U.S. patent application number 10/638903 was filed with the patent office on 2004-07-01 for drilling fluid, apparatus, and method.
This patent application is currently assigned to Grain Processing Corporation. Invention is credited to Abbott, David W., Wiesner, Thomas A..
Application Number | 20040124013 10/638903 |
Document ID | / |
Family ID | 31978323 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040124013 |
Kind Code |
A1 |
Wiesner, Thomas A. ; et
al. |
July 1, 2004 |
Drilling fluid, apparatus, and method
Abstract
Disclosed are drilling fluids suitable for use in connection
with oil well drilling. The drilling fluids of the invention
include in one embodiment a liquid base, an alkyl glucoside, such
as methyl glucoside, and a borehole stability promoter that
includes a maltodextrin, a carboxyalkyl starch, a
hemicellulose-containing material, or a mixture of the foregoing.
In another embodiment, the drilling fluid includes a liquid base
and molasses solids, preferably in combination with an alkyl
glucoside and more preferably in further combination with one of
the aforementioned borehole stability promoters. In another
embodiment, the drilling fluid includes sorbitol, preferably in
conjunction with a borehole stability promoter. The drilling fluids
of the invention surprisingly have a reduced tendency to swell
shale as compared with known drilling fluids. Also disclosed are a
drilling apparatus and process. The drilling apparatus includes a
drill string, which may be conventional, that is fluidically
coupled to a source of drilling fluid, the source of drilling fluid
including the drilling fluid of the invention. The process of the
invention includes the step of circulating the drilling fluid of
the invention through a drill string during borehole drilling.
Inventors: |
Wiesner, Thomas A.;
(Muscatine, IA) ; Abbott, David W.; (Muscatine,
IA) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
TWO PRUDENTIAL PLAZA, SUITE 4900
180 NORTH STETSON AVENUE
CHICAGO
IL
60601-6780
US
|
Assignee: |
Grain Processing
Corporation
Muscatine
IA
52761
|
Family ID: |
31978323 |
Appl. No.: |
10/638903 |
Filed: |
August 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60406604 |
Aug 28, 2002 |
|
|
|
Current U.S.
Class: |
175/65 |
Current CPC
Class: |
C09K 8/206 20130101;
C09K 8/514 20130101; C09K 8/08 20130101 |
Class at
Publication: |
175/065 |
International
Class: |
E21B 021/00 |
Claims
What is claimed is:
1. A drilling fluid comprising: a liquid base selected from the
group consisting of water, water-miscible liquids, and mixtures
thereof; sorbitol, said sorbitol being present in at least an
amount effective to inhibit shale swelling; and a borehole
stability promoter selected from the group consisting of a
maltodextrin, a carboxyalkyl starch, hemicellulose, and mixtures
thereof, said borehole stability promoter being present in at least
an amount effective to inhibit shale swelling.
2. A composition according to claim 1, wherein said liquid base
comprises water.
3. A composition according to claim 1, wherein said liquid base
includes polyglycerine.
4. A composition according to claim 3, wherein said liquid base
includes polyglycerine and water.
5. A composition according to claim 1, said borehole stability
promoter comprising hemicellulose.
6. A composition according to claim 5, wherein hemicellulose is
present in said drilling fluid in an amount ranging from about
0.002 to about 0.2 lbs./gallon by dry basis weight.
7. A composition according to claim 5, wherein said hemicellulose
comprises a hemicellulose fraction obtained via alkaline hydrolysis
of corn hulls.
8. A composition according to claim 1, said borehole stability
promoter comprising a maltodextrin.
9. A composition according to claim 8, wherein said maltodextrin is
present in an amount ranging from about 0.002 to about 0.2
lbs./gallon by dry basis weight.
10. A composition according to claim 1, said borehole stability
promoter comprising a mixture of maltodextrin and
hemicellulose.
11. A composition according to claim 10, wherein said borehole
stability promoter is present in a total amount ranging from about
0.002 to about 0.2 lbs./gallon by dry basis weight.
12. A composition according to claim 1, said borehole stability
promoter comprising a carboxymethyl starch.
13. A composition according to claim 12, said carboxymethyl starch
having a DS of about 0.2.
14. A composition according to claim 12, said borehole stability
promoter comprising a mixture of carboxymethyl starch and
maltodextrin.
15. A composition according to claim 12, said borehole stability
promoter comprising a mixture of carboxymethyl starch and
hemicellulose
16. A drilling apparatus comprising: a drill string; at least one
pump for circulating a drilling fluid through at least a portion of
said drill string, said pump being fluidically connected to a
source of drilling fluid, said drilling fluid comprising: a liquid
base selected from the group consisting of water, water-miscible
liquids, and mixtures thereof; sorbitol; and a borehole stability
promoter selected from the group consisting of a maltodextrin, a
carboxyalkyl starch, hemicellulose, and mixtures thereof, said
borehole stability promoter being present in at least an amount
effective to inhibit shale swelling.
17. A drilling process comprising the steps of: cutting a borehole
into the earth using a drill string; and circulating a drilling
fluid through at least a portion of said drill string, said
drilling fluid comprising: a liquid base selected from the group
consisting of water, water-miscible liquids, and mixtures thereof;
sorbitol; and a borehole stability promoter selected from the group
consisting of a maltodextrin, a carboxyalkyl starch, hemicellulose,
and mixtures thereof, said borehole stability promoter being
present in at least an amount effective to inhibit shale
swelling.
18. A composition comprising: sorbitol; and a borehole stability
promoter, said borehole stability promoter being selected from the
group consisting of a maltodextrin, a carboxyalkyl starch,
hemicellulose, and mixtures thereof, said borehole stability
promoter being present in an amount ranging from about 0.1% to
about 5% by dry basis weight of said alkyl glucoside.
19. A composition comprising: sorbitol; and an alkyl glycoside,
said alkyl glycoside being selected from among the .alpha.-form,
the .beta.-form, and mixtures thereof, said alkyl glycoside
selected from among the methyl, ethyl, propyl, and butyl glucosides
of glucose, maltose, maltotriose, and maltotetraose.
20. A composition comprising: sorbitol; and molasses solids, said
molasses solids being present in at least an amount effective to
inhibit shale swelling.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The invention is in the area of drilling fluids used in
connection with drilling wells, such as oil wells and water wells.
The invention is also directed towards a drilling apparatus and
process.
BACKGROUND OF THE INVENTION
[0002] In drilling a well or other similar borehole, a drill bit is
operatively coupled, usually by a drill string, to a drive which
rotates the drill bit to cause the drill bit to bore into the
earth. A drilling fluid, or drilling mud, is circulated through the
borehole annulus. The drilling fluid passes through the drilling
string and to the surface through the drill bit for cooling and
lubricating the drill bit and for carrying rock cuttings generated
by the cutting action of the bit to the surface. The drilling fluid
may be a gas, but more typically is a liquid.
[0003] Many liquids suitable for use as drilling fluids are known.
Some drilling fluids are oil-based. Such oil-based fluids suffer
from a number of drawbacks, particularly, their adverse effects on
the environment. Oil-based fluids also can be costly to purchase
and to dispose of.
