GB2108175A - Oil base fluids containing an organophilic clay gellant - Google Patents

Abstract

An oil base fluid containing the reaction product of an organic cationic compound and a smectite-type clay, wherein the organic cation has the formula: <IMAGE> where R1 is a beta , gamma -unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2-6 carbon atoms, or mixtures thereof; R2 is an alkyl group having 8-60 carbon atoms; R3 & R4 are individually a beta , gamma -unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2-6 carbon atoms, an alkyl group, an alkyl group having 1-22 carbon atoms or mixtures thereof, and X is phosphorus or nitrogen.

Description

SPECIFICATION Oil base fluids containing organophilic clays This invention relates to organophilic organiclay complexes which are dispersible in organic liquids to form a gel therein. More particularly such gels are useful in oil base muds and oil base packer fluids.

It is well known that organic compounds containing a cation will react with clays which contain a negative layer-lattice and exchangeable cations to form organophilic organic-clay products. The reaction of an organic cation containing at least one alkyl group of at least 10 carbon atoms with clay generally results in organoclays swellable in certain organic liquids.

Prior publications include U.S. Pat. No. 2,531,427, and U.S. Pat. No. 2,966,506, both incorporated herein by reference, and the book "Clay Mineralogy", 2nd Edition, 1 968 by Ralph E. Grim (McGraw Hill Book Co., Inc.), particularly Chapter 10, Clay-Mineral-Organic Reactions; pp. 356-368-lonic Reactions, Smectite; and pp.392-401 - Organophillic Clay-Mineral Complexes.

Maximum gelling (thickening) efficiency fronm these organoclays is achieved by adding a low molecular weight polar organic dispersing material to the composition. Such materials are disclosed in U.S. Patents: O'Halloran 2,677,661; McCarthy et al. 2,704,276; Stratton 2,833,720; Stratton 2,879,229; and Stansfield et al. 3,294,683. The use of such dispersion aids was found unnecessary when using particular organophilic clays derived from substituted quarternary ammonium compounds as disclosed in Finlayson et al. 4,105,578 and Finlayson 4,208,218.

Prior organophilic clays have exhibited limited broad range gelling utility due to fluctuating dispersion and viscosity properties. While the materials disclosed in U.S. Patent 4,105,578 have not shown such deficiencies, such materials are difficult and costly to produce.

Summary of the Invention An oil-base fluid of this invention which comprises an organophilic gellant comprising the reaction product of an oil phase, and from about 1 to about 50 Ibs. per barrel or an organic cationic compound and a smectite-type clay having a cation exchange capacity of at least 75 milliequivalents per 100 grams of said clay, the organic cationic compound containing:: a) a first member selected from the group consisting of a ss,y-unsaturated alkyl group, having less than 7 aliphatic carbon atoms and a hydroxyalkyl group having 2 to 6 carbon atoms and mixtures thereof, (b) a second group comprising a long chain alkyl group having 8 to 60 carbon atoms and (c) a third and fourth member selected from a group consisting of a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms, an arlkyl group, and an alkyl group having 1 to 22 carbon atoms and mixtures thereof; and wherein the amount of said organic cationic compound is from 90 to 140 milliequivalents per 100 grams of said clay, 100% active clay basis.

Detailed Description of the Invention The oil base fluid of the present invention consists of an oil phase and from about 1 to about 50 Ibs. per barrel of an organophilic clay gellant. Preferably, the fluid is non-aqueous.

A suitable oil phase of this invention may be crude petroleum and fractions thereof, including but not limited to diesel oil, kerosene, fuel oil, light lubricating oil fractions, and heavy naphtha having a boiling range between about 300 to 600"F. The preferred material is diesel oil.

The amount of the organophilic clay employed is that amount which is effective in obtaining the necessary degree of gellation (thickening) of the oil-base fluid for the intended application, that is, drilling fluid or packer fluid. The minimum concentration of organophilic clay needed to gel a particular fluid is dependent upon factors such as the type of organophilic clay used, the characteristics of the oil phase and emulsified water phase if any, and the maximum temperature to which the fluid is to be raised. The maximum concentration of organophilic clay is limited to that which will form a pumpable fluid.

