CA1185779A - Aqueous wellbore service fluids - Google Patents

Abstract

Abstract of the Disclosure A wellbore service fluid is provided which contains water, a water soluble electrolyte and as a thickening agent at least one of an amine, a salt of an amine, or quaternary ammonium salt which functions to increase the viscosity of the fluid in the presence of said electrolyte.

Description

77~
--1~

AQUEOUS WELLBORE SERVICE FLUIDS

Thi~ invention relates to aqueous wellbore servire fluids, including drilling fluids, completion fluids, work over fluids, packer fluids, fracturirlg fluids and the like, which may be employed in various well servicing operations. More specifically, it relates to thic:kened, substantially solids-f:ree high electro].yte-containing aqueous fluids which are employed as a base fluid to prepaxe many types of wellbore service fluids.

Essentially solids-free aqueous 1uids con-tai~ing electrolytes have some advantages over clay-based fluids for preparing wellbore service. fluids because: (a) they do not noxmally contain undesirable solids which can cause foxmation damage, (b) they contain hydration inhibiting materials such as pota~-sium chloride, calcium chloride or ~he like, which are important to prevent damage to clay containing forma tions, and (c) they can be prepared over a wide range of densities.

The viscosity of high electrolyte-containing aqueous fluids is, however, difficult to control because of the high elPctrolyte concentration. Thickened fluids 28,986 F

~2 are desirable for carrying solids, e.g. in cleaning out wells, drilling and the like. Likewise, thickened fluids resist water loss, which may be damaging to petroleum producing subterranean formations.

Hydroxy alkyl celluloses have been employed to thicken electrolyte~containing aqueous fluids to improve the solid carrying capacity thereof. Likewise, starch has been em~loyed to aid in water loss control of these fluids, but with limited success. However, these materials are difficult to disperse and dissolve in concentrated electrolytes at ambient temperature;
the viscosity of the resulting solutions tend to de-crease with an increase in temperature; and the hydroxy alkyl celluloses are subject to shear degradation under normal operating conditions.

Certain quaternary ammonium salts have been shown to impart viscoelastic properties to a~ueous solution.s, S. Gravsholt "Viscoelasticity in Highly Dilute ~queous Solutions of Pure Cationic Detergents", ~ournal of Colloid and Interface Science, Vol.57, No.
3, December 1976, pp. 575-577. Gravsholt showed that cetyl trim~thyl ammonium bromide would not impart viscoelastic properties to water but that cetyl tri-methyl ammo~ium salicylate and certain other aromatic anion-containing guaternary amines would. In U.S.
Patent 3,292,698, a mixture of cyclohexyl ammonium chloride and undecane-3-sodium sulfate was taught to induce viscoelastic properties to a formation flooding liquid containing less than about 3.5 percent by weight of sodium chloride. Higher levels of sodium chlvride were said to destroy the viscoelastic properties of the fluid. In British Patent No. 1,443,244, a specific 28,986-F -2;

~3~ ~ '7'7~

ethoxylated or propoxylated tertiary amine ls employed to th,icken an aqueous solution of a strong mineral acid. U.S. Patent 3,917,536 teaches that cer-tain pri-mary amines may be employed in subterxanean formation acidizing solu-tions to retard ~he reaction of the acid on the formatlon. The amine may be more readily dis~
persed into the acid solution wlth the use of a dis-persing agent such as a quaternary amine.

It is a feature oE the present invention to provide a high electrolyte-containing aqueous wellbore service fluid which has improved VisCOSlty character-istics over a wide range of wellbore conditions; is easier to prepare at the well site and has better shear stability and consistent viscosity over a wide tempera-ture range.

The improved aqueous wellbore service fluidof the present invention can be employed in well-known wellbore services such as, perforation, clean-up, long ,term shut-ins, drilling, placement of gravel packs, and the like. These services are well known in the art and are taught, for example, in U. S. Patent Nos. 3,993,570;
3,176,950; 3,126,950; 2,898,294 and in C. M. Hudgens et al "High Density Packer Fluids Pay Off in South Louisiana":
World Oil, 1961, pp. 113-119,.

As employed herein, "ppg" means pounds per -gallon. Also, when "percent" or "%" are employed, khey mean percent by weight unless otherwise specified.

28,986-F -3-The present invention comprises an aqueous wellbore service fluid comprislng:
water, a suffi~ient quantity of at least one water soluble salt to increase the density of sald fluid to within a range of from 12 to 21 lbs/gal, and a sufficient quan-tity of at least one thickener soluble in said fluid to increase the viscosity of said fluid to at least 50%
over the viscosity of the salt containing fluid, said thickener being at least one member selected from the group consis~ing of: (a) an amine correspondlng to the formula Rl - N wherein Rl is at least about a C16 aliphatic group which may be branched or stralght chained and which may be saturated or unsa~uratedi R2 and R3 are each independently, hydrogen or a Cl to about C6 aliphatic group which can be branched or st,raigh-t chalned, saturated or unsaturated and ~hich may be substituted with a group which renders the R2 and/or R3 group more hydrophilic; (b) salts of said amine corresponding to the formula Rl - N -H X wherein ., 28,986-F _4_ ,, . ,!