[0004] Other drilling fluids are water-based or constitute an
emulsion of oil in water or water in oil. Such fluids often are
inexpensive compared to oil-based fluids, and are less costly to
dispose of. Water-based fluids also pose less of a risk to the
environment than do oil-based fluids. One drawback associated with
water-based fluids is that the water in the fluid tends to promote
borehole instability, particularly when shale is encountered in the
drilling process. The water-based fluid may adsorb and absorb into
pores in the shale, thus causing the shale to swell and thereby
tending to cause the borehole to collapse.
[0005] In recognition of this drawback, water-based drilling fluids
have incorporated an alkyl glycoside, such as methyl glucoside,
into the drilling fluid. It is known that methyl glucoside serves
as a borehole stabilizing agent that functions by inhibiting shale
swelling. The mechanism of action of methyl glucoside is not fully
understood, but is believed to be associated with gel formation or
an ion exchange phenomenon. It is generally believed that the
methyl glucoside, in adding gel strength to the drilling fluid,
causes more rapid formation of filter cake on the borehole wall
thereby allowing less water filtrate to reach the surrounding
shales. This is believed to reduce swelling and sloughing of the
shale.
[0006] While known drilling fluids that include methyl glucoside
are satisfactory, there remains room for improvement in such fluids
in the area of borehole stability. It is a general object of the
invention to provide a drilling fluid that is suitable for use in
borehole drilling. Another general object is to provide a drilling
apparatus and process that incorporate the drilling fluid of the
invention.
THE INVENTION
[0007] It has now been discovered that both maltodextrins, on the
one hand, and hemicellulose-containing materials, on the other
hand, function to assist glycosides in promoting borehole stability
in a drilling fluid. It has further been found that carboxyalkyl
starches, in particular carboxymethyl starches, also function to
assist glycosides in promoting borehole stability. Surprisingly,
these ingredients promote borehole stability more so than other
organic species of similar origin or chemical structure when used
in conjunction with an alkyl glucoside. In accordance with the
invention, a drilling fluid comprises a liquid base, an alkyl
glycoside, which preferably is methyl glucoside; and a borehole
stability promoter that comprises a maltodextrin, a carboxyalkyl
starch, and/or hemicellulose. Also encompassed by the invention is
a drilling fluid that includes methyl glucoside and cellulose. The
invention also encompasses a drilling apparatus and a process for
drilling. The drilling apparatus comprises a drilling string that
is fluidically coupled to a source of drilling fluid, the drilling
fluid including in one embodiment a liquid base, an alkyl
glycoside, and one or more of a maltodextrin, a carboxyalkyl
starch, and a hemicellulose-containing material and, in another
embodiment, a liquid base, an alkyl glycoside, and cellulose. The
process of the invention includes the steps of circulating the
drilling fluid of the invention through a drill string as a
borehole is cut into the earth, optionally in conjunction with
hemicellulose, a maltodextrin, a carboxyalkyl starch and/or
cellulose.
[0008] It has further been found that desugared molasses functions
effectively as a borehole stabilizing agent. In accordance with
another embodiment of the invention, a drilling fluid comprises a
liquid base, optionally an alkyl glucoside, and a borehole
stabilizing agent that comprises desugared molasses solids. Also
encompassed by this embodiment of the invention are a drilling
apparatus and a process for drilling. More generally, the various
boreholes stabilizing agents discussed hereinabove may be combined
with the alkyl glucoside to form a drilling fluid. Thus, for
instance, the drilling fluid may comprise an alkyl glucoside,
desugared molasses solids, and one or more of hemicellulose, a
maltodextrin, and a carboxyalkyl starch. Alternatively, the
molasses solids may be solids from a molasses that has not been
desugared.
[0009] It has further been found that sorbitol functions as a
borehole stabilizing agent, alone in a liquid base or in
combination with molasses solids, an alkyl glucoside, and/or a
borehole stability promoter. In accordance with one embodiment of
the invention, a drilling fluid comprises a liquid base, sorbitol,
and one or both of an alkyl glucoside and molasses solids,
optionally in conjunction with a borehole stability promoter. In
accordance with another embodiment, a drilling apparatus includes a
drill string that is fluidically coupled to a source of drilling
fluid, the drilling liquid comprising a liquid base and sorbitol.
In yet another embodiment of the invention, a process for drilling
includes the steps of circulating a drilling fluid through a drill
string as a borehole is being cut into the earth, the drilling
fluid including a liquid base and sorbitol.
[0010] Other features and embodiments of the invention are
discussed hereinbelow and are set forth in the pending claims.
BRIEF DESCRIPTION OF THE DRAWING
[0011] The FIGURE is a schematic representation of an oil well
drilling apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] The drilling fluid of the invention generally comprises in
one embodiment a liquid base, an alkyl glycoside, and a borehole
stability promoter, and may include other components and additives
as may be deemed appropriate. In another embodiment, the drilling
fluid comprises a liquid base, molasses solids, optionally in
conjunction with an alkyl glucoside or a borehole stability
promoter, and further optionally including other components and
additives as may be deemed appropriate.
[0013] The liquid base used in the drilling fluid of the invention
comprises water, a water-miscible liquid, or a mixture of a
water-miscible liquid with water. If the liquid base includes
water, the water may be provided from any suitable source. For
example, when the oil drilling apparatus is off-shore or near the
ocean, sea water is the preferred liquid base inasmuch as it is
freely available. The water may also comprise treated water,
softened water, tap water, natural or artificial brine, or other
suitable water source.
[0014] The water miscible liquid may be glycerine, polyglycerine, a
polyether, a polyol, or other suitable water miscible liquid. The
liquid base may be present in any amount suitable to carry,
dissolve and/or suspend the components of the drilling fluid.
Preferably, the liquid base is present in the drilling fluid in a
total amount ranging from about 5 to about 7.5, more preferably,
about 5.5 to about 6 lbs./gallon. It is further contemplated that
the liquid base may be used in an oil-based system that comprises
an emulsion of oil in water or water in oil. The drilling fluid of
the invention in one embodiment further includes an alkyl
glycoside. Alkyl glycosides are a known class of industrial
chemicals and are formed by the substitution of the hemiacetal
hydroxyl group of a lower order saccharide (i.e., a polysaccharide
having a degree of polymerization less than about 7) with an alkyl
radical having from one to four carbon atoms. The alkyl radical may
be methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl or t-butyl,
and the saccharide may be, for example, glucose, maltose,
maltotriose, or maltotetraose.
[0015] The alkyl glycoside used in conjunction with the invention
is preferably methyl glucoside. Most preferably, the methyl
glucoside is provided in the form of MeG-206, an aqueous methyl
glucoside solution sold by Grain Processing Corporation of
Muscatine, Iowa. MeG-206 is a 60% aqueous solution of methyl
glucoside, the methyl glucoside being present in a 2:1 ratio of
.alpha.:.beta. isomers (this ratio should be regarded as
approximate). The methyl glucoside also may be provided in the form
of MeG-365, also sold by Grain Processing Corporation of Muscatine,
Iowa. MeG-365 is a 65% aqueous solution of methyl glucoside which
exists in the solution as a 2:1 ratio of .alpha.:.beta. isomers
(this ratio also should be regarded as approximate). Another
suitable methyl glucoside may be provided as a 70% 1:1
(approximate) mixture of .alpha.: .beta. methyl glucoside isomers.
