CA2088344C

CA2088344C - Drilling fluid additive and method for inhibiting hydration

Info

Publication number: CA2088344C
Application number: CA 2088344
Authority: CA
Inventors: Arvind D. Patel; Henry C. Mclaurine
Original assignee: MI LLC
Current assignee: MI LLC
Priority date: 1992-04-10
Filing date: 1993-01-28
Publication date: 2004-08-03
Anticipated expiration: 2013-01-28
Also published as: CA2088344A1

Abstract

This invention relates to drilling fluid. additives that suppress clay swelling within a subterranean well and to methods for controlling clay swelling during the drilling of a subterranean well. A trihydroxy alkyl amine is reacted with an alkyl halide or a water soluble quaternary amine to form a quaternized trihydroxy alkyl amine. The reaction products can also include condensed reaction products of quaternized trihydroxy alkyl amines.
The quaternized reaction products are characterized by low toxicity and compatibility with anionic drilling fluid components. The products are added to water base drilling fluids which are circulated throughout a well.
The drilling fluid additives and the method of controlling clay swelling provide for improved control of the rheological properties of drilling fluids along with increased environmental and drilling fluid compatibility.

Description

MIDR:473 METHOD FOR INHIBITING HYDRATION
The invention relates to drilling fluid additives which suppress clay swelling within a subterranean well.
The invention is particularly directed to hydration inhibiting additives for drilling fluids comprising hydroxyalkyl quaternary ammonium compounds which are compatible with anionic polymers and are environmentally acceptable.
In rotary drilling of subterranean wells numerous functions and characteristics are expected of a drilling fluid. A drilling fluid should circulate throughout the well and carry cuttings from beneath the bit, transport the cuttings up the annulus, and allow their separation at the surface. At the same time, the drilling fluid is expected to cool and clean the drill bit, reduce friction between the drill string and the sides of the hole, and maintain stability in the borehole's uncased sections. The drilling fluid should also form a thin, low-permeability filter cake that seals openings in farmations penetrated by the bit and act to reduce the unwanted influx of formation fluids from permeable rocks.
Drilling fluids are typically classified according to their base material. In oil-base fluids, solid particles are suspended in oil, and water or brine may be emulsified with the oil. The oil is typically the continuous phase.
In water-base fluids, solid particles are suspended in water or brine, and oil may be emulsified in the water.

~~~u~t~

The water is typically the continuous phase. Oil-base fluids are generally more effective in stabilizing water-sensitive shales than water-base fluids. However, environmental concerns have limited the use of oil-base drilling fluids. Accordingly, oil drilling companies have increasingly focused on water-base fluids.
Three types of solids are usually found in water base drilling fluids: (1) clays and organic colloids added to provide necessary viscosity and filtration properties, (2) heavy minerals whose function is to increase the drilling fluid's density, and (3) formation solids that become dispersed in the drilling fluid during the drilling operation.
The formation solids that become dispersed in a drilling fluid are typically the cuttings produced by the drill bit's action and the solids produced by borehole instability. Where the formation solids are clay minerals that swell, the presence of either type of formation solids in the drilling fluid can greatly increase drilling time and costs. The overall increase in bulk volume accompanying clay swelling impedes removal of cuttings from beneath the drill bit, increases friction between the drill string and the sides of the borehole, and inhibits formation of the thin filter cake that seals formations.
Clay swelling can also create other drilling problems such as loss of circulation or pipe sticking that can slow drilling and increase the drilling costs.
'In the North Sea and the United States Gulf Coast, drillers commonly encounter argillaceous sediments in which the predominant clay mineral is sodium montmorillonite (commonly called "gumbo shale"). Gumbo shale is notorious for its swelling. Thus, given the frequency in which gumbo shale is encountered in drilling subterranean wells, the -3- ~~'i~~~l~
development of a substance and method for reducing play swelling has long been a goal of the oil and gas exploration industry.
The mechanisms of clay swelling are well known. Clay minerals are crystalline in nature. The structure of a clay's crystals determines its properties. Typically, clays have a flaky, mica-type structure. Clay flakes are made up of a number of crystal platelets stacked face-to-face. Each platelet is called a unit layer, and the surfaces of the unit layer are called basal surfaces.
A unit layer is composed of multiple sheets. One sheet is called 'the octahedral sheet, and is composed of either aluminum or magnesium atoms octahedrally coordinated with the oxygen atoms of hydroxyls. Another sheet is called the tetrahedral sheet. The tetrahedral sheet consists of silicon atoms tetrahedrally coordinated with oxygen atoms.
Sheets within a unit layer link together by sharing oxygen atoms. When this linking occurs between one octahedral and ene tetrahedral sheet, one basal surface consists of exposed oxygen atoms while the other basal surface has exposed hydroxyls. It is also quite common for two tetrahedral sheets to bond with one octahedral sheet by sharing oxygen atoms. The resulting structure, known as the Hoffman structure, has an octahedral sheet that is sandwiched between the two tetrahedral sheets. As a result, both basal surfaces in a Hoffman structure are composed of exposed oxygen atoms.
The unit layers stack together face-to-face and are held in place by weak attractive forces. The distance between corresponding planes in adjacent unit layers is called the c-spacing. A clay crystal structure with a unit ~~ JJ~~~~:
layer consisting of three sheets typically has a c-spacing of about 9.5 x 10-~ mm.
In clay mineral crystals, atoms having different valences commonly ;gill be positioned within the sheets of the structure to create a negative potential at the crystal surface. In that case, a ration is adsorbed on the surface. These adsorbed rations are called exchangeable rations because they can trade places with other rations when the clay crystal is in water. In addition, ions can also be adsorbed on the clay crystal edges and exchange with other ions in the water.
The type of substitutions occurring within the clay crystal structure and the exchangeable rations adsorbed on the crystal surface greatly affect clay swelling, a property of primary importance in the drilling fluid industry. Clay swelling is a phenomenon in which water molecules surround a clay crystal structure and position themselves to increase the structure's c-spacing. Two types of swelling can occur.
Surface hydration is one type of swelling in which water molecules are adsorbed on crystal surfaces. Hydrogen bonding holds a layer of water molecules to the oxygen atoms exposed on the crystal surfaces. Subsequent layers of water molecules then line up to form a quasi--crystalline structure between unit ~.ayers which results in an increased c-spacing. All types of clays swell in this mariner.
Osmotic swelling is a second type of swelling. Where the concentration of rations between unit layers in a clay mineral is higher than the ration concentration in the surrounding water, water is drawn between the unit layers and the c-spacing is increased. Osmotic swelling results in larger overall volume increases than surface hydration.