The concentration of organophilic clay within the range of about 1 to 50 Ibs. per barrel (42 gallon barrel) will generally provide a sufficiently gelled fluid for broad applications. Preferably about 1 to about 10 Ibs. per barrel are employed in the preparation of oil-base drilling fluids whereas amounts from about 6 to 50 Ibs. per barrel have been found adequate for the preparation of oil-base packer fluids. It has been found that when the organophilic clay is mixed into the oil-base fluid, essentially complete gelling is achieved at low shear mixing. The resulting oil-base fluid is a stable oil-base fluid at surface temperatures below -20 F and down-hole temperatures up to 500"F. The formation of the stable fluid occurs in a matter of minutes following addition and low shear mixing of the organophilic clay in the oil base fluid.

A packer fluid is prepared in accordance with this invention by adding to an oil medium the organophilic clay. The composition of the packer fluid is regulated as discussed above to provide a pumpable composition. The optional emulsifiers, weighting agents, and fluid loss control materials may be added at any time. It is only necessary to obtain a stable the fluid prior to usage of the fluid. Once prepared, the packer fluid is transferred, such as by pumping, into a well bore or to tubing canulas, at least one portion of which is to be filled.

The oil-base drilling fluid can be prepared and used either before drilling commences or while drilling is in progress. The method of adding the ingredient to prepare the fluid is not critical.

Mixing is accomplished with conventional devices capable of employing a low shear mixing force. Greater mixing force may be employed even though not necessary. Once prepared, the drilling fluid is transferred, such as by pumping, into a well bore and circulated to the bit and through the borehole in contact with the walls thereof.

The organophillic clays of this invention can be prepared by admixing the clay, quaternary ammonium compound and water together, preferably at a temperature within the range from 20"C to 100'C, and most preferably from 35"C to 77"C for a period of time sufficient for the organic compound to react with the clay particles, followed by filtering, washing, drying and grinding. The quarternary compound is added in the desired milliequivalent ratio, preferably dispersed in isopropanol or water. In using the organophilic clays in emulsions, the drying and grinding steps may be eliminated. When the clay, quaternary ammonium compound and water are admixed in such concentrations that a slurry is not formed, filtration and washing steps may be eliminated.

The organic cationic compounds useful in this invention may be selected from a wide range of materials that are capable of forming an organophilic clay be exchange of cations with the smectite-type clay. The organic cationic compound must have a positive charge localized on a single atom or on a small group of atoms within the compound. Preferably the organic cation is selected from the group consisting of quarternary ammonium salts, phoshonium salts, and mixtures thereof, as well as equivalent salts. The organic cation preferably contains at least one member selected from each of two groups, the first group consisting of a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms and mixtures therof and the second group consisting of a long chain alkyl group.

A representative formula of the organic cation is:

wherein R1 is selected from the group consiting of a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms and mixtures thereof; R2 is a long chain alkyl group having 8 to 60 carbon atoms; R3 and R4 are selected from a group consisting of a ss,y-unsaturated alkyl having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms, an aralkyl group, an alkyl group having from 1 to 22 carbon atoms and mixtures thereof; and x is phosphorous or nitrogen.

R, The ss,y-unsaturated alkyl group may be selected from a wide range of materials. These compounds may be cyclic or acyclic, unsubsituted or substituted. ss,y-unsaturated alkyl radicals should contain less than 7 aliphatic carbon atoms. The aliphatic radical of the ss,y-unsaturated alkyl radicals preferably contains less than 4 aliphatic carbons. The P,y-unsaturated alkyl radical may be substituted with an aromatic ring that is conjugated with the unsaturation of the fl,'y moiety. The p,y- radical may also be substituted with both aliphatic radicals and aromatic rings.

Representative examples of cyclic ss,y-unsaturated alkyl groups include 2-cyclohexenyl and 2cyclopentenyl. Representative examples of acyclic ss,y-unsaturated alkyl groups containing 6 or less carbon atoms include propargyl 2-propenyl; 2-butyenyl- 2-pentenyl; 2-hexenyl; 3-methyl-2 butenyl; 3-methyl-2-pentenyl; 2, 3-diemthyl-2-butenyl; 1,1 -dimethyl-2-propenyl; 1.2-dimethyl-2- propenyl; 2,4-pentadienyl; and 2,4-hexdienyl. Representative examples of acyclic-aromatic substituted compounds include 3-phenyl-2-propenyl; 2-phenyl-2-propyenyl; and 3-(4-methoxyphenyl)-2-propenyl. Representative examples of aromatic and aliphatic substituted materials include 3-phenyl-2-cyclohexenyl; 3-phenyl-2-cyclopentenyl. The alkyl group may be substituted with an aromatic ring.