More generally, any other suitable mixture of methyl glucoside
isomers may be employed in conjunction with the invention.
[0016] The alkyl glycoside may be present in any amount effective
to inhibit shale swelling. Preferably, when the alkyl glycoside is
methyl glucoside, the methyl glucoside is present in the drilling
fluid in an amount ranging from about 2 to about 4 lbs./gallon of
the drilling fluid (dry basis MeG).
[0017] In another embodiment of the invention, the drilling fluid
comprises or includes molasses solids. It is contemplated that
either molasses solids from molasses that has not been desugared or
molasses solids from desugared molasses may be employed in this
embodiment. Molasses is the by-product of the process used to
extract sugar from sugar beet or cane sugar molasses or from other
types of molasses (e.g., sorghum or citrus molasses). Preferred
embodiments of the invention make use of desugared sugar beet
molasses or sugar cane molasses (this molasses generally has not
been desugared).
[0018] With respect to sugar beet molasses, as is well known in the
art, sugar beets are used to produce commercial grade sugar that
serves as a substitute for the often more expensive cane sugar. The
older of the two most widely used processes of removing sugar from
sugar beets involves cleaning the beets and slicing them into thin
chips. The sliced beets are then subjected to a sugar extraction
process whereby hot water is passed over the beets for
approximately one hour. This process removes most, but not all, of
the sugar from the beets in the form of beet "juice." The beets are
then pressed in screw presses to remove the remaining juice
therefrom. The juice is then subjected to a process called
carbonation, whereby small clumps of chalk are provided in the
juice to filter out any non-sugars. The chalk is then filtered from
the juice, which is then evaporated a syrup. The syrup is then
boiled until sugar crystals form therein. Once the crystals form,
the resulting mixture is centrifuged to separate the crystals from
the remaining product, which remaining product is characterized as
molasses. Desugared sugar beet molasses preferably is prepared by a
process known as the Steffen process, in which a calcium
precipitate is formed to remove additional sugar. This process is
described briefly in U.S. Pat. No. 5,639,319 to Daly, which
purports to teach the use of desugared sugar beet molasses as a
tire ballast. Another process for desugaring molasses involves an
ion exchange reduction of the sugar content. With respect to cane
sugar molasses and desugared sugar cane molasses, these products
may be obtained via any method or process known in the art or
otherwise found to be suitable. Likewise, sugar beet or other types
of molasses may be obtained via any other method known in the art
or found to be suitable.
[0019] In either instance, the molasses is a liquid that contains
approximately 60 to 80% solids, often 60 to 75% solids. The solids
contained in the sugar beet or other molasses are not particularly
well characterized, but generally speaking, the molasses generally
includes residuals, organic acids, salts, proteinaceous material,
and other materials. In some embodiments of the invention, molasses
or desugared molasses is used alone as the drilling fluid in a
drilling process or apparatus. For this embodiment, the molasses
can be said to comprise a liquid base (water) in which is carried
desugared molasses solids or, more generally, molasses solids. It
should be noted that although the invention encompasses embodiments
wherein molasses solids are obtained via drying a molasses solution
to solids, the invention is not limited thereto, and the "liquid
base" and "molasses solids" or "desugared molasses solids" may
together comprise either conventional molasses or conventional
desugared molasses that has been diluted. More preferably, the
desugared sugar beet molasses or other molasses or desugared
molasses is diluted with a liquid base such as water to a solids
content of about 20% to about 60%. In accordance with a highly
preferred embodiment of the invention, the drilling fluid includes
both an alkyl glucoside and desugared molasses solids. In this
embodiment, the alkyl glucoside and the desugared sugar beet
molasses solids may be present in any proportion with respect to
each other and preferably are present in a total solids content in
the drilling fluid ranging from about 40% to about 80%.
[0020] In some embodiments, the drilling fluid includes sorbitol,
in lieu of or in addition to molasses solids or an alkyl glucoside.
Sorbitol may be obtained commercially, or may be prepared by
hydrogenating glucose. The sorbitol may be used in the drilling
fluid in any amount effective to inhibit shale swelling.
Preferably, the sorbitol is present in an amount of 40-50% solids;
more preferably, about 50-70% solids. One preferred drilling fluid
includes 60% sorbitol.
[0021] In accordance with preferred embodiments of the invention,
the drilling fluid further includes a borehole stability promoter,
sometimes called a stability agent, sometimes call a stability
agent that is selected from among maltodextrins, carboxymethyl
starches, and hemicellulose. With respect to hemicellulose,
hemicellulose is a term used to refer to a wide variety of
heteropolysaccharides found in association with cellulose in plant
species. The hemicellulose functions to inhibit shale swelling, and
may further function as a fluid loss control agent. The
hemicellulose may be added in a purified form. Most preferably, the
hemicellulose-containing material is produced in accordance with
the teachings of U.S. Pat. No. 4,038,481 (Antrim et al.), which
discloses the alkaline hydrolysis of corn hulls to yield plural
phases including a hemicellulose-rich fraction. The
hemicellulose-rich fraction prepared in accordance with the
teachings of this patent may be used as the
hemicellulose-containing material without subsequent isolation or
purification, or this fraction may be concentrated or otherwise
modified. The alkaline hydrolysis itself preferably is conducted
using potassium hydroxide as the alkaline hydrolyzing species.
Potassium is itself believed to function as a shale stability
enhancer in a drilling fluid, and thus the potassium hydroxide
digest of corn hulls is believed to be particularly suitable for
use in conjunction with the invention. More economically, an
unrefined aqueous slurry (for example, an alkaline digest of corn
hulls) may be used. More generally, hemicellulose may be provided
in an unpurified, somewhat "crude" form or in a highly purified
form with the purer hemicellulose being preferred from a technical
standpoint, but with cruder forms being more economical. In some
instances a greater amount of the crude hemicellulose may be
desired to achieve the same results as by adding a purer form of
hemicellulose. One form of hemicellulose is known as "wood
molasses." Wood molasses may be obtained commercially; one wood
molasses is sold under the trademark TEMULOSE by Temple-Inland
Forest Products Corp. of Diboll, Tex.
[0022] The hemicellulose-containing material is used to provide
hemicellulose in the drilling fluid in an amount effective to
inhibit swelling of shale. Preferably, if the drilling fluid does
not include a maltodextrin, the hemicellulose is present in an
amount ranging from about 0.002 to about 0.2 lbs./gallon by dry
basis weight. In this embodiment of the invention, these amounts
are irrespective of the amount of any cellulose in the drilling
fluid.
[0023] The drilling fluid may also include a maltodextrin in lieu
of or in addition to the hemicellulose-containing material.
Maltodextrins are oligo- or poly-saccharides in which the
saccharides are linked exclusively or predominantly by 1-4
linkages. In preferred embodiments, at least 50 percent of the
saccharide units in the maltodextrin are linked via 1-4 linkages.