~~~U~x However, only certain clays, like sodium montmorillonite, swell in this manner.
Exchangeable cations found in clay minerals greatly impact the amount of swelling that takes place. The exchangeable cations compete with water molecules for the available reactive sites in the clay structure. Cations with high valences are more strongly adsorbed than ones with low valences. Thus, clays with low valence exchangeable cations will swell more than clays whose exchangeable cations have high valences. Sodium cations are the exchangeable cations in gumbo shale. As the sodium cation has a low valence, it easily disperses into water, thereby giving gumbo shale its notorious swelling characteristics.
Although a number of compounds are known for their effectiveness in inhibiting reactive shale formations, _ several factors affect the practicality of using swelling inhibitor additives in drilling fluids. First, the inhibitor must be compatible with the other drilling fluid components. The driller of subterranean wells must be able to control the rheological properties of drilling fluids by using additives such as bentonite, anionic polymers and weighting agents. Thus, drilling fluid additives should also provide desirable results but should not inhibit the desired performance of other additives. However, many swelling inhibitors will react with other drilling fluid components, resulting in severe flocculation and precipitation.
Second, current drilling fluid components must be environmentally acceptable. As drilling operations impact on plant and animal life, drilling fluid additives should have low toxicity levels and should be easy to handle and to use to minimize the dangers of environmental pollution -6- y and harm to operators. Moreover, in the oil and gas industry today, it is desirable that additives work both onshore and offshore and in fresh and salt water environments.
Several attempts have been made to improve the shale inhibition of water-base drilling fluids. One method to reduce clay swelling is to use salts in drilling fluids, such as potassium chloride and calcium chloride. Although, salts generally reduce the swelling of clays, salts also tend to flocculate the clays resulting in both high fluid losses and an almost complete loss of thixotropy. Further, increasing salinity often decreases the functional characteristics of drilling fluid additives.
In order to avoid the disadvantages of salts as swelling inhibitors, other additives have been examined.
Other methods examined for controlling clay swelling have _ centered on the use of surfactants in drilling fluids.
Since they are adsorbed on the surfaces of clays, surfactants added to drilling fluids compete with water molecules for clay reactive sites and thus serve to reduce clay swelling. Surfactants can be either cationic, anionic, or nonionic. Cationic surfactants dissociate into organic cations and inorganic anions, while anionic surfactants dissociate into inorganic cations and organic anions. Nonionic surfactants do not dissociate. Cationic polymers have proven to be generally more effective shale inhibitors than anionic polymers.
Several cationic polymer systems for water-base fluids have been proposed. One system, a brine-base system, examined two dialkyl dimethyl quaternary ammonium salts (diquats) of the following general formula:

CH3 Cl CH3_- ( CHZ ) x:-CHz-N'-CHZ- ( CHZ ) X-CHI

wherein x=10 or 16. Although the shorter chain diquat (x=10) was more effective in recovering shale than the longer chain diquat (x=16), the tests indicated that the ability of the diquat.s to inhibit shale appeared to be hindered by their limited solubility .in water.
Another attempt examined three trimethyl alkyl ammonium chlorides (quests) of i~he following general formula:
CH;, C1-CH3 N+-CHZ (-CHZ ) X CH3 wherein x=10, 14 or ::~6.
The quest with the shortest chain (x=10) showed the best shale recovery. However, drilling fluids formulated using the quest in conjunction with potassium chloride in a drilling fluid formulation generated large amounts of foam. Consequently, the three quests were judged unsuitable for use in drilling.
Based on the failure of brine--base systems employing potassium chloride and quaternary compounds, alternative cationic polymers were evaluated. Cationic polymers were again used in conjunction with potassium chloride. The brine-base system employed potassium chloride and three _8__ additional quaternized polymers having the following formulas:
(I) OH CH3 Cl-- ( CH,-CH---CHZ-N+-) W

poly(dimethylamine-co-epichlorohdrin) (III
poly(N,N-di.methyl-3,S-dimethylene piperidinium chloride) (III) Jn N,~'CM3 H3C/..N
~-polyimidazoline Formula I exhibited the best shale recovery. A
drilling fluid formula was prepared using conventional viscosifiers, fluid loss additives, the shale inhibitor' of formula I anal potassium chloride. The cationic polymer was found to be incompatible with the conventional anionic additives, i.e., bentonite, xanthan gum, carboxy methyl cellulose (CMC), polyacrylates, etc. A non-ionic viscosifier, hydroxyethyl cellulose, and a non-ionic fluid loss agent, pregelatinized starch, were used as substitutes to overcome the incompatibility problem. Further details regarding the described brine-base systems described above are reported in Beihoffer et al., "The Development of an n~
H3C/ eCH3 _9_ Inhibitive Cationic Drilling Fluid for .'~l i.r.-Hole Coring Applications," SPE-19953 presented at the 1990 SPE/IADC
Drilling Conference held in Houston, Feb. 27-t~Iarch ?_, 1990, the subject matter of which may be referred to for further details.
Although the described cationic polymers are effective shale inhibitors, the incompatibility of the polymers with common anionic drilling fluid additives is a disadvantage.
Moreover, the cationic polymers are highly toxic. Since environmental concerns are of ever increasing importance, a search for compatible cationic polymers having low toxicity has resulted.
1_5 One effort identified two cationic polymers having low toxicity and good shale inhibition when used together. The first polymer is a high molecular weight cationic polyacrylamide. The second polymer is a quaternary polyamine. In the drilling fluid formulation, the high molecular weight polyacrylamide was u:>ed for shale encapsulation, and the low molecular weight polyamine was used for swelling suppression. Although the two polymers had low toxicity, they were totally incompatible with anionic polymers in fresh water. Adding salts, such as sodium chloride, to increase the ionic concentration, alleviated the precipitation problem. I(owever, the polymers also caused flocculation of the bentoni.te component of the drill ing f Lu i d . 'I'I~ i ;> probl e:~~ was corrected by adding polyvinyl alcohol to tire f ormulation as a deflocculant. Additional details of r_he desc~_~ibed system, including toxicity tests and additional bac~:ground on water adsorption and shale inhibiti«r. ~:~c~ in I?etz et al., "An Environmentally Acceptable and yield-Practical, Cationic Polymer Mud System," SPE-23064 presented at the 3 5 Of f shore Europe Conference he 1d i n Aberdeen , .September 3-E~

-1.~-1991, the subject matter of which may be referred to for further details.
Although research has identified cationic polymers which are effective shale inhibitors for use as drilling fluid additives, other cationic polymers with improved compatibility and low taxicity are desired.
The present invention comprises drilling fluid additives for reducing the problems associated with clays which swell in the presence of water. A particular advantage of the additives of the present invention is their compatibility with common anionic drilling fluid components their low toxicity.
Generally, the additives of the invention are quaternary alkyl amines which are the reaction products of a trihydroxy alkyl. amine of the following general formula:
CHI, ) n--~H
HO--CCHZ)ri N-(CHI)"--0H
wherein n=1-3, and an alkyl halide or water soluble quaternary amine of the following general formula:
R-X
wherein R is selected from the group consisting of alkyl radicals having up to 4 carbon atoms, water soluble quaternary amines or combinations thereof, and X is a halogen selected from the group consisting of chlorine, bromine, iodine or combinations thereof. The reaction products are believed to be quaternary alkyl amines having the following general structure:

R.
X' HO- C CH2 ) n N+- C CHz ) n--OH
CHZ ) n-OH
wherein n, R and X are defined as above.
In addition, the additive can be the polymerized condensation product of the above described reaction products. The condensed product is believed to have the following general structure:
( CHz ) "-OH ( CHZ ) I,--0H
- (--0-- ( CHz ) ri N+- ( CHZ ) n---O--- C CHz ) n-N+- ( CHz ) n-O-) -X_ ~ X_ R R
wherein n, R, and X are defined as above.
The condensed trihydroxy quaternary amine product preferably has a molecular weight. ranging from about 200 to about 15,000 with a preferred molecular weight range' from about 350 to about 5000. However, for practical purposes the upper limit of the molecular weight is governed by maximum viscosities appropriate for polymer manufacture.
The present invention comprises drilling fluid additives for reducing the problems associated with clays which swell in the presence of water. A particular advantage of the additives of the present invention is their low toxicity and their compatibility with common anionic drilling fluid components.

