U.S. patent application number 09/788580 was filed with the patent office on 2001-08-23 for spotting fluid and method of treating a stuck pipe.
Invention is credited to Hayatdavoudi, Asadollah.
Application Number | 20010016561 09/788580 |
Document ID | / |
Family ID | 23296706 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016561 |
Kind Code |
A1 |
Hayatdavoudi, Asadollah |
August 23, 2001 |
Spotting fluid and method of treating a stuck pipe
Abstract
The method for releasing the stuck pipe of the present invention
uses a combination of components which oxidize the mud cake and
generated gas bubbles to create an upward buoyancy for the oxidized
mud cake. The spotting method of the present invention comprises
adding to the borehole in the region of the stuck pipe: 1) an
oxidizer which oxidizes the mud cake; and 2) at least one component
which reacts in the borehole to generate a gas. Optionally, but
preferably, the spotting method further uses a lubricant which is
added to the borehole in the region of the stuck pipe. The
lubricant acts to lubricate the oxidized parts of the mud cake.
Also disclosed is a spotting fluid system comprising 1) an oxidizer
which oxidizes the mud cake, 2) at least one component which reacts
in the borehole to generate a gas, and, optionally a lubricant
which acts to lubricate the oxidized parts of the mud cake.
Inventors: |
Hayatdavoudi, Asadollah;
(San Ramon, CA) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
23296706 |
Appl. No.: |
09/788580 |
Filed: |
February 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09788580 |
Feb 21, 2001 |
|
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09332094 |
Jun 14, 1999 |
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Current U.S.
Class: |
507/100 |
Current CPC
Class: |
C09K 2208/02 20130101;
C09K 8/02 20130101; E21B 31/03 20130101; Y10S 507/94 20130101 |
Class at
Publication: |
507/100 |
International
Class: |
C09K 007/00 |
Claims
What is claimed is:
1. A method for dislodging a stuck pipe in a well bore of a
downhole well drilling operation comprising adding to the borehole
in the region of the stuck pipe: 1) an oxidizer; 2) at least one
component which reacts in the well bore to generate a gas; and 3)
optionally, a reducer.
2. The method of claim 1, wherein the component which reacts in the
well bore to generate a gas reacts with the oxidizer or reducer to
generate said gas.
3. The method of claim 1, wherein the generated gas is carbon
dioxide, hydrogen, oxygen, nitrogen, or a combination thereof.
4. The method of claim 2, wherein the gas generating component is
selected from the group consisting of hydrazine, sodium
bicarbonate, manganese oxide and hydrogen peroxide.
5. The method of claim 1, further comprising adding (4) a lubricant
or a penetration rate enhancer to the well bore.
6. The method of claim 5, wherein the lubricant is added to the
well bore between the oxidizer and the component which reacts in
the well bore to generate a gas.
7. The method of claim 5, wherein the lubricants or penetration
rate enhancer is selected from the group consisting of synthetic
esters or synthetic esters in combination with vegetable oil,
surfactants, mineral oil, glycol, glycerol, alcohols, low toxicity
hydrocarbon or mixtures thereof.
8. The method of claim 5, wherein the lubricant is a drilling fluid
comprising at least one of the following drilling fluid modules
(A)-(E): (A) an alkaline first module that contains (a) a source of
caustic, (b) a natural wax, (c) a natural thinner, (d) glycerol,
and (e) phosphoric acid and/or boric acid; (B) a second module
prepared by reacting (f) aluminum metal with the components of said
alkaline first module thereby forming a soluble alkali metal
aluminate; (C) a third module comprising said components of said
first module in combination (g) with at least one of an alkali
metal phosphate, borate and sodium silicate; (D) a fourth module
comprising said components of said first module in combination with
(h) a saturated or unsaturated carboxylic acid source, and
optionally a synthetic oil and a surfactant, and/or (E) a fifth
module comprising said components of said first module in
combination with (h) a saturated or unsaturated carboxylic acid
source, and (g) at least one of an alkali metal phosphate, borate
and sodium silicate.
9. The method of claim 8, wherein the lubricant or penetration rate
enhancer comprises the fifth module of the modular drilling
fluid.
10. The method of claim 1, further comprising the step of applying
mechanical force to the drill string after the addition of the
components to the well bore.
11. The method of claim 1, wherein the oxidizer is hydrogen
peroxide.
12. The method of claim 2, wherein the component which reacts with
the oxidizer is a hypochlorite or a peroxide.
13. The method of claim 12, wherein the hypochlorites are selected
from the group consisting of sodium hypochlorite, potassium
hypochlorite, lithium hypochlorite, calcium hypochlorite and
magnesium hypochlorite; and the peroxide is selected from the group
consisting of hydrogen peroxide alkali metal peroxides, alkaline
earth metal peroxides and manganese group peroxides.
14. The method of claim 12, wherein the component which reacts with
the oxidizer is sodium hypochlorite.
15. The method of claim 11, wherein the hydrogen peroxide is added
to the well in a solution with fresh water or brine, the
concentration of the hydrogen peroxide is between about 1.5% to
about 5.0% by weight or volume.
16. The method of claim 14, wherein the sodium hypochlorite is
added to the well in a solution with fresh water or brine, the
concentration of the sodium hypochlorite is between about 1.0 and
10.0% by weight or volume.
17. The method of claim 5, wherein the component which reacts in
the well bore reacts with a component in the lubricant or
penetration rate enhancer.
18. The method of claim 17, wherein the component which reacts in
the well bore is sodium bicarbonate.
19. The method of claim 18, wherein the lubricant or penetration
rate enhancer contains an acid which will react with the sodium
bicarbonate.
20. A spotting fluid system for dislodging a stuck pipe in a well
bore of a downhole well drilling operation comprising: 1) an
oxidizer; 2) at least one component which reacts in the well bore
to generate a gas; and 3) optionally a reducer.
21. The spotting fluid system of claim 20, further comprising a
lubricant or a penetration rate enhancer.
22. The method of claim 21, wherein the lubricant is at least one
of the following drilling fluid modules (A)-(E): (A) an alkaline
first module that contains (a) a source of caustic, (b) a natural
wax, (c) a natural thinner, (d) glycerol, and (e) phosphoric acid
and/or boric acid; (B) a second module prepared by reacting (f)
aluminum metal with the components of said alkaline first module
thereby forming a soluble alkali metal aluminate; (C) a third
module comprising said components of said first module in
combination (g) with at least one of an alkali metal phosphate,
borate and sodium silicate; (D) a fourth module comprising said
components of said first module in combination with (h) a saturated
or unsaturated carboxylic acid source or synthetic ester, and/or
(E) a fifth module comprising said components of said first module
in combination with (h) a saturated or unsaturated carboxylic acid
source, and (g) at least one of an alkali metal phosphate, borate
and sodium silicate.
23. The spotting fluid system of claim 20, wherein the oxidizer is
hydrogen peroxide or sodium hypochlorite.
24. The spotting fluid system of claim 20, wherein the component
which reacts in the borehole to generate gas is a hypochlorite or a
peroxide.
25. The spotting fluid system of claim 24, wherein the
hypochlorites are selected from the group consisting of sodium
hypochlorite, potassium hypochlorite, lithium hypochlorite, calcium
hypochlorite and magnesium hypochlorite; and the peroxide is
selected from the group consisting of hydrogen peroxide, alkali
metal peroxides, alkaline earth metal peroxides and manganese group
peroxides.
