U.S. patent application number 12/012872 was filed with the patent office on 2008-08-07 for cryogenic drilling method.
Invention is credited to James Q. Maguire.
Application Number | 20080185184 12/012872 |
Document ID | / |
Family ID | 39675196 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080185184 |
Kind Code |
A1 |
Maguire; James Q. |
August 7, 2008 |
Cryogenic drilling method
Abstract
A method of drilling a wellbore using a cryogenic fluid to
prevent sloughing of the wellbore during drilling operations is
provided. The method includes providing non-rotatable tubing
constructed of a material capable of withstanding temperatures of
at least about -320.degree. F. and back pressure exerted on the
tubing during the drilling operations, the tubing having an
internally disposed electric power cable extending the length
thereof. A drill bit constructed of materials capable of
withstanding cryogenic temperatures of at least about -320.degree.
F., is operably connected to a distal end potion of the tubing. A
power source capable of rotating the drill bit, the power source
operable connected to the drill bit via the electric power cable
such that upon activation of the power source the bit is caused to
rotate. A liquid cryogenic material is injected into the tubing for
cooling the drill bit of about -320.degree. F. during drilling
operations and to freezing the formation and thereby preventing
sloughing of shale and infiltration of water into the wellbore.
Inventors: |
Maguire; James Q.; (Norman,
OK) |
Correspondence
Address: |
DUNLAP CODDING & ROGERS, P.C.
PO BOX 16370
OKLAHOMA CITY
OK
73113
US
|
Family ID: |
39675196 |
Appl. No.: |
12/012872 |
Filed: |
February 6, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60899712 |
Feb 6, 2007 |
|
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Current U.S.
Class: |
175/17 |
Current CPC
Class: |
E21B 36/001 20130101;
E21B 21/08 20130101; E21B 19/22 20130101; E21B 4/04 20130101 |
Class at
Publication: |
175/17 |
International
Class: |
E21B 36/00 20060101
E21B036/00 |
Claims
1. A method of drilling a wellbore without use of drilling muds to
lift chips out of the wellbore and preventing sloughing of a
formation into an annulus of the wellbore, the method comprising:
providing a coil of tubing wherein the tubing is constructed of a
material capable of withstanding cryogenic temperatures and a back
pressure exerted on the tubing during drilling operations, the
tubing having an internally disposed electric power cable extending
the length thereof, the electric power cable being at approximately
75% super-compressibility because of the cryogenic temperatures
inside the tubing; a drill bit constructed of materials capable of
withstanding cryogenic temperatures, the drill bit operably
connected to a distal end potion of the tubing; a power source
capable of rotating the drill bit, the power source operable
connected to the drill bit via the electric power cable such that
upon activation of the power source the bit is caused to rotate;
and injecting a cryogenic fluid via the tubing to cool the drill
bit and the formation thereby and freeze the formation and prevent
sloughing of shale and infiltration of water into the wellbore.
2. The method of claim 1 wherein the tubing further comprises at
least one electrically operated orifice mandrel for permitting
controlled amounts of the cryogenic fluid to be injected into the
annulus of the wellbore to maintain the annulus of the wellbore and
the portion of the formation adjacent the wellbore at a desired
cryogenic temperature.
3. The method of claim 1 wherein the tubing further comprises a
plurality of spatially disposed electronically operated orifice
mandrels for permitting controlled amounts of cryogenic fluid to be
injected into the annulus of the wellbore to maintain the portion
of the formation adjacent the wellbore at a desired cryogenic
temperature.
4. The method of claim 3 wherein the electronically operated
orifice mandrels are position at approximately every 1000 feet of
the tubing.
5. The method of claim 3 wherein the cryogenic fluid is liquid
nitrogen and wherein an effective amount of liquid nitrogen is used
to maintain the temperature of the drill bit at approximately
-320.degree. F. and the temperature in the annulus of the wellbore
and the portion of the formation surrounding the wellbore at a
temperature of at least -50.degree. F.
6. The method of claim 1 the cryogenic fluid is liquid nitrogen and
wherein an effective amount of liquid nitrogen is used to maintain
the temperature of the drill bit at approximately -320.degree. F.
and the temperature in the annulus of the wellbore and the portion
of the formation surrounding the wellbore at a temperature of at
least -50.degree. F.
7. The method of claim 6 wherein the tubing further comprises at
least one electrically operated orifice mandrel in fluid
communication with the cryogenic fluid in the tubing for permitting
controlled amounts of the cryogenic fluid to be injected into the
annulus of the wellbore at predetermined locations to maintain the
portion of the formation adjacent the wellbore at a desired
cryogenic temperature.