The hydroxyalkyl group may be selected from a hydroxyl subsituted aliphatic radical having from 2 to 6 aliphatic carbons wherein the hydroxyl is not subsituted at the carbon adjacent to the positive charged atom. The alkyl group may be subsituted with an aromatic ring.

Representative examples include 2-hydroxyethyl; 3-hydroxypropyl; 4-hydroxypentyl; 6-hydroxyhexyl; 2-hydrosxypropyl; 2-hydroxybutyl; 2-hydroxypentyl; 2-hydroxyhexyl; 2-hydroxycyclohexyl; 3-hydrocyclohexyl; 4-hydroxycyclohexyl; 2-hydroxycyclopentyl; 3-hydroxycyclopentyl; 2-methyl2-hydroxylpropyl; 3-methyl-2-hydroxybutyl; and 5-hydroxy-2-pentenyl.

R2 The long chain alkyl radicals may be branched or unbranched, saturated or unsaturated, substituted or unsubstituted and should have from 8 to 60 carbon atoms in the straight chain portion of the radical.

The long chain alkyl radicals may be derived from naturally occurring oils including various vegetable oils, such as corn oil, coconut oil, soybean oil, cottonseed oil, and castor oil and various animal oils and fats such as tallow oil. The alkyl radicals may be derived synthetically from alhpa olefins.

Representative examples of useful branched, saturated alkyl radicals include 12-methylstearyl; and 12-ethylstearyl. Representative examples of useful branched unsaturated radicals include 1 2-methyloleyl and 1 2-ethyloleyl. Representative examples of unbranched saturated radicals include lauryl; stearyl; tridecyl; myristal (tetradecyl); pentadecyl; hexadecyl; hydrogenated tallow; docosonyl. Representative examples of unbranched, unsaturated and unsubstituted long chain alkyl radicals include oleyl, linoleyl; linolenyl, soya and tallow.

R3 and R4 R3 and R4 are individually seleoted from a group consisting of (a) a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, described above, (b) a hydroxyalkyl group having 2 to 6 carbon atoms, described above; (c) a cyclic or acyclic alkyl group having 1 to 22 carbon atoms, and (d) an aralkyl group which includes benzyl and substituted benzyl moieties including fused ring moieties having linear or branched chains of 1 to 22 carbon atoms in the alkyl portion of the aralkyl group.

The long chain alkyl group of R3 and R4 may be linear or branched, cyclic or acyclic, substituted or unsubstituted, containing 1 to 22 carbon atoms. Representative examples of useful alkyl groups include methyl; ethyl; propyl; 2-propyl; iso-butyl; cyclopentyl; and cyclohexyl.

The alkyl radicals may be derived from sources similar to the long chain alkyl radical of R2 above.

Representative examples of an aralkyl group would include benzyl and those materials derived from compounds such as benzyl halides, benzhydryl halides, trityl halides, 1-halo-1-phenylalkanes wherein the alkyl chain has from 1 to 22 carbon atoms such as 1-halo-1-phenylethane; 1 halo-1-phenyl propane; and 1-halo-1-phenyloctadecane; substituted benzy moities such as would be derived from ortho-, meta- and para-chlorobenzyl halides, para-methoxybenzyl halides, ortho-, meta- and para-nitrilobenzyl halides, and ortho-, meta- and para-alkylbenzyl halides wherein the alkyl chain contains from 1 to 22 carbon atoms; and fused ring benzyl-type moieties such as would be derived from 2-halomethyl-napthalene, 9-halomethylanthracene and 9-halomethylphenanthrene, wherein the halo group would be defined as chloro, bromo, iodo, or any other group which serves as a leaving group in the nucleophilic attack of the benzyl type moiety such that the nuceliphile replaces the leaving group on the benzyl type moiety.

A quaternary compound is formed of the above described organic cationic compound and an anionic radical which selected from the group consisting of chloride, bromide, nitrite, hydroxide, acetate and mixtures thereof. Preferably the anion is selected from the group consisting of chloride and bromide, and mixtures thereof, and is more preferably chloride, although other anions such as iodide, acetate, hydroxide, nitrite, etc., may be present in the organic cationic compound to neutralize the cation.

Organic cationic salts may be prepared by methods as disclosed in U.S. 2,335,356, 2,775,617 and 3,136,819.

For convenience of handling it is preferred that the total organic content of the organophilic clay reaction products of this invention should be less than about 50% by weight of the organoclay. While higher amounts are usable, the reaction product is difficult to filter, dry and grind.