More preferably, at least about 60 percent of the saccharide units
are linked via 1-4 linkages; even more preferably, at least about
80 percent of the saccharide units are so linked. While the
drilling fluid may incorporate any maltodextrin or mixture of
maltodextrin species, the invention is particularly applicable to
mixtures of maltodextrin species in which at least a portion of the
maltodextrins in the mixture have a degree of polymerization (DP)
greater than 5. Preferably, at least one of the maltodextrin
species in the mixture has a DP of 8 or more. More preferably, at
least one species has a DP of at least 10. For example, in some
embodiments of the invention, a maltodextrin mixture in which at
least 80 percent of the maltodextrin species in the mixture have a
DP greater than 5 is used, and in some such embodiments, preferably
at least 60 percent have a DP greater than 8. In another
embodiment, a maltodextrin in which at least 80 percent of the
maltodextrin species have a DP greater than 10 is used. In some
embodiments of the invention, the DP profile of the maltodextrin is
such that at least 75 percent of the maltodextrin species in the
mixture have a DP greater than 5 and at least 40 percent of the
species in the mixture have a DP greater than 10. The maltodextrins
may include saccharide species having an odd DP value, and the
profile may be partially defined by a saccharide species having a
DP value of 1, for example, dextrose or sorbitol. The mixture
further may include other saccharide species or other components.
Such starting materials may be obtained conventionally, for
example, by the partial hydrolysis of starch.
[0024] Suitable maltodextrins are sold under the trademark
MALTRIN.RTM. by Grain Processing Corporation of Muscatine, Iowa The
MALTRIN.RTM. maltodextrins are mixtures of malto-oligosaccharides.
Each MALTRIN.RTM. maltodextrin is characterized by a typical
dextrose equivalent value (DE) and DP profile. Suitable MALTRIN
maltodextrins that may be incorporated as borehole stability
promoters in accordance with the invention, include, for example,
MALTRIN.RTM. M040, MALTRIN.RTM. M050, MALTRIN.RTM. M100,
MALTRIN.RTM. M150, and MALTRIN.RTM. M180. Typical approximate DP
profiles for the subject Maltrin maltodextrins are set forth in the
following table (the DP profiles being approximate as indicated in
the Table):
1 Typical DP profile (% dry solids basis) DP profile M180 M150 M100
M050 M040 DP > 8 46.6 .+-.4% 54.7 .+-.4% 67.8 .+-.4% 90.6 .+-.4%
88.5 .+-.4% DP 8 3.9 .+-.2% 4.8 .+-.1.5% 4.5 .+-.1.5% 1.5 .+-.1%
2.0 .+-.1% DP 7 9.5 .+-.2% 9.1 .+-.1.5% 7.0 .+-.1.5% 1.5 .+-.1% 2.4
.+-.1% DP 6 11.4 .+-.2% 8.4 .+-.1.5% 6.1 .+-.1.5% 1.4 .+-.1% 1.8
.+-.1% DP 5 5.9 .+-.2% 4.7 .+-.1.5% 3.3 .+-.1.5% 1.3 .+-.1% 1.3
.+-.1% DP 4 6.4 .+-.2% 5.5 .+-.1.5% 3.7 .+-.1.5% 1.1 .+-.1% 1.4
.+-.1% DP 3 8.3 .+-.2% 6.7 .+-.1.5% 4.2 .+-.1.5% 1.0 .+-.1% 1.4
.+-.1% DP 2 6.2 .+-.2% 4.8 .+-.1% 2.5 .+-.1% 0.8* .+-.1% 0.9*
.+-.1% DP 1 1.8 .+-.1.5% 1.3 .+-.1% 0.7* .+-.1% 0.8* .+-.1% 0.3*
.+-.1% DE** = 18 DE = 15 DE = 10 DE = 5 DE = 5 *Minimum Value = 0%
**Dextrose Equivalent Value
[0025] Other suitable maltodextrins as may be known or discovered
also may be considered useful in conjunction with the
invention.
[0026] The maltodextrin may be present in any amount effective to
inhibit shale swelling. When the drilling fluid includes a
maltodextrin borehole stability promoter and does not include
hemicellulose, the maltodextrin preferably is present in a total
amount ranging from about 0.002 to about 0.2 lbs./gallon, more
preferably about 0.01 to about 0.15 lbs./gallon by dry basis weight
of the maltodextrin. In this embodiment of the invention, these
amounts are irrespective of the amount of cellulose in the drilling
fluid.
[0027] The borehole stability promoter alternatively or
additionally may comprise a carboxyalkyl starch, preferably a
carboxymethyl starch. Carboxymethyl starches are known in the art,
and the preparation of such starches is described in Modified
Starches: Properties and Uses (Wurzburg, O. B., Ed.) 1986 p.
187-88. When the drilling fluid includes a carboxymethyl starch but
does not include any other borehole stability promoter, the
carboxymethyl starch preferably is present in the drilling fluid in
an amount ranging from about 0.002 to about 0.2 lbs./gallon, more
preferably about 0.01 to about 0.15 lbs./gallon. In this
embodiment, these amounts are irrespective of the amount of
cellulose in the composition. The carboxyalkyl starch may have a
degree of substitution (DS) of any suitable value. Adequate results
may be obtained when the starch has a DS of about 0.2.
[0028] The drilling fluid of the invention may incorporate a
borehole stability promoter that includes a maltodextrin and
hemicellulose in any combination of two or more of the foregoing.
In such case, the total amount of the combined borehole stability
promoter present in the drilling fluid preferably ranges from about
0.002 to about 0.2 lbs./gallon by dry basis weight, irrespective of
the amount of cellulose in the drilling fluid, with the
maltodextrin, starch, and hemicellulose being present in any amount
relative to one another. More generally, the borehole stability
promoter may be present in any amount effective to inhibit shale
swelling.
[0029] The drilling fluid further preferably includes a salt,
preferably sodium or potassium chloride. Salts are believed to
assist the alkyl glycoside or molasses solids or sorbitol and/or
the borehole stability promoter in inhibiting shale swelling. When
sea water is used as the liquid base, or when the bore formation
includes salt water, salt will be present in the form of sodium
chloride. Other salts that may be incorporated in the composition
of the invention include potassium chloride, calcium chloride,
sodium acetate, potassium acetate, calcium acetate, and the like.
The salt is preferably present in the drilling fluid in an amount
ranging from about 0.15 to about 0.8 lbs./gallon by dry basis
weight but, more generally, may be present in any amount effective
to assist in inhibiting shale swelling.
[0030] The drilling fluid may include further additives as may be
appropriate. Examples of additives that are known in the art
include barite, and other weighting agents, bentonite,
low-and-medium-yield clays, salt water clay, iron oxide, calcium
carbonate, starch, carboxymethylcellulose, acrylonitrile, gums,
molecularly dehydrated phosphate, tannin compound, quebracho,
lignins, lignosulfate, mica, sugar cane fibers, and granular
materials. Generally, the drilling fluid may contain other
ingredients such as weighting agents, viscosifiers, fluid loss
reducing additives, rheological modifying additives, emulsifiers,
seepage loss control additives, lubricity additives, defoamers, pH
control additives, dispersants, and so forth, all of such materials
being solubilized, suspended or dispersed in the drilling fluid in
such amounts as may be appropriate. It is generally contemplated
that any other suitable additive as is known or as may be
discovered may be employed in connection with the invention.