26. The spotting fluid system of claim 25, wherein the hypochlorite
is sodium hypochlorite.
27. The spotting fluid system of claim 21, wherein the oxidizer is
hydrogen peroxide, the drilling fluid is the fifth module, and the
component which reacts in the borehole to generate gas is sodium
hypochlorite.
28. An article of manufacture comprising the spotting fluid system
of claim 20, wherein a first container comprises the oxidizer, a
second container comprises at least one component which reacts in
the well bore to generate a gas.
29. An article of manufacture comprising the spotting fluid system
of claim 22, wherein a first container comprises the oxidizer, a
second container comprises at least one component which reacts in
the well bore to generate a gas and the third container comprises
one of the modules of the modular drilling fluid.
30. The article of manufacture of claim 29, wherein the first
container comprises hydrogen peroxide, the second container
comprises sodium hypochlorite, and the third container comprises
the fifth module of the drilling fluid.
31. A method of dislodging a stuck pipe in a borehole of a down
hole well drilling operation using a drilling mud comprising, as a
drilling fluid, at least one of the following modules (A)-(E) (A)
an alkaline first module that contains (a) a source of caustic, (b)
a natural wax, (c) a natural thinner, (d) glycerol, and (e)
phosphoric acid and/or boric acid, (B) a second module prepared by
reacting (f) aluminum metal with the components of said alkaline
first module thereby forming a soluble alkali metal aluminate, (C)
a third module comprising said components of said first module in
combination (g) with at least one of an alkali metal phosphate,
borate and sodium silicate, (D) a fourth module comprising said
components of said first module in combination with (h) a saturated
or unsaturated carboxylic acid source, or (E) a fifth module
comprising said components of said first module in combination with
(h) a saturated or unsaturated carboxylic acid source, and (g) at
least one of an alkali metal phosphate, borate and sodium silicate;
said method comprising adding to the borehole a solution comprising
(I) hydrogen peroxide and (ii) water or brine.
32. The method of claim 31, wherein the concentration of the
hydrogen peroxide in the solution is about 1.5% to about 5.0% by
weight or volume.
33. A completion fluid comprising water or brine, a gel and at
least one of the following at least one of the following modules
(A)-(E) of a modular drilling fluid: (A) an alkaline first module
that contains (a) a source of caustic, (b) a natural wax, (c) a
natural thinner, (d) glycerol, and (e) phosphoric acid and/or boric
acid, (B) a second module prepared by reacting (f) aluminum metal
with the components of said alkaline first module thereby forming a
soluble alkali metal aluminate, (C) a third module comprising said
components of said first module in combination (g) with at least
one of an alkali metal phosphate, borate and sodium silicate, (D) a
fourth module comprising said components of said first module in
combination with (h) a saturated or unsaturated carboxylic acid
source, or (E) a fifth module comprising said components of said
first module in combination with (h) a saturated or unsaturated
carboxylic acid source, and (g) at least one of an alkali metal
phosphate, borate and sodium silicate.
34. A method of dislodging a stuck pipe in a borehole of a downhole
well drilling operation comprising adding to the well at least one
of the following modules (A)-(E) of a modular drilling fluid: (A)
an alkaline first module that contains (a) a source of caustic, (b)
a natural wax, (c) a natural thinner, (d) glycerol, and (e)
phosphoric acid and/or boric acid, (B) a second module prepared by
reacting (f) aluminum metal with the components of said alkaline
first module thereby forming a soluble alkali metal aluminate, (C)
a third module comprising said components of said first module in
combination (g) with at least one of an alkali metal phosphate,
borate and sodium silicate, (D) a fourth module comprising said
components of said first module in combination with (h) a saturated
or unsaturated carboxylic acid source, or (E) a fifth module
comprising said components of said first module in combination with
(h) a saturated or unsaturated carboxylic acid source, and (g) at
least one of an alkali metal phosphate, borate and sodium silicate.
Description
TECHNICAL FIELD
[0001] The present invention relates to a spotting fluid system
used to dislodge a stuck drill pipe in subterranean drilling
operations. In addition, this invention relates to a method of
dislodging a stuck drill pipe which is lodged in subterranean
formations.
BACKGROUND OF THE INVENTION
[0002] The drilling of oil and gas wells is accomplished by using
rotary drilling techniques. In these rotary drilling techniques, a
drilling mud is circulated through the drill pipe, out the bit
nozzles and it is returned to the surface via an annulus. The
drilling mud serves to cool and lubricate the drill bit and drill
pipe. In addition, the drilling mud develops a hydrostatic head to
counterbalance formation pressures and removes cuttings from the
borehole. Further, the drilling mud helps reduce the friction
forces between the drill pipe and the borehole.
[0003] Even though a drilling mud is used during the subterranean
drilling operations, drill bits and drill pipes still become lodged
in subterranean formations from time to time. The term "stuck pipe"
is conventionally used in the drilling industry to describe this
problem. "Stuck pipe" is not limited to drill pipes, but includes
drill pipes, drill collars, drill bits, stabilizers, reamers,
casings, tubing and other items or tools which may become lodged in
drilling operations. When a stuck pipe becomes lodged, it can not
be raised, lowered or rotated. A stuck pipe increases the cost of
drilling a well due to downtime of the drilling operation. In
extreme cases, a stuck pipe may cause the abandonment of the
drilling operation at a particular site, if the stuck pipe can not
be economically released.
[0004] There are many causes of stuck pipe. The industry
categorizes the causes as either differential or mechanical
sticking.
[0005] Differential sticking occurs during most drilling
operations. The hydrostatic pressure exerted by the drilling mud
column is greater than the formation fluid pressure. In permeable
formations, the mud filtrate flows from the borehole into the rock
pores and builds up a filter cake. A pressure differential exists
across the filter cake which is equal to the difference between the
pressure of the mud column and the pressure of the formation.
[0006] When a pipe is central in the borehole, the hydrostatic
pressure, due to the mud overbalance, acts in all directions around
the pipe. If, however, the pipe touches the filter cake, the mud
overbalance acts to push the pipe further into the filter cake,
thus increasing the contact area between the pipe and the filter
cake. Filtrate is still expelled and squeezed from the filter cake
between the pipe and the formation thus shrinking the cake and
allowing the pipe to penetrate further into the filter cake,
thereby further increasing the contact area. If the pressure
difference is high enough and acts over a sufficiently large area,
the pipe may become stuck. Differential sticking usually occurs
when the pipe has been motionless for a period of time, e.g., when
making a pipe connection or during surveying.
[0007] The force required to pull differentially stuck pipe free
depends on many factors including:
[0008] (1) The difference in the pressure between the borehole and
the formation. Any overbalance adds to side forces which may exist
due to the deviation of the hole.
[0009] (2) The surface area of the pipe embedded in the wall cake.
The thicker the cake or the larger the pipe diameter, the greater
this area generally is.
[0010] (3) The bond developed between the pipe and the wall cake is
a very significant factor, being directly proportional to the
sticking force. This can include frictional, cohesive and adhesive
forces. It generally tends to increase with time, making it harder
to pull the pipe free.
[0011] Differential sticking may be distinguished from other forms
of sticking, such as mechanical sticking. Mud circulation is not
interrupted as there is no obstruction in the borehole to stop the
flow, as would be the case for pipe stuck due to hole bridging or
caving. It is not possible to move or rotate the pipe in any
direction.