The amount of organic cation added to the clay for purposes of this invention must be sufficient to impart to the clay enhanced dispersion characteristic desired. This amount is defined as the millequivalent ratio which is the number of milliequivalents (M.E.) of the organic cation in the organoclay per 100 grams of clay, 100% active clay basis. The organophilic clays of this invention must have a milliequivalent ratio from 90 to 140 and preferably 100 to 1 30.

At lower milliequivalent ratios the organophilic clays produced are not effective gellants. At higher milliequivalent ratios the organophilic clays are poor gellants. However, the preferred milliequivalent ratio within the range from 90 to 140 will vary depending on the characteristics of the organic system to be gelled by the organophilic clay.

The manner in which the organic cation functions in the orsänophilic clay reaction products of this invention is not fully known. The unique properties associated with the compositions of this invention are believed however to relate to the electron withdrawing and donating portions of the cation and particularly to the essential presence ot at least one long chain alkyl group coupled with a ss,y-unsaturated alkyl group or a hydroxyalkyl group. When bonded to a positively charged atom the long chain alkyl group appears to function as an electron donor which aids in delocalizing the positive charge. More importantly however it enables the clay platelets to be separated sufficiently to allow further separation under moderate shear tondi tions.In contrast, the ss,y-unsaturated alkyl group appears to create a delocalization of the positive charge which may result from a resonance inductive effect occurring with the unsaturated alkyl group. This effect does not occur to any significant extent with other prior art saturated alkyl groups. The enhanced function of the short chain hydroxyalkyl group appears to be related to the internal covalent bonded polar activating moiety, namely the hydroxyl group when not adjacent the positive charged atom. This effect is negated when the hydroxyl moiety is located on a carbon atom adjacent t-thè positive charged atom or on an alkyl carbon greater than 6 carbon atoms.

Suitable smectite-typaclays occur natural-ly or may be prepared synthetically. Such clays include montmorillonite, bentonite, beidellite, hectorite, saponite, and stevensite. In particular smectite-type clays should have a cation exchange capacity of at least 75 milliequivalents per 100 grams of clay. Particularly desirable types of clay are naturally-occurring Wyoming varieties of bentonite and hectorite, a magnesium-lithium silicate clay. Suitable clays may also be synthesized by conventional means including pneumatolitic and hydrothermal methods.

The clays, especially the bentonite type clays, are preferably converted to the sodium form if they are not already in this form. This can conveniently be done by preparing an aqueous clay slurry and passing the slurry through-a bed of cation exchange resin in the sodium form.

Alternatively, the clay can be mixed with water and a soluble sodium compound such as sodium compound such as sodium carbonate and sodium hydroxide followed by shearing the mixture with a pugmill or extruder.

The cation exchange capacity of the smectite-type clays can be determined by the ammonium acetate method.

The clay is preferably dispersed in water in a weight concentration ranging from about 1 to about 80% and preferably from about 2% to 20%, and more preferably from about 2% to about 7%. The slurry is agitated prior to reaction.

The organic cationic compounds of the invention were prepared by standard prior art methods starting with an amine having the desired number of long chain alkyl groups bonded to the nitrogen atom. This long chain alkyl amine was then reacted by reductive alkylation with an aldehyde or by nucelophilic displacement of an alkyl halide to form the desired quaternary ammonium compound.

The fluid of this invention may contain an aqueous phase which includes aqueous solutions of inorganic salts such as sodium chloride and calcium chloride. While addition of these salts is optional, such salts increase the osmotic pressure of the water phase to stabilize formations containing hydratable clays.

The concentration of water in the fluid is determined by factors such as fluid weight requirements, flow properties desired, bottom-hole temperatures and the operational requirements of drilling, coring, or completion. In general, it has been found preferably to employ a volume percent of water ranging from about 2 to 50%. This range renders the oil-base fluid fireresistant upon-exposure to temperatures that would ignite it. In addition, the fluid has excellent tolerance to water contamination; and fluid flow properties can be controlled at values comparable to those of water-based fluids.

In using an aqueous phase in the fluid, conventional emulsifiers should be employed for the water-in-oil phase. In the non-aqueous fluid, emulsifiers may also be used. The amount of emulsifier employed is primarily dependent upon the amount of water present and the extent of emulsification desired. Generally from 2 to 30 Ibs. per barrel and preferably from 1 to 1 5 Ibs.

per barrel have been found satisfactory to achieve the emulsion stability.