., -5~ '7~

R1, R2 and R3 are the same as defined hereinbefore and X is an inorganic or organic salt forming anion;
or (c) a quaternary ammonlum salt of said amlne corres~
ponding to the formula R N~ R X~ wherein R1, R2 ~ R3 and X are the same as hereinbefore defined and R4 independently constitu~es a group which has previously been set forth for ~2 and R3, none of R1, R2, R3 or R~ are hydrogen, and the ~2~ R3 and R4 groups of the amine salt and quaternary ammonium salt may be fo~ned into a heterocyclic S or 6 member ring structure which lncludes tne nitrogen atom of the amine.

The aqueous wellbore service fluid may have a density rangin~ from'as low ~s about 8.5 ppg, preferably about 12 ppg, to about 21 ppg. It has been found that the higher density fluids are more difflcult to thic~en because of the high electroly~e content. It is at these higher densities, e.g. about 15 ppg and higher, -that the practice of the present invention is par-ticu-larly useful. However, advantages are also achieved in the lower density flui.ds.

The density is achieved by dissolving one or more water soluble inorganic salts in water to provide a substantially solids-free fluid. Naturally occurring brines and seawater can be employed if desired. Prefer-ably, the aqueous wellbore service fluid contains at 28,986-F -5-6~ 16,~

least about 3 percent of a water soluble salt of potassium, calcium or sodlum. In addition, the aqueous fluid may contain other soluble salts of, for example, zinc, lithium, chromium, iron, copper, and the like. Preferably inorganic chlorides and/or bromides are employed because of the high denslty which can be achieved, but other salts such as sulfates, nitrates, etc. can be employed.
The only restriction is that the sâlts must be compatible with the particular thickening agent employed to thicken the aqueous fluid. By compatible it is meant, for example, that the salt does not detrimentally interfere with the ~thickening function of the thickening agent and/or undesirable quantities of precipitates are formed. As examples of useful water soluble salts, reference may be had to Table I, Column 3, of U. S.
Patent No. 2,898,294 28,986-F -6--7~

One preferred agueous wellbore service fluid contains a mixture of at least calcium bromide and zinc bromide to provide an aqueous solution having a density of at least about 15 ppg. The solution may also contain other water soluble salts such as calcium chloride and th~ like.

A preferred aqueous solution for use in deep wells reguiring a fluid having a density greater than about 15 ppg is one which contains, as percent by weight:
ZnBr2 about 5% to about 35%;
CaBr2 about 25% to about 45%;
CaCl2 about 5% to about 20%;
water about 30% to about 40%; and thickener about 0.5% to about 2%.

A preferred thickening agent for the above d~ined ~luid having a density of above about 16.5 ppg i8 a tertiary amine of the formula C18H35N(CH2CH2OH)2.

The thickening agent employed in the inven tion comprises at least one of the thickening agents defined h~reinbefore under Summary of the Invention.
It is found that with certain solutions, a mixture of two or more thickeners may be preferred.

Preferaoly, X is an inorganic anion such as a sulfate, nitrate, perchlorate or halide. A halide, (C1, Br or I) is preferred, Cl and Br being most pre ferred. X may also be an aromatic organic anion such as salicylate, naphth~lene sulfonate, p and m chloro-benzoates, 3,5 and 3,4 and 2,4~dichlorobenzoates, 28,986-F 7-t butyl and ethyl phena~e, 2,6 and 2,5~dichlorophenates,

2,4,5~trichlorophenate, 2,3,5,6~tetrachlorophenate, p-methyl phenate, m-chlorophenate, 3,5,6 trichloropico-linate, 4-amino-3,5,6-trichlorpicolinate, 2,4-dichloro-phenoxyacetate, toluene sulonate ~,~ naphthols, p.plbisphenol A. The thickening agent should be chosen such that the anion is compatible with the electrolyte present in the aqueous solution such that undesirable precipitates are ~ot formed. Also, the specific anion chosen will depend to some clegree on the specific amine structure.

The thickening agent is employed in an amount which is sufficient to increase the viscosity of the aqueous fluid at least 50 percen~ ov~r the viscosity thereof without the addition of the thickener as meas~
ured on a Haake Rotovisco Viscometer at about 20C and a shear rate of 160 sec 1 The exact quantity and specific thickener or m.ixture oE thickeners to be employed will vary depending on the concentration o and specific soluble salt~s) employed to make up ~he solution, the viscosity de-sired, the temperature of use, the p~ of the solution, and other similar factors. The co~centration of the thickener can range from about 0.05 to about 5 percent, preferably from about 0.2 to about 3 percent of the aqueous wellbore service fluid. Simple laboratory procedures can be employed to det~rmine the optimum conditions for any particular set of parameters. For example, when a non-protonated amine is employed as the thickener, the pH of the aqueous fluid can affect to some degree the effectiveness of particular amines.
More acidic solutions are required for some amines to be dissolved therein. It is thought that this is 28,986-F -8-~5~
_g _ because the amine must become protonated before it will become effectively dissolved in the fluid.

~ pecific wellbore service fluids found to be useful in the practice of the invention are set forth in the following Table I.