8. The method of claim 6 wherein the tubing further comprises a
plurality of spatially disposed electronically operated orifice
mandrels in fluid communication with the cryogenic fluid in the
tubing for permitting controlled amounts of cryogenic fluid to be
injected into the annulus of the wellbore at predetermined
locations to maintain the portion of the formation adjacent the
wellbore at a desired cryogenic temperature.
9. The method of claim 9 wherein the cryogenic fluid is liquid
nitrogen.
10. The method of claim 1 wherein the cryogenic fluid is liquid
nitrogen.
11. The method of claim 1 further comprising providing at least one
turbo expander operably connected to and in fluid communication
with the annulus of the wellbore for compressing and cooling the
cryogenic fluid recovered from the annulus to a temperature
substantially corresponding to a temperature of the cryogenic fluid
initially injected into the tubing.
12. A method of drilling a wellbore using a cryogenic fluid to
prevent sloughing of the wellbore during drilling operations, the
method comprising: providing non-rotatable tubing constructed of a
material capable of withstanding temperatures of at least about
-320.degree. F. and a back pressure exerted on the tubing during
the drilling operations, the tubing having an internally disposed
electric power cable extending the length thereof, the electric
power cable being at approximately 75% super-compressibility
because of the cryogenic temperatures inside the tubing; a drill
bit constructed of materials capable of withstanding cryogenic
temperatures of at least about -320.degree. F., the drill bit
operably connected to a distal end potion of the tubing; a power
source capable of rotating the drill bit, the power source operable
connected to the drill bit via the electric power cable such that
upon activation of the power source the bit is caused to rotate;
and injecting a liquid cryogenic material into the tubing for
cooling the drill bit of about -320.degree. F. during drilling
operations, the liquid cryogenic material freezing the formation
and preventing sloughing of shale and infiltration of water into
the wellbore.
13. The method of claim 12 wherein the liquid cryogenic material is
liquid nitrogen, the liquid nitrogen is injected into the tubing at
a temperature at about -320.degree. F. and wherein the method
further comprises providing at least one turbo-expander operably
connected to and in fluid communication with an annulus of the
wellbore for compressing and cooling liquid nitrogen and nitrogen
vapor recovered from the annulus of the wellbore to a temperature
of about -320.degree. F. prior to recirculating the liquid nitrogen
to the drill bit via the tubing.
14. The method of claim 13 wherein the tubing further comprises at
least one electrically operated orifice mandrel for permitting
controlled amounts of the cryogenic fluid to be injected into the
annulus of the wellbore to maintain the annulus of the wellbore and
the portion of the formation adjacent the wellbore at a desired
cryogenic temperature.
15. The method of claim 13 wherein the tubing further comprises a
plurality of spatially disposed electronically operated orifice
mandrels for permitting controlled amounts of cryogenic fluid to be
injected into the annulus of the wellbore to maintain the portion
of the formation adjacent the wellbore at a desired cryogenic
temperature.
16. The method of claim 15 wherein the electronically operated
orifice mandrels are position at approximately every 1000 feet of
the tubing.
17. The method of claim 15 wherein an effective amount of liquid
nitrogen is injected into the wellbore to maintain the temperature
of the drill bit of approximately -320.degree. F. and the portion
of the formation surrounding the wellbore of at least -50.degree.
F.
18. The method of claim 17 wherein the tubing further comprises at
least one electrically operated orifice mandrel in fluid
communication with the cryogenic fluid in the tubing for permitting
controlled amounts of the cryogenic fluid to be injected into the
annulus of the wellbore at predetermined locations to maintain the
portion of the formation adjacent the wellbore at a desired
cryogenic temperature.
19. The method of claim 18 wherein the tubing further comprises a
plurality of spatially disposed electronically operated orifice
mandrels in fluid communication with the cryogenic fluid in the
tubing for permitting controlled amounts of cryogenic fluid to be
injected into the annulus of the wellbore at predetermined
locations to maintain the portion of the formation adjacent the
wellbore at a desired cryogenic temperature.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/899,712, filed on Feb. 6, 2007, the
disclosure of which is hereby incorporated into this disclosure in
its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a new, revolutionary method
of drilling oil and gas wells. In one aspect, the present invention
relates to a method of drilling a wellbore using a cryogenic fluid
to prevent sloughing of the wellbore during drilling operations,
while increasing the rate of penetration (ROP) and permit drilling
of deep hot zones in a formation.
BACKGROUND
[0003] Various types of techniques have hereto have been proposed
for the drilling of oil and gas wells. For example, drilling muds
have been circulated during the drilling of a well to remove chips
from the wellbore which are produced during the drilling
operation.