[0012] When a pipe sticks, the driller usually tries to free it by
mechanical movement, e.g., by pulling, jarring or, if the pipe was
moving immediately prior to sticking, trying to move the pipe in
the opposite direction. Frequently this fails to release the pipe
and there is, of course, a limit to the force which can be applied,
since too much force could pull the pipe apart and make the
situation worse.
[0013] If the pipe remains stuck, it is then sometimes the practice
to apply a pipe release agent, commonly called a "spotting fluid".
These spotting fluids are chemically active mixtures, which may be
oil or water based, which are placed over the stuck region in an
attempt to free the pipe, if mechanically working the pipe fails to
release the pipe. These spotting fluids are believed to act by
attacking the mud filter cake. They are positioned in the borehole
by pumping the spotting fluid down the hole to the stuck region in
the form of a slug, also known as a pill. The pill generally
contains sufficient material to cover the stuck zone and extend
slightly beyond the area of the stuck zone. Pills frequently are
left to soak the cake until the pipe is free or attempts to free
the pipe are abandoned.
[0014] Over the years, many spotting fluids and spotting methods
have been developed to lubricate the area of the stuck pipe which
has become lodged and to aid in the releasing of the drill bit from
the formation, freeing a stuck drill pipe.
[0015] In one prior art stuck pipe treatment, hydrocarbon oils,
such as diesel oil, are injected into the borehole in the area of
the stuck pipe. The mixture of the diesel oil and drilling mud
provides a low density, lubricating environment around the stuck
point of the drill. Further, the hydrocarbon rises due to its
buoyancy, which causes the removal of the mud around the stuck
point and makes well bore pressure (P.sub.w).ltoreq.the formation
pressure (P.sub.f) See, for example, U.S. Pat. No. 3,217,802 to
Reddie.
[0016] Attempts have been made to improve the effectiveness of
hydrocarbon based spotting fluids by adding additional components
to the hydrocarbon based spotting fluids. For example, U.S. Pat.
No. 5,671,810 to Hodge et al. adds a carboxylic acid or a
polycarboxylic acid and a surfactant to a hydrocarbon spotting
fluid; U.S. Pat. No. 4,436,638 to Walker et al., adds a
propoxylated C.sub.18-C.sub.32 alcohol and an oil soluble
emulsifier to a hydrocarbon based spotting fluid; and U.S. Pat. No.
4,427,564 to Brownawell et al. adds a propoxylated lactone acid and
an oil soluble emulsifier to a hydrocarbon based spotting
fluid.
[0017] In a different approach, U.S. Pat. No. 2,900,026 to Trusheim
discloses the addition of at least a 10 percent solution of
hydrogen peroxide to a borehole having a stuck drill pipe to
disintegrate the wall cake which causes the lodging to the drill
pipe. In addition, this patent teaches that the addition of a small
amount of caustic soda and soda will aid the action of the hydrogen
peroxide.
[0018] Aqueous spotting fluids have also been previously used in
the art. U.S. Pat. No. 4,466,486 to Walker discloses a method for
freeing stuck drill pipes by adding a mixture of water or brine
with a cellulose polymer or a polyether polymer as a spotting
fluid. Further, other methods for freeing stuck pipes include using
water-based spotting fluids, such as U.S. Pat. No. 4,230,587 to
Walker, which discloses a mixture of water or brine with a mixture
of polyethylene glycols as a spotting fluid; U.S. Pat. No.
4,494,610 to Walker, discloses a spotting fluid comprising a lower
alcohol with another component, such as water, and optionally
weighting agent; and U.S. Pat. No. 4,614,235 to Keener et al.,
discloses adding a mono or polyalkylene glycol ether to a water
based spotting fluid.
[0019] Recently, acid and ester based spotting fluid have been
prepared and used to release stuck pipes. In particular, a
carboxylic acid, such as acetic acid as is disclosed by U.S. Pat.
No. 5,247,992 to Lockhart; fatty acid alkyl esters containing
spotting fluids are disclosed by U.S. Pat. No. 4,964,615 to Mueller
et al.; and a spotting fluid which is non-toxic and comprises
glycerol-phosphoric acid ester and a polyacyloxy polycarboxylic
acid esters of mono and/or diglycerides is disclosed in U.S. Pat.
Nos. 5,002,672 and 5,127,475 to Hayes et al.
[0020] Finally, a multi-step spotting method is disclosed by U.S.
Pat. No. 5,415,230 to Fisk, Jr. et al. In the first step of this
patent, a spotting pill containing brine is pumped into the region
of the stuck pipe and allowed to soak. A second spotting pill is
pumped into the region of the stuck pipe and is also allowed to
soak. The second spotting fluid can be any spotting fluid known to
those skilled in the art. The spotting fluid is allowed to soak in
place for an extended period or until the pipe becomes free.
SUMMARY OF THE INVENTION
[0021] The present invention employs a very different approach
employing a multi-component addition to the borehole. The method
for releasing the stuck pipe of the present invention uses a
combination of components which oxidize the mud cake, and generates
gas bubbles through reaction with the mud cake to create an upward
buoyancy for the oxidized mud cake, as well as general lightening
of the hydrostatic head column at the same time. The spotting
method of the present invention comprises adding to the borehole in
the region of the stuck pipe:
[0022] 1) an oxidizer which oxidizes the mud cake;
[0023] 2) at least one component which reacts in the borehole to
generate a gas; and
[0024] 3) optionally, at least one component which contains a
reducer.
[0025] In a second aspect of the present invention the spotting
method further uses a lubricant which is added to the borehole in
the region of the stuck pipe. The lubricant acts to lubricate the
oxidized parts of the mud cake and the pipe.
[0026] In a third aspect of the present invention, a spotting fluid
system is disclosed. The spotting fluid system comprises at least
two separate components, a) an oxidizer which oxidizes the mud
cake; and b) at least one component which reacts in the borehole
with the oxidizer to generate a gas. The spotting fluid system can
optionally contain a lubricant which acts to lubricate the oxidized
parts of the mud cake and the pipe. In addition, an article of
manufacture comprising at least two or three separate containers,
depending whether or not the lubricant is present. A first
container or containers comprise the oxidizer, a second container
or containers comprise a component, which will react in the
borehole to generate gas bubbles and a third container or
containers, which are optional, comprise the lubricant.
Additionally, a reducer can be added to one of the containers,
provided it will not react with the other components in the
container. As an alternative, the reducer can be present in a
separate container.
[0027] Another aspect of this invention is a method for dislodging
a stuck pipe in a borehole of a downhole well drilling operation
which comprises adding to the borehole a solution comprising (i) an
hydrogen peroxide and (ii) water or brine. It has been discovered
that of solution of hydrogen peroxide, at a relatively low
concentration, can be used to dislodge a stuck pipe, if the a
drilling mud comprises, as a drilling fluid, at least one of the
following modules (A)-(E)
[0028] (A) an alkaline first module that contains (a) a source of
caustic, (b) a natural wax, (c) a natural thinner, (d) glycerol,
and (e) phosphoric acid and/or boric acid,
[0029] (B) a second module prepared by reacting (f) aluminum metal
with the components of said alkaline first module thereby forming a
soluble alkali metal aluminate,
[0030] (C) a third module comprising said components of said first
module in combination (g) with at least one of an alkali metal
phosphate, borate and sodium silicate,
[0031] (D) a fourth module comprising said components of said first
module in combination with (h) a saturated or unsaturated
carboxylic acid source, or
[0032] (E) a fifth module comprising said components of said first
module in combination with (h) a saturated or unsaturated
carboxylic acid source, and (g) at least one of an alkali metal
phosphate, borate and sodium silicate.
