectively, and a bottom 60.
[0030] Turning now to FIG. 4, a cross sectional view of the
recirculation tank is shown along the line 4-4 from FIG. 3. As
shown in FIG. 4, the recirculation tank includes an opening 62
which may be connected to a conduit 47 as shown in FIG. 5. The
conduit connected to the opening 62 may be further connected to a
pump 48 of conventional means which serves to supply a flow of the
solid particles and drilling fluid in the recirculation tank to the
first centrifuge 92. In a preferred embodiment as shown in FIG. 4,
the bottom 60 may be angled so as to direct any particles settling
on the bottom to the opening 62 for pickup and processing by the
centrifuges. The recirculation tank 50 may also include a cover 64
that is positionable over the recirculation tank as shown in FIG.
6. Cover 64 may be connected to the recirculation tank by a hinge
or other suitable pivot 66 so that the cover may be opened to
permit depositing of solid material in the recirculation bin or
closed so as to aid in depositing of solid material directly into
the shale bin 70. In a preferred emobidment as shown in FIG. 6, the
cover 64 opens inwardly into the recirculation tank 50. The cover
64 may be retained in a closed position over the recirculation tank
50 by any suitable means, such as, for example, by a chain (not
shown) suspended from the secondary platform 96 connected to the
free end 67 of the cover 64 at an appropriate position to
substantially cover the recirculation tank. It will be appreciated
by those of skill in the art that other methods of retaining the
cover in a closed position may also be applied to the present
apparatus.
[0031] The recirculation tank 50 is sized such that the addition of
solid particles and cleaned drilling fluid at the top and the
removal of the same from the bottom produces a sufficient agitation
as to prevent the settling of a large quantity of particles before
being drawn into the opening 62. In practice, the applicant has
found that a distance of approximately about 18 inches or less
between the first and second longitudinal walls 52 and 54,
respectively, is sufficient to prevent excessive settling of any
solid particles in the recirculation tank with a distance of 12
inches being preferred.
[0032] Referring back to FIG. 1, drilling fluid pumped out of the
recirculation tank 50 is directed to the first centrifuge 92 for
further solids separation. The first centrifuge separates the
solids from the drilling fluid/solid particles mixture and deposits
the solid particles in the shale bin 70. The cleaned drilling fluid
is then returned to the recirculation tank 50. Furthermore, in a
preferred embodiment, the system also includes a second centrifuge
for separating the solids from the drilling fluid in the mud
storage tank 20 of the drilling rig. The solid/drilling fluid in
the mud storage tank 20 is pumped by a conventional pump to the
centrifuge. The centrifuge separates the solids from the liquids
and deposits the solids in the shale bin 70. The cleaned drilling
fluid is then returned to the mud storage tank 20.
[0033] Solids removed from the drilling fluid by centrifuges 92 and
94 as well as solids not requiring centrifuging are preferably
stored in a shale bin 70 adjacent to the first end 44 of the skid
42. Bin 70 is defined by four walls and floor 80 at a region of the
skid adjacent to the recirculation tank 50. The first and second
walls 72 and 74 respectively of the bin 70 are transverse to the
longitudinal length of the skid 42 while the third and fourth walls
76 and 78 are substantially parallel the longitudinal length of the
skid. Preferably, as shown in FIGS. 5 and 6, the bottom of each of
the walls of the bin 70 may be offset towards the center of the bin
so as to angled the wall. Alternatively, the walls of the bin 70
may be substantially vertical or the fourth wall 78 may
alternatively include a hinged bottom to facilitate access for
removing solid particles from the bin 70.
[0034] In certain circumstances during drilling, for example when
the drilling fluid is being changed from a water based drilling
fluid to an oil based drilling fluid, it may be desirable to use a
flocculating agent to promote the removal of solids from the
drilling fluid. To address this need, the system of the present
invention may include a flocculent source for adding a flocculating
agent to the drilling fluid. Preferably, the flocculent source
comprises at least one compartment for holding and mixing a
flocculating agent and a delivery system to deliver flocculating
agent to the centrifuges. Preferably, flocculating agent is added
to the drilling fluid at the inlets of pumps supplying the
centrifuges so the agent is mixed with the drilling fluid prior to
centrifuging. Flocculating agents are conventional and may include
a calcium water solution or a polymer based flocculating agent.
According to a preferred embodiment, the fluid cleaning system 40
of the present invention includes two strip tanks 102 for holding a
calcium water solution and two polymer tanks 104 for holding a
polymer flocculating agent.
Operation
[0035] In use, the drilling fluid cleaning system 40 of the present
invention is operated according to different schemes depending on
the drilling stage.
[0036] During drilling of the "surface hole" (the first portion of
the borehole), water based drilling fluid is commonly used to
protect groundwater aquifers. During drilling of the surface hole,
larger particles may be deposited directly into the shale bin 70
and the cover 64 of the recirculation tank positioned over the
recirculation tank. The large particles may thereby slide over the
cover 64 and into the shale bin 70. The second centrifuge 94 may
also be used to remove smaller particles from the drilling fluid 18
from the mud storage tank 20 whereby the particles are deposited in
the shale bin 70 and the cleaned drilling fluid returned to the mud
storage tank 20.
[0037] During changeover of the drilling fluid from a water based
drilling fluid to an oil based drilling fluid, the recirculation
tank 50 may remain covered by cover 64. The drilling fluid 18 in
the mud storage tank 20 may be pumped into the second centrifuge 94
to remove any particles in the drilling fluid. In addition, calcium
water from the strip tanks 102 or a polymer flocculating agent from
the polymer tanks 104 may be added to the inlet of the centrifuge
94 along with the drilling fluid to enhance the separation of the
solid particles from the drilling fluid. Thereafter the solid
particles may be deposited in the shale bin 70 while the drilling
fluid is returned to one or more of the strip tank 102, polymer
tank 104 or mud storage tank 20. When the water based drilling
fluid is sufficiently cleaned of particles it may be disposed of in
a sump on or off site.
[0038] During drilling with oil based drilling fluid, the cover 64
to the recirculation tank 50 may be positioned off of the
recirculation tank and the larger particles from the shale shaker
26 may be deposited in the recirculation tank. As previously
indicated, the recirculation tank 50 contains a second fluid, which
may be a drilling fluid similar to the drilling fluid as is used to
drill the well. The drilling fluid and solid particles are drawn
out of the recirculation tank 50 at opening 62 and passed through
the first centrifuge 92. The centrifuge removes the solids and
deposit them into shale bin 70 and returns the drilling fluid to
the recirculation tank 50. The second centrifuge 94 draws the
drilling fluid 18 from the mud storage tank 20, removes the solids
from the drilling fluid and returns the drilling fluid to the tank
20. The solids are thereafter deposited in the shale bin 70. The
solids in the shale bin may thereafter be removed for land
spreading or disposal by other means.
[0039] It will be appreciated that as the foregoing equipment is
located on a field transportable skid, transportation to and from a
drilling site is greatly simplified as compared to the
transportation of various equipment separate from each other. In
addition, the close proximity of all of the equipment set out above
will greatly facilitate the switch over between different types of
drilling fluid as well as switching over from removing solids from
the drilling fluid to removing the water based drilling fluid from
the drilling system.
[0040] While specific embodiments of the invention have been
described and illustrated, such embodiments should be considered
illustrative of the invention only and not as limiting the
invention as construed in accordance with the accompanying
claims.
* * * * *