28,986-F 9-~ ~ 7~

h O
rl

3 ~ ~ ~
~-1 a) ~1 ~ ~3 O
O U~ ~ ~
O ~q ~t O #
a) o t.) o ~ ~ ~ ~I t` a) ,i r~ co . , O u~ h rl o ~D ~ r` ~ Ln o ~ o ~D ~ ~ ~ ~
V O
V~

U~ Nl C`l N N N N N N ~ N ~
h h ~ ~I h ~ N N N N
q~ m a: m u m o ~ m v m m ,~ h m 3 ::1 V U V V UV V N O V N
o ~q O h U~ r~
h ~ ~ ~1 0 o o oo o C` o ~
O rl ~1 H ~ l U

~! C) o~
a) o a~
h~
P~ ~ O
~1 ~
,1 ~ o h ~ tn O ~

m~

V o ~ _ o o o ~) o o V

o g o ~o U~

28, 986-F -10-35~o9~
N

h ~ ~ O 0 ~
O U~ U~ N ~ N ~ N ~ ~ t") ~ ~ ~ U~

~ O ~ #
rl ~7 0 ~ O O d' O O ~ O O ~ O ~
O p.~ ~) Lt') ~ N r l ~ N r-l ~ N ~I tr~ N O
O Lt) ~1 ~1 N ~J M N N ~1 N N N ~1 N N S-l 3 C) C~ C~ N C.) ~) ~ ~ C~ M U V M X
~

~ o ~ ~ ~ ~ ~
o ~ ~
~ ~ o o c~ o o ~ o ~ ~o C) O P~ h p~ ~3 ~:/ O

~ o u~ ~ o a~

C ~ r ,~ U
~ ~ ~ ~ O O

N~ Ln rl c~ o o ~ e o ~
O
o *

28, 986-F

Examples of other thickeners which can be employed include oleyl methyl bis~hydroxyethyl) ammonium chloride; octadecyl methyl bis(hydroxyethyl) ammonium 1 bromide; octadecyl tris(hydroxyethyl3 ammonium bromide;
and octadecyldimethylhydroxyethyl ammonium bromide cetyldimethyl hydroxyethyl ammonium bxomide; cetyl methyl bis(hydroxyethyl~ammonium salicylate; cetyl methyl bis(hydroxyethyl)ammonium 3,4-dichlorobenzoate;
cetyl tris~hydroxyethyl)ammonium iodide; bis(hydroxy-ethyl) soyaamine; N~methyl, N-hydro~yethyl tallow amine; bis(hydroxyethyl)octadecylamine; cosyl dimethyl-hydroxyethyl ammonium bromide; cosyl methyl bis(hydroxy-ethyl) ammonium chloride; cosyl tris(hydroxyethyl) ammonium bromide; docosyl dimethylhydroxyethyl ammonium bromi.de; docosyl methyl bis(hydroxyethyl~ammonium chloride; docosyl tris(hydroxyethyl)ammonium bromide;
hexadexyl ethyl bis(hydroxyethyl)ammonium chloride, hexadecyl isopropyl bisthydroxyethyl)ammonium iodide;
N,N-dihydroxypxopyl hexadecylamine, ~-methyl, N-hydroxy-ethyl hexadecylamine; N,N-dihydroxyethyl octadecylamine, N,M-dihydroxypropyl oleylamine; N,N-dihydroxypropyl soya amine; N,N-dihydroxypropyl tallow amine; N-butyl hexadecyl amine; N-hydroxyethyl octadecylamine; N-hydroxy-ethyl cosylamine; cetylamine, N-octadecyl pyridinium ~5 chloride; N-soya-N-ethyl moxpholinium ethosulfate;
methyl-l-oleyl amido ethyl-2-oleyl imidazolinium~methyl sulfate; methyl-1-tallow amido ethyl-2-tallow imidazo-liniwn-methylsulfate.

It has been ound that as the concentxation of the soluble salt in the aqueous solution increases the thickener should be more hydrophilic. This can be achieved by employing thickeners having a specific combination of Rl and R2-R~ groups to provide such 28,986-F ~12-hydrophillic character. It has also been found that the X component of the thickener affects, to some degree, the effectiveness of the thickener in specific a~ueous solutions. For example, organic anions ~x ) generally are found to function more effectively in lower density fluids, e.g., less than 49% CaBr2, because of their solubility. Thickeners having an inorganic anion cons~ituent are generally more effective over a broader density range than are thickeners containing an organic anion.

To prepare the a~ueous wellbore service fluid of the present invention, the thickener is added to an aqueous solution to which has been dissolved a quantity of at least one water soluble salt to pxovide a solution having a desired density. Standard mixing procedures known in the art can be employed since heating of the solution and special agitation conditions are normally not necess~ry. Of course, if used under conditions of extreme cold such as found in Alaska, normal heatin~
procedures should be employed. It has been found in som~ instances preferable to dissolve the thickener into a lower molecular weight alcohol prior to mixing it with the aqueous solu~ion. The lower molecular weight alcohol (e.g., isopropanol) functions as an aid to solublize the ~hickener. Other such agen~s can also be employed. A defoaming agent such as a poly-glycol may be employed to preven~ undesirable foam during the preparation of the service fluid.