[0033] In another aspect of this invention, one or more modules of
a modular drilling fluid, described above, can also be used as a
spotting fluid. Typically, the drilling fluid is added as a
spotting fluid in a well where the mud has not previously been
treated with one or more of the modules of the modular drilling
fluid. However, one or more modules of the modular drilling fluid
can be used in drilling mud already treated with one or more
modules of the modular drilling fluid, as a spotting fluid.
[0034] In a final aspect of this invention, a completion fluid,
containing one or more of the modules of the modular drilling fluid
is also disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1, shows a scanning electron image of a mud filter
cake.
[0036] FIGS. 2A, 2B, 2C, 2D and 2E show a scanning electron image
of a filter cake treated with a 1.5% or 3.0% solution of hydrogen
peroxide alone.
[0037] FIGS. 3A, 3B, 3C show a scanning electron image of a filter
cake treated with a 1.5% solution of hydrogen peroxide and a 0.8%
concentration of module 5 of the modular drilling fluid at a
magnification of .times.50, .times.100 and .times.2000,
respectively.
[0038] FIGS. 4A, 4B, 4C show a scanning electron image of a filter
cake treated with a 3.0% solution of hydrogen peroxide, a 0.8%
concentration of module 5 of the modular drilling fluid at a
magnification and 5.25% solution of sodium hypochlorite of
.times.50, .times.500 and .times.2000, respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0039] In the present invention, the order in which the components
of the spotting fluid of the first three aspects of this invention
are added or injected into the well is not critical. It is
preferred, however, that the oxidizer is first added to the
borehole so that the mud filter cake will be oxidized prior to the
addition of the component which reacts in the well bore to generate
a gas. Likewise, when a lubricant is used in the spotting fluid and
spotting method of the present invention, it can be added before
the oxidizer, before the gas generating component, or after both
the oxidizer and the gas generating component. Preferably, the
lubricant, when added, is added in between the oxidizer and the
component which will generate gas.
[0040] The oxidizer used in the method of dislodging the stuck pipe
and in the spotting fluid of this invention is a component which
will oxidize the mud filter cake. Any component which will react to
oxidize the mud cake can be used. In addition, the oxidizer tends
to swell the mud cake. Examples of such components include hydrogen
peroxide; hypochlorites, such as sodium hypochlorite, potassium
hypochlorite, lithium hypochlorite, calcium hypochlorite or
magnesium hypochlorite; or peroxides, such as hydrogen peroxide,
alkali metal peroxides, alkaline earth metal peroxides or manganese
group peroxides. Of these oxidizers, hydrogen peroxide is
preferred.
[0041] The oxidizer portion of the spotting fluid and method of the
present invention can be added or injected to the borehole alone or
added or injected as a solution. In considering handling aspects,
it is preferable that the oxidizer is added as a solution. Any
acceptable carrier can be used to form a solution with the
oxidizer, so long as the carrier does not interfere with the
oxidation of the filter cake. Example of acceptable carriers
include, but are not limited to, mineral oil, water, brine, etc.
Typically, the carrier for the oxidizer is selected so that it is
compatible with the drilling mud used in the particular drilling
operation. For example, if a water-based drilling mud is being used
in the drilling operation, the oxidizer can be added or injected
into the borehole in a solution with fresh water or brine.
Likewise, if an oil-based drilling mud is being used, the carrier
for the oxidizer is selected accordingly.
[0042] The concentration of the oxidizer in the solution can be up
to about 95% by weight or volume. From a practical stand point, the
oxidizer is present in the solution in an amount up to 50% by
weight or volume, preferably in an amount between 1 and 10% by
weight or volume, and most preferably between 1.5 and 5% by weight
or volume. Preferably, the oxidizer used in the method of this
invention and spotting fluid system is hydrogen peroxide.
Preferably, the hydrogen peroxide is in fresh water or brine at a
concentration of about 1.5 to 5% by weight or volume.
[0043] The oxidizer or oxidizer in solution can further contain a
weighting agent. Weighting agents are added to adjust the density
of the oxidizer to correspond to the density of the drilling mud
used in the drilling operation. The change in density can be an
increase (positive weighting) or a decrease (negative weighting).
Examples of weighting agents include barite, hematite, calcium
carbonate, iron carbonate, foams, mist and others known to those
skilled in the art. Foams and mist are examples of negative
weighting agents. The weighting agent is added to the oxidizer or
reducer in an amount up to about 90% by weight or volume, however,
the amount of the weighting agent will vary from well to well. The
appropriate amount of weighting agent is typically determined by
personnel at the drilling site.
[0044] The oxidizer is pumped through the drill pipe to the site of
the stuck pipe. Once in the region of the stuck pipe, the oxidizer
will oxidize, diffuse into and swell the mud filter cake. This
filter cake is typically thick and "sticky" and is formed across
the permeable formation in the stuck pipe section of the borehole.
Often, due to the existence of a high differential pressure between
the well bore (P.sub.w), and the formation pressure (P.sub.f),
(P.sub.w>P.sub.f), the filter cake grows to a point that the
hole diameter becomes smaller than the external diameter of the
drill string and the bottom hole assembly. This causes the bottom
hole assembly to stick differentially to the hole wall or to become
imbedded in the thick filter cake.
[0045] As stated above, the addition of the oxidizer oxidizes and
swells the filter cake and sometimes disintegrates the filter cake
so that the lubricant and component which generates gas in the
borehole of the present invention are not needed. But this usually
depends on the severity of the problem, including thickness and
make-up of the mud filter cake.
[0046] A second component of the spotting fluid or spotting process
of the present invention is component which will react in the
borehole to generate gas. The gas can be any gas, including but not
limited to, carbon dioxide, hydrogen, oxygen, nitrogen and others.
The generation of gas lowers the density of the mud filter cake
surrounding the stuck portion of the pipe and creates an upward
buoyancy for these mud cake particles. The gas pressure generated
in the borehole creates a blistered and bubbling permeable
formation which enables the pipe to break free from the mud filter
cake and, hence, become unstuck. Not wishing to be bound by theory,
it is believed that the gas bubbles migrate upward through the mud
column, along with the lubricant, when present, thereby decreasing
the well bore pressure P.sub.w, with respect to the formation
pressure, P.sub.f. When P.sub.w.ltoreq.P.sub.f, the pipe will
become free upon exertion of some mechanical pulling or turning
action. In addition, as the generated gas is subjected to a reduced
pressure, for examples as the gas reaches the surface or permeates
the filter cake, the gas expands. As the gas volume expands, the
well bore pressure must decrease. This also causes stuck pipe
differential pressure to reverse itself from P.sub.w>P.sub.f to
P.sub.w.ltoreq.P.sub.f thus releasing the stuck pipe and destroying
the wall filter cake.
[0047] Any component which will generate gas by reaction with
another component in the borehole can be used. It is noted,
however, that components which will or could have an adverse effect
of the drilling operations or which will produce hazardous
byproducts should be avoided. For example, components which will
react violently, or explode, should be avoided. Examples of gas
generating component include components which will react with the
oxidizer. If the oxidizer is hydrogen peroxide, examples of gas
generating components include sodium hypochlorite, potassium
hypochlorite, lithium hypochlorite, calcium hypochlorite and
magnesium hypochlorite; and peroxides such as alkali metal
peroxides, alkaline earth metal peroxides and manganese group
peroxides. The by-products of these components are typically salts
of the metals, water and gas. If the oxidizer is one of the
components mentioned above for the gas generating component, the
gas generating component can be, for example, hydrogen
peroxide.
