US2946748A - Liquid hydrocarbon gels and uses thereof - Google Patents

Description

z Pat n e -M1 6 196 LIQUID HYDROCA RBON GELS AND USES THEREOF Charles S. Steiner, Homewood, and Paul Gibson, Chicago, Ill., assignors to Swift 8: Company, Chicago, 111., a corporation of Illinois No Drawing. Filed May 8, 1956, Ser. No. 583,352

14 Claims. (Cl. 252-855) This invention in general relates to gels made from petroleum oil and fractions thereof and with particular reference to gelled hydraulic fracture fluids. More specifically, the invention relates to gels of petroleum oil and fractions thereof, the gelling agent being a mix ture of alkali metal or ammonium soaps wherein at least about 10% comprises soaps of aliphatic acids having at least 20 carbons. I

The process which has become known as hydraulic fracture of oil or gas bearing subterraneanformations is sharp break in pressure (in theory the point of fracture) after which the pressure remains fairly constant at a lower level as the fluid in theory penetrates the new crack. Thereafter, the pressure is relieved, and the Well is put into production.

We are aware that the theory of hydraulic fracture is not universally accepted. There are those who propose that the fluid jets issuing from perforations in the casing at the pay zone etch cuts through the blocked area imme diately surrounding the bore hole to the more permeable areas more remote from the bore. Others have proposed that the hydraulic fluid drives the water block immediately surrounding the hole into the more remote areas of the formation Without actual fracture. Regardless of theory, I it has been observed that the application of increasing pressure to a hydraulic fluid in'the well bore'resultsin a sharp break in pressure, afterwhich the pressure levels In the process, fluid is pumped into the well at a oils or its fractions, agents which tend to thicken the oil and hence decrease its filtrate rate and increasev ability to suspend small particles are commonly employed. Soaps of fatty acids and naphthenic acids are commonly used as gelling agents in petroleum base fracturing fluids; In addition to alkali metal soaps, other fatty acid soaps of ammonia, metals of the alkali metal and alkaline earth series, or polyvalent metals such as cadmium, mercury, cobalt, lead, nickel and aluminum have been suggested as gelling agents for petroleum base fracturing fluids, Red oil soaps, (sodium oleate) and soaps of tall oil fatty acids (a mixture of fatty acids with small amounts of rosin acids) are among the most common gelling agents used in hydraulic fracture operations. Tall oil fatty acids are, for the purposes of this invention, considered to be low grade liquid fatty acids. Stearic acid has-very little propensity to promote gelation when neutralized in petroleum hydrocarbons by aqueous caustic,

lt-has been established that therelease of hydraulic pressure after the sharp break in pressure diesnot result in return'of the formation to its original condition, but 7.

rather, the formation will exhibit substantial increase in permeability. However, the permeability io'ff the forma tion maybe furtherdncreased'by the use of'oil-inert small particles such as sand, metalchips, crushed shelL} etc. {These particles are suspendedjin the hydraulicfluid by virtue of the 'viscous natur e of fthe gel. Underthe p fracture theorygthey enter the formation with the fluid;

at'the point of fracture. When the pressureis released' and the fracturing fluid flows from the formation, these" materials remain to prop the formation tent at the' point of fracture; r H

a The gels of gel-type fracturing fluids must first be broken or theirviscosity reduced before they may be easilyremoved from the formation: There are several meansfor breaking the'gel, among which are included the addition of a gehbreakercr peptizer 'which may be incorporated in the viscous fracture fluid, said gel breakerbecomingeffective-after a time delay? Water, for-example,- in amounts'between 1 and 3% by volume becomes'effective to'breaksome fatty acid soap-hydro carbon gels after several hours and maybe incorporated "in the" gel by 'emulsificationi Certain other-peptizing' off at a substantially constant lower'level; This type: of treatment of pay zones in general results in increased 1 production of oil and/ or gas. In viewofthe factthat i' the term hydraulic fracture has beenwidely accepted by those in the art to describe the foregoing process of well treatment, We shall employ the same terminology to describe the process of hydraulic pressure treatment with the understanding that we are not limited specifically to any particular theory.