Generally, the additives of the invention are quaternary i=rihydroxy alkyl amines. Particularly, preferred compounds are those which are the reaction product of a trihydroxy alkyl amine and an alkyl halide or another water' soluble quaternary amine obtained by reacting the compounds according to the following general reaction:
( CHZ ) ~ ---OH
HO- ( CHZ ) n-N- ( CH? ) n--OH + R-X >
R
Cl-HO---- ( CH2 ) n-_N+_ ( CH2 ) n-OH
CHz ) n---OH
wherein n=y-3, R is selected from the group consisting of alkyl radicals having up to 4 Carbon atoms, water soluble quaternary amines or combinations thereof, and X is a halogen selected from the group consisting of chlorine, bromine, iodine or combinations thereof, Preferred trihydroxy alkyl. amines are trimethanolamine, triethanolamine and tripropanolamine.
Especially preferred are quaternary trihydraxy alkyl amines, such as triethanolamine, reacted with an alkyl halide, such as methyl chloride. The product resulting from the reaction of triethanolamine and methyl chloride is the quaternary compound triethanolamine methyl chloride.
Another preferred embodiment is t;he reaction product of a trihydroxy alkyl amine with an another water soluble quaternary amine. For example, an effective diquat -1.3 -results from reacting triethanolamf.ne with a water soluble quaternary amine. Especially preferred water soluble quaternary amines are those having the following general formula:

R2 - N~ ~ R4 ..~ g X-wherein R1, RZ and R3 are alkyl groups having up to 3 carbon atoms and preferably 1 ~:0 2 carbon atoms, R4 is a hydroxy alk~~l having up to 4 carbon atoms, and X is a halogen selected from the group consisting of chlorine, bromine, iodine or combinations thereof.
In addition, the additive can be the polymerized condensation product of the above described reaction products. For example, the additive can be the condensed product of a trihydro~y alkyl quaternary amine having the following general formula:
( CH~'~ n--OH ( CHZ ) n-OH
- (--~- ( CHZ ) ri N+- ( CHI ) n--O--- ( CHl ) n-N+- ( CHz ) n-O-) -R R
wherein n=1-3, R is selected from the group consisting of alkyl radicals having up to 4 carbon atoms, water soluble quaternary amines, or combinations thereof, and X is a halogen selected from the group consisting of chlorine, bromine, iodine or combinations thereof.

~ G7 <3 s~ ~0 ;' ~.i :5 J :a '_'W_i _14_ The polymerized additives preferably have a molecular weight ranging from about 200 to about 15,000 with a preferred molecular weight ranging from about 350 to about 5000; however, for practical purposes the upper limit of the molecular weight is governed by maximum viscosities appropriate for polymer manufacture.
Methods of preparing quaternary amines are well known to those of ordinary skill in the art. In general, effective quaternary amines can be formed by heating the trihydroxy alkyl amine and alkyl halide, or other water soluble quaternary amine compound, to a temperature up to about 120°C, preferably between about 65°C and 120°C.
The reactants are maintained at the desired temperature up to about 10 hours, and preferably from about 2 to about 10 hours, or until the reaction is completed.
Generally, the reaction is complete when the tertiary amine value is approximately zero. This point can be _ determined by appropriate analytical techniques.
The polymerized additives are prepared generally by condensation polymerization. In a preferred method of preparing the polymerized additives, the trihydroxy alkyl amine component is first condensed, arid then the condensates are quaternized. Quaternization of the polymerized compounds is performed generally according to the procedure described above for the quaternization of the trihydroxy alkyl amine.
In performing the condensation procedure it is contemplated that several catalysts can be employed.
Generally, base catalysts should be employed, as opposed to acid catalysts. Catalysts which are believed to be effective in preparing polymeric additives having low toxicity and compatibility with anionic drilling fluid additives include, but are not limited to, sodium t)f3~
-15- ~~t~U.3 ~~
hydroxide, calcium hydroxide, potassium hydroxide and the like. Acid catalysts such as zinc chloride and calcium chloride do not appear to provide polymeric additives having the characteristics of low toxicity and compatibility. One theory is that the acid catalysts react with the hydroxy groups of the amine compounds.
However, only routine screening is required to identify catalysts appropriate for use in preparing the polymerized additives of the present invention having the characteristics of both compatibility with anionic drilling fluid additives and low toxicity.
The additives of the present invention are added to a drilling fluid in concentrations sufficient to deal with the clay swelling problems at hand. Concentrations between about 0.5 pounds per barrel (ppb) and 10 ppb are generally contemplated and are considered to be functionally effective.
It is essential that the drilling fluid ultimately selected and formulated for use in any particular well application be balanced to the conditions of the well.
Therefore, although the base ingredients remain the same, i.e., salt or fresh water and the drilling fluid additives of this invention, other companents can be added.
Specifically, materials generically referred to as gelling materials, thinners, fluid loss control agents, and weight materials are typically added to water base drilling fluid formulations. Of these additional materials each can be added to the formulation in a concentration as rheologically and functionally required by drilling conditions. Typical of gel materials used in aqueous based drilling fluids are high molecular weight polymers such as PHPA, bentonite and salt gel.