In addition to the water soluble salts and thickening agents described hereinbefore, the aqueous wellbore service fluid may contain other co~ventional constituents which perform specific desired functions, 28,986-F -13-e.g., corrosion inhibitors, propping agents, fluid loss additives, and the like.

The 1uids defined herein can be employed in standard wellbore treatment services employing tech~
niques and equipment well known in -the art. They may be used to control a well during certain wellbore operations such as durins the pex~oration of liners and the like. They can also be employed as packer fluids, drilling fluids and the like.

The following examples are illustrative o aqueous wellbore service fluids of the present invention.

ExamE~e_l The rheological behavior of 0.5 percent oleyl methyl bis(2-hydroxyethyl) ammonium chloride in a 53%
aqueous CaBr2 wellbore service fluid over a shear rate range of 0.6-3900 sec l was determined. The fluid was prepared by combining 0.21 g of C18~35N ~CH~C~20H)~ Cl (added as 0.29 g of commercially available 75%
active Ethoquad 0/12) with 39.63 g of 53~ CaBr2 aqueous soLution.

The solution was prepared by adding the Ethoguad 0/12 to the 53% CaBr2 solution and shaking on a mechanical shaker overnight at room temperature. A
clear, very viscoelastic solution with a layer of stable foam on top resul-ted from this procedure.

The viscosity of -the so prepared fluid was measured at three temperatures (approx. 23C, 43C and 28, 986-F -14~

60C) as a f~mction of shear rate. The lowest shear rate (0.66 sec 1) measurement was determined employing a Brookfield LTV viscometer with a UL adaptox. Twenty milliliters (ml) of solution were slowly removed from the bottom of a sample bottle to avoid introducing foam into the annulus between the rotating cylindrical bob and the stationary cup wall. The calculated viscosities at the shear rate of 0.6 rpm (0.66 sec 1) are tabulated below in Table II for the three temperatures. The readings changed with time so the viscosity in centi-poise ~cps) is reported in Table II as a range and not as a single value. This characteristic indicates the elastic, non-Newtonian nature of the solution.

TABLE II

Temperature No. of Viscosity C_ Readings (cps) 59.S-60 3 370 - 530 The viscosity of samples taken at higher shear rates were measured on a Haake Rotovisco using the NV
double~gap cup system. The rotor is a hollow cylinder wh.ich fits over a stationary cylindrical stator on the inside with the othex cylindrical stator being the inside wall of the stainless steel cup containing the sample solution. The eight ml of fluid required for the test were delivered from a hypodermîc syringe. Torque is recorded on a single pen strip chart at successively increasing shear rates. Shear rate is increased stepwise by increasing the rotor xpm.

28,986-~ -15-Individual torque readings were taken at three temperatures. The t~mperature, shear rat~ and calculated viscosities are set forth in the following Table III.

TABLE III

Teml~. She~r Rate (sec 1) Viscosity ~cps) 25C 5.4 54 " 10.8 81 " 21.6 58.5 " 43.1 45 " ~6.2 32.6 " 173 26.4 " 345 20.3 " 690 16.6 " 1380* 13.9 " 1380* 17.0 " 2760 14.0 " 173 26.4 43.1 5.4 169 " 10.8 117 " 21.6 g9 " 43.1 86.3 " 86.2 60.~
" 173 37.1 ~5 " 345 21.9 " 690 16.1 " 13~0* 12.2 " 1380* 13.4 " 2760 ll.g " 173 38.5 61.6 10.8 99 " 21.6 67.5 " 43.1 56.3 " 86.2 40.5 " 173 28.4 " 345 20.5 " 690 14.5 " 1380* 10.5 " 1380* 12.3 " 2760 8.5 " 173 28.7 * Duplicate readings at different head scales of the instrument.

28,986~F -16 Example 2 A 40.3% aqueous CaBr2 solution was thickened with 1% of cetyl trimethyl ammonium salicylate, ~C16-H33(CH3)3N salicylate ] as follows:

0.131 g of salicylic acid was mixed with 9.47 g of 0.1 M C16H33N (CH3)30H solution and the resulting solution mixed with 30.4 g of a 53% aqueous CaBr2 solution.

Af~er dissolu~ion, a clear, slightly yellow solution of high viscosity was formed.

Viscosity measurements were made on a Brook field LTV viscometer with UL adaptor and the results are tabulated below:

TABLE IV

15Shear Rate Temp.No. ofViscosity (~ec 1~ C ~eadin~ s~ _ . _ 0.33 23 3524 - 4g2 0.66 23 Off Scale 0.66 27.5 3 317 - 307 ~00.66 37.5 3 lg5 - 144 0.66 50 3 62 - 66 Example 3 A quaternary ~mmonium salt of the formula:

C18H35N -~CH2CH20H)2 Cl (Ethoquad 0/12 28,986-F -17-was employed to thicken an agueous electrolyte solution as follows.

