US2708974A - Treatment of oil-bearing formation - Google Patents

Description

May 24, 1955 P. w. FISCHER ET AL 2,703,974

TREATMENT oF OIL-BEARING FORMATION Filed Aug. 20, 1951 .ZZ/Z6: 2. .Sar/wirf@ .Sima/Ya an y Viana/.2f ZA/0MM,

2,708,974 TREATMENT F OIL-BEARING FORMATION Paul W. Fischer, East Whittier, and Theodore J. Nowak, San Pedro, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of Californa Application August 20, 1951, Serial No. 242,654 Claims. (Cl. 166--33) This invention relates generally to a method for plugging water-bearing sands located in oil-producing formations. More particularly, this invention relates to a method for the selective plugging of water sands Without substantially aiiecting oil production with slow setting greases which after placement in the formation set up to form the plug.

Many processes have been devised for the plugging of oil-bearing formations in an attempt to block and seal off the water-bearing strata while keeping oil-bearing strata open for free ow of oil. In general, such processes have not been entirely satisfactory owing to the lack of selectivity. Thus in the case of cementing, the liquid cement enters all formations indiscriminately and is as elcctive in blocking oil strata as water strata.

The present invention is based on the discovery of slow setting grease-like compositions which can be pumped into the bore hole and thence into the formation to be plugged, and thereafter set up to a grease-like consistency after entering the formation. The plugging compositions employed in practice of the invention are selective in their action and preferentially enter water-bearing strata. They have poor oil resistance but good water resistance so that the plug formed is permanent with respect to water ow. However, such compositions are oil-dispersible to the extent that oil can continue to flow through strata which have been blocked.

It is therefore an object of this invention to block preferentially the water-bearing strata of an oil-bearing formation.

It is another object of this invention to inject slow setting greases into an oil-bearing formation while in a fluid State and to permit the grease to set up within the interstices of the formation.

It is another obje-ct of this invention to react alkali metal and ammonium soaps of rosin acids such as abietic acid, dehydroabietic acid, dihydroabietic acid, and other rosin acid derivatives with aluminum soaps in an oilbearing formation.

Other objects and advantages of this invention will become apparent to those skilled in the art as the description thereof proceeds.

Briefly, this invention relates to a method for the selective plugging of oil-bearing formations with slow setting grease-like compositions. The grease-like composition is prepared by mixing alkali metal and/ or ammonium soaps of rosin acids with aluminum soaps of fatty acids, unsaturated fatty acids, cycloalkyl acids and/ or mixtures thereof in the presence of a mineral oil. The mixture is at irst a readily pumpable fluid which can be readily forced into even small grained oil-bearing sands without appreciable formation of any lter cake to impede its flow. After a period of time, such as 0.5 to 6 hours, the fluid sets up to a grease varying in consistency from a soft butter to a greasy solid depending upon the nature of the particular composition. In one modification of the invention a or in conjunction with, the soap of the rosin acid. The

use of free rosin acid tends to extend the time required for the composition to set to the desired grease-like consistency.

A particular advantage of the plugging agent of this invention lies in its ability to enter water-bearing formations selectively and in preference to oil-bearing formations so that the principal blocking action takes place in the water-bearing formations. After the placement and setting of the plugging agent, a ow of oil is more effective in dislodging the block than is a corresponding flow of water. Thus the plug tends to permit oil iiow while preventing a corresponding water ow.

A solvent is employed for dissolving and/ or dispersing the two kinds of soaps and serves as an oil base for the resulting grease structure. The solvent will generally comprise at least about and generally about 90% or more by weight of the plugging composition. Various solvents may be employed for this purpose, such as hydrocarbons, halogenated hydrocarbons, nitro-hydrocarbons, alcohols, ketones, ethers, and the like. The solvent is usually a mineral oil and is preferably a petroleum distillate boiling generally between about 300 F. and 900 F. and preferably between about 400 F. and 700 F. Aromatic-rich hydrocarbon stocks are especially suitable, and a particularly desirable solvent is one obtained by the solvent extraction of lower boiling hydrocarbon distillates to concentrate Van aromatic-rich fraction boiling between about 400 F. and 700 F. Such fractions are obtained in the normal solvent refining of kerosene and diesel fuel stocks.

The plugging composition usually contains between about 2% and 7% of an alkali metal or ammonium soap of a rosin acid, or of a free rosin acid, or of a mixture of a free rosin acid and an alkali metal or ammonium soap of a rosin acid.