-16- ~ 3~'~3 ei v' Similarly, it has been found beneficial to add lignosulfonates as thinners for water base drilling fluids. Typically lignosulfonates, modified lignosulfonates, polyphosphates and tannins are added.
In other embodiments, low molecular weight polyacrylates can also be added as thinners. Thinners are added to a drilling fluid to reduce flow resistance and gel development. Other functions performed by thinners include reducing filtration and cake thickness, counteracting the effects of salts, minimizing the effects of water on the formations drilled, emulsifying oil in water, and stabilizing mud properties at elevated temperatures.
In addition, the drilling fluid composition of this invention may optionally contain a weight material. The quantity depends upon the desired density of the final composition. The preferred weight materials include, but _ are not limited to, barite, iron oxide, calcium carbonate and the like.
Finally, fluid loss control agents such as modified lignite, polymers and modified starches and cellulose can be added to the water base drilling fluid system of this invention.
As indicated, the additives of the invention are selected to have low toxicity and to be compatible with common anionic drilling fluid additives such as polyanionic cellulose (PAC), polyacrylates, polyacrylamides, lignosulfonates, xanthan gum, etc.
Several preferred embodiments of the invention were prepared for use in the following examples. In addition, several samples of condensates were prepared using various catalysts.

Triethanolamine methyl chloride was prepared by mixing 60 grams of triethanolamine with 20 grams of distilled water. 20 grams of methyl chloride was then added to the solution. The solution was heated at about 65°C for approximately 6 hours. Upon completion of the reaction the excess methyl chloride was evaporated. The reaction product is bela.eved to be as follows:

HO-CHy__CHz-N~._CHZ-CHl--OH
CH2-CHz--OH
In an alternative embodiment, an improved drilling fluid additive was formed by reacting triethanolamine with N,N,N-trimethyl-2-hydroxy--3-chloropropane ammonium chloride to form a water soluble diquat. The reaction was conducted generally according t:o the procedure set forth above for the preparation of the triethanolamine methyl chloride. The reactants have t:he following formulas:
CH2 CH~-OH CH", N-CHz-CHZ-0H + CH3~--N+-CHz-CH-CHZ-Cl CHZ-CHz-OH CH; OH
The resulting product is believed to have the following structure:
CH,3 CHZ-°CHZ-~OH
Cl' CH3-N+-CHI-CH-CHz-N+-CHZ CHZ-0H
CHI OH C'HZ-CHZ-OH

Condensates of triethanolamine were prepared using various catalysts, followed by quaternization of the condensates. In general, the condensate samples were prepared by mixing 200 grams of triethanolamine with 1 to 10% of the catalyst by weight. The catalysts employed in preparing the samples were sodium hydroxide, zinc chloride and calcium chloride.
Generally, the mixtures were heated between about 100°C to about 250°C for several hours until the desired condensation was achieved. The condensation water was distilled off during the reaction. The triethanolamine condensates were then quaternized generally according to the procedure set forth for the preparation of the triethanolamine methyl chloride described above.
The following table summarizes the samples prepared and discussed in the following examples.
_ TABLE 1 SAMPLE # COMPOUND
1 Triethanolamine-methyl chloride 2-7 Triethanolamine methyl chloride condensates 8 2-hydroxy-N,N,N-tri-methyl-N',N',N'-tris(2-hydroxy-ethyl) 1,3-propane diammonium dichloride The following table summarizes the viscosities of the triethanolamine condensates and the catalysts used in the preparation of each sample.

s7 n -, :e .a -19- ~r ~ L.'~ l.3 ~.i ~a~: l SAMPLE VISCOSITYfCPS) CATALYST

2 10,500 NaOH

3 20,000 CaCl2 4 12,500 ZnClz 5 30,000 CaCl2 6 20,000 NaOH

7 80,000 CaCl2 The viscosities indicated in Table 2 are for the triethanolamine cor~densates prior to quaternization.
The following examples are submitted for the purpose of illustrating the toxicity and performance characteristics of the present quaternized tr.ihydroxy alkyl amines and condensates thereof. The tests were conducted in accordance with the procedures in APT
Bulletin RP 13B-2, 1990. The following abbreviations are - sometimes used in describing the results discussed in the examples:
"PV" is plastic viscosity which is one variable used in the calculation of viscosity characteristics of a drilling fluid.
"YP" is yield point which is another variable used in the calculation of viscosity characteristics of drilling fluids.
"GELS" is a measure of the suspending characteristics and the thixotropic properties of a drilling fluid.
"F/L" is fluid loss and is a measure of fluid loss in milliliters of drilling fluid at 100 Asia.