The compositions may optionally contain conventional weighting agents such as barite for controlling fluid density between 7.5 and 22 Ib/gal as well as fluid loss control agents.

the mectite-type clays used in the Examples were hectorite and Wyoming bentonite. The clay was slurried in water and centrifued to remove essentially all of the non-clay impurities which may amount to 10% to about 50% of the starting clay composition. The Wyoming bentonite clay slurry was passed through a bed of.cation exchange resin to convert it to the sodium form.

The organic cationic compounds exemplified are representative of the cations of the invention and are not intended to be inclusive of the only operative compounds. The following examples are given to illustrate the invention but are not deemed to be limiting thereof.

All percentages given are based upon weight unless otherwise indicated. Plastic viscosity, yield point, and ten second gels were measured by-the procedure described in API RP13B, American Petroleum Institutes Standard Procedure for Testing Fluids, 6th Ed., April 1 976.

Barrels (bbl) and gallons are U.S. measure.

Example 1 Allyl methyl di(hydrogenated-tallow) ammonium chloride (abbreviated AM2HT).

824.7 g methyl di(hydrogenated-tallow) amine, 350 ml isopropyl alcohol, 250 g NaHC03, 191.3 g are placed allyl chloride, and 10 g ailyl bromide (as a catalyst) in a 4-liter reaction vessel equipped with a condenser, the mixture is heated and allowed to reflux. A sample was removed, filtered, and titrated with HCI and NaOH . The reaction was considered complete at 0.0% amine HCI and 1.8% amine. The final analysis showed an effective gram molecular weight of 831.17.

Examples 2-4 A 3% clay slurry, the sodium form of Wyoming bentonite for Examples 2 and 3 and hectorite for Example 4, was heated to 60"C with stirring. An isopropyl alcohol solution of organic cationic compound, ethanol methyl di(hydrogenated tallow) ammonium chloride (EM2HT) (Armak Co. Division of Akzona Corp.) at 80% activity in Example 2 and AM2HT, prepared in Example 1, for Examples 3 and 4 was added to the clay slurry and stirred for 20 minutes. The organoclay was collected on a vacuum filter. The filter cake was washed with 60"C water and dried at 60"C. The dried organoclay was ground using a hammer mill to reduce the particle size and sieved through a U.S. Standard 200 mesh screen.

Examples 5-8 0.63 bbl of diesel oil, 8 pounds emulsifier (Invermul, NL Industries, Inc.), 8 pounds filtration control, amine lignite (Duratone HT, NL Industries, Inc.) 4 pounds lime, 0.11 bbl. of water was stirred for 20 minutes.

22 pounds of calcium chloride, 325 pounds of barite (Baroid, NL Industries, Inc.) and 5 pounds of the two bentonite clay thickeners prepared in Examples 2 and 3 in addition to two commercial products, dimethyl di (hydrogenated-tallow) ammonium chloride C2M2HTl/benton- ite and benzyl methyl di(hydrogenated-tallow) ammonium chloride [BM2HT]/ bentonite.

The mixed fluid was tested at 95"F. for standard rheology data and the results are shown in Table 1. None of the Examples settled following stirring: Table 1 Yield 10 sec. 10 min.

Point Gel Gel Example Gellant #/ #/ #/ No. Compound 100ft2 100ft2 100ft2 5 EM2HT/bentonite 18 9 13 6 AM2HT/bentonite 20 11 14 7 2M2HT/bentonite 30 16 19 8 BM2HT/bentonite 24 14 18 The unstirred batches of Examples 5-8 were rolled at 150"F for 16 hours and no settling was noted in any Example. The batches were tested at 80"F for standard rheology data as in Example 5. The results are shown in Table 2 below. None of the Examples settled.

Table2 Yield 10 sec. 10 min.