The term rosin acid is employed to denote both gum and wood rosins and also derivatives of such rosins such as are obtained by hydrogenation, dehydrogenation, disproportionation, decarboxylation, isomerization, polymerization or combinations of such processes. Such methods of modifying 'gum and wood rosins are well known in the art. The rosin or modified rosin may also be fractionated as by solvent extraction to produce various acidic fractions which may be employed in this invention.

A particularly suitable rosin soap is one obtained from the acids obtained by the disproportionation of ordinary rosin. The natural rosin is contacted with an active hydrogenation catalyst in the absence of added hydrogen at an elevated temperature until it contains at least about 40% of dehydroabietic acid and less than about 1% of abietic acid. Upon distillation, the disproportionated rosin may be separated into a plurality of cuts. The middle fraction ranging from 50% to 90% is the preferred acid for the preparation of rosin soaps for employment in this invention.

The dehydrogenation or disproportionation reaction is carried out by contacting the rosin or rosin material at an elevated temperature with an active hydrogenation catalyst in the absence of added hydrogen to effect a dehydrogenation or disproportionation reaction. Catalysts such as palladium, platinum, nickel, copper chromite, etc., are suitable. The catalyst may be supported on a carrier, such as granular alumina, fibrous asbestos, or activated charcoal. Dehydrogenation or disproportionation with a palladium catalyst, for example, may be conducted either by a batchwise or continuous procedure. Thus, the rosin may be agitated with about 5% to 20% by weight of a palladium catalyst supported on activated carbon (1% to 2% palladium) at about 300 F. to about 600 F. for about one to about five hours. In the continuous process, the molten rosin flows over the supper molecule.

3 ported palladium catalyst at a temperature within the range of about 450 F. to about 600 F. for a period of about one-fourth hour to about one hour.

If desired, the dehydrogenated or disproportionated rosin may be hydrogenated, before or after fractional distillation, and before conversion to the alkali metal salt, by contacting the dehydrogenated or disproportionated rosin with hydrogen in the presence of a hydrogenation catalyst at a suitable temperature and pressure.

The rosins which may be dehydrogenated or disproportionated for the preparation of these soaps may be gum or wood rosin. The wood rosin may be refined prior to its dehydrogenation by any suitable method, e. g., by crystallization, by treatment with an absorbent such as fullers earth, or by a combination of any of these methods. If desired, the rosin may be isomerized by treatment with an acidic isomerizing agent prior to dehydrogenation.

The distillation of the dehydrogenated or disproportionated rosin may be conducted either batchwise or on a continuous scale in a flash distillation still. In the latter case, the low end and middle cut are fractionally condensed separately. If the batch distillation procedure is employed, the vapor temperature varies depending upon the amount of middle cut desired, pressure of distillation, type of still, etc., but generally ranges from about 410 F. to about 530 F., when the distillation pressure is about 5 to about 10 mm. A light end, varying from about 5% to 30% of the charge, preferably from about to 20%, depending upon the rosin used for dehydrogenation, conditions of dehydrogenation, etc.` is removed and a middle cut comprising about to 90% of the charge, preferably about to 80, is taken. The distillation residue represents from about 5% to 25% of the charge.

The middle cut of distilled dehydrogenated or disproportionated rosin is converted into an alkali metal salt by neutralization with an alkali metal base. Among the alkali metal bases suitable for this reaction are the hydroxides, carbonates, etc. of lithium, sodium, potassium, etc. The rosin acid soaps are, in general, prepared from the corresponding acids or soaps thereof by saponification, metathesis or any other of the methods which are well known in the art.

In general, the aluminum soap component is prepared from acids having between about 10 and 30 carbon atoms The presence of unsaturated acids in general increases the time of gelation while high concentrations of unsaturated and/or cycloalkyl acids favor progressively longer gelation times. composition will gel within a reasonable time, the average composition of the acid or acid mixture from which the aluminum soap is prepared should have the formula CnHzn-l-x(COOH) wherein n is an integer between 10 and 30 and x is greater than -2 and preferably greater than -l. In no case will x exceed l however.

The aluminum soap may be prepared from such acids as capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nondecylic acid, arachicic acid, behenic acid, lignoceric acid, citronellic acid, undecylenic acid, oleic acid, elaidic acid, ricinoleic acid, erucic acid, brassidic acid, linoleic acid, geranic acid and the like. Cyclic acids, such as the cycloalkyl acids derived from petroleum, e., naphthenic acids, may also be employed. The preferred aluminum soap is preferably prepared from a mixture of two or more acids and preferably such acid mixtures will contain both saturated and unsaturated acids.