A solution was prepared by mixing 0.33 g Ethoquad 0/12 with 49.67 g of a solution containing 17.2% CaC12/43.7% CaBx2/39.1% H20, having a density of about 15 ppg. After dissolving by mechanically shaking, there was some foam. The aqueous solution also contained 0.4 perce~t by weight of a corrosion i~hibi~or comprising a mixture of N-octyl pyridinium bromide and ammonium thiocyanate. Using the pro-cedures of Example 1, the rheolo~y of the fluid was measured on the Haake Rotovisco NV system and the calculated viscosity and shear rate da~a is set forth in the following Table V.

28,986-F -18-TABLE V

Shear Rate ( sec 1 ~
2S.3C 43.1 49.5 ~I 86.2 47 3 " 173 ~4 7 " 3~5* 40.8 " 345* 41. ~
" 690 43.6 " 1380* 38 5 " 1380* 36 ~
" 2760 33.6 " 3902* 32.3 " 3902* 31.5 " 13~0 37 4 " 690 44 6 " 6gO 3~ 1 ~' 345 gl 1 " 173 44.4 Il 86.2 47-3 20 45.5 21.6 75.6 " 43 ~ 1 72 " 86.2 60.8 " 173 50.1 " 345 40 8 " 3~5 36 5 " 690 35.2 " 1380 29.4 " 2760* 26.1 " 2760* 24.8 " 3902 23.1 " 1380 30.3 " 690 33.9 " 345 40.9 " 173 50.1 3~ " 86.2 60.8 62.7 10.~ 126 " 21.6 105.3 " ~1.6 117 " 43.1 94.5 " 86.2 77.4 " 173 63.5 " 345* 47.3 " 345* ~9.6 " 690 35.7 " 1380 25.8 28,986 F -19--20~

TABLE V (Continued) Tem~. Shear Rate (sec ~ Viscositx (cps) 62.7 2760 19.4 " 3902* 18 7~ 3gO2* 17.3 " 13~0 26.1 " 690 35.2 " 345 45.9 " 173 ~4.5 " 86.~ 82.1 " 43.1 105.3 85.7 21.6 75.6 " ~3.1 71.1 " 86.2 61.4 " 173 48.9 " 345* 37.5 " 345* 3g.1 ~90 , 30 " 1380 21.9 " ~760 16.6 " 3902 13.7 " 1380 21.3 " 69~ 29.7 " 3g8 37.9 " 173 51.1 " 86.3 64.4 " 43.1 76.5 * Duplic~te readings at different head scales of the instrument~

Example 4 An agueous solution was made up at room temperature containing 0.33 g of Ethoguad 0/12 (Example 1) in 49.67 g of a 15.5 ppg aqueous solution containing 15.1% CaCl2, 40.7% CaBr2, 6.8% Zn~r2 and 37.4% water.
The resulting solution was clear and viscous. Viscosity measurements are set forth in the following Table VI.

A similar solution was prepared at room temperature as a~ove except that a mixture of amines was employed. The solution contained 0.25 g of 28,986~F -20~

-21~

Ethoquad 0/12, 0.13 g of C16H3~N ~C~3)3 Cl ( qu 16-50/50% active) and 49.62 g of the 15.5 ppg density aqueous solution defined directly hereinbefore. The so prepared solution was viscous and clear. Viscosity measurements were made as described directly herein-before and are set forth in the following Table VII.

The solution containing the mixture of thickening agents demonstrated higher viscosities than did the solution containing the single thickener. This demonstrates the fl xibility of being able to control the viscosity of high density aqueous ~luids by the practice of the present inven~ion.

28,986-F -21 ~ t7~

TABLE VI

Temp . C Shear Rate ( sec l ~ Viscosity ( c~s 10.8 133 " 21. . ~ 113 " 43.1 93.9 " 86.~ 80.8 " 173 68.5 " 345* 44.4 " 345* 47.
" 690 2g .7 " 13~0 21.2 " 2760 16.6 " 3902 15.0 " 13~0 21.5 " 345 4~.5 " 173 75 ~ 7 " 21. ~ 111.9 21.6 82.9 " 43.1 74.3 " 86.2 63.8 " 173 54.2 " 345* 4~ .3 " 3~5* 40.5 " 6~0 27.3 " 1380 1~ .4 " 2760 12.9 " 3902 ~1.4 " 345 40.0 ~3.1 26.6 " 86.2 27.4 " 173 27.4 " 345 24.6 " 690* 19.8 " 690* 20.0 " 1380 14.9 " 2760 10.9 Il 3902 9 7 87 173 4.4 " 3*5 4.2 " 690 4.4 " 1380 5.0 " 2760 6.8 " 3902 7.2 " 2760 6.5 " 138~ 5.6 5.1 * Duplicate readings at different head scales of the instrument .

28,986-F ~22 ~35~

TABLE VII

Temp. CShear Rate (sec_1~ Viscoslty (cps) 10.8 344 21.6 260 43.1 164 86.2 102 173 63.8 345* 42.1 345* 48.7 10 " 6~0 37.8 ' 138Q 31.1 ~760 23.7-20.3 3902 18.6~26.3 15'' 1385 375 7 ~6 153 55.2 10.8 266 20~' 21.6 167 32.7 128 " 172* 79.2 Z5,, 172* 867 56 690 43.3 1380 40.5 2760 34.7 345 62.2 " 173 69.4 89 10.8 117 35'' 32 7 47-3 " 86.2 31.3 " 173 22 345 12.5 690 7.8 40'' 1380 5,5 2760 4.1 " 3902* 4-3 ,. 3902* 4-3 " 690 4.3 5 * Duplicate readings at different h~ad scales of the instrument.