Point Gel Gel Example #/ #/ No. 100ft2100ft2 100ft2 5 19 9 14 6 17 12 15 7 20 13 18 8 21 14 19 Examples 9-13 350 ml. batches of of fluids consisting of 0.60 bbl of diesel oil, 8 pounds emulsifier (Invermul, NL Industries, Inc.), 8 pounds amine lignite filtration control aid (Duratone, NL Industries, Inc.), 5 pounds lime, 0.20 bbl of 11.0 per gallon, calcium chloride, aqueous 320 pounds of barite (Baroid, NL Industries, Inc.) was admixed, stirred, for 1 5 minutes in a Hamilton Beach mixer and cooled to 28"F in an ice bath.A 6 Ib/bbl concentration of the clays EM2HT/bentonite, AM2HT/bentonite and AM2HT/hectorite produced in Examples 2, 3, and 4 respectively in addition to two commercial clays 2M2HT/bentonite and BM2HT/bentonite described in Examples 7 and 8 were stirred into the cold fluid batches over a 5 minute period at low shear with a Lightnin mixer. The cold examples in a viscometer cup, were placed on a Fann 35 viscometer and stirred at 600 rpm while the temperature rose to 70"F. The batches were then placed in a preheated cup jackets set at 126 F and allowed to heat to 110"F.The plastic viscosity, yield point and 10-sec gal were measured at every 5 F increment between 30 to 70'F and at every 10"F increment between 70 to 110 F. The results of the measurements are presented in Fig. 1.

Examples 13-17 at 115"F were stirred for 15 minutes in a Hamilton Beach mixer and cooled to 80 "F and tested as with Example 5. The results are presented in Table 3 below.

Table 3 Yield 10 sec. 10 min.

Point Gel Gel Example #/ #/ No. 100ft2 100ft2 100ft2 9 42 15 19 10 56 22 27 11 68 38 46 12 50 21 26 13 50 23 28 Example 14-17 Fluids consisting of 0.41 bbl of diesel oil and 12 pounds of gellant clays prepared in Example 2 and 3 in addition to commercial clays 2M2HT/bentonite and BM2HT/bentonite were admixed and stirred for five minutes in a Hamilton Beach mixer at low speed. Fluids consisting of 0.41 bbl of diesel oil, 18 pounds asphalt (Baroid Asphalt, NL Industries, Inc.) and 275 pounds of barite, (Baroid, NL Industries, Inc.) were prepared and admixed with the prepared fluids above to form 350 ml batches which stirred for 1 5 minutes in a Hamilton Beach mixer.

350 ml samples of Examples 14 through 1 7 were tested for rheological properties as in Example 5 at 93"F. The results are presented in Table 4 below.

Table 4 Yield 10 sec. 10 min.

Point Gel Gel Example &num;/ &num;/ No. 100ft2 100ft2 100ft2 14 26 7 54 15 30 11 48 16 54 34 74 17 25 11 40 350 ml samples of Examples 1 4 through 17 were hot rolled at 150"F for 1 6 hours. After cooling the batches to 80"F, settling of solids were checked prior to measurement of rheological properties as in Example 5 at 93"F. The results are shown in Table 5 below.

Table 4 Yield 10 sec. 10 min.

Point Gel Gel Example #/ #/ No. 100ft2 100ft2 100ft2 14 57 14 73 15 80 38 116 16 91 55 100 17 69 39 108 Example 4 shows improved results when mixed in a nonaqueous fluid. These results show improvements in forming a gel quickly and remaining low at a 10 minute gel indicating a maintenance of pumpability.

350 ml samples of Examples 14 through 1 7 were hot rolled at 150"F for 1 6 hours. After cooling the batches to 80"F, settling of solids were checked prior to measurement of rheological properties as in Example 5 at 93"F. The results are shown in Table 5 below.

Table 5 Yield 10 sec. 10 min.

Point Gel Gel Example &num;/ #/ #/ No. 100ft2 100ft2 v l OOft2 14 85 11 55 15 105 31 83 16 120 45 82 17 99 41 78 Example 18-21 350 ml batches of fluids consisting of 0.69 bbl of diesel oil, 6 pounds emulsifier (EZ nul, NL Industries, Inc.), 0.1 2 bbl of water, 225 pounds of barite, (Bariod, NL Industries, Inc.), 24 pounds of calcium chloride and 6 pounds of gellant clays EM2HT/bentonite and AM2HT/bentonite prepared in Example 2 and 3 respectively in addition to 2M2HT/bentonite and BM2HT/bentonite were admixed and stirred for 20 minutes in a Hamilton Beach mixer.

350 ml batch of Examples 18 through 21 were tested for rheological properties as in Example 5 at 88"F. The results are presented in Table 6 below.

Table 6 10 sec. 10 min.

Point Gel Gel Example Gellant &num;/ #/ No. Gellant Compound 100ft2 100ft2 100ft2 1 8 EM2HT/bentonite 9 4 5 19 AM2HT/bentonite 8 5 6 20 2M2HT/bentonite 9 5 6 21 BM2HT/bentonite 8 4 5 350 ml sample of Example 18 through 21 were hot rolled at 150"F for 16 hours. After cooling the batches to 80"F, settling of solids was checked prior to measurement of rheological properties as in Example 5 at 84"F. The results are shown in Table 7 below.

