CA1100300A - Treating subterranean well formations - Google Patents
Treating subterranean well formationsInfo
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- CA1100300A CA1100300A CA318,724A CA318724A CA1100300A CA 1100300 A CA1100300 A CA 1100300A CA 318724 A CA318724 A CA 318724A CA 1100300 A CA1100300 A CA 1100300A
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
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- General Life Sciences & Earth Sciences (AREA)
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Abstract
TREATING SUBTERRANEAN WELL FORMATIONS
Abstract of the Disclosure A method of treating a subterranean well formation wherein a low pH highly viscous thixo-tropic treating fluid is introduced into the for-mation. The treating fluid is formed by combining an aqueous acid solution with an aqueous alkali metal silicate solution and a gelling agent whereby a highly viscous polymerized alkali metal silicate gel of low pH is produced followed by shearing of the gel to impart thixotropic properties thereto.
Abstract of the Disclosure A method of treating a subterranean well formation wherein a low pH highly viscous thixo-tropic treating fluid is introduced into the for-mation. The treating fluid is formed by combining an aqueous acid solution with an aqueous alkali metal silicate solution and a gelling agent whereby a highly viscous polymerized alkali metal silicate gel of low pH is produced followed by shearing of the gel to impart thixotropic properties thereto.
Description
` ~03~0 In the treatment of sub~erranean well formations it is often desirable or necessary to introduce a lo~ pH highly viscous treating fluid ;nto the formation. For example, in hydraulic fracturing processes carried out in subterranean formations, i.e., creating and/or propping fractures in formation, highly viscous fracturing fluids of low pH are often utilized with or without propping agent suspended therein. Commonly, such frac-turing fluids are pumped into a formation being treated at a rate and pressure sufficient to produce one or more fractures therein.
Continued pumping of the fracturing fluid extends the fractures, and when the fracturing fluid contains propping agent suspended therein, the propping agent is left in the fracture. Because the fracturing fluid is of low pH, minerals in the formation are dissolved whereby the pore spaces therein are opened or enlarged and the permeability of the formation increased.
Highly viscous well formation treating fluids are particu-larly advantageous in carrying out fracturing and/or acidizing procedures in that such fluids are capable of opening one or more fractures to a width sufficient to place propping agent therein without excessive leak-off of the fluid, and such highly viscous - fluids are capa~e of maintaining propping agent in suspension ~or long periods of time without excessive settling. However, problems nave be~n encountered in the use of high viscosity low pB treatiny fluids utilized heretofore, e.g., complexed natural 2S gum and cellulose derivative gels, in that such gels generally 110~3~0 become less viscous when high formation temperatures are en-countered, i.e., above about 140F, and/or break down and become less viscous in the presence of acid. Such reduction i~n viscosity in well formation treating fluids can often produce undesirable results. For examp]e, if the fluid is used as a fracturing fluid with propping agent suspended therein, a reduction in the vis-cosity of the fluid allows the propping agent to rapidly settle resulting in inadequate propping of fractures produced. Also, heretofore used complexed gels often cause significant damage to the formation treated therewith, i.e., bring about a reduction in the permeability thereof.
In carrying out the treatment of su~terranean well formations using highly viscous fluids, it is desirable that the fluids be ~hixotropic, i.e., that the fluids have the property of developing a :~ow viscosity in turbulent flow, but exhibiting a high viscosity when at rest, the transition being reversible. By the present invention, methods of treating subterranean well formations with highly viscous thixotropic treating fluids of low pH which are stable at high temperatures and which are relatively non-damaging to the treated formation are provided.
The method of the present invention for treating a subter-ranean well formation comprises combining an aqueous acid solution ith an agueous alkali metal silicate solution having a pH greater than a~out 11 and a gelling agent comprised of a solution of a water soluble organic solvent and an ethoxylated fatty amine ~ 3-11003~10 thereby forming a low pH highly viscous polymerized alkali metal silicate gel, shearing the gel to obtain a highly viscous treating fluid having thixotropic properties and then introducing the treating fluid into the subterranean well formation.
The invention in its broadest aspect relates to a method of forming a low p~ highly viscous thixotropic fluid for use in treating a subterranean well formation compris-ing the steps of: combining an aqueous solution of acid other than hydrofluoric acid with an aqueous alkali metal silicate solution having a pH of greater than about 11 in an amount sufficient to lower the pH of the resulting mix-ture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized alkali metal silicate gel; combining a,gelling agent with said polymerized alkali metal silicate gel, said gelling agent consisting of a solution of a water soluble organic solvent and a mixture of ethoxylated fatty amines having the general formula:
( CH2CH20 ) xH
R - N
( CH2CH20 ) yH
wherein: R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms, and x and y each have a value in the range of from 0 to about 10 but both x and y are not 0;
said ethoxylated fatty amine is present in said gelling agent in an amount in the range of from about 10~ to about 80% by weight of said gelling agent; combining additional aqueous solution of acid other than hydrofluoric acid with said polyme~ized alkali metal silicate gel-gelling agent llOQ3QO
mixture in an amount sufficient to obtain a mixture con-taining excess acid in the range of from about 1~ to dbout 28% by weight of said mixture; and shearing said mixture to thereby obtain a highly viscous thixotropic treating fluid.