[0031] The invention further encompasses a drilling fluid additive
composition that includes in one embodiment an alkyl glycoside and
a borehole stability promoter that is selected from among a
maltodextrin, a carboxyalkyl starch, hemicellulose, and mixtures of
the foregoing and that includes in another embodiment molasses
solids in conjunction with one or more of the foregoing borehole
stability promoters and/or in conjunction with an alkyl glycoside.
In yet another embodiment, the additive includes sorbitol in
conjunction with one or more the foregoing borehole stability
promoters. In another embodiment, the additive includes sorbitol in
combination with an alkyl glucoside or in conjunction with molasses
solids. In accordance with this embodiment of the invention, the
liquid base is not present, or is present in a smaller amount than
is intended in the final drilling composition. The composition may
be supplied to drillers, for example, to be used as an additive to
seawater or brine in forming a drilling fluid in situ or may be
supplied to fabricators of drilling fluid to be blended with a
liquid base. In accordance with this embodiment of the invention,
the hemicellulose, starch, and/or maltodextrin preferably are
present in an amount ranging from about 0.1% to about 5% by the dry
basis weight of the alkyl glucoside or molasses solids (or total
dry weight of the molasses solids and alkyl glucoside). The
composition may be dry or may be in liquid form, with the
hemicellulose, starch, and maltodextrin being dissolved in a
liquid. The composition of this embodiment of the invention may
include other ingredients, such as salts or other additives, which
other ingredient may be employed in such amounts as may be
desired.
[0032] The invention also encompasses a drilling fluid that
includes methyl glycoside or other alkyl glycoside and cellulose,
the alkyl glycoside being present in at least an amount effective
to inhibit shale swelling, and the cellulose being present in an
amount of at least about 0.1% by weight of the alkyl glycoside. It
is contemplated that cellulose may assist the alkyl glycoside in
promoting borehole stability. Preferably, the cellulose is present
in an amount of from about 0.1% to about 5% by weight of the alkyl
glycoside. In this embodiment of the invention, the amount of
cellulose in the drilling fluid is irrespective of the amount of
dry hemicellulose or maltodextrin in the drilling fluid. In another
embodiment, a drilling fluid comprises molasses solids and
cellulose, the cellulose being present in an amount ranging from
about 0.1% to about 5% by weight of the molasses solids. Also
encompassed is a drilling fluid that includes sorbitol and
cellulose.
[0033] The invention also encompasses a drilling apparatus. With
reference to the FIGURE, the apparatus is shown generally at 10 and
includes a drill string 11, the drill string 11 generally including
a drive 12, a drill stem 14, and a drill bit 15 (the drive 12 is
shown as a top drive, but other configurations, such as a rotary
table, are possible). The drill stem 14 may include components such
as drill collars, drill pipe and a kelly (not separately shown).
The drill string 11 is fluidically connected to a source 16 of
drilling fluid which comprises the drilling fluid of one or more
embodiments of the invention. Generally, the source 16 will be
suction tanks 17 that are fluidically coupled to mud pumps 18 and
optionally a mud pit (not shown). The mud pump circulates fluid
through the drill string 11, i.e., through and around the drill bit
and/or through the annulus between the drill stem and the borehole.
The apparatus generally may take any other conventional or
otherwise suitable form and is not limited to the configuration
shown in the FIGURE.
[0034] The invention also encompasses a process for drilling. The
process includes the step of circulating the drilling fluid of one
or more embodiments of the present invention through the drill
string of a drilling apparatus during drilling operations. No
special apparatus is contemplated by the process of the invention,
but instead the process is contemplated to be useful in connection
with any suitable drilling apparatus.
[0035] The following examples are provided to illustrate the
present invention, but should not be construed as limiting in
scope.
EXAMPLES
[0036] VOLCLAY clay bentonite tablets (American Colloid Company,
Skokie, Ill.) were soaked in various drilling fluids and observed
over a period of time to simulate the effect of the drilling fluid
on shale in a well bore. The stability of each bentonite pellet was
evaluated according to the following scale:
[0037] 1=unaltered
[0038] 2=hard, intact but loose on surface
[0039] 3=swollen, softening, still intact
[0040] 4=together, but no integrity
[0041] 5=dissolved
[0042] These evaluations were designed to evaluate the drilling
fluids as against one another, rather than to directly evaluate
efficiency in actual borehole conditions.
[0043] The drilling fluids were prepared using as alkyl glycosides
MeG-206 (a 60% aqueous solution of methyl glucoside existing as a
2:1 ratio of .alpha.:.beta. ratio isomers). MeG-365 (a 65% aqueous
solution of methyl glucoside existing as a 2:1 ratio of
.alpha.:.beta. isomers), and a 70% aqueous solution of methyl
glucoside existing as a 1:1 ratio of .alpha.:.beta. ratio)
(designated hereunder as MeG-207). As borehole stability promoters,
MALTRIN.RTM. M040, M100, and M180 (maltodextrins available from
Grain Processing Corporation of Muscatine, Iowa) and the soluble
fraction resulting from alkaline treatment of corn hulls
(designated hereunder as "HC") were used. As a control, drilling
fluids were prepared using only water and using only MeG-365 or
MeG-207, without the addition of hemicellulose, maltodextrin, or
molasses. All of the drilling fluids were prepared at an initial pH
of 7 unless otherwise indicated.
[0044] Control
[0045] Drilling fluids were prepared with MeG-365 and MeG-207. The
stability of the bentonite pellets in each fluid was evaluated. The
stability of the pellets in pure water also was evaluated. The
following results were obtained.
2 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 24 hr. H.sub.2O 4 4.5 5 5
5 365 2 2.5 3 4.5 5 207 1 1 1.5 2 3
[0046]
3 Drilling Fluid 1 hr. 2 hr. 4 hr. 20 hr. 30 hr. 365 2 2 3.5 4.5 5
207 1 1 1.5 2.5 3
[0047]
4 Drilling Fluid 1 hr. 4 hr. 8 hr. 24 hr. 32 hr. 56 hr. 365 1.5 3
3.5 4.5 -- -- 207 1 1.5 2 3.5 4 5
[0048]
5 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 24 hr. 48 hr 365 1.5 2 3
3.5 4.5 -- 207 1 1 1.5 1.5 3 --
[0049] The bentonite pellets were substantially unstable in water,
and fared only somewhat better in the drilling fluids that included
methyl glucoside and water but that did not include maltodextrin,
hemicellulose, or molasses.
Example 1
MeG+Maltodextrin
[0050] Drilling fluids were prepared using methyl glucoside and
maltodextrin, and the bentonite stability test was repeated for
each fluid. The following results were obtained. Maltodextrin
percentages in these tables express weight percent maltodextrin by
dry basis of methyl glucoside.