The hydraulic fluids which are generally used are miscible with the interstitial crude oil, e.g., oily liquids,

such as crude petroleum oils, a refined fraction of crude carbon fluids often is increased by the addition of other,

compositions to the base fluid. In the'caseof petroleum agents may be injected into the fracture prior to or afterf the viscous hydraulic-fluid 'In some instanceg' theheat; I

of th'e formation alone, particularly in deep wells, is sufficient to -reduce the viscosity of thegel to a point where it may be'removed by producing the well. jWater soluble airlines such; as ethanolamine and; other similar mean st compounds have been suggested as-effective'} Y gel breakers of l soap-hydrocarbon :gels. "Other suitable materials areammonia, alkali oxides" and hydroxides; dsl g in lal acids. 011s method ofgelbreaking I is the addition of about 1% based on 'the'volume'ofthe w fracturing fluid ofthe gelbreaker i in a suitable solvent.

- such ,as gasoline which-is thenpumped into the well following the fracture liquid to reduce the. viscosity -or break The "gelling agents used the industryceni prise theaforementioned soaps of acids'bet'ween' 14and. 18 carbons. v as little as about 10% of fatty' acid soaps of aca'rbon' A chiain leng'th of 20 or more substantially increases; gel

marine oils are suggested as a source for the manufacture viscosity for a given amount of gelling'agent'and' decreases water sensitivity of the gel. The fatty acids of a carbon chain length of 20 or moreare found mainly in fish and. whale oils. Hence, the-"fatty acids of these apartto some ex- 7 We have discovered that the presenceofj;

of the gelling agents of this invention. These fatty acids of a carbon chain length of 20 or more include saturated acids such as n-eicosanoic (arachidic), n-docosanoic (behenic) and n-tetracosanoic (lignoceric) acids; and unsaturated acids such as A -eicosenoic (gadoleic), A docosenoic (cetoleic), A f-docosenoic (erusic) and A -tetracosenoic (selacholeic) eicosatetraenoic (arachidonic), eicosapentaenoic; docosapentaenoic; docosahexaenoic; and tetracosahexaenoic acids.

The fish fatty acids may be used per se as the gelling agent of the instant invention, or the fish fatty acids may be blended with fatty acids such as steanic, oleic or palmitic, or mixtures thereof such as tallow fatty acids, vegetable oil fatty acids, tall oil fatty acids, etc., as long as the content of C and above acid soaps is maintained above about 10%.

While compositions containing unsaturated acids show improvement in gel characteristics over the comparable prior art gelling agents, We prefer to hydrogenate the fatty acids to an iodine value between about and 12-, preferably between '0 and 4. Hydrogenation to give a product comprising essentially all saturated acids has at least two advantages over an unhydrogenated composition containing appreciably more unsaturated acids. The saturated acids can be flaked more easily to provide easierhandling of [the product, and the gel produced by the saturated acid soaps is of a definitely smoother consistency and has better sand suspension qualities.

We have further found that we can produce a gel with the ammonium soap of fatty acid mixture containing at least acids of a chain length of C and above, which gel is. stable under conditions of field use except where high bole temperatures are encountered. The ammonium soap is prepared by addition of concentrated ammonium hydroxide solution or slow addition of anhydrous ammonia to the hydrocarbon fluid containing the fatty acid mixture heretofore described.

The gels are made by adding the fatty acids to the liquid to be gelled, the petroleum or triglyceride oil. After the fatty acids have been mixed with the liquid, an excess of alkali is added. While some fatty acid mixtures require 50% caustic soda to produce satisfactory gels in petroleum oils, the gels of the instant invention may be produced satisfactorily with caustic soda, which is considerably easier to handleparticularly in the oil fields. We have discovered further that gelation may be achieved even more rapidly and with less excess alkali by using a 50/50 mixture of ammonium hydroxide and caustic soda.

The field. use of the invention follows the same general pattern. The fluid to be gelled, generally apetrol eum liquid hydrocarbon, containing sand or other inert particlesgis mixed *with about 0.5-3.0% by weight of the fatty acid compositions of this invention in the umper truck tanks. Upon adding and mixingan excess of strong alkali, neutralization of the fatty acids oc-.

curs-resulting in the gelation of the fluid. The gel;

is then pumped into the well hole, and pressure is built up until there is a sharp break in the pressure.

Our invention maybe further understood from the following examples:

EXAMPLE I Fully hydrogenated menhaden fatty acids (about 31% C and above acids) was mixed in varied ratios with rubber grade stearic acid and 10% sulfated tallow fatty acids. The fatty acids were added, one percent byweight, to. l00 cc. of kerosene, and 0.8 cc. of 25 NaOH solu tion was added with vigorous agitation. The viscosity of each gel was measured by drawing 50 cc. of the prepared gel into a 50 cc. volumetric pipette, and the time required for the liquid level to drop to the bottom of the pipette bulb was used as a measure of viscosity. The following is a tabulation of results observed with-various mixtures:

Table I Percent Percent Hyd. Menhaden Fatty Sulfated Percent Flow Time,

Acids Tallow Stearic Min.