The nature of the final grease and the setting time are both influenced by the ratio of the rosin soap or of the rosin acid to the aluminum soap and the nature of the acyl groups of the aluminum soap. The aluminum soap is usually fixed in the range of 1.5% to 5% and the rosin acid soap or rosin acid is then increased until the In order that the desired consistency of the final grease is obtained. Where insufficient rosin acid soap or acid is employed the composition will not set up and where too much is employed the gelling time is decreased. Where the aluminum soap is prepared from saturated fatty acids the gelling time is shortened and it maybe lengthened by increasing the unsaturation or cyclo-alkyl groups of the aluminum soap.

The principal ingredients of the plugging compositions include the rosin acid and/or soap, the aluminum soap, and the solvent. In certain cases small amounts, such as 0.1% to 5% by weight, of other components may be added to the plugging composition in order to improve its plugging and adhering characteristics. Thus natural and synthetic resins may be incorporated in the composition. A particularly suitable synthetic resin is the mixture of polymers obtained from the polymerization of beta-pinene. Other synthetic resins which may be employed include polymers of butadiene, pentadiene, methyl pentadiene, styrene, acrylic acid, and the like or mixtures thereof. Other materials which may be added include dihydroabietyl maleate.

Figure l illustrates the volumetric flow of a plugging composition through an oil-saturated core and the backflow of kerosene through the core after placement and setting of the plugging composition.

Figure 2 shows the volumetric flow of the plugging composition through a water-saturated core and the backflow of Water through the core after placement and setting of the plugging composition.

Perhaps the process of this invention can best be understood by reference to the following specific examples:

EXAMPLE I Two cylinders of Ohio sandstone were prepared which were about 5.85 cm. in length and which had a ratio of length (cm.) to area (cm.2) of 1.168. The one core was saturated with kerosene until the core contained only irreducible water, i. e., further saturation of kerosene did not lower the water content. This core represented an oil-saturated formation. The other core was saturated with a 3% sodium chloride solution in water until no further amounts of kerosene could be removed by such treatment, i. e., until the core contained only irreducible kerosene. This core represented a watersaturated strata in an oil-bearing formation.

A kerosene extract fraction boiling between about 400 F. and 600 F. was selected as the solvent for the plugging composition. The material contained approximately by volume of aromatic hydrocarbons and hada gravity of 21.5 API.

An aluminum soap was prepared by metathesis of the sodium soaps of a mixture of acids containing about 60% by weight of lauric acid, 20% by weight of oleic acid and 20% by weight of naphthenic acids obtained from petroleum stocks boiling between about 400 F. and 800 F.

The rosin soap was the soap of a disproportionated rosin containing less than about 1% by weight of abietic acid and which was saponiied with the equivalent amount of sodium hydroxide under pressure to obtain the soap. A polymer of beta-pinene having a melting point of about 207 F. was employed to increase the adhesiveness of the composition.

The following formulation was employed as the plugging composition:

Grams Kerosene extract 900 Disproportionated rosin soap 25 Aluminum soap l5 Water l0 Beta-pnene resin l0 Total V960 The foregoing composition when first mixed was fluid and Pumpable and after about two hours set upto a grease .5 Y gelling composition enters.r the water-saturated Ycore quite readily. The results with Figure 1 are not absolutely comparable however due to` variations between the applied pressure with respect to time after mixing. The results do show however that the lluid readily enters the watersaturated core. When the plugged core was backwashed with 3% salt water at 135 F., 100 p. s. i. was insuflicient to cause a breakthrough and 200 pounds was required for a breakthrough.

EXAMPLE II A series of experiments was performed to determine the effect of concentration of soaps, type of rosin acid or soap and type of metal soap employed on the setting having the 'consistency similar to that et butter when the latter can be spread with a knife.

A sample of the unset plugging composition was pumped through each of the two sandstone samples with progressive increases of pressure at 135 F. With the elapse of time the pressure required to produce a given ow increased considerably due to the gelling of the plugging composition. After determining the flow of plugging composition with respect to time at the varying pressures, each of the sandstones was then backwashed using kerosene for the kerosene saturated core and 3% salt solution for the Water saturated core. The pressure required to force fluids through the two cores in this manner was then determined over a period of time.