28,986-F -23-7~9 ~24-The following illustrates the fact that the amount of thickener and mixtures thereof which are effective can vary and that preliminary screening tests should be made prior to field use. The same thickening agent was employed as in the immediately preceding Example 4 except in different proportion: 0.17 g of Ethoquad 0/12 and 0.25 g Arquad 16-50 were mixed with 49.58 g of the same 15.5 ppg density solution defined in Example 4 hereinbefore. A very thick and viscoelastic fluid was formed. However, there was some insoluble materials ~loating on top. Upon heating to 70C, the viscosity became low and the solution became unstable and formed two distinct phases. ~he fluid would not find general utility as a wellbore service fluid as contemplated herein.

Example 5 A variety of different thickeners were screened to determine their effectiveness to thicken an aqueous solution containing 53% by weight o~ CaBr2. The char-actexistics of the resulting fluids are tabula~ed in thefollowing Tables VIII, IX and X. When viscosity data is shswn, it was calculated employiny data generated on a Haake Rotovisco NV system as described hereinbefore and set forth in one o~ the following Tables IX and X.

28,986-F 24-~~ o -u~ o u~ h a)u~
O
R ~
OO ~ r~ O O ,1 0 0 :~ N . u~ u2 N :1 ~
O ~1 0 ~ O O p~l O O
U~ O ~ tQ U~
~_1 ~1~~ lQ ~ ~ ~ h. ~ )~ ~
q~ ~O N ~ O ~ a)~ ~ ~1) 0 O ~I h rl rl ~ ~ r~

~ U
U~ ~ O
O 3a.~ 5 H ~ ~_~
tl3 o~ o ~ o c~
~10 U IU O u~ O rt l--t rt E3 m t~ u~ o ,~
Ort OO~
H

~t C) ~ E~ Ll~
O O O
~t O O O Il-) O O c:~ O

m ~t ~
tr~l ~ ~ +Z~ a +z~
~ U~ ~ ~P ~ ~
.,, . ~ ~ ~ ~ P: = CO
rt ~Dh 0 ~R ~ ~ ~ V
U ~ V ~
o ~) ~: m v a 28, 986- F -25-~57~7~

tn a) N

S~ O O
. ~
~ ~ ~ O O
~1 h ~ h S-l C) 3 V V

O ~
,_ c) Q~ O a ~ t~ ~ ~1 '~ ~ ~ ~
,~ ~ h E~

~v~

p: = _ +~_~
~ Lr~ ~
U .
S~

28, 986-F 26-~27-TABLE IX

Temp. C Shear Rate ~ec ll* Viscoslt~ (cps)*
5-4 492~6**
" 10.8 3~9.2 " 21.6 219 " 43.1 1~7.
" 8~.2 300.1 " 172.5 273.1 il 345 1~6.~
" 689.9 106.9 5.4 2728.9 " 21.6 1131.3 " ~6.2 S33.3 " 172.~ 3~8~2 " 345 1~5.1 " 689.9 129.3 " 1379.8 73.7 " 2759.7 39.9 5.4 1278.2 " 10.8 1035 ~1.6 794 5 " 86.2 347.6 " 172.5 211.6 ~ 689.9 73,7 " 1379.8 44.7 " 2759.7 23.3 * Da~a as printed out from computer interfaced wi-th Rotovisco NV.
** Since thickener was not entixely in solution, the lower viscosities were expected.

28,986-F -27-TABLE X

Tem~. CShear Rate (sec 1)*Visco~it, (rps~
~.4 1830.8 " 21.6 561.3 5 " 86.2 161.g " 172.5 86.4 " 345 57.2 " 1379.~ 15.7 5.4 12~7.S
10" 10.8 676.5 " 43.1 215.5 " B6O2 455.5 " 172.5 281.7 " 6~9.9 9~.~
15" 1379.8 56.5 90.3 5.4 1555.~
~' 10.8 125g.8 " 21.6 872.2 i' 8~.~ 261.2 20" 172.5 149 " 689.9 47.5 " 1379.8 27.9 2759.7 17.1 " 3902.~ 13.7 2 5 * Data as printed out from compu~er inter~aced with ~otovisco NV.

Ex, ~ mparative Tests ~n electrolyte solution of about 16 ppg density was prepared containing 1~ ZnBr2; 37% CaBr2;
30 12% CaC12 and 37% water. The fluid los~ property of this fluid was determined employing a thickener as described hereinafter. A particulate ~luid loss additive was also employed in some of ~he tests. The particulate fluid loss additive comprised a mixture of particulate aliphatic hydrocarbon resins~ A comparative series of ~ests were run employing hydroxy e~hyl cellu-lose as a fluid loss additive. The fluid loss tests 28,986-F -28~

were run on Brea Sandstone according to the API-RP39 standard fluid 105S test using 1 inch by 1 inch Brea sandstone instead of filter paper. All the tests were I conducted at 150F and 600 psi. The thickener con-5 sisted of Ethoquad 0/12 (Example 1). To each 300 ml fluid sample containing the thickener, one drop of polypropylene oxide was added to control foaming. As a comparison, several solutions containing hydroxyethyl cellulose were tested in the same manner~ The hydroxy-ethyl cellulose was a commercially available product purchased under the trademark Vatrosol 250HHR~ The results of ~hese ~ests are set for~h in the following Table XII. This data illustrates the favorable fluid loss properties achieved by the practice of the invention.