EXample 1 Test results indicate that significant reductions in clay swelling can be obtained by adding the trihydroxy alkyl quaternary amines of the present invention to drilling fluids. The following experiment shows the inhibition of bentonite clay. The reduction in normal yield point and viscosity indicates the inhibition of clay.
The experiment was carried out by adding 8 grams of the test sample to 330 ml of distilled water. 50 grams of bentonite clay was then added to the solution and the mixture was sheared for 30 minutes in a Hammilton Beach-mixer and the rheology was measured by viscosity meter according to the APT procedure described above. The control contained only the bentonite clay and distilled water. The result: are summarized below in Table 3.

Rheology C 75 F.
RPM Sample 1 sample 6 Control 100 ~ 4 w 6 3 2 ___ 3 3 2 ___ PV/YP 4/~ 4/2 10/280 Example 2 Samples of the additives of the present invention were also tested for compatibility with common anionic drilling fluid components. A 7.-2% solution of anionic Trade-mark -21- ~~~~3r~~~i~
polymers (poly PAC LV - low viscosity polyanionic cellulose and PHPA - partially hydrolyzed polyacrylamide) were prepared in distilled water. 30 percent aqueous solutions of the samples of this invention were added to the polymer solutions. The precipitation of the anionic polymers from the solution indicated non-compatibility of the samples with anionic polymers. The results of the experiment are summarized in the following table.

COMPATIBILITY COMPATIBILITY

SAMPLE yPAC LV) y,PHPA) As indicated, polymers condensed employing the sodium hydroxide catalyst resulted in a condensed product that was compatible with anionic drilling fluid components. The acid catalyzed polymers failed to produce a product 'that was compatible. Having identified this characteristic in the preparation of the polymers of the present invention, those of ordinary skill in the art can identify by routine screening other suitable catalysts which produce the condensed trihydroxy alkyl quaternary amines having the characteristic of compatibility with anionic polymers.
Example 3 Testing was conducted to assess the toxicity levels associated with using the trihydroxy alkyl amines of the present invention. The United States Environmental Protection Agency has specified a Mysid shrimp bioassay as the means for assessing marine aquatic toxicity of drilling fluids. A detailed account of the procedure for measuring toxicity of drilling fluids is described in Duke, T.W., Parrish, P.R.; "Acute Toxicity of Eight Laboratory Prepared Generic Drilling Fluids to Mysids (Mysidopsis)" 1984 EPA-600/3-84-067, which may be referred to for further details.
For purposes of understanding the term "low toxicity" within the context of this application, the term refers to an LCSO of greater than 30,000. Although 30,000 has been the number used for purposes of evaluation it should not be considered a limitation on the scope of this invention. Rather, the tests provide a context for the use of the term "low toxicity" as used in the present invention which will be readily understood by _ those of ordinary skill in the art. Other LCso values may be viable in various environmental settings. An LCS~
value of greater than 30,000 has been equated to an "environmentally compatible" product. The results of the 96 hour toxicity tests are provided below.

SAMPLE LCS,~ ( 9 6 HOURS ) 1 > 1,000,000 ppm 2 > 1,000,000 ppm 3 < 10,000 ppm 4 < 10,000 ppm 5 < 10,000 ppm 6 > 1,000,000 ppm 7 < 10,000 ppm g > 1,000,000 ppm '~f~tj~~;~ ~;
-23- ~~J~J:~t3~~' The data indicate that the samples which are compatible with anionic polymers are non-toxic while the compounds which are non-compatible with anionic polymers are toxic. Accordingly, the trihydroxy alkyl quaternary amines, arid condensed products thereof, of the present invention are characterized by both compatibility with anionic polymers used in drilling fluids and low toxicity.
Example 4 Drilling fluids were prepared to test the effectiveness of the additives of the present invention in a simulated drilling fluid system. Drilling fluids were prepared using common drilling fluid additives and three tests were conducted.
Drilling fluid #1 contained 40 pounds per barrel _ bentonite gel in addition to other drilling fluid additives. After heat aging at 150°F., the viscosities were too thick to measure, indicating an unusable drilling fluid due to hydration of the clays. Drilling fluid #2 had 33.8 grams of potassium chloride and 10 pounds per barrel prehydrated gel slurry. Even w:Ithout extra gel, the theologies were higher than for drilling fluid #3 which contained prehydrated gel as well as 40 pounds per barrel bentonite gel. The theology tests for drilling fluid #3 indicate that the trihydroxy alkyl quaternary amines of the present invention prevented bentonite from swelling in a simulated drilling fluid system. The components of the three drilling fluids are provided below in Table 6.