The data are presented graphically in Figures 1 and 2 l5 characteristics of the composition. The data are tabulated for these experiments. Figure 1 shows the curve for the in Table 1. The compositions contained a metal soap, introduction of the gelling composition into the core a rosin derived soap (or acid), and a solvent which was representing an oil sand wherein` after aboutl hour a the same aromatic solvent employed in Example I. In pressure differential of 300 p. s. i. eiected a small throughcertain cases the aluminum or other metal soap was disput of the gelling composition. After placement of the solved in the solvent by heating to 250 F. and the gelling composition and backwash with kerosene at 135 clear resulting solution was cooled and mixed with the F., a breakthrough of the gel was found at between 50 rosin acid and/ or rosin acid soap in the cold to determine and 100 p. s. i. as is indicated by the steep vertical line the cold setting characteristics. In other cases 'the three at the end of the curve. components were simply mixed in the cold and allowed Figure 2 for the water-saturated core shows that the 2:5 to stand.

TABLE 1 Effect of rosin acids and rosin acid soaps on the setting characteristics of greases employing metallic soaps including aluminum soaps Metal DR0-Sind erive Run No. Metal Soap Soap Rosin Acid Soap or Acid b Soap, Remarks Employed Percent Pe ent by Weight rc by Wt.

Al Stearatc. 0. 5 Disproportonated Rosin.- Viscous oil; grease formed by heating at 180 F.

l. 0 Slight grease without heating.

2. 0 Grease formed in 10 minutes.

3. 0 Heavy grease formed in 10 miu- (1 5 Slight grease formed in l hour.

2. 0 Moderate grease formed in 1 hour.

o. 5 No grease formed in 2 hours.

1. 0 Slight grease in 2 hours.

2. 0 Grease formed in l5 minutes.

3. 0 Heavy grease formed in 10 minutes. No grease in 4 hours.

HeaIvy grease in 5 minutes.

o. No grease in 2 hours.

Do. Grease formed in l hour. Grease formed in 25 minutes.

Heavy grease in 1 hour. Medium grease in 1 hour.

Tall Oil Soap Disproportonated Acid b. Rosin l.- Disproportionated Rosin.. 350 F. heated rosin Displroportionated Rosin.-

Rosin Heavy grease in 1 hour. Disproprotionated Acidb No grease in 2 hours. Rosin Acid l' Do.

Do: Medium grease immediately. Ligl grease in 4 hours.

o. Light grease in l hour. Medium grease in 1 hour. Heavy grease almost immediately.

l Al mixed soap is the aluminum soap of a mixture of 400-800 F. naphthenic acid and 20% by weight of oleic acid.

free rosin acid.

e Grease formed on heating 16 hours at 180 F.

of acids containing 60% by weight of lauric acid, 20%

by weight is used to designate expressly the use of the -'Examination of Table'l shows that the'use'of a` disproportionated rosin acid soap and disproportionated rosin acid with the aluminum mixed soap (same as that employed-in Example I) gave greases which did set up but only after a reasonable time. The use of rosin acid in place of rosin acid soap generally causes the mixture to remain more iiuid for a longer period or set up after some heating. Aluminum stearate causes fairly rapid setting while neither cobalt oleate nor zinc stearate produced a grease in six hours. A mixed aluminum soap such as the one employed above is preferred in that reasonably long setting times are then obtained. In certain cases, mixtures of aluminum soaps with other metal soaps may be employed to give satisfactory setting times.

EXAMPLE III In another series of experiments plugging compositions were prepared from the aluminum mixed soap and solvent Compositions containing 2.5% by weight of aluminum mixed soap and the sodium soap of disproportionated rosin with a free rosin acid Dispropor R tionated Olm Run Typo of Rosin Acid, No. Amd Soap Acid Percent Remarks Percent b Wt s by wt. Y

46 6 Disproportionated 2 Heavy grease in 15 Acid. min. 47 6 do 4 Light grease in 6 hours. 48 4 4 Medium grease in 5 min. 49 2 6 Heavy grease in 5 min. 50 6 2 Heavy grease 1n 10 min. 51 6 4 Do. 52 4 4 Do. 53 2 6 D0.

The foregoing data show that mixtures of a rosin acid soap and a rosin acid may be employed with the aluminum soap to form slow setting greases. The use of free acid tends to reduce the time of setting.

Other trivalent metal soaps may be substituted for the aluminum soaps such as ferric soaps and the like. In other cases the aluminum soap may be partly substituted with divalent metal soaps such as cobalt oleate, zinc stearate and the like. Aluminum soaps are preferred to all other soaps of trivalent metals however.