[0004] Air or gas drilling has also been employed in the drilling
of oil and/or gas wells. In air or gas drilling techniques, air or
gas is substituted for drilling muds for removing chips from the
wellbore. Air or gas drilling (hereafter referred to as gas
drilling) has a significantly greater penetration rate than mud
drilling for many well known reasons. Since penetration rate is one
of the most significant factors in determining the cost of drilling
a well, gas drilling should have become widely used; however, gas
drilling has some rather serious drawbacks that have prevented
acceptance of the air drilling method except where certain strict
conditions are met. Where, for example, excessive water influx into
the low pressure wellbore occurs, large amounts of gas are required
to lift the water from the bore hole. Also where certain shales
swell or hydrate in the presence of an influx of water into the
borehole, the shale will become loosened and slough into the
borehole necessitating large quantities of shale and cuttings to be
lifted out of the wellbore. If enough shale is loosed, the drill
pipe may even become stuck.
[0005] Another technique for drilling oil and gas wells is
disclosed in U.S. Pat. No. 3,612,192 wherein air drilling of a
formation is enhanced by cooling the air to a cryogenic temperature
of approximately -200.degree. F. by compressing the air to a
pressure from about 50 to 100 pounds per square inch absolute. The
cooled air is then injected through a pipe to the drill pipe where
the cooled air circulates around the drill bit and up an annulus
formed between the walls of the wellbore and the drill pipe. The
cooled air from the annulus of the wellbore passes to a cutting
trap and filter. The outlet of the cutting trap and filter is then
passed through a heat exchanger and thereafter discharged into the
air.
[0006] While the prior cut is replete with various methods and
techniques for drilling oil and gas wells, each of the prior art
methods and techniques suffer from numerous disadvantages such as,
for example, drill bit life, rate of penetration (ROP), problems
associated with drilling into and through deep hot zones and the
likes. Therefore, new and improved methods and techniques for
drilling oil and gas wells are constantly being sought. It is to
such a new and revolutionary method of drilling oil and gas wells
that the present invention is directed.
SUMMARY OF THE INVENTION
[0007] Broadly, the method of the present invention relates to
drilling of a wellbore without the use of drilling muds to lift
chips out of a wellbore while at the same time preventing sloughing
of the formation into an annulus of the wellbore. More specifically
the method involves providing a coil of tubing wherein the tubing
is constructed of a material capable of withstanding cryogenic
temperatures and back pressure exerted on the tubing during
drilling operations. The tubing, which is maintained in a
non-rotating condition during drilling, is provided with an
internally disposed electric power cable extending the length
thereof. The electric power cable, which is at approximately 75%
super-compressibility because of the cryogenic temperatures inside
the tubing, is connected at one end to a drill bit which is
operably connected to a distal end potion of the tubing. The
electric power cable is connected at its other end to a power
source so that upon activation of the power source the drill bit is
caused to rotate. A cryogenic fluid, such as liquid nitrogen, is
passed through the tubing to cool the drill bit and freeze the
formation so that sloughing of shale and infiltration of water into
the wellbore is prevented.
[0008] The liquid cryogenic material, e.g. liquid nitrogen, is
injected into the tubing in an amount sufficient to maintain the
temperature of the drill bit at approximately -320.degree. F. and
the temperature in the annulus of the wellbore at the position of
the formation surrounding the wellbore at a temperature of at least
about -50.degree. F.
[0009] The coil of tubing, which is non-rotatable is provided with
at least one, and more desirably a plurality, of electrically
operated orifice mandrels which are connected to the electric power
cable and in fluid communication with the cryogenic fluid in the
tubing such that, upon energizing the orifice mandrels, controlled
amount of the cryogenic fluid are injected into the annulus of the
wellbore at predetermined locations to maintain portions of the
formation adjacent the wellbore at the desired temperature.
[0010] In order to maintain the wellbore at the desired cryogenic
temperature, at least one turbo-expander is operably connected to
and in fluid communication with the annulus of the wellbore. Thus,
vapors, and/or cryogenic fluid, exiting the annulus of the wellbore
are compressed and cooled to cryogenic temperatures, e.g.
-320.degree. F. prior to recirculating the cryogenic liquid to the
drill bit via the tubing.
[0011] The method of the present invention will increase the rate
of penetration (ROP) many times over, eliminate all wellbore
problems and permit the drilling of deep hot zones.
[0012] When employing such drilling techniques the rate of
penetration (ROP) will greatly exceed present methods and the
method will provide the following benefits: [0013] 1. Thermal shock
will significantly lower the strength of rock. [0014] 2. Because of
bit cooling much better bit life will occur. [0015] 3. Bit rotation
can be greatly increased resulting in very significant ROP. [0016]
4. Use of a hammer bit will be particularly effective in view of
thermal shock and expansion pressure of the vaporizing nitrogen.