6 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 24 hr. 365 + 5% M040 1 1
1.5 1.5 2 365 + 5% M100 1 1 1.5 1.5 2.5 365 + 5% M180 1.5 1.5 2 2
4
[0051]
7 Drilling Fluid 1 hr. 2 hr. 4 hr. 20 hr. 30 hr. 365 + 1% M040 1.5
2 2.5 4 4 365 + 3% M040 1 1.5 1.5 2.5 3
[0052]
8 Drilling Fluid 1 hr. 4 hr. 8 hr. 24 hr. 365 + 0.5% M100 1.5 2 3.5
4 365 + 1% M100 1 1.5 1.5 3.5
[0053] As set forth above, the bentonite pellets generally were
more stable in the drilling fluids of Example 1 than in the control
drilling fluids.
Example 2
MeG+Maltodextrin+NaCl
[0054] Drilling fluids were prepared using MeG, maltrodextrin, and
sodium chloride. The bentonite stability test was repeated for each
fluid, and the following results were obtained. Sodium chloride
percentages in these tables express weight percent sodium chloride
by dry basis weight of methyl glucoside.
9 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 24 hr. 365 + 5% 1 1 1 1.5
2 M040 + 10% NaCl 365 + 5% 1 1 1.5 1.5 2 M100 + 10% NaCl 365 + 5% 1
1.5 1.5 2 4 M180 + 10% NaCl
[0055]
10 Drilling Fluid 1 hr. 2 hr. 4 hr. 20 hr. 30 hr. 365 + 1% 1.5 1.5
1.5 2 3 M040 + 5% NaCl 365 + 3% 1 1 1.5 2 3 M100 + 5% NaCl
[0056]
11 Drilling Fluid 1 hr. 4 hr. 8 hr. 24 hr. 365 + 0.5% M040 + 2%
NaCl 1.5 1.5 2.5 3.5 365 + 1% M100 + 2% NaCl 1 1.5 1.5 3 365 + 0.5%
M100 + 5% NaCl 1.5 2 2 3.5 365 + 1% M100 + 5% NaCl 1 1.5 1.5
3.5
[0057] As seen, the addition of sodium chloride to the drilling
fluid rendered the fluid retention less aggressive toward the
bentonite pellets.
Example 3
MeG+HC
[0058] Drilling fluids were prepared using MeG and the
hemicellulose fraction of alkaline treated corn hulls. The
bentonite stability tests were repeated, and the following examples
were obtained. Hemicellulose percentages in these tables are
expressed as weight percent dry hemicellulose provided in the HC
solution by dry basis MeG.
12 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 365 + 0.6% hemicellulose
1 1 1 1.5 365 + 0.6% hemicellulose 2.5 3.5 4 4.5 (solution diluted
to 50%)
[0059]
13 Drilling Fluid 1 hr. 2 hr. 4 hr. 20 hr. 30 hr. 365 + 1% 1 1 1 2
2.5 hemicellulose
[0060]
14 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 24 hr. 48 hr. 207 + 0.5%
1 1 1 1 1.5 1.5 hemicellulose 365 + 0.6% 1 1 1 1.5 -- --
hemicellulose
[0061] As seen, the bentonite pellets were substantially more
stable in the drilling fluids prepared using MeG and hemicellulose
than in the drilling fluids prepared using only MeG.
Example 4
[0062] MeG+HC+NaCl
[0063] Drilling fluids were prepared using MeG, the hemicellulose
and sodium chloride. The bentonite stability tests were repeated
and the following results were obtained.
15 Drilling Fluid 1 hr. 2 hr. 4 hr. 20 hr. 30 hr. 365 + 1% 1 1 1
1.5 2 hemicellulose + 5% NaCl
[0064]
16 Drilling Fluid 1 hr. 4 hr. 8 hr. 24 hr. 32 hr. 56 hr. 365 + 0.5%
1 1.5 2 2 2.5 3 hemicellulose + 2% NaCl 365 + 1% 1 1 1.5 1.5 2 2.5
hemicellulose + 5% NaCl
[0065] As seen, the bentonite pellets were substantially more
stable in the drilling fluids thus prepared then in the control
drilling fluids. Addition of salt to the drilling fluid reduced the
aggressiveness of the fluid towards the bentonite pellets.
Comparative Examples 1-11
[0066] Drilling fluids were prepared using MeG and other organic
additives in accordance with the following table. The bentonite
stability test was repeated for each drilling fluid, giving the
following results:
17 Drilling Fluid 1 hr. 2 hr. 4 hr. 8 hr. 24 hr. 365 + 10% NaCl* 2
2.5 3.5 4 5 365 at pH 10 2.5 3 3.5 4 5 365 + 5% 2 2.5 3 3 --
hydroxy-propyl starch* 365 + 2% 2 2.5 2.5 4 -- corn starch* 365 +
2% 1.5 2 2.5 3.5 4.5 solubilized starch* 365 + 2% 2 2.5 3.5 4 4.5
polyethylene oxide* 365 + 2% 1.5 2.5 3.5 4 4.5 ethoxylated starch*
365 + 2% 1.5 2 3 4 4.5 acid modified starch* 365 + 2% 1.5 2 3.5 4
4.5 cationic starch* 365 + 2% 1.5 2 3 4.5 -- sum arabic* 365 + 2% 1
1 1.5 2 -- guar gum* *dry basis MeG.
[0067] As seen, the bentonite pellets generally were not as stable
in the drilling fluids of the comparative examples as in the
drilling fluids of the invention. These results demonstrate the
surprising benefits of using maltodextrin and/or hemicellulose as a
borehole stability promoter as compared with other organic
species.
Example 5
Water Activity
[0068] The water activity, or relative humidity that exists in the
space above the drilling fluid in an enclosed container, was
evaluated for each of the drilling fluids of the invention and for
control drilling fluids. It is believed that the stability of
wellbore formations in a drilling fluid generally improves as the
water activity value of the drilling fluids decreases.
[0069] The following results were obtained:
18 Water activity @ 25.degree. C. Drilling Fluid (Control) Pure
H.sub.20 1.01 (as measured) MeG-365 0.864 MeG-207 0.789 MeG-207
diluted to 65% solids 0.851 Drilling Fluid (Invention) MeG-207 +
0.5% hemicellulose.sup.(1) 0.780 MeG-365 + 0.5%
hemicellulose.sup.(1) 0.889 MeG-365 + 1% hemicellulose.sup.(1)
0.836 MeG-365 + 2% hemicellulose.sup.(1) 0.816 MeG-365 + 0.5%
hemicellulose.sup.(1) + 2% NaCl.sup.(2) 0.810 MeG-365 + 0.5%
hemicellulose.sup.(1) + 5% NaCl.sup.(2) 0.727 MeG-365 + 1%
hemicellulose.sup.(1) + 5% NaCl.sup.(2) 0.768 MeG-365 + 0.5%
Maltodextrin.sup.(2) 0.844 MeG-365 + 1% Maltodextrin.sup.(2) 0.855
MeG-365 + 2% Maltodextrin.sup.(2) 0.845 MeG-365 + 0.5%
Maltodextrin.sup.(2) + 2% NaCl.sup.(2) 0.820 MeG-365 + 0.5%
Maltodextrin.sup.(2) + 5% NaCl.sup.(2) 0.759 MeG-365 + 1%
Maltodextrin.sup.(2) + 2% NaCl.sup.(2) 0.811 MeG-365 + 1%
Maltodextrin.sup.(2) + 5% NaC.sup.(2)l 0.756 .sup.(1)by net basis,
on dry MeG basis. .sup.(2)On dry basis MeG.