Table 7 Yield 10 sec. 10 min.

Point Gel Gel Example #/ #/ #/ No. 100ft2 lOOft2 100ft2 18 11 5 8 19 11 5 5 20 15 8 14 21 9 4 5 Mud cake and filtrate were stirred back into the respective samples and the batches were aged for 16 hours at 350"F.

Each batch was cooled to 80"F, checked for solids settling and electrical stability. The batches were stirred for 5 minutes and tested as with Example 5. HT-HP filtrates were conducted on each batch at 350"F. The results are shown in Table 8 below.

Table 8 Yield 10 sec. 10 min.

Point Gel Gel Example #/ #/ No. 100ft2 100ft2 100ft2 18 8 5 5 19 10 4 5 20 12 5 6 21 8 4 5 Example 22-27 350 ml batches of packer fluids consisting of 0.633 of diesel oil, 8 pounds emulsifier (Invermul, NL Industries, Inc.), 0.11 bbl of water, 325 pounds of barite, (Baroid, NL Industries Inc.), 8 pounds filtration aid (Duratone, NL Industries, Inc.), 22 pounds of calcium chloride, 4 pounds lime and 9 pounds of gellant clays EM2HT/bentonite, AM2HT/bentonite, and AM2HT/hectorite prepared in Example 2, 3 and 4 respectively in addition to three commercial clays, dimethyl di(hydrogenated-tallow) ammonium chloride, 2M2HT/bentonite; benzyl methyl di-(hydrogenated-tallow) ammonium chloride, M2HT/bentonite; and dimethyl di(hydrogenatedtallow) ammonium chloride, 2M2HT/hectorite were admixed and stirred for 20 minutes in a Hamilton Beach mixer.

350 ml sample of Examples 22 through 27 were tested for rheological properties as in Example 5 at 92"F. The results are presented in Table 9.

Table 9 Yield 10 sec. 10 min.

Point Gel Gel Example #/ &num;/ No. Gellant Compound 100ft2 100ft2 100ft2 22 EM2HT/bentonite 36 11 1 6 23 AM2HT/bentonite 42 18 23 24 AM2HT/hectorite 55 23 27 25 2M2HT/bentonite 60 22 33 26 BM2HT/bentonite 51 24 28 27 BM2HT/hectorite 65 32 39 Mud cake and and filtrate were stirred back into each batch and the batches were aged at 350"F for 1 6 hours. Each batch was cooled to 80"F, checked for solids settling and electrical stability. The batches were admixed, stirred for 10 minutes and tested as with Example 5 at 90"F. The results are shown in Table 10 below.

Table 10 Yield 10 sec. 10 min.

Point Gel Gel Example &num;/ &num;/ No. 100ft2 100ft2 100ft2 22 20 16 24 23 28 23 27 24 31 30 33 25 34 18 26 26 26 24 29 27 37 28 35 350 ml batches of Examples 23, 24 25 and 37 were aged for 1 6 hours at 300"F, 400"F and 450"F. The batches were tested as above at 99"F and the results are shown in Table 11.

Table 11 Yield 10 sec. 10 min.

Tempera- Point Gel Gel Example ture #/ #/ No. F 100ft2 100ft2 100ft2 23 300 21 21 23 400 45 14 30 450 13 9 16 r 24 300 31 30 33 400 150 41 57 450 80 22 35 25 300 38 28 37 400 27 11 20 450 9 8 14 27 300 37 28 35 400 120 40 60 450 40 17 30 It will be obvious to one skilled in the art that the invention may be varied in many ways.

Such variations are not regarded as a departure from the spirit and scope of the invention and all such modifications are intended to be included within the scope of the following claims.

Claims (18)

1. An oil-base fluid comprising an oil phase and from about 1 to 50 Ibs. per barrel of an organophilic clay geliant comprising the reaction produce of an organic cationic compound and a smectite-type clay having a cation exchange capacity of at least 75 milliequivalents per 100 grams of said clay, wherein said organic cation has the formula

wherein R1 is selected from the group consisting of a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms and mixtures thereof; R2 is a long chain alkyl group having 8 to 60 carbon atoms;R3 and R4 are individually selected from the group consisting of fl,y-unsaturated alkyl groups having 2 to 6 carbon atoms, an aralkyl group, an alkyl group having from 1 to 22 carbon atoms and mixtures thereof; X is selected from a group consisting of phosphorous and nitrogen; and wherein the amount of said organic cationic compound is from 90 to 140 milliequivalents per 100 grams of said clay, 100% active clay basis.