[0017] 5. Superconductivity will permit the installation of a very
large electric motor. [0018] 6. Because of rapid expansion of
vaporizing nitrogen, fractures should occur ahead of the drilling
surface and increase the effect of thermal shock. [0019] 7. The
high pressures resulting from the vaporization of nitrogen used in
cooling the electric motor can be used to increase the impact force
of the hammer bit which will also increase weight on the bit.
[0020] 8. The "air drilling" effect will greatly increase ROP
compared to normal mud drilling. [0021] 9. The effect on hole
conditions will be dramatic. With the hole frozen, no slumping will
occur and the hole will stay completely to gauge. [0022] 10. No
lost circulation will occur because of the "air drilling" effect.
[0023] 11. The volume of nitrogen to be used will more than remove
cuttings in a timely manner. [0024] 12. Except for deep drilling
below the formation freezing depth (perhaps 20,000 feet) there will
be no need to run intermediate casing. This will be a significant
time and cost saving. [0025] 13. The method, by freezing the walls
of the hole, will eliminate water incursion and eliminate
temperature problems. [0026] 14. Also, the cryogenic temperatures
will significantly increase the strength of the coil tubing,
increase bit life and strength.
[0027] The use of coil tubing will significantly decrease the cost
of the drilling operation; however, the greatest saving will be in
reduced drilling time. It is difficult to estimate the reduced
drilling time but theoretically a 15,000 foot well can be drilled
in 3 days.
[0028] The method of the present invention is also unique in that
it eliminates much of the equipment and costs associated with
rotary drilling with mud and normal air drilling. Instead of mud
pumps, rotary drilling motors, circulation equipment and air
compressors required in air drilling, the method of the present
invention maintains a 700 psi back pressure on the casing vent,
thus eliminating the need for any air compressors. The only energy
requirements are for generating electricity and a considerable
amount of the electricity can be generated by compressors operated
off the turbo expanders.
[0029] The coil tubing unit eliminates the need for large rotary
rigs, except for very deep drilling, and also increases the rate of
penetration (ROP) by eliminating drill pipe connections.
[0030] Further, the method of the pressure does not require any new
equipment but only variations to existing equipment. For example,
metals used in the fabrication of the equipment will have to be
altered to allow for cryogenic service but equipment such as coil
tubing, turbo expanders, electric driven bits and hammer bits are
all widely known and commercially available equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a pictorial representation, partially in
cross-section, of a drilling system utilizing a cryogenic drilling
method in accordance with the present invention.
[0032] FIG. 2 is a pictorial representation of the drilling system
utilizing the cryogenic drilling method of the present
invention.
[0033] FIG. 3 is a schematic diagram of the drilling system for
drilling oil and gas wells utilizing the cryogenic drilling method
of the present invention.
DETAILED DESCRIPTION
[0034] Referring now to the drawings, shown therein is a pictorial
representation of a drilling system 10 utilizing a cryogenic
drilling method of the present invention. A drilling rig 12 is set
on a desired location 14 where a wellbore 16 is to be drilled. The
drilling equipment of the drilling rig 12 includes coil tubing 18,
such as a three and one-half inch coil tubing, having an electric
power cable 20 extending throughout the length of the coil tubing
18. The electric power cable 20 will be at approximately
seventy-five percent super-compressibility because of the cryogenic
fluid, i.e., the liquid nitrogen, injected down the coil tubing 18
will be at approximately -320.degree. F. Thus, an electric motor 22
operably connected to a distal end portion 24 of the coil tubing
18, can be operated at a higher horse power than under normal
conditions where power is supplied to electric motor 22.
[0035] A drill bit 26, such as a rotary cutting bit or a hammer
drill bit, is operably connected to the distal end portion 24 of
the coil tubing 18 is that upon providing power to the motor 22 via
the electric power cable 20, the drill bit 26 is caused to rotate
and commence the desired drilling of the borehole 16 in a
subterranean formation.