Materials Fluid 1 Fluid Fluid 10 ppb Bentonite Slurry (prehydrated ) 152 ml 152.m1 152 ml Seawater 152 ml 152 ml 152 ml Lube 167 7.0 ml 7.0 ml 7.0 ml Polymer A --- --- 8.0 ml PolyPac Ultra Low 1.5 ml 1.5 ml 1.5 ml KC1 --- 33.8 g -__ Barite 60 60 60 KOH 0.75 0.75 0.75 XCD Polymer 0.5 0.5 0.5 Bentonite Gel 40 --- 40 Aged 16 hours @ 150 Rolling F., Table 7 below summarizes the rheology tests for the three drilling fluids.

a'~~ ~ '~
~~t~;~~~.~i Rheology RPM Fluid 1 Fluid 2 Fluid 3 600 * 50 43 300 * 34 24 200 * 27 17 100 * 19 9 6 * 6 2 3 * 5 1 PV * 16 19 yp * 18 5 GELS * 4/13 2/4 pH * 8.2 8,0 API F/L * 10.4 ml 8.8 ml * Viscosity to high to measure.
_ Although the preferred embodiment of this invention has been described in some detail, it should be appreciated that a variety of embodiments will be readily available to a person utilizing such drilling fluid additives for a specific end use. The description of the composition and method of this invention is not intended to be limiting on this invention, but is merely illustrative of the preferred embodiment of this invention, Other drilling fluid additives and methods of suppressing clay hydration which incorporate modifications or changes to that which has been described herein are equally included within this application.

Claims

1. A water-base drilling fluid for use in drilling wells through a formation containing a clay which swells in the presence of water, said drilling fluid comprising:
(a) a. weight material selected from the group consisting of barite, iron oxide, calcium carbonate, magnesium carbonate, and combinations thereof; and (b) the reaction product of a trihydroxy alkyl amine of the following general formula:
wherein n=1-3, with an alkyl halide or a water soluble quaternary amine of the following general formula:
R~X
wherein R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine, and X is a halogen selected from the group consisting of chlorine, bromine, iodine, and combinations thereof, said reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid components, said compatibility being demonstrated by failure of said reaction product to yield a precipitant in the presence of anionic polymers, said reaction product being present in the drilling fluid in sufficient concentration to reduce the swelling of a clay which swells in the presence of water.

2. The drilling fluid of claim 1 wherein the trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine.

3. The drilling fluid of claim 1 wherein R is methyl.

4. The drilling fluid of claim 1 wherein X is chlorine.

5. The drilling fluid of claim 1 wherein the trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine, and R is methyl and X is chlorine.

6. The drilling fluid of claim 1 wherein said water soluble quaternary amines are those having the following general formula:
wherein R1, R2 and R3 are alkyl groups having up to 3 carbon atoms, Y is a hydroxy alkyl having up to 4 carbon atoms, and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

7. The fluid of claim 1 wherein the reaction product is a trihydroxy alkyl amine alkyl halide or a trihydroxy alkyl amine quaternary amine having the following general formula:
wherein n=1-3, R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine, and X
is a halogen selected from the group consisting of chlorine, bromine and iodine, said reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid additives.

8. The drilling fluid of claim 7 wherein the reaction product is triethanolamine methyl chloride.

9. A water-base drilling fluid containing the condensed reaction product of a trihydroxy alkyl amine of the following general formula:
wherein n=1-3, with an alkyl halide or water soluble quaternary amine compound of the following general formula:
R-X
wherein R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine, and X is a halogen selected from the group consisting of chlorine, bromine, iodine, and combinations thereof, said condensed reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid components, said condensed product present in the drilling fluid in sufficient concentration to reduce the swelling of a clay which swells in the presence of water.

10. The drilling fluid of claim 9 wherein said trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine.

11. The drilling fluid of claim 9 wherein X is chlorine.

12. The drilling fluid of claim 9 wherein R is methyl.

13. The drilling fluid of claim 9 wherein the trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine, and R is methyl and X is chlorine.

14. The drilling fluid of claim 9 wherein said water soluble quaternary amines are those having the following general formula:
wherein R1, R2 and R3 are alkyl groups having up to 3 carbon atoms, Y is a hydroxy alkyl having up to 4 carbon atoms, and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

15. The drilling fluid of claim 9 wherein the condensed product is a trihydroxy alkyl quaternary amine having the following general formula:
wherein n=1-3, R is selected from the group consisting of alkyl radicals having up to 4 carbon atoms, water soluble quaternary amines, or combinations thereof and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

16. The drilling fluid of claim 15 wherein said condensed reaction product is the condensed form of triethanolamine methyl chloride.