Example 6
[0070] A drilling fluid comprising MeG-365, 5% MALTRIN.RTM. M040
(on dry basis MeG), and 0.6% hemicellulose (on dry basis
hemicellulose) is prepared.
Example 7
[0071] A drilling composition comprising 50% polyglycerine, 20%
water, 1% hemicellulose (dry basis), and 29% MeG (2:1
.alpha.:.beta.)(dry basis) is prepared. The MeG is obtained from
MeG-365.
Example 8
[0072] A drilling composition comprising 50% polyglycerine, 20%
water, 1% maltodextrin (MALTRIN.RTM. M180) (dry basis), and 29% MeG
(2:1 .alpha.:.beta.)(dry basis) is prepared. The MeG is obtained
from MeG-360.
Example 9
[0073] A composition comprising 65% MeG and 2.5% hemicellulose is
prepared (balance water). The composition is suitable for addition
to seawater to form a drilling fluid.
Example 10
[0074] A drilling fluid comprising the following ingredients is
prepared:
19 350 lbs. Fresh Water 20 lbs. Bentonite 4 lbs. Lime 3 lbs.
Polysaccharide deflocculant 0.75 lb. KOH 1-2 lbs. Drilling Starch
0.25 lb. Lignite 10-30 lbs. MeG (2:1 .alpha.:.beta.) 0.1-0.3 lbs.
Hemicellulose
Example 11
[0075] A composition comprising the following ingredients is
prepared:
20 350 lbs. Fresh Water 20 lbs. Bentonite 4 lbs. Lime 3 lbs.
Polysaccharide Deflocculant 0.75 lb. KOH 1-2 lbs. Drilling Starch
0.25 lb. Lignite 10-30 lbs. MeG (2:1 .alpha.:.beta.) 0.1-0.3 lbs.
Maltodextrin (MALTRIN .RTM. M040)
Example 11
[0076] A composition comprising the following ingredients is
prepared:
21 250 lbs. Sea Water 11 lbs. KCl 100 lbs. Bentonite 0.50 lb. NaOH
1-4 lbs. Drilling Starch 10-30 lbs. MeG (2:1 .alpha.:.beta.)
0.1-0.3 lbs. Hemicellulose
Example 13
[0077] A composition comprising the following ingredients is
prepared:
22 250 lbs. Sea Water 11 lbs. KCl 100 lbs. Bentonite 0.50 lb. NaOH
1-4 lbs. Drilling Starch 10-30 lbs. MeG (2:1 .alpha.:.beta.)
0.1-0.3 lbs. Maltodextrin
Example 14
[0078] Corn hulls from a corn wet milling operation are wet
screened through a U.S. No. 6 screen at about 50.degree. C. using
sufficient water to substantially remove the fine fiber, most of
the starch and some of the protein and lipid material present. The
hulls remaining on the screen are then slurried in water and the pH
of the slurry is adjusted with lime to pH 6.5 and treated at
79.degree. C. for 1 hour with a B. subtilis alpha-amylase (obtained
from Genencor International) at a dosage of about 3 liquefons/g
(units as defined by Genencor) of hull solids. The hulls are
filtered, washed and dried to a moisture range of 5 to 10 percent
in a forced air oven at 70.degree. C.
[0079] Fifty-two grams (50.6 g d.b.) of the hulls are slurried in
1000 ml of 69 percent aqueous ethanol (v/v) containing 5 g of
reagent grade NaOH, and the slurry is heated in a Parr model 4522
pressure reactor at 100.degree. C. for 3 hours. The reaction
mixture, at a temperature of about 50.degree. C., is then filtered
through a Buchner funnel using Whatman No. 3 filter paper.
[0080] The filter cake is then extracted by refluxing at about
82.degree. C. with 1000 ml of 69 percent aqueous ethanol (v/v) for
one hour, and the mixture is filtered at a temperature of about
50.degree. C. through a Buchner funnel using Whatman No. 3 paper.
The filter cake is next slurried in 1000 ml of 69 percent aqueous
ethanol (v/v), and the slurry is adjusted with diluted HCl to pH 2
and is filtered as above. The filtrate is next combined with the
filtrates from the two previous filtrations. The combined filtrates
then are adjusted to pH 2 with HCl, and evaporated to dryness. The
residue is dried in a vacuum oven at 70.degree. C.
[0081] To extract the hemicellulose, the filter cake from the above
procedure is slurried in 1000 ml of deionized water, held at room
temperature for about two hours, and filtered through a coarse
sintered glass funnel. This procedure is repeated a second time.
The filtrates from these two extractions are combined and
concentrated to about 10 percent solids by evaporation of the water
on a vacuum rotary evaporator at a temperature of 40.degree. C. and
a vacuum of about 20 inches of mercury. The concentrated
hemicellulose solution is then dried on a drum drier having a
surface temperature of 130.degree. C., and the dried hemicellulose
is ground in a Waring blender.
[0082] The hemicellulose is added to 10 kg MeG-365 in an amount of
2.5% hemicellulose (on dry basis MeG) to form a drilling fluid.
Example 15
[0083] Various drilling fluids were prepared as set forth in detail
below. The ability of each fluid to stabilize shale was evaluated
by measuring the amount of time required for a bentonite clay
pellet to break down (as was determined when the pellet had reached
or passed "4" on the scale discussed in the earlier Examples). For
control purposes, drilling fluids that included methyl glycoside
but that did not include a borehole stability promoter were
evaluated. The compositions of the drilling fluids that were
prepared and the results of the stability tests are set forth
below.
23 Drilling Fluid Time to pellet breakdown 365 <1 day 207 <2
days
[0084]
24 Time to pellet Drilling Fluid breakdown 365 + 4% M040 + 4% KOH 7
days 365 + 4% CMS + 4% KOH >25 days 365 + 2% CMS + 4% KOH 5 days
365 + 1% CMS + 4% KOH 4 days 365 + 2% CMS + 2% KOH 4 days 365 + 1%
CMS + 2% KOH 3 days
[0085] CMS is carboxymethyl starch having a DS of 0.2
[0086] It is thus seen that both the maltodextrin and the
carboxymethyl starch tested functioned as borehole stability
promoters.
[0087] As a control for Examples 16 through 20, the following
drilling fluids were evaluated.
25 Drilling Fluid 4 hr. 8 hr. 16 hr. MeG-206 3 3.5 4 MeG-207 1.5 2
2
Example 16
[0088] Five hundred g dry basis corn hulls containing 766 g water
was added to sufficient water to give a total weight of 5000 g. The
stirred slurry was heated and maintained at 82.degree. C. to
96.degree. C. for two hours. The hot slurry was then filtered
through a No. 60 Mesh A.S.T.M.E. Standard Testing Sieve. The
retained solids were subjected to a second treatment of slurrying,
stewing, and filtering, and then to a third treatment of slurrying,
stewing, and filtering. The retained solids were crumbled, placed
on screens, and allowed to air-dry at room temperature.