[0036] It may be desired to provide at least one, and desirably a
plurality of electrically operated orifice mandrels 28 for
permitting controlled amounts of the cryogenic fluid to be injected
into an annulus 30 of the wellbore 16 to maintain the annulus 30 of
the wellbore 16 and the portion of the formation adjacent the
wellbore 16 at the desired cryogenic temperature. The electrically
operated orifice mandrels 28 are connected to the coil tubing 18 so
that fluid communication is maintained between the electrically
operated orifice mandrels 28 and the coil tubing 18. In addition,
the electrically operated orifice mandrels 28 are operably
connected to the electric power cable 20 so that selective or all
of the electrically operated orifice mandrels 28 can be activated
from the surface by supplying power to the electrically orifice
mandrels 28 via the electric power cable 20. The presence, as well
as the number of electrically operated orifice mandrels 28 employed
will vary widely depending upon the depth to which the wellbore 16
is drilled. For example, when using the coil tubing 18 to drill
depths greater than about 1,000 feet, one of the electrical
operated orifice mandrels 28 is positioned on the coil tubing 18 at
approximately every 1,000 feet of the coil tubing 18. As previously
stated, the use of the electrically operated orifice mandrels 28
permit given amounts of cryogenic fluid, i.e., liquid nitrogen, to
be injected into the annulus 30 of the wellbore 16 to maintain the
annulus 30 of the wellbore 16 and thus the portion of the formation
surrounding the wellbore 16 at desired temperatures.
[0037] Electrically operated orifice mandrels are commercially
available and their installation and operation are well known in
the art. Thus, no further discussion of the electrically operated
orifice mandrels 28 is believed necessary to enable a person to
fully understand and practice the method of the present
invention.
[0038] A cryogenic liquid, herein after referred to as liquid
nitrogen, is injected down the coil tubing 18 at various rates
depending on the depth of drilling. Every 1,000 feet one of the
electrically operated orifice mandrels 28 is activated so that
liquid nitrogen can be injected into the annulus 30 of the wellbore
16. This will permit the introduction of fresh liquid nitrogen into
the annulus 30 of the wellbore 16 in addition to the volumes of
cryogenic vaporous nitrogen coming from formation drilled downhole.
This refrigeration will keep the walls of the annulus 30 of the
wellbore 16 frozen.
[0039] Because of heat of vaporization, (approximately 47% of total
refrigeration), the liquid nitrogen will engage the drill bit 26 at
a temperature of about -320.degree. F. The -320.degree. F. liquid
nitrogen will cool the drill bit 26 and partially vaporize thus
removing the cuttings from the wellbore 16 and drastically lowering
the temperature of the drilling surface. The drastic reduction of
the drilling surface causes "thermal shock" which reduces the
strength of the rock and permits a significant increase in the rate
of penetration of the drill bit 26 into the formation.
[0040] The thermal shock will also cause fractures to occur ahead
of the bit 26, permitting liquid nitrogen to enter the drilling
surface ahead of the drill bit 26 and increase the effect of
thermal shock. Additionally, the rate of penetration will occur
because the cryogenic temperature will permit the drill bit to be
rotated at much higher speeds than normal.
[0041] In addition, one may desire to use a hammer bit as the drill
bit 26. When the hammer bit rises it permits the bottom of the
hammer bit to be cooled so that when it strikes the drilling
surface the hammer bit drastically increases the effect of thermal
shock. The hammer bit can be constructed so that after striking the
drilling surface it will be held in a raised position for a brief
period of time (i.e. some fractions of a second) to permit a lower
surface of the hammer bit to be cooled.
[0042] The electric motor 22 will drive the drill bit 26 operably
connected to the distal end portion 24 of the coil tubing 18 in
response to power provided to the electric motor 22 via the
electric power cable 20 disposed within and extending the length of
the coil tubing 18. As previously stated, since the liquid nitrogen
will be at approximately -320.degree. F., the electric power cable
20 Will be at approximately 75% of super-compressibility which will
substantially reduce the electric friction in the electric cable
20. As a result, the electric motor 22 can be a much larger
electric motor and as such the electric motor 22 permits even
faster rotation of the drill bit 26 and a higher rate of
penetration.
[0043] As the vaporized liquid nitrogen leaves the drilling surface
and starts up the annulus 30 of the wellbore 16, it will be
reinforced by the introduction of liquid nitrogen from at least one
of the electrically operated orifice mandrels 28 which injects
approximately -320.degree. F. liquid nitrogen at a position
approximately 50 feet from the drilling surface. The cryogenic
temperatures of the liquid nitrogen immediately freeze the hot
formation face and prevent any fluids from entering the wellbore
16. By preventing any water from entering the annulus 30 of the
wellbore 16 "air" drilling is practical.
[0044] When employing the method of the present invention wellbore
16 stability will be excellent. All the wellbore surface is frozen
solid to at least about -50.degree. F. and the electrically
operated orifice mandrels 28 located at about every 1,000 feet of
the coil tubing 18 are designed to inject additional liquid
nitrogen into areas far up the wellbore 16 to insure that the area
of the formation surrounding the wellbore 16 remains frozen. Thus,
in production operations, formation damage will be eliminated by
drilling with liquid nitrogen.