[0048] Other components which will react in the borehole to
generate gas can be used. These components can react with
components in the drilling mud, lubricants or other additives
present in the borehole. An example of such a component is sodium
bicarbonate, which will generate carbon dioxide. Sodium bicarbonate
is an attractive gas generating component since it is relatively
easy to handle, relatively inexpensive and will react with acids or
bases present in the borehole. Further, the sodium bicarbonate may
be lightened by the lubricant, polymers or waxes. In one aspect of
the present invention, an acid, such as citric acid, acetic acid,
oxalic acid or other carboxylic acids, boric acid, phosphoric acid
or vinegar having an acidity of 5% or more, is added to or injected
into the borehole. The acid can be added, for example, in a
lubricant (discussed hereinbelow) which is injected or added to the
borehole. Once this acid is in the borehole, the gas generating
component is added and will react with the acid to generate a gas,
in this case, carbon dioxide. Alternatively, the gas generating
component can be added to the borehole, followed by the addition of
another component which will react with this gas generating
component.
[0049] Other examples of gas generating components include
hydrazine, and manganese oxide among others. In addition, the gas
generating component may react with the reducer.
[0050] The gas generating component of the spotting fluid and
spotting method of the present invention can be added or injected
to the bore hole alone or added or injected as a solution. In
considering handling aspects, it is preferable that the gas
generating component is added in a solution. Any acceptable carrier
can be used to form a solution with the gas generating component,
so long as the carrier does not interfere with the gas generating
capacity or ability of this component. Examples of acceptable
carriers include, non-toxic mineral oil, water, brine, etc.
Typically, the carrier for the oxidizer is selected so that it is
compatible with the drilling mud used in the particular drilling
operation. For example, if a water-based drilling mud is being used
in the drilling operation, the gas generating component can be
added or injected into the borehole in a solution with fresh water
or brine. Likewise, if an oil-based drilling mud is being used, the
carrier for the oxidizer is selected accordingly.
[0051] The concentration of the gas generating components in the
solution can be up to about 95% by weight or volume. From a
practical stand point, the gas generating component is present in
the solution in an amount up to 60% by weight or volume and
preferably in an amount between 1 and 10% by weight or volume.
Preferably, the gas generating component used in the spotting
method and in the spotting fluid system of the present invention is
sodium hypochlorite when the oxidizer is hydrogen peroxide.
Preferably, the sodium hypochlorite is in fresh water or brine at a
concentration of about 1.0 to 10% by weight or volume.
[0052] The gas generating component or solution thereof can further
contain a weighting agent. As stated above, weighting agents are
added to adjust the density of the gas generating component to
correspond to the density of the drilling mud used in the drilling
operation. The change in density can be an increase (positive
weighting) or a decrease (negative weighting). Examples of
weighting agents include barite, hematite, calcium carbonate, iron
carbonate, foams, mist and others known to those skilled in the
art. Foams and mist are examples of negative weighting agents. The
weighting agent is added to the gas generating component in an
amount up to about 60% by weight or volume, however, the amount of
the weighting agent will vary from well to well. The appropriate
amount of weighting agent is typically determined by personnel at
the drilling site.
[0053] Optionally, any component which acts as a reducer can also
be added to the well and can be part of the spotting fluid system.
Like the oxidizer and gas generating component, the reducer can be
added in a solution.
[0054] In the spotting method and spotting fluid system of the
present invention, a lubricant can also be used or is part of the
system. Any lubricant typically used in drilling operations can be
used as a lubricant of the present invention. Examples of
lubricants include, but are not limited to, mineral oil, glycols,
esters, vegetable oils, synthetic oils and fatty acid sources. In
addition, drilling fluid compositions having lubricating properties
can also be used. Examples of such drilling fluids include the
modular drilling fluid described U.S. Pat. No. 5,755,295. This
modular drilling fluid system can be conveniently formulated as at
least one of the following modules:
[0055] (1) an alkaline first module that contains a source of
caustic, a natural wax, and a natural thinner;
[0056] (2) a second module prepared by reacting aluminum metal with
the components of the alkaline first module thereby forming a
soluble alkali metal aluminate;
[0057] (3) a third module containing the components of the first
module in combination with at least one of an alkali metal
phosphate, alkali metal borate and sodium silicate;
[0058] (4) a fourth module containing the components of the first
module in combination with a C.sub.1-24 saturated or C.sub.2-24
unsaturated carboxylic acid source, a surfactant, and a
preservative; and
[0059] (5) a fifth module containing the components of the first
module in combination with a carboxylic acid source, a surfactant,
a preservative, and at least one of an alkali metal phosphate,
alkali metal borate and sodium silicate.
[0060] It has further been discovered that a combination of
glycerol and phosphoric and/or boric acid added to any one of the
forgoing modules can further improve some properties of this
modular drilling fluid. The improved properties include improved
lubricity of the drilling mud, mud thinning and mud viscosity
control, decreased bit "balling" tendencies, decrease in the
cohesive or shearing resistance beneath the drill bit and improved
control of phase separation of the mud. This modified modular
drilling fluid, mud and associated methods of using the modified
fluid and mud are the subject U.S. patent application 09/083,051,
filed on May 22,1998. In addition, a salt water-based drilling mud
is disclosed in U.S. patent application 09/236,568, which contains
the modular drilling fluid.
[0061] Module 1
[0062] Module 1 is the principal drilling fluid additive. It can be
used alone or in combination with one or more of the other modules
as discussed herein below. Module 1 is a caustic (alkaline)
drilling fluid. Caustic can be sodium or potassium hydroxide. This
composition further comprises one or more natural waxes and one or
more natural thinner. Typically the pH of a Module 1 formulation is
11 or greater. Such a high pH increases the dispersability of the
mud, thereby facilitating the drilling operation.
[0063] A natural wax used in this composition facilitates the
formation of emulsions and assists in coating solid particles
released by drilling. Exemplary natural waxes which can be used in
the composition are montan wax, waxes extracted from carnauba palm
tree, cotton lintres, lignite deposits, and the like.
[0064] A natural thinner is also provided in Module 1, and as used
herein refers to a natural colloidal clay dispersion. Exemplary
natural thinners include lignins, tannins and negatively charged
derivatives of humic acid.
[0065] The combination of caustic, natural wax, and natural thinner
as described above is sometimes referred to herein as a "scour kier
liquor", or its equivalent lignin and tannins and is a principal
ingredient of the instant drilling mud system. Preferably, the
first module is composed of a "scour kier liquor" which contains a
caustic at a pH of 11 or above, as well as a natural wax and a
natural thinner, such as a lignin and/or a tannin. The scour kier
liquor referred to herein is typically obtained by the alkaline
digestion of cellulosic fibers, e.g., cotton pulp, and is described
further herein below.
[0066] A preferred scour kier liquor is commercially available from
Barnhardt Industries (Charlotte, N.C.). The kier liquor may also be
combined with oxidizing agents such as peroxide, sodium
hypochlorite, and the like.
[0067] This module may further comprise glycerol, phosphoric acid
and/or boric acid, and optionally a gel. The glycerol, phosphoric
acid and/or boric acid is added to produce glyceroborates e.g.,
glyceroboriborate, and glycerophosphates.