[0089] One hundred g dry basis of the treated corn hulls thus
obtained were added to a solution already containing 1610 mL 190
proof ethanol, 390 mL water, and 20 g 50% NaOH in a reaction flask
equipped with a reflux condenser and mechanical stirring. The
stirred reaction mixture was heated to the reflux temperature and
then refluxed for three hours at the reflux temperature of
78.degree. C. The reaction mixture was cooled to 40.degree. C., and
then it was vacuum filtered across a 40-60.degree. C. fritted glass
funnel. The retained solids were returned to the reaction flask and
reslurried in a solution already containing 1610 mL 190 proof
ethanol and 390 mL water. The slurry was heated to reflux
temperature and then refluxed for one hour at the reflux
temperature of 78.degree. C. The reaction mixture was cooled to
20.degree. C., and then it was vacuum filtered across a
40-60.degree. C. fritted glass funnel. The retained solids were
reslurried in a solution already containing 1610 mL 190 proof
ethanol and 390 mL water at 20.degree. C., and then the pH of the
slurry was adjusted to 6.5 with 5.8N hydrochloric acid. The slurry
was then vacuum filtered across a 40-60.degree. C. fritted glass
funnel.
[0090] The retained solids were reslurried in 2000 mL water in a
reaction flask equipped with a reflux condenser and mechanical
stirring. The stirred mixture was heated to the reflux temperature
and then refluxed for two hours at the reflux temperature of
98.degree. C. The mixture was cooled to 50.degree. C., and then was
vacuum filtered across a 40-60.degree. C. fritted glass funnel. The
filtrate, referred to as FILTRATE A, which contained corn hull
hemicellulose, was retained. The retained solids were reslurried in
2000 mL water in a reaction flask equipped with a reflux condenser
and mechanical stirring. The stirred mixture was heated to the
reflux temperature and then refluxed for two hours at the reflux
temperature of 98.degree. C.
[0091] The mixture was cooled to 50.degree. C., and then it was
vacuum filtered across a 40-60.degree. C. fritted glass funnel. The
filtrate, referred to as FILTRATE B, containing the corn hull
hemicellulose, was retained. The retained solids were reslurried in
2000 mL water in a reaction flask equipped with a reflux condenser
and mechanical stirring. The stirred mixture was heated to the
reflux temperature and then refluxed for two hours at the reflux
temperature of 98.degree. C. The mixture was cooled to 50.degree.
C., and then it was vacuum filtered across a 40-60.degree. C.
fritted glass funnel. The filtrate, referred to as FILTRATE C,
containing the corn hull hemicellulose was retained. The combined
FILTRATES A, B, and C containing the corn hull hemicellulose were
assayed to contain 54.5 g solids. Combined filtrates A, B, and C
then were spray dried. The resulting hemicellulose was formulated
into an adhesive paste by mixing 15 parts weight hemicellulose of
the spray-dried hemicellulose with 85 parts water.
[0092] A drilling fluid comprising 48.5% MeG-206 (60% solids),
46.5% desugared sugar beet molasses, and 3% hemicellulose was
prepared as described above and evaluated for bentonite pellet
stability. The following results were obtained.
26 4 hr. 8 hr. 16 hr. 1.5 2 2
[0093] As seen, this product established satisfactory results.
Example 17
[0094] A drilling fluid composed of 48% MeG-206 (60% solids), 48%
desugared sugar beet molasses (60% solids) and 4% corn hull
hemicellulose prepared as in Example 16 was prepared and evaluated
for bentonite pellet stability. The following results were
obtained.
27 4 hr. 8 hr. 16 hr. 2 1.5 1.5
[0095] As seen, this product exhibited excellent results.
Example 18
[0096] A drilling fluid composed of 97% MeG-206 and 3% corn hull
hemicellulose prepared as in Example 16 was prepared and evaluated
for bentonite pellet stability.
[0097] The following results were obtained.
28 4 hr. 8 hr. 16 hr. 2 3 3.5
[0098] As seen, this product exhibited somewhat satisfactory
results.
Example 19
[0099] A drilling fluid comprising 50% MeG-206 and 50% desugared
sugar beet molasses was prepared and evaluated for bentonite pellet
stability. The following results were obtained.
29 4 hr. 8 hr. 16 hr. 1.5 2.5 2.5
[0100] As seen, this product exhibited satisfactory results.
Example 20
[0101] A drilling fluid comprising 49% MeG-206, 49% desugared sugar
beet molasses, and 2% corn hull hemicellulose prepared in
accordance with the teachings of U.S. Pat. No. 6,063,178 to
McPherson et al., assignor to Grain Processing Corporation of
Muscatine, Iowa was prepared and evaluated for bentonite pellet
stability. The following results were obtained.
30 4 hr. 8 hr. 16 hr. 1 1.5 1.5
[0102] As seen, this product exhibited excellent results.
Example 21
[0103] The following drilling fluids were evaluated for bentonite
pellet stability at 16 hours. The results are shown following the
description of the drilling fluid. In this example, the
hemicellulose was a dry solid prepared in accordance with the
description provided in prior U.S. Pat. No. 6,063,178.
31 Drilling Fluid 16 hr. MeG-206 4 Desugared Sugar Beet Molasses
(60% solids) 2.5 98% MeG-206 + 2% hemicellulose 3 98% Desugared
Sugar Beet Molasses 2 (60% solids) + 2% hemicellulose
Example 21
[0104] A drilling fluid comprising desugared cane sugar molasses
that has been diluted to 30% solids with salt water is circulated
through a drill string.
Example 23
[0105] The following drilling fluids were prepared and evaluated
for shale stability as in the foregoing examples.
[0106] Example 23A Meg 206
[0107] Example 23B Sorbitol (60% aqueous solution)
[0108] Example 23C Meg 206, 3% crude hemicellulose (as is)
[0109] Example 23D Sorbitol+3% crude hemicellulose (as is)
[0110] The following results were observed.
32 Example 1 hr. 2 hr. 4 hr. 6 hr. 8 hr. 23A 1.5 1.5 3 3.5 4 23B 2
2 2 2.5 3 23C 1 1 1 1 1 23D 1 1 1 1 1
[0111] Thus, the foregoing general objects have been satisfied. The
invention provides a drilling fluid that is suitable for use in
connection with borehole drilling. The invention further provides a
drilling apparatus and method that incorporate the improved
drilling fluid.
[0112] While particular embodiments of the invention have been
shown, it will be understood that the invention is not limited
thereto since modifications may be made by those skilled in the
art, particularly in light of the foregoing teachings. For
instance, the pH or salt content of the disclosed fluids may be
modified, or, more generally, other components may be altered. It
is therefore contemplated that the invention encompasses the
subject matter of the following claims and equivalents thereof. All
references cited herein are hereby incorporated by reference in
their entireties.
* * * * *