Drilling In Unfrozen Wellbore
[0045] It is believed that the method of drilling the wellbore 16
using the method of the present invention will be feasible to a
depth of approximately 20,000 feet, the depth where the formation
temperatures reach about +300.degree. F. After this temperature,
the wellbore 16 normally cannot be frozen nor can reservoir fluids
be controlled under normal practice. However, even at formation
temperatures of +400.degree. F. to +500.degree. F. the area 1 to 2
inches from the wellbore may remain frozen because of the
continuous injection of fresh liquid nitrogen in accordance with
the method of the present invention.
[0046] To extend the method of the present invention to depths
hotter than +300.degree. F. and in the event the formation at from
1 to 2 inches of the wellbore 16 does not remain frozen, one may
set a string of intermediate casing near the +300.degree. F. area
of the formation. After WOC, drilling will continue as before with
liquid nitrogen at -320.degree. F. being injected down the coil
tubing 18 and through the drill bit 26. The cryogenic liquid
nitrogen will still cool the drill bit 26 as before, permit very
fast bit rotation and permit thermal shock to occur. The result
will be very fast rate of penetration. Thus, a change will occur on
the effect of "air" drilling.
[0047] To control the formation pressure of high pressure, oil, gas
or water zones, an exit valve 31on an intermediate wellbore annulus
32 needs to be closed so that the pressure of the vaporized
nitrogen will build up to control these pressures. The exit valve
31 can then be cracked to keep the intermediate wellbore annulus
pressures just above the total depth pressure. Using this method,
depths as deep as 50,000 feet can be reached. The controlling
factor is providing steel strong enough to reach 50,000 feet and
also to control the hot temperature in the coil tubing 18 and
casing during production operations.
[0048] When drilling to depths much below 15,000 feet, coil tubing
18 cannot be used in its present design parameters. Improvements
can be made but probably not enough to go below 25,000 feet. To
drill below a depth of 25,000 feet a special automatic drilling rig
maybe required wherein 3 joints of pipe can be stacked in the rig
and run like one joint is presently run. The rig will also need to
be enclosed so that cryogenic temperature can be maintained.
Connections every 90 feet are much slower than the coil tubing 18
but much faster than drilling at very deep depths today. However,
when utilizing the joints of pipe as described above, the joints of
pipe, like the coil tubing 18, is not rotated. That is only the
drill bit 26 rotates when using the cryogenic method of drilling
disclosed herein.
Method To Run Casing
[0049] To run intermediate casing or production casing, special
measures must be taken. Prior to reaching casing depth a mouse hole
of 100 feet depth should be drilled and 3 joints of casing should
be made up. Then the 3 joint stand should be stacked until the
weight accumulation of the rig is reached. This will permit rapid
running of casing particularly with an automatic hands free
rig.
[0050] After reaching casing total depth, the wellbore 16 should be
circulated with liquid nitrogen through the drill bit 26 and all
the electrically operated orifice mandrel 28 for a period of about
one hour. After the circulating period, the coil tubing 18 is
pulled from the wellbore 16. When the coil tubing 18 has been
pulled, 3-joint strands of casing are run. Because of cryogenic
temperatures, the casing, like the coil tubing 18 of the drill but
26 should contain 9% nickel.
[0051] When the complete string is run to T.D., the wall of the
wellbore 16 will still be frozen. To prepare the well for
cementing, hot vaporous nitrogen is circulated down the casing and
around into the annulus 30 of the wellbore 16. The hot vaporous
nitrogen need to be circulated only long enough to heat up the
outer 2 inches of the wellbore 16 and keep the rest of the wellbore
16 frozen to prevent fluids from entering the wellbore 16. After
heating, arctic type cement is circulated into the annulus 30 of
the wellbore 16 and allowed to set.
[0052] To speed up cement healing, hot vaporous nitrogen is
circulated down the coil tubing 18 inside the casing. After WOC,
complete well if at T.D. or if intermediate casing, resume drilling
with liquid nitrogen as before.
[0053] Another option compensate for expansion or contraction of
the casing string while the casing is at cryogenic temperatures or
heats up during cementing or production operations, a sliding
mandrel should be included in the casing string. When all drilling
operations are completed and production operations need to begin,
the sliding mandrel can be enclosed with cement when the casing
string is cemented.
Method to Shutoff High Pressure Gas Zone
[0054] To combat a high pressure gas zone, drill into the top of
the zone then set a packer 33 on the string of coil tubing 18 and
begin injecting liquid nitrogen into the top of the zone. This will
result in liquid nitrogen penetrating deep into the zone which will
assure that any moisture or water contained in the gas will freeze
into hydrates inside the zone rather than in the wellbore 16.