17. A method of reducing swelling of clay in a well comprising circulating in the well a water base drilling fluid comprising:
(a) a weight material selected from the group consisting of barite, iron oxide, calcium carbonate, magnesium carbonate and combinations thereof; and (b) a functionally effective concentration of an additive formed from the reaction product of a trihydroxy alkyl amine of the following general formula:
wherein n=1-3, with an alkyl halide or water soluble quaternary amine compound of the following general formula:
R-X
wherein R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof, said reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid components, said compatibility being demonstrated by failure of said reaction product to yield a precipitant in the presence of anionic polymers.

18. The method of claim 17 wherein said trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine.

19. The method of claim 17 wherein X is chlorine.

20. The method of claim 17 wherein R is methyl.

21. The method of claim 17 wherein the trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine, and tripropanolamine, and R is methyl and X is chlorine.

22. The method of claim 17 wherein said water soluble quaternary amines are those having the following general formula:
wherein R1, R2 and R3 are alkyl groups having up to 3 carbon atoms, Y is a hydroxy alkyl having up to 4 carbon atoms, and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

23. The method of claim 17 wherein the reaction product is a trihydroxy alkyl amine alkyl halide or a trihydroxy alkyl amine quaternary amine having the following general formula:
wherein n=1-3, R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine and X is a halogen selected from the group consisting of chlorine, bromine and iodine, said additive being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid additives.

24. The method of claim 23 wherein the reaction product is triethanolamine methyl chloride.

25. A method of reducing swelling of clay in a well comprising circulating in the well a water-base drilling fluid containing a functionally effective concentration of an additive formed from the condensed reaction product of a trihydroxy alkyl amine of the following general formula:
wherein n=1-3, with an alkyl halide or water soluble quaternary amine compound of the following general formula:
R-X
wherein R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof, said condensed reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid components.

26. The method of claim 25 wherein the condensed product is a trihydroxy alkyl quaternary amine having the following general formula:
wherein n=1-3, R is selected from the group consisting of alkyl radicals having up to 4 carbon atoms, water soluble quaternary amines and combinations thereof and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

27. The method of claim 26 wherein said product is the condensed form of triethanolamine methyl chloride.

28. A method for controlling shale hydration in the drilling of subterranean wells comprising adding (a) a weight material selected from the group consisting of barite, iron oxide, calcium carbonate, magnesium carbonate and combinations thereof; and (b) adding a functionally effective amount of a quaternized trihydroxy alkyl amine to a drilling fluid, said amine comprising a reaction product of a trihydroxy alkyl amine of the following general formula:
wherein n=1-3, with an alkyl halide or a water soluble quaternary amine of the following general formula:
R-X
wherein R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof, said reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid components, said compatibility being demonstrated by failure of said reaction product to yield a precipitant in the presence of anionic polymers and injecting said drilling fluid into a subterranean well.

29. The method of claim 28 wherein said trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine.

30. The method of claim 28 wherein X is chlorine.

31. The method of claim 28 wherein R is methyl.

32. The method of claim 28 wherein the trihydroxy alkyl amine is selected from the group consisting of trimethanolamine, triethanolamine and tripropanolamine and R is methyl and X is chlorine.

33. The method of claim 28 wherein said water soluble quaternary amines are those having the following general formula:
wherein R1, R2 and R3 are alkyl groups having up to 3 carbon atoms, Y is a hydroxy alkyl having up to 4 carbon atoms and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

34. The method of claim 28 wherein the reaction product is a trihydroxy alkyl amine alkyl halide or a trihydroxy alkyl amine quaternary amine having the following general formula:
wherein n=1-3, R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine, and x is a halogen selected from the group consisting of chlorine, bromine and iodine, said additive being further characterised by (1) low toxicity and (2) compatibility with anionic drilling fluid additives.

35. The method of claim 34 wherein the reaction product is triethanolamine methyl chloride.

36. A method for controlling hydration in the drilling of subterranean wells comprising adding a functionally effective amount of the condensed form of the reaction product of a trihydroxy alkyl amine of the following general formula to a water-base drilling fluid:
wherein n=1-3, with an alkyl halide or water soluble quaternary amine compound of the following general formula:

R-X
wherein R is an alkyl radical having up to 4 carbon atoms, or a water soluble quaternary amine, and X is a halogen selected from the group consisting of chlorine, bromine, iodine, and combinations thereof, said condensed reaction product being further characterized by (1) low toxicity and (2) compatibility with anionic drilling fluid components, and injecting said drilling fluid into a subterranean well.

37. The method of claim 36 wherein the condensed product is a trihydroxy alkyl quaternary amine having the following general formula:
wherein n=1-3, R is selected from the group consisting of alkyl radicals having up to 4 carbon atoms, water soluble quaternary amines, and combinations thereof, and X is a halogen selected from the group consisting of chlorine, bromine, iodine and combinations thereof.

38. The method of claim 36 wherein said product is the condensed form of triethanolamine methyl chloride.