Other aspects of this application are claimed in a divisional application.
A variety of alkali metal silicates can be utilized in accordance with the present invention, e.g., sodium, potassium, lithium, rubidium and cesium silicate. Of these, sodium silicate is preferred, and of the many forms in which sodium silicate exists, those having an Na20:Si02 ~eight ratio in the range of from about 1:2 to about 1:4 are most preferred. A specifically preferred material for use in accordance with the method of the present invention is a commercially available aqueous sodium silicate solution having a density of 11.67 pounds per gallon, an Na20:Si02 weight ratio of about 1:3.22 (Grade 40) and having the following approximate analysis:
Component% by Weight Na20 9.1 Si02 29.2 Water 61.7 TOTAL 100.00 A variety of acids can also be used, either organic or inorganic as well as acid producing materials.
Examples of inor~anic acids which can be used are hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. Examples of organic acids which can be used are formic acid and acetic acid. An example of an - 4a -'~, ~ ~.
11003~0 acid forming material which can be used is benzotrichloride.
Of the acids and acid forming materials which can be used, hydrochloric acid, sulfuricacid, phosphoric acid and mixtures of such acids are preferîed with hydrochloric acid being the most preferred. As will be understood by those skilled in the art, hydrofluoric acid cannot be utilized in that its reaction with silicates has an adverse affect on the formation of polymerized silicat~ gel.
In preparing a highly viscous fluid having thixotropic pro-perties and a low pH for treating a subterranean well formation, an aqueous alkali metal silicate solution having a pH of;greàter than about 11 is first prepared. Such a solution using Grade 40 sodium ~ilicate solution starting material is prepared by mixing about 5 parts by volume Grade 40 sodium silicate solution with about g5 parts by volume water. The resultlng solution has a pH
in the range of from about 11 to about 12, and a viscosity of about 1 centipoise. To this solution is added an aqueous acid solution, such as a 20 Bé aqueous hydrochloric acid solution, while agi-tating the mixture, to lower the p~ of the mixture to a value in the range of from about 7.5 to about 8.5 whereby ~he alkali metai silicate polymerizes to form a hi~hly viscous rigid gel. While a polymerized silicate qel will form at pH ~evels other than from about 7.5 to about 8.5, the rate of formation of the gel is ~reatest in such range.
Upon polymerization of the alkali metal silicate in the manner 110~3~0 described above, a highly crosslink~d risid gel structure is formed which is not soluble in water, but wnich is gelatinous due to water being entrapped in the polymer structure. In order to~impart thixotropic properties to the polymerized silicate gel, it is sheared by mixing or agitation, preferably while the polymerization reaction is taking place. It is believed the shearing of the gel divides it into fine particles carrying static charges which will not agglomerate into a ~ass and which exhibit thixotropic proper-ties, i.e., a low viscosity in turbulent flow but a high viscosity when at rest or at low shear rates.
Additional aqueous acid solution is added to the gel to ob-tain a low pH treating fluid of desired acia strength. For example, additional acid solution can be added to the gel in an amount sufficient to o~tain a mixture containing excess acid in a quantity in the range of from about 1 percent to about 5 percent by weight of the mixture. However, the addition of excess acid to the poly-merized silicate gel causes ~he gel to thin out and lose its thixotropic properties to some degree. This is believed to be due to the fact that the sheared gel particles have negative static charges ~hich cause the particles to repel each other which in turn gives the gel its thixotropic properties. When excess acid is added to the gel, the negative charges are at least partially neutralized which decreases the thixotropic properties. In order to overcome tnis problem and to increase the viscosity of the gel mixture containlng excess acid, a viscosity increasing ~1~03~0 chemical wnich also ~unctions as a surfactant, hereinafter referr~
to as a "gelling agent", is combined with the polymerized sodium silicate gel prior -to adding the excess acid therewi~h. It is believed the surface active properties ol the gelling agent pre-Yent the c~arged particles from agglomerating in the presence of acid and thereby prevent the corresponding thinning out and loss of thixotropic properties.
A gelling agent suitable for use in accordance with this invention is comprised of a solution of a water soluble organic solvent and an ethoxylated fatty amine-having the general formula:
~(CH2CH20) xH
R - N
(CH2CH2O) yH
wherein:
~ is selected from saturated and unsaturated aliphatic gxoups having in the range of from about 8 to about 22 carbon atoms, and mixtures thereof, and x and y each have a value in the range of from 0 to about lO.
- ~he preferred ethoxylated fatty amines and mixtures thereof useful herein are those wherein the average sum of the values of x and y in the amines used is in the range of from about 1.8 to about 2.2.
Mixtures of ethoxylated terti.ary fatty amines derived from fats and oils such as coconut oil, soy ~ean oil, and tallow are particularly suitable for use in accordance with the present invention.
A preferred mixtllre of ethoxylated fatty amines is a mixture of amines of the general formula:
' . ~(C,H2CH20) XH
R N\
~ CH2CH20)yH
wherein:
is selected from the group consisting of saturated and unsaturated chains of aliphatic groups having in the range of from about 14 to about 18 carbon atoms ar,d mixtures of such groups; and wherein the average sum of the values of x and y in the mixture of ethoxylated amines is equal to 2.