[0055] After drilling through the complete zone, continue to inject
liquid nitrogen deep into the zone. Then begin injecting warm
vaporous nitrogen down the coil tubing 18 followed by very hot
steam. This will warm up the previous cryogenic temperature coil
tubing 18 and permit liquid water to reach the gas zone.
[0056] After injecting all the water/steam into the gas zone follow
it with additional volumes of liquid nitrogen. This will cause the
previously injected water to freeze all void spaces and shut off
the flow of any gas.
[0057] An alternative to this is the probability that high pressure
gas flows, because they contain some small amounts of water and at
least moisture, will immediately form gas hydrates and freeze over
in the formation.
Drilling Below Freezing Point
[0058] The before-discussed cryogenic drilling method will not be
able to keep the wellbore 16 frozen when the temperature increases
to about +300.degree. F. unless the first 1 or 2 inches can be kept
frozen. To drill below this point it will be necessary before
reaching it to run intermediate 9% nickel casing and cement it in
or control it with a packer only. Then, resume drilling with liquid
nitrogen as before. The same rate of penetration should occur as
thermal shock will still weaken the rock and at an increased rate,
the drill bit 26 will still be cooled therefore a high rotation
rate will continue and the hammer bit effect will continue to
probably greater effect. What will be missing is the "air" drilling
effect previously employed.
[0059] Fluids can still be prevented from entering the wellbore 16
by closing the intermediate casing surface vent valve 3land
allowing the pressure from the injected liquid nitrogen to build up
to a value exceeding the BHP. When this point is reached, maintain
it by venting enough nitrogen to remain constant.
[0060] By employing the method of the present invention, drilling
can still be maintained at very high rates of penetration to depths
of very high temperatures perhaps to 50,000 feet. To alleviate
excessive pressure on zones above the drilling point, controlled
volumes of gas could be vented in a limited under-balanced
situation. A smaller volume of the liquid nitrogen included in the
coil tubing will be directed into a smaller conduit to cool the
electric motor. This nitrogen will vaporize and will greatly
increase its pressure. Part of this high pressure can be used in
the hammer bit to increase the force of impact. The remainder will
increase the force emitting from the bit.
Production of Liquid Nitrogen
[0061] To drill a well employing liquid nitrogen may require 50,000
gallons of liquid nitrogen per day to drill to a depth of about
5,000 feet. To drill to a depth of about 30,000 feet 400,000 to
500,000 gallons of liquid nitrogen per day may be required. These
volumes would be difficult or impossible to use because of costs
and even more, so transportation problems.
[0062] Referring now to FIGS. 2 and 3, to generate the volume of
liquid nitrogen necessary, it is believed desirable that one
produce the liquid nitrogen on site by employing one or more turbo
expanders 40 and affiliated equipment. This can be accomplished by
first injecting liquid nitrogen from a trailer mounted cryogenic
tank 42 into the coil tubing 18 via a cryogenic pump 44. The liquid
nitrogen from the cryogenic pump 44 is then passed into a coil
tubing assembly 50 which is an insulated enclosure containing a
reel or spool of the coil tubing 18. The coil tubing is removed
from the coil tubing assembly 50 and directed to the drilling rig
12 for drilling the wellbore 16. It should be noted that the coil
tubing 18 is maintained in a non-rotating condition during
drilling, the only portion which is rotated, is the drill bit 26
which is rotatably connected to a distal end portion 24 of the coil
tubing 18. Once the liquid nitrogen has been disposed within the
wellbore 16 the liquid nitrogen is returned to the top of the
surface casing. If the casing discharge pressure is held to about
700 PSI and the temperature is held at about -50.degree. F., the
gaseous nitrogen recovered is capable of operating the turbo
expanders 40. Thus, the gaseous nitrogen and any entrained liquid
nitrogen is injected two two-stage turbo expanders 40 and a liquid
nitrogen exiting the turbo expanders 40 is delivered to and stored
in the cryogenic trailer tank 42. The liquid nitrogen is then
injected by the high pressure cryogenic pump 44 into the coil
tubing 18 for further drilling. By recycling the liquid/gaseous
nitrogen, the system becomes a substantially closed system.
[0063] The turbo expanders 40 produce an effective amount of energy
to run the electric motors 46 which, in turn, are coupled to the
electric motor 48 of the coil tubing assembly 50. The coil tubing
assembly 50 includes, the spool or coil of tubing 18 and the
electric motor 48. The electric motor 48 serves as a source of
power for the electric motor 22 mounted on the distal end portion
24 of the coil tubing 18 which, upon activation, rotates or
activates the drill bit 26.