An important characteristic of the plugging compositions of this invention resides in the ability to change from a readily pumpable uid into a grease-like solid upon standing at a temperature in the range of 50 to 150 F. such as prevail in oil bearing formations. Consistency of the compositions may be conveniently determined by means of the API Shearometer Test described in API Recommended Practice 29, 3rd edition, May 1950. The compositions on initial mixing show relatively low gel strength and normally show a Shearometer value below about 40 lbs./ 100 sq. ft.l When these compositions are allowed to stand however',they assume a greaselike structure and show a Shearometer value above 50 1bs./ 100 sq. ft. After the period of setting the compositions cease to be pumpable by ordinary liquid pumps.

' The foregoing disclosure of this invention is not to be considered as limiting since many variations may be made -by those skilled in the art without departing from th'e` spirit or scope of the'following claims.

We claim:

`1. The method of differentially shutting off water in 8 an oil lwell''penet'ra'tir'i'g both oiland'VW'ater-bea'rin'g formations which comprises forming a plugging composition consisting essentially of an organic solvent having dissolved therein between about 1.5 and about 5 per cent by weight of an aluminum soap of an organic acid containing from about 10 to about 30 carbon atoms and sutilcient of a material selected from the class consisting of rosin acids and alkali metal and ammonium soaps of rosin acids to cause the composition to set to a greaselike consistency upon standing; forcing said composition while still in the liquid state down the well and into said formations; and maintainings'aid composition in said formations until said grease-like consistency is attained.

2. The method of claim 1 wherein the organic solvent is a mineral oil and the material selected from the class consisting of rosin acids and alkali-metal and ammonium soaps of rosin acids is present in the plugging composition in an amount representing between about'2 and about 8 per cent by weight of the entirecomposition.

3. The method of claim 2 wherein the organic solvent is an armomatic-rich petroleum distillateboiling between about 400 F. and about 800 F.

4. The method of claim 2 wherein the material selected from the class of rosin acids and alkali metaland ammonium soaps of rosin acids is anv alkali metal soap of disproportionated rosin.

5. The method of claim 2 wherein the aluminum soap is an aluminum soap of a mixture comprising about 60 per cent by weight of lauric acid, 20 per cent by weight of naphthenic acids boiling in the range 400 F.-800 F. and `20 per cent by weight of oleic acid.

6. The method of claim 2 wherein the aluminum soap is aluminum stearate.

7. The method of claim 2 wherein the material selected from the class consisting of rosin acids and alkali metal and ammonium soaps of rosin acids is a mixture of rosin acids and alkali metal soaps of rosin acids.

8. The method of claim 2 wherein the material selected from the class consisting of rosin acids and alkali metal and ammonium soaps of rosin acids is a mixture of disproportionated rosin and the sodium soap of disproportionated rosin.

9. The method of differentially shutting off water in oil wells penetrating both oiland water-producing formations which comprises forming a plugging composition consisting essentially of kerosene having dissolved therein between about 1.5 and about 5 per cent by weight of an aluminum soap of a fatty acid containing from about 10 to about 30 carbon atoms and between about 2 and about 8 per cent by weight of an alkali metal rosin acid soap, forcing said composition while still in the liquid state into said formation, and maintaining said composition in said formations until said composition sets to a greaselike consistency.

10. The method of claim 9 wherein the alkali metal rosin acid soap is the sodium soap of disproportionated rosin.

References Cited inthe le of this patent UNITED STATES PATENTS Butcosk et al. I Dec. 13,

Claims (1)

1. THE METHOD OF DIFFERENTIALLY SHUTTING OFF WATER IN AN OIL WELL PENETRATING BOTH OIL- AND WATER-BEARING FORMATIONS WHICH COMPRISES FORMING A PLUGGING COMPOSITION CONSISTING ESSENTIALLY OF AN ORGANIC SOLVENT HAVING DISSOLVED THEREIN BETWEEN ABOUT 1.5 AND ABOUT 5 PER CENT BY WEIGHT OF AN ALUMINUM SOAP OF AN ORGANIC ACID CONTAINING FROM ABOUT 10 TO ABOUT 30 CARBON ATOMS AND SUFFICIENT OF A MATERIAL SELECTED FROM THE CLASS CONSISTING OF ROSIN ACIDS AND ALKALI METAL AND AMMONIUM SOAPS OF ROSIN ACIDS TO CAUSE THE COMPOSITION TO SET TO A GREASELIKE CONSISTENCY UPON STANDING; FORCING SAID COMPOSITION WHILE STILL IN THE LIQUID STATE DOWN THE WELL AND INTO SAID FORMATIONS; AND MAINTAINING SAID COMPOSITION IN SAID FORMATIONS UNTIL SAID GREASE-LIKE CONSISTENCY IS ATTAINED.

Images