28,986-F -2g-TABLE XII
_ _ _ _ Time (Minutes~Fluid Loss (milliliters) ke ~ 2.6 54 6.
9 12.6 16 21.2 32.6 39.0 B. Test Solution-1% Thickener and 0.5~ Particulate Fluid Loss Additive __ _ _,_ _ , ... _ . _ ..... __ 1.0

4 1.6 g 2.0 1516 2.6 3.0 3.~

Test Solution (0.22%3 Hydroxyeth ~ Cellulose 1 4.6 204 14.0 9 30.0 16 57.0 95.0 Not measured 28,986-F -30~

~31-D. Test Solution-1.5 lb/gal (0.22%~ Hydro~yethyl Cellulose ~us 5~QParticulate Fluid Loss Additi e 1 3.6 4 8.0 9 11.0 13.0 13.2 E. Test Solut_on-0.2~_Thlckener 1 ~.
4 7.0 g 15.6 16 27.0 ~5 47.0 15 30 Sg.0 F~ Test Solution-0.2% Thickener plus 1.5% Particulate Fluid Loss Additive _~
1 .0 47.0 ~0 9 3.2 4.8 Z5 . 7~2 8.4 Example ?_and Comparative Tests Several thickening agents were evaluated for use in a~ueous fluids having densities of greater than 15 ppg. In each example (data set forth in the following Table XII), 0.9 ml of a thickener was added to 35 ml of the indicated high density fluid.
The thickener was employed as a 75 percent active solution in isopropanol. The resulting mixtures 28,9g6-F -31-were shaken on a mechanical shaker for 3 hours and thr~e days later the viscosities were measured at room temperature ~about 75F) employing a Brookfield viscometer at a shear rate of 60 rpm employing a number 2 or 4 spindle. The data employing th number 4 spindle is marked with an asterisk. The data indi~
cates that ~he thickening agents were more effective in the higher density fluids.

The results are tabulated in the following Table XII.

TABLE XII

_Vlscosity (cps) 15.5 pp~16.5 ppg 17.5 ppg Thicken n~ Agent ~ 3) ~ L___ bis(2-hydroxyethyl)- 45 3250* 850*
oleylamine bis(2-hydroxyethyl)- 40 2500* 550*
soyaamlne bis(2-hydroxyethyl)~ 40 1900* 420 tallowamine bis(2-hydroxyethyl)- 45 300* 60 octadecylamine ~one 28 25 25 none 50* 40* 40*

(2) Solution contained 15% CaCl2; 41% CaBr2; 6% ZnBx2 and 38% H20.
(3 ) Solution contained 10% CaC12; 34% Ca~r2; 20% ZnBr2 and 36% H20.
( 4 ) Solution contained 6% CaCl2; 28% CaBr2; 33% ZnBr2 and 33% H20.

28,986-F 32--Example 8 A solu~ion was prepared by dilution of a 40 g sample of 1.5% solution ~0.6 g of C22H46(CH3)2N C2H4HB
+ 39.4 g of 17.5 ppg f~uid) with 80 g of 17.5 ppg fluid to prov1de ~.5% of the surfactant in the solution. The 17.5 ppg fluid contained 6% CaCl; 28% CaBr2; 33% ZnBr2, and the remainder water. The sample was heated to approximately 85C with occasional shaking to produce a clear, homogeneous solution which was hazy at room temperature. The viscosity was measuxed in a ~aake Rotovisco as described in Example 1. These data axe tabulated in Table XIII and show good thickening at room and intermediate tempexatures, and falling off at 8~C. The viscositiPs are from a computer printout inter~ace with the Haake Rotovisco.

28,986-F ~33~

-34~

TABLE XIII

Temp- C Shear Rate (sec 11 .15co~iLy Ir~5 26 5.4 1025 " 10.~ 789.7 " 21.6 439.~
" ~3.1 241.7 86.2 149.7 " 172.5 107.1 " 345 67.6 10 ~I 689.9 48.9 " 1379.8 38.7 " 2759.7 31.~
" 3902.4 29.6 54 5.4 635 15 ~' 10.8 436.7 " ~1.6 31705 " 43.1 ~05.3 " 86.2 166.6 " 172.5 64.9 20 ~' 3~5 35.7 " 689.9 25.1 " 1379. a 17 " 2759.7 14.1 ll 3902.~ 13.2 25~5~.5 86.2 10.1 ~' 172.5 9-3 " 345 8.7 " 689.9 8.4 " 1379.~ 8.4 30 ~' 2759.7 7.1 " 2759.7 9.7 " 3902.4 10.4 28,986 F 34-Example 9 A solution was prepared by diluting a 50 g sample of 1-5% solution ~0.75 g of C20H41(CH3)2N C2H40HBr ~ 49.25 g of 19.2 ppg fluid) with 50 g of 19.2 ppg fluid to provide 0.75% of the thickening agent in the fluid. The fluid contained 56~ ZnBr2~ 19% CaBr2 and 25% H20. The sample was heated to 85C to provide rapid dissolution. The appearance at this temperature was a clear viscous solution which was also clear when cooled to xoom temp~rature (21-22C). After standing a number of days, the sample tended to be-come hazy although warming (approximately 30-35C3 restored the original clear appearance. The viscosity of the fluid was determined as a function of shear rate on a ~aake Rotovisco with a computer printout as previously described. The results are set forth in the following Table XIV.