[0068] The addition of glycerol, in accordance with the present
invention, boosts the lubricity of the module. This is due to
glycerol's low molecular weight and high solubility in water-based
or oil based muds. Glycerol further facilitates the rapid diffusion
of the modular drilling fluid in the mud filter cake, porous media
(e.g., rock) and clay masses adhering to the stuck section of the
drill pipe. Glycerol is added in an amount between 0.0027% by
volume to 95% by volume of the module, preferably in an amount up
to 40% by volume.
[0069] Phosphoric acid and/or boric acid is added to this module.
Typically, the phosphoric acid and/or boric acid is added in an
amount between 0.0008% and 95% by volume, preferably up to 35% by
volume, assuming a 70% or higher concentration of the acid. The
phosphoric acid and/or boric acid will react with the glycerol in a
condensation reaction to produce a phosphate, a borate ester or
combination of borophosphate esters. Due to the temperature and
pressure in the borehole, a reaction of the glycerol with
phosphoric acid and/or boric acid further takes place in the
borehole. This reaction product has an anionic head, comprising the
phosphate or the borate anions which will coat, attach, adhere or
associate with the cations on the edge of the clay particles. The
attraction between the anionic heads and the cations of the clay
edges causes an increase in the total negative charges of the clay
particles thus deflocculating or dispersing of the clay slurry or
mud filter cake, clay adhering to the stuck section of the drill
pipe (so-called bit "balling" phenomenon) and the weakening of the
clay "cements" holding the rock grains together.
[0070] The weakening of the clay "cements" further decreases the
strength of the mud and the compressed and thickened mud wall
around the stuck section of the drill string, through a capillary
action by the modular drilling mud or fluid system. Once
penetrating the structure of the clay "cement" through capillary
pressure, the anionic heads of the phosphate, borate or combination
borophosphate esters will deflocculate and weaken the cement. This
is like driving a wedge between adjacent cemented particles in the
region of the stuck pipe section.
[0071] In addition, the phosphate, borate or combination
borophosphate esters will have tails that allow for solubility of
the esters in the water phase of the drilling fluid. With this
solubility, the filtrate of the modular drilling fluid is allowed
to diffuse through capillary action into the porous media (e.g.,
rock or thick, compressed mud wall in the stuck section of the
pipe).
[0072] The gel is optionally added to the modular drilling mud or
fluid system to reduce phase separation and settling of the
particles during storage. The gel further controls the excessive
loss of the components of the spotting fluid system to which the
modular drilling fluid system is added. Typically, the gel is added
in an amount of 0.001 lb. to 100.0 lb. per barrel, preferably in an
amount of 0.001 to 10.0 lb. per barrel.
[0073] Module 2
[0074] This module represents a thickener or oil solidifier in
which aluminate ions have been provided. Whenever the aluminate
ions are added to the drilling fluid prior to pulling the drill
assembly out of the hole, the gel strength of the mud increases.
This means that the thixotropic properties of the drilling fluid
can be changed as desired, thus permitting cuttings entrained in
the mud to be suspended. This module is added to the spotting
system and method when there is a loss of thixotropic
characteristics in the drilling mud. In addition, whenever any of
Module 1, discussed above, and Modules 3 and 4, discussed below,
are combined with oil, the addition of Module 2 causes the oil to
solidify, i.e., to a rubbery or thick grease. The degree of oil
solidification can be readily altered by adjusting the
concentration of aluminum metal, which results in a change in the
concentration of aluminate ions.
[0075] Preferably, the second module is an aluminated scour kier
liquor in which aluminum metal has been reacted with the scour kier
liquor to produce aluminate ions in the presence of lignins and/or
tannins. The aluminate ions react with the lignins and tannins,
thereby crosslinking them and increasing the cutting suspension
capability of the drilling mud. Any alkali metal aluminate can be
used, however, a particularly preferred alkali metal aluminate is
sodium or potassium aluminate.
[0076] A preferred Module 2 formulation can be prepared by
combining aluminum metal, in the form of shavings, fines, and the
like, with sodium hydroxide or potassium hydroxide and water in the
presence of lignins or tannins. In the manufacture process of the
caustic soda, the caustic reacts with the aluminum metal to produce
sodium aluminate or potassium aluminate and hydrogen gas. Some of
the aluminate ions so formed react with the lignins or tannins,
thereby crosslinking them. It is believed that whenever the
cross-linked product is added to a clay suspension a partially
reversible net charge is placed on the clay particles, which
increases the gel strength of the mud. This is clearly shown in
Tables 1 and 2 of U.S. Pat. No. 5,755,295. This is a strongly
desired property especially while the drilling fluid is quiescent
in a horizontal, lateral, directional or deviated hole, e.g., in
river crossing, environmental remediation wells, or trenching
operations.
[0077] A suitable Module 2, or thickener, can be typically prepared
by adding 0.2-1.5 lb. of Al metal to 1 bbl of scour kier
liquor.
[0078] Module 3
[0079] Module 3 of the modular drilling fluid system represents a
primary thinner formulation. Functionally, this module
counter-balances Module 2. In this primary thinner composition, one
least one of an inorganic phosphate, an inorganic borate and an
inorganic silicate is combined with a caustic thinning composition
as in Module 1. Optionally, lignite can be combined with the other
components of this module. The resulting formulation is a high pH
super thinner. Considering the components of the composition, good
performance at both low and high temperatures is expected.
[0080] A particularly preferred composition with a primary thinner
of Module 3 comprises scour kier liquor (containing waxes and other
organic materials) in combination with trisodium phosphate (TSP)
and sodium silicate. Another preferred formulation includes scour
kier liquor, lignite, and TSP, or a mono-, di-, or tri-sodium,
potassium, or cesium phosphate, sodium acid pyrophosphate, sodium
orthophosphate, borates and sodium silicate. When using this
composition, the waxes and other organic material (or lignite when
it is used) can effectively coat colloid particles to protect them
from attack by contaminants while dispersing them at the same time
controllably, which produces a stable suspension condition.
[0081] A preferred formulation for module 3 can be prepared by
combining with 1 bbl of scour kier liquor, each of 1-50 lb of
trisodium phosphate, 0.25-2 lb sodium silicate, and 1-10 lb of
borax. The borax is an optional component that is useful in some
applications.
[0082] Whenever lignite and hot water are used in an amount of
about 1.0 to 3.0 pounds per gallon of hot water and, for example,
TSP is added, the viscosity of this newly discovered reaction
product can be varied from about that of water, representing a thin
fluid, to that of a solid tar or asphalt, a very thick material.
This material can be used, for instance, to plug a fracture in the
hole or to prevent mud losses from the hole. This variation in
viscosity is due to variations in the concentration of TSP in the
composition.
[0083] Module 4
[0084] This module provides a secondary thinner formulation as well
as a surfactant and preservative, which can be combined with any of
the previous modules as needed.
[0085] Preferred components in this module are those which enhance
the emulsification of oil, such as a saturated or unsaturated
carboxylic acid rich source, e.g., vegetable oil or a natural ester
such as cottonseed oil, jojoba oil, and the like. Preferably, the
carboxylic acid source is a C.sub.1-24 saturated or C.sub.2-24
unsaturated carboxylic acid or a synthetic ester, such as,
polyalphaolefin. This component affords a secondary thinning
capability. Other preferred anionic or nonionic emulsifiers
(surfactants) include those having a suitable HLB
(hydrophilic-lipophilic balance), alkylbenzene sulfonates,
tergitol, or TRITON (available from Union Carbide Corp., Danbury,
Conn.).