[0064] As more clearly shown in FIG. 3, the cryogenic pump 44 pumps
the cryogenic liquid nitrogen into the wellbore 16 being drilled by
the drilling rig 12 via the coil tubing 18. The liquid nitrogen
which is returned to the surface casing is then pumped to a
centrifugal cutting trap 52 wherein cuttings are separated and
forwarded to a pit 54. The liquid nitrogen recovered from the
wellbore 16 is passed through a filter 56 and into one of the turbo
expander 40. The liquid nitrogen recovered from the turbo expander
40 is then passed through a separator 58 and into the second turbo
expander 40 for further treatment. Upon leaving the second turbo
expander 40 the liquid nitrogen is passed through a distillation
tower 60 before being stored in the trailer mounted cryogenic tank
42. When additional nitrogen is required in the drilling operation
the recycled liquid nitrogen is pumped from the trailer mounted
cryogenic tank 42 into the coil tubing via the cryogenic pump
44.
[0065] The only transported liquid nitrogen required in the
practice of the present invention is the initial volume required to
activate the turbo expanders 40. After this the turbo expanders 40
recycle the necessary nitrogen except for that required for the
continuing volume expansion due to drilling. For a 5,000 foot well
the volume of nitrogen required would be about 2700 gallons to
permit recycling of nitrogen to the turbo expanders the nitrogen
must be cleaned and to accomplish this a central cuttings trap and
air filter will be used to remove cuttings and dust.
[0066] The method of the present invention not only solves the
nitrogen problem but permits the use of very large volumes of
liquid nitrogen so that the wellbore 16 can be kept frozen to very
low temperatures and will be helpful in deep drilling.
[0067] It is believed that up to 15,000 cubic feet or equivalent
liquid nitrogen be used in the first 5,000 feet of drilling and up
to 15,000,000 cubic feet in very deep drilling. Substantially all
of the nitrogen will be recycled through the turbo expanders.
Equipment Illustration
[0068] To illustrate the equipment used an its configuration,
consider the liquid nitrogen generated by the turbo expanders 40
entering the cryogenic liquid nitrogen trailer tank 42. Using the
cryogenic pump 44 the liquid nitrogen is pumped into trailer
mounted coil tubing 18, which is enclosed in an air free insulated
enclosure, and down to the drill bit 26. For deep drilling a
cryogenic insulated enclosure may be installed around the drilling
derrick rig 12.
[0069] All equipment would be trailer mounted for quick
transportation FIGS. 1, 2 and 3 show the configuration of
equipment. Further, all equipment in contact with the cryogenic
liquid must be fabricated of materials capable of handling the
cryogenic temperatures. An example of such of a material is
stainless steel containing about 9% nickle.
SUMMARY
[0070] The advantage of using liquid nitrogen are as follows:
[0071] 1. The (-320.degree. F.) temperature will eliminate bit heat
thus greatly increase bit life. [0072] 2. The (-320.degree. F.)
temperature will permit the bit rotation to be greatly increased
thus greatly increasing ROP. [0073] 3. The (-320.degree. F.)
temperature will result in significant thermal shock thus lowering
the strength of the rock and result in increased ROP, and also
cause thermal fractures to occur ahead of the drilling surface.
[0074] 4. A hammer bit can be used to help cool the cutting surface
as the bit rises vertically and would be particularly efficient
because of thermal shock. [0075] 5. The stability of the borehole
will be solid. Because the wall temperature will vary between
-320.degree. F. at the bottom of the hole to -50.degree. F. at the
top, the frozen wall will prevent borehole enlargement. [0076] 6.
The method will freeze any water entering the borehole thus
permitting "air" drilling (liquid nitrogen). [0077] 7. The method
will eliminate the flow of high pressure gas into the borehole.
[0078] 8. By using an electric motor to drive the bit, the power
cable will be at about 75% of super conductivity (-320.degree. F.),
therefore reducing the electric resistance and permitting a larger
horsepower motor to drive the bit even faster. [0079] 9. Drilling
with liquid nitrogen will also alter the need for multiple casing
strings. In liquid nitrogen drilling, one drills the same size
borehole to total depth, eliminate the influx of all fluids into
the wellbore and end up with a frozen wellbore. [0080] 10. Drilling
with liquid nitrogen will greatly affect the problems relating to
heat in deep drilling on associated equipment. [0081] 11. Cryogenic
temperatures will strengthen coil tubing and permit deeper
drilling. [0082] 12. The method permits drilling to 50,000 feet
even beyond the ability to freeze the wellbore. [0083] 13. Thermal
shock should eliminate crooked holes as the formation directly
below the bit should immediately lose strength, while the area
sideways to the bit will remain strong and thus resist being
drilled.
* * * * *