28,986-F -35-TABLE XIV

Temp. C Shear Rate (sec 1) Vi _OI~EL~
27 10.8 104.~
" 21.6 116.8 " 43.1 87.8 " 86.2 66.5 " 172.5 50.1 " 345 39.
" 689.9* 34.3 " 689.9* 34.3 " 1379.8 29.5 " 27~9.7 25.8 " 3902.4 24.5

5 4 4 13~.6 " 10.8 125.7 " 5.4 13~.6 " 10.~ 12~.7 " 21.6 123.3 " 43.1 117.2 " 86.2 99.3 " 172.5 79.1 " 345 63.8 689.9 4~-5 " 1379.8 35.7 " 275~.7 27.6 " 3902.4 24.~
~1.6 50.8 " 43.1 47.1 " 86.2 g4.3 " 172.5 42.6 " 345 3g.1 " ~89.9* 36.8 " 68g.g* 36.8 " 1379.8 31 " ~75g-7 25.6 " 3902.~ 22.9 * Duplicate readings at different heat scale of instrument.

28,g86-F ~36-

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An aqueous wellbore service fluid comprising:
water, a sufficient quantity of at least one water soluble salt to increase the density of said fluid to within a range of from 12 to 21 lbs/gal, and a sufficient quan-tity of at least one thickener soluble in said fluid to increase the viscosity of said fluid to at least 50%
over the viscosity of the salt containing fluid, said thickener being at least one member selected from the group consisting of: (a) an amine corresponding to the formula wherein R1 is at least about a C16 aliphatic group which may be branched or straight chained and which may be saturated or unsaturated;
R2 and R3 are each independently, hydrogen or a C1 to about C6 aliphatic group which can be branched or straight chained, saturated or unsaturated and which may be substituted with a group which renders the R2 and/or R3 group more hydrophilic; (b) salts of said amine corresponding to the formula wherein R1, R2 and R3 are the same as defined hereinbefore and X- is an inorganic or organic salt forming anion;
or (c) a quaternary ammonium salt of said amine corres-ponding to the formula wherein R1, R2, R3 and X- are the same as hereinbefore defined and R4 independently constitutes a group which has previously been set forth for R2 and R3, none of R1, R2, R3 or R4 are hydrogen, and the R2, R3 and R4 groups of the amine salt and quaternary ammonium salt may be formed into a heterocyclic 5 or 6 member ring structure which includes the nitrogen atom of the amine.

2. The wellbore service fluid of Claim 1 wherein the thickening agent is employed in an amount ranging from about 0.05 to about 5 percent by weight of the fluid.

3. The wellbore service fluid of Claim 1 wherein the water soluble salt comprises a combination of calcium chloride, calcium bromide and zinc bromide in an amount and weight ratio to provide a density of at least 15 pounds per gallon of fluid.

4. The wellbore service fluid of Claim 1 wherein the density of the fluid is at least about 15 pounds per gallon of fluid.

5. The wellbore service fluid of Claim 1 wherein the thickening agent comprises at least one member selected from C16H33N(CH3)3 salicylate; oleyl methyl bis(2-hydroxyethyl)ammonium chloride;

C16H33N+(CH3)3CL-; C18H37 ; bis(2-hydroxyethyl)oleylamine; bis(2-hydroxyethyl)soya-amine; bis(2-hydroxyethyl)tallowamine; bis(2-hydroxyethyl)-octadecylamine; C18H35N(CH2CH2OH)2; C22H45(CH3)2N+CH2CH2OHBr-or C20H41(CH3)2N+CH2CH2OHBr-.

6. The wellbore service fluid of Claim 1, wherein the water soluble salt comprises from 5% to 35%
ZnBr2; from 25% to 45% CaBr2; from 5% to 20% CaCl2 from 30 to 40% water, and from 0.5 to 20% of said thickening agent, all percentages being in percent by weight of the fluid.

7. The wellbore service fluid of Claim 1 wherein X- is Cl- or Br-.

8. In the method of perforating an interval of casing in a wellbore wherein a sufficient quantity of fluid is placed in the wellbore adjacent to the interval to be perforated to maintain pressure on the formation which is at least as great as the formation pressure, the improvement which comprises as the fluid the aqueous wellbore service fluid of Claim 1, 5 or 6.

9. In the method of servicing a wellbore wherein an aqueous fluid is placed in the wellbore and in contact with an oil and/or gas producing formation the improvement which comprises employing as the fluid the aqueous wellbore service fluid of Claim 1, 5 or 6.