[0086] The preservative present in this module helps to protect
against bacteria and is preferably a chelating agent, such as table
salt, driller salt and salts of ethylenediamine tetraacetate (EDTA)
and borax. Other suitable preservatives include boric acid or
derivatives thereof and salt.
[0087] A representative formulation of this module is as follows in
a water base (1 bbl): 1-10 lb borax, 0.5-10 lb borateam (which
includes a sulfonated alkyl benzene-anionic surfactant), and 0.2-1
lb EDTA (Na or K salt). About 0.5-10 lb of TRITON (a nonionic
surfactant) can also be optionally provided.
[0088] The carboxylic acid of module 4 will also react with the
organic or inorganic acid of phosphoric acid and/or boric acid,
when present. This reaction occurs in the bore hole under the
temperature and pressure of bore hole. The reaction product is a
phosphate lipid, a borate lipid or a combination borophosphate
lipid. Like the phosphate esters and borate esters described above,
the phosphate lipid and borate lipids have anionic head which are
attracted to the cations of the edge of the clay particles. Hence,
these lipids have a similar function and effect as the esters
described above.
[0089] Module 5
[0090] This module represents a combination of Modules 1, 3 and 4
discussed above. This composition is a
super-thinner-dispersant-lubricant formulation that is preferably
used in treatments of 0.5 to 2.0% by volume in the mud system, such
as fresh water mud, lime mud or salt mud. Use of this combination
of Modules 1, 3, and 4 increases the deflocculation, lubricity and
thinning dramatically.
[0091] Functionally, in the combined modules a polymerized
phosphate and/or borate ester is formed which possesses the high
lubricity properties of esters as well as the thinning capabilities
of negatively charged phosphate and/or borate ions. The amount of
esterification can be easily altered by adjusting the concentration
of phosphate and/or borate.
[0092] A preferred composition for this module, is formed by
combining the compositions of modules 1, 3, and 4 in the amounts
detailed above with an oil base. Preferably, the oil, such as
cottonseed oil or a synthetic oil like polyalpholefin (PAO), is
provided in an amount up to 90% of the total volume. Preferably up
to 10%, but optionally up to 20%, of the oil content can be
replaced with a mineral oil, such as FGA.
[0093] The composition identified herein as formulation (I) is
composed of scour kier liquor (SKL) or equivalent lignin and
tannins, TSP, sodium acid pyrophosphate (SAPP), borax, borateam,
cottonseed oil and water in the relative amounts indicated
above.
[0094] Each of the forgoing modules can further contain additives
such as graphite, to improve the color of the composition. In
addition other additives can be added to improve the smell of the
modules. These additives will be readily apparent to those skilled
in the art and should be selected so that the properties of the
drilling mud are not adversely affected.
[0095] In the spotting method and spotting fluid system of the
present invention, the preferred lubricant is module 5 of the
modular drilling fluid. Particularly preferred is module 5
containing glycerol, and phosphoric and/or boric acid. This
provides the best all-around properties for the spotting fluid and
spotting method of the present application.
[0096] In the preferred spotting method of the present invention
the oxidizer, lubricant and gas generating component are added or
injected into the borehole in the following manner.
[0097] First, a "head" portion or "pill" is added or injected into
the borehole. The head portion contains the oxidizer which will
oxidize the mud cake in the stuck region.
[0098] Second, a "middle" portion or "pill" is then added or
injected into the borehole. This middle portion contains a
lubricant described above which lubricates the oxidized parts of
the mud cake.
[0099] Third, a "tail" portion or "pill" is then added or injected
into the borehole. This tail portion is reactive in the borehole
and results in the generation of bubbles of gas, thereby reducing
the density of the mud surrounding the stuck portion and generating
upward buoyancy. The gas pressure creates a blistered and bubbling
mud cake or mud which enables the pipe to move, hence become
unstuck. The formation of gas bubbles creates a system wherein the
pressure in the stuck region is less than or equal to the mud
column pressure. In other words, the reaction causes the
differential pressure to be equalized or reversed
(P.sub.w.ltoreq.P.sub.f- ), thus releasing the differentially stuck
pipe. Moreover, the buoyancy, lubricity plus oxidation and/or
reduction or disintegration of the thick and compressed cake
results in the cake having no cohesion, whereby it is lifted
upwardly, facilitating elimination of the stuck portion. The
reaction is usually with the oxidizer in the head portion and
components present in the lubricant.
[0100] The head portion preferably contains hydrogen peroxide or
sodium bicarbonate w in a solution. The concentration of the
hydrogen peroxide or sodium bicarbonate in the solution is
preferably about 1.5 to 10.0% by weight or volume of the solution,
preferably 1.5 to 5.0% by weight or volume.
[0101] The lubricant is then added or injected into the borehole.
As is stated above, the preferred lubricant is module 5 of the
modular drilling fluid of application Ser. No. 09/083,051, filed on
May 22, 1998. This module, with its high concentration of an oil,
e.g. vegetable oil may also provide for lifting of the mud cake, in
addition to the lubricating action. This module can be charged with
sodium bicarbonate.
[0102] Finally, after addition of the lubricant, the component
which will generate gas bubbles is added to the well. Preferably,
the component is sodium hypochlorite and/or acids, such as citric
acid, acetic acid, other carboxylic acids, boric acid, phosphoric
acid, vinegar having an acidity of 5% or more, dilute hydrochloric
acid, or a mud acid. The preferred form to add sodium hypochlorite
is as a solution in water or brine at a concentration of about 1 to
50% by weight or volume, preferably 1-10% by weight or volume.
[0103] Examples of possible gas generation reactions which can be
used in the present invention include, but are not limited to, any
one of the following equations:
[0104] 1. Sodium bicarbonate and citric acid
3NaHCO.sub.3.fwdarw.3Na.sup.++3(HCO.sub.3).sup.-
3Na.sup.++3(HCO.sub.3).sup.-+C.sub.6H.sub.8O.sub.7(citric
acid).fwdarw.3CO.sub.2.Arrow-up
bold.+Na.sub.3C.sub.6H.sub.5O.sub.7.3H.su- b.2O
[0105] 2. Sodium bicarbonate and boric acid
NaHCO.sub.3.fwdarw.Na.sup.++(HCO.sub.3).sup.-
(HCO.sub.3).sup.-+B(OH).sub.3.fwdarw.CO.sub.2.Arrow-up
bold.+B(OH).sub.4.sup.-
[0106] 3. Calcium phosphate and sodium bicarbonate
Ca(H.sub.2PO.sub.4).sub.2.2H20+2NaHCO.sub.3.fwdarw.2CO.sub.2.Arrow-up
bold.+4H.sub.20+Na.sub.2Ca(HPO.sub.4).sub.2
[0107] 4. Hydrazine reactions to give nitrogen
N.sub.2H.sub.4+4OH.sup.-.fwdarw.N.sub.2.Arrow-up
bold.+4H.sub.2O
N.sub.2H.sub.4+O.sub.2.fwdarw.N.sub.2.Arrow-up bold.+2H.sub.2O
[0108] 5. Hydrogen peroxide and sodium hypochlorite
H.sub.2O.sub.2+NaOCl.fwdarw.H.sub.2O+NaCl+.sub.2.Arrow-up bold.