2. An oil-base packer fluid comprising an oil phase, and from about 6 to 50 Ibs. per barrel of an organophilic clay gellant comprising the reaction product of an organic cationic compound and a smectite-type clay having a cation exchange capacity of at least 75 milliequivalents per 100 grams of said clay, wherein said organic cation has the formula: i i

wherein R, is selected from the group consisting of a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms and mixtures thereof.R2 is a long chain akkyl group having 8 to 60 carbon atoms; R3 and R4 are individually selected from the group consisting of a B,y-unsaturated alkyl group, a hydroxylalkyl group having 2 to 6 carbon atoms, an aralkyl group, an alkyl group having from 1 to 22 carbon atoms and mixtures thereof; X is selected from a group consisting of phosphorous and nitrogen; and wherein the amount of said organic cationic compound is from 90 to 140 milliequivalents per 100 grams of said clay, 100% active clay basis.

3. In a method of insulating casing in a wellbore which comprises pumping an oil-base packer fluid in an annular space within said wellbore and thereafter gelling said packer fluid, the improvement comprises a packer fluid having an oil phase, and from about 6 to about 50 Ibs.

per barrel of an organohphilic clay gellant comprising the reaction product of an organic cationic compound and a smectite-type clay having a cation exchange capacity of a least 75 milliequivalents per 100 grams af said clay, wherein said organic cation has the formula:

wherein R, is selected from the group consisting of a ss,y-unsaturated alkykl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms and mixtures thereof; R2 is a long chain alkyl group having 8 to 60 carbon atoms;R2 and R4 are individually selected from the group consisiting of a ss,y-unsaturated alkyl group having less than 7 aliphatic carbon atoms, a hydroxyalkyl group having 2 to 6 carbon atoms, an aralkyl group, an alkyl group having from 1 to 22 carbon atoms and mixtures thereof; X is selected from a group consisting of phosphorous and nitrogen; and wherein the amount of said organic cationic compound is from 90 to 140 milliequivalents per 100 grams of said clay, 100% active clay basis.

4. The gellant of Claim 1, 2 or 3 wherein said smectite-type clay is selected from the group consisting of hectorite and sodium bentonite.

5. The gellant of Claim 1, 2 or 3 wherein R1 is a ss,y-unsaturated group selected from a group consisting of cyclic groups, acyclic alkyl groups having less than 7 carbon atoms, acyclic alkyl groups substituted with aromatic groups, aromatic groups substituted with aliphatic groups and mixtures thereof.

6. The gellant of Claim 1, 2 or 3 wherein R, is a hydroxyalkyl group selected from a group consisting of cyclic groups, acyclic aliphatic groups and mixtures thereof, said aliphatic groups having the hydroxyl substitution on C2 to C6.

7. The gellant of Claim 1, 2 or 3 wherein R2 has from 1 2 to 22 carbon atoms.

8. The gellant of Claim 7 wherein R2 is a long chain fatty acid group.

9. The gellant of Claim 1, 2 or 3 wherein the amount of said organic cation is from 100 to 1 30 milliequivalents per 100 grams of said clay, 100% active clay basis.

10. The fluid of Claim 1 wherein said fluid comprises additionally a dispersed aqueous phase comprising from about 2 to about 50% by volume water.

11. The fluid of Claim 10 wherein said fluid comprises additionally a water-in-oil emulsifier.

1 2. The fluid of Claim 11 wherein said emulsifier comprises from about 2 to about 30 Ibs.

per barrel of said fluid.

1 3. The packer fluid of Claim 2 or 3 wherein said fluid comprises additionally a dispersed aqueous phase comprising from about 2 to about 50% by volume water.

14. The packer fluid of Claim 1 3 wherein said fluid comprises additionally a water-in-oil emulsifier.

1 5. The packer fluid of Claim 14 wherein said emulsifier comprises from about 2 to about 30 pounds per barrel of said fluid.

1 6. The fluid of Claim 1 wherein said fluid is non-aqueous.

17. The fluid of Claim 2 or 3 wherein said fluid is non-aqueous.

18. The fluid of Claim 1 wherein said gellant comprises about 1 to about 10 pounds per barrel of said fluid.