Fatty Acid Acids 10 0.0 0.91 10 16 0.89 10 25 0.80 10 30 0.83 10 35 0.70 10 0. 68 y 10 50 0.63 10 60 0.58 10 90 0.45 0 100 0.42 100% kerosene 0. 41

EXAMPLE II Kerosene and about one percent of fully hydrogenated fatty acids from each of whale oil, seal oil, herring oil, and sardine oil were thoroughly mixed, and a slight excess of 25 NaOH solution was added. After vigorous agitation, a smooth, non-stringy gel was formed in each instance. The gels had good sand suspension properties.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A gelled liquid hydrocarbon comprising a liquid hydrocarbon and about 05-30% by weight of .a gelling Y agent consisting essentially of a member from the group consisting of alkalirnet'al and ammonium soaps of aliphatic, monocarboxylic acids of at least 14 carbons,

at least 10% of said aliphatic acids having at least 20 carbons.

2 A gelled liquid hydrocarbon comprisinga liquid hydrocarbon and about 0.5 31076 by weight of a gelling agent consisting essentially of amember from the group consisting of alkali metal andamrnonium soaps of aliphatic, substantially saturated, monocarboxylic acids of at least 14 carbons, at least 10% of said acids having at least 20 carbons.

3. The composition of claim 1 wherein the aliphatic acids are marine oil fatty acids.

4. The composition of claim 2 wherein the aliphatic acids are hydrogenated menhaden oil fatty acids.

5. The composition of claim 2 wherein the aliphatic acids are hydrogenated herring oil fatty acids. I I

6. The composition of claim 2 whereinthe aliphatic acids are hydrogenated whale oil fatty acids.

The composition ofclaim 2 wherei the aliphatic acids are hydrogenated sardine oil fatty acids. a

8. The composition of claim 2 wherein thealiphatic acids are hydrogenated seal oil fatty acids. v

9 A gelled liquid hy drocar bon comprising a liquid hy rocarbon. and about us-3.0% by weight of a gelling agent consistingessentiaHy of alkali metal soaps of a mixture of; monocarboxylic acids, at least 10% of said acids being aliphatic acids having at least 20 carbons, the remainder of said acids being a mixture of aliphatic acids havingat least 14 carbons.

10. The composition of'cla im 9 wherein s aidacids are substantially saturated acids. y

11. A method for improvement of the permeability of a subterranean formation to the flowof oil and gas,v

the step which comprises: pumping a gelled liquid comprising a liquid hydrocarbon gelled with a gelling agent consisting essentially of about 0.5-3.0% by weight of said hydrocarbon of a mixture of alkali metal and ammonium soaps of aliphatic monocarboxylic acids having at least l4 carbons, at least 10% of said acids having a chain length of at least 20 into the .bore of a well ata rate; suflicient to increase the pressure of said liquid at least until there is a sharp break in pressure.v

12. The method of claim 11 wherein substantially all of said aliphatic acids are saturated acids.

13. A method of claim 12 wherein the aliphatic acids are derived from hydrogenated marine oils.

14. A hydraulic fluid for high pressure treatment of oil and gas bearing formations which comprises: a gelled liquid hydrocarbon; oil inert solid propping materials suspended therein; and a gelling agent consisting essentially of 0.53.0% by weight of said hydrocarbon of a member from the group consisting of alkali metal and ammonium soaps of a mixture of aliphatic monocarboxylic acids having at least 14 carbon atoms, at least 10% of said acids having a chain length of at least 20.

References Cited in the file of this patent UNITED STATES PATENTS Brunstrum Jan. 21, Brunstrum et a1. Jan. 21, Morway et al. Nov. 20, Morway et a1. Ian. 1, Clark May 13, McChrystal Jan. 26, Johnson Aug. 24,

Claims (1)

1. A GELLED LIQUID HYDROCARBON COMPRISING A LIQUID HYDROCARBON AND ABOUT 0.5-3.0% BY WEIGHT OF A GELLING AGENT CONSISTING ESSENTIALLY OF A MEMBER FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM SOAPS OF ALIPHATIC, MONOCARBOXYLIC ACIDS OF AT LEAST 14 CARBONS, AT LEAST 10% OF SAID ALIPHATIC ACIDS HAVING AT LEAST 20 CARBONS.