[0109] 6. Permanganate and oxalic acid
2MnO.sub.4(aq)+6H.sup.++5H.sub.2C.sub.2O.sub.4.fwdarw.2Mn.sup.2++10CO.sub.-
2.Arrow-up bold.+8H.sub.2O
[0110] 7. Acetic acid and Sodium bicarbonate
2NaHCO.sub.3.fwdarw.2Na.sup.++2(HCO.sub.3).sup.-
2Na.sup.++2(HCO.sub.3).sup.-+HC.sub.2H.sub.3O.sub.2(acetic
acid).fwdarw.CO.sub.2.Arrow-up bold.+Na.sub.2CO.sub.3+H.sub.2O
+H.sup.++[C.sub.2H.sub.3O.sub.2].sup.-
[0111] Finally, it has been discovered that the addition of
hydrogen peroxide in a solution water or brine, can dislodge a
stuck pipe, alone, if the drilling mud is a drilling mud
comprising, as a drilling fluid, at least one of the following
modules (A)-(E)
[0112] (A) an alkaline first module that contains (a) a source of
caustic, (b) a natural wax, (c) a natural thinner, (d) glycerol,
and (e) phosphoric acid and/or boric acid,
[0113] (B) a second module prepared by reacting (f) aluminum metal
with the components of said alkaline first module thereby forming a
soluble alkali metal aluminate,
[0114] (C) a third module comprising said components of said first
module in combination (g) with at least one of an alkali metal
phosphate, borate and sodium silicate,
[0115] (D) a fourth module comprising said components of said first
module in combination with (h) a saturated or unsaturated
carboxylic acid source or a synthetic ester such as
polyalphaolefin, or
[0116] (E) a fifth module comprising said components of said first
module in combination with (h) a saturated or unsaturated
carboxylic acid source, and (g) at least one of an alkali metal
phosphate, borate and sodium silicate.
[0117] Surprisingly, it has also been discovered that at relatively
low concentrations of hydrogen peroxide to a borehole having a
stuck pipe, will result in the freeing of the stuck pipe. Prior art
method using hydrogen peroxide required high concentrations of
hydrogen peroxide. In the present invention, the concentration of
hydrogen peroxide can be a little as 1.5% and is preferable in a
concentration of less than 5.0%.
[0118] It has also been discovered that the addition of one of the
modules of the modular drilling fluid can be effective as a stuck
pipe treatment. As is shown in Example 1 below, the addition of
module 5 of the modular drilling fluid will effectively release a
stuck pipe.
[0119] The amount of each of the pills of the spotting fluid in the
present invention used to release a stuck pipe varies depending on
the diameter of the hole, the length of the stuck section, and the
other factors, such as fluid loss in the formation. Typically, an
excess amount of the pills is added to the well to account for
losses and to extend above and below the stuck section of the pipe.
In the present invention, the amount of the individual pills or
entire spotting system generally ranges between 1 and 1000 bbl.
[0120] The inventor has also discovered that a completion fluid,
containing one of the forgoing modules is also effective in the
methods of this patent. A completion fluid is added to the hole to
displace the mud and the completion fluid contains no solids. The
completion fluid invades the formation and physically plugs and
prevents flow from the well. Typically, a completion fluid is water
or brine with heavy gel and/or polymeric components. The inventor
has found that adding one of the modules of the modular drilling
fluid to these components, a very effective completion fluid is
prepared.
[0121] The invention will now be described by way of examples which
illustrate the present invention but do not limit it.
EXAMPLE 1
[0122] One hundred fifty gallons of Module 5 is prepared by mixing
75 gallons cottonseed oil(with preservatives), 1 quart of glycerol,
1 quart of phosphoric acid, 4 lb. of gel, 42 gallons of water, 10
lb. of salt (NaCl), 1 quart of EDTA, 1 quart of boric acid, 10 lb.
of borateem, 6 lb. of borax, 12 gallons of hot water (150.degree.
F.), 30 lb. of trisodium phosphate, 25 lb. of lignite, 1 quart of
caustic soda, 25 lb. of graphite.
[0123] 125 gallons of Module 5 was added to a well having a stuck
casing in Mississippi Canyon Field. Approximately 200 barrels of a
drilling mud was present in the spotting operation. After Module 5
was added to the area of the stuck portion of the pipe and allowed
to soak, surprisingly after about 20 minutes to about one hour the
casing was released from the formation by applying mechanical force
to the drill string.
EXAMPLE 2
[0124] (Preparation of the Filter Cake)
[0125] A mud filter cake was prepared containing bentonite (gel), a
weighting agent comprising barite, water, Module 5, prepared in
Example 1 above, caustic soda, lignite and sodium polyacrylamide.
The mud filter cake was formed in accordance with the API standard
of 100 psi pressure differential and 30 min. time of
filtration.
EXAMPLE 3
[0126] The mud filter cake prepared in accordance with Example 2,
was treated with a 1.5% or 3.0% solution of hydrogen peroxide and
allowed to soak for a period of time. The scanning electron images
are show in the figures of FIG. 2. FIG. 2A shows, at .times.50
magnification, a filter cake treated with a 1.5% solution of
hydrogen peroxide alone. FIG. 2B shows the same treated mud at
.times.1000 magnification. (FIG. 2C) shows the mud filter cake
treated with a 3.0% solution of hydrogen peroxide alone, at
.times.50 magnification, and (FIG. 2D), shows the same at
.times.1000 magnification.
[0127] Comparing these figures to FIG. 1, it can be seen that the
hydrogen peroxide tends to form potholes in the mud filter cake
which indicates a disintegration of the sticky, thick mud filter
cake. Further, it can be seen that the 3% solution of the hydrogen
peroxide is more effective at oxidizing the mud filter cake than
the 1.5% solution of hydrogen peroxide.
EXAMPLE 4
[0128] The mud filter cake prepared in accordance with Example 2,
was treated with a 1.5% solution of hydrogen peroxide and allowed
to soak for a period of time. Then an addition of 0.8%
concentration of Module 5, prepared in Example 1 was added to the
filter cake and allowed to soak. FIGS. 3A, 3B and 3C show a
scanning electron image of a filter cake at a magnification of
.times.50, .times.100 and .times.2000, respectively. Again note the
formation of potholes in the filter cake which shows that the
combination of the hydrogen peroxide and the Module 5 are effective
at disintegrating, the mud filter cake.
EXAMPLE 5
[0129] The mud filter cake prepared in accordance with Example 2,
was treated with a 3.0% solution of hydrogen peroxide and allowed
to soak for a period of time. Then an addition of 0.8%
concentration of Module 5, prepared in Example 1 was added to the
filter cake and allowed to soak. Finally, a 5.25% solution of
sodium hypochlorite was added to the filter cake. FIGS. 4A, 4B, 4C
show a scanning electron image of a filter cake treated at
.times.50, .times.500 and .times.2000, magnification, respectively.
As can be seen, the addition of all three components to the mud
filter cake, the potholes formed in the mud filter cake are larger,
indicating the oxidation, blistering and removal or lifting of
particles from the filter cake by the generation of the oxygen gas
from the reaction of the hydrogen peroxide and the sodium
hypochlorite. The combination of the hydrogen peroxide and sodium
hypochlorite is very effective in releasing stuck pipes.
[0130] It is additionally pointed out that the sodium hypochlorite
could be added to the filter cake before the addition of the
hydrogen peroxide. Stated another way, the order in which the
components of the spotting fluid and method of the present
invention are added to a borehole can be reversed.
* * * * *