In the most preferred embodiment, x and y each have a value of l (one).
Examples of such amines are those derived from fatty acids o~ the type hexadecyl, tallow, soya and oleyl, either saturated or unsaturated and as pure components or mixtures.
_ A variety of organic solvents can be utilized in the gelling agent so long as such solvents are capable of dissolving the ethoxylated fatty amines and are water soluble. Examples of such water soluble organic solvents include al~anols having in the range of about 1 to 5 carbon atoms per molecule, such as methanol, ethanol, sopropanol and t-butanol; ~etones having in the range of about 3 to 6 carbon atoms per molecule, such as acetone and ~10~3@0 methylethyl ketone; polyhydroxy compounds having in the range of about 2 to o cax~on atoms per molecule, such as et~ylene glycol and glycerine; ethers having in the ranye of about 2 to 6 carbon atoms per molecule, such as dioxane and tetrahydrofuran; com-- pounds containing both ether and alcohol functions having in the range of a~out 4 to 8 carbon atoms per molecule, such as diethylene glycol and triethylene glycol; organic acids having in the range of about l to lO carbon atoms per molecule, such as formic acid, malonic acid, acetic acid, gluconic acid, levu-linic acid and propionic acid; esters having in the range of about 2 to 6 carbon atoms per molecule, such as methyl ~ormate, dimethyl oxylate and dimethyl malonate; and lactones having in the range of about 3 to 5 carbon atoms per molecule, such as beta-propyl lactone and gamma-butyl lactone. Due to the desirably low freezing point and/or high flash point ~tag closed cup) of the resulting gelling agent, the organic acids are preferred with acetic acid being the most preferxed.
The water soluble organic solvent useful herein is preferably ~ in liquid phase at the temperature at which it is mixed with the ethoxylated fatty amines. Furthermore, mixtures of the organic solvents can be used. An example is a mixture o~ methanol and gluconic acid.
The gellin~ agents useful herein can ~e prepared ~y mixin~
the water solub~e organic solvents with the ethoxylated fatty
Continued pumping of the fracturing fluid extends the fractures, and when the fracturing fluid contains propping agent suspended therein, the propping agent is left in the fracture. Because the fracturing fluid is of low pH, minerals in the formation are dissolved whereby the pore spaces therein are opened or enlarged and the permeability of the formation increased.
Highly viscous well formation treating fluids are particu-larly advantageous in carrying out fracturing and/or acidizing procedures in that such fluids are capable of opening one or more fractures to a width sufficient to place propping agent therein without excessive leak-off of the fluid, and such highly viscous - fluids are capa~e of maintaining propping agent in suspension ~or long periods of time without excessive settling. However, problems nave be~n encountered in the use of high viscosity low pB treatiny fluids utilized heretofore, e.g., complexed natural 2S gum and cellulose derivative gels, in that such gels generally 110~3~0 become less viscous when high formation temperatures are en-countered, i.e., above about 140F, and/or break down and become less viscous in the presence of acid. Such reduction i~n viscosity in well formation treating fluids can often produce undesirable results. For examp]e, if the fluid is used as a fracturing fluid with propping agent suspended therein, a reduction in the vis-cosity of the fluid allows the propping agent to rapidly settle resulting in inadequate propping of fractures produced. Also, heretofore used complexed gels often cause significant damage to the formation treated therewith, i.e., bring about a reduction in the permeability thereof.
In carrying out the treatment of su~terranean well formations using highly viscous fluids, it is desirable that the fluids be ~hixotropic, i.e., that the fluids have the property of developing a :~ow viscosity in turbulent flow, but exhibiting a high viscosity when at rest, the transition being reversible. By the present invention, methods of treating subterranean well formations with highly viscous thixotropic treating fluids of low pH which are stable at high temperatures and which are relatively non-damaging to the treated formation are provided.
The method of the present invention for treating a subter-ranean well formation comprises combining an aqueous acid solution ith an agueous alkali metal silicate solution having a pH greater than a~out 11 and a gelling agent comprised of a solution of a water soluble organic solvent and an ethoxylated fatty amine ~ 3-11003~10 thereby forming a low pH highly viscous polymerized alkali metal silicate gel, shearing the gel to obtain a highly viscous treating fluid having thixotropic properties and then introducing the treating fluid into the subterranean well formation.
The invention in its broadest aspect relates to a method of forming a low p~ highly viscous thixotropic fluid for use in treating a subterranean well formation compris-ing the steps of: combining an aqueous solution of acid other than hydrofluoric acid with an aqueous alkali metal silicate solution having a pH of greater than about 11 in an amount sufficient to lower the pH of the resulting mix-ture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized alkali metal silicate gel; combining a,gelling agent with said polymerized alkali metal silicate gel, said gelling agent consisting of a solution of a water soluble organic solvent and a mixture of ethoxylated fatty amines having the general formula:
( CH2CH20 ) xH
R - N
( CH2CH20 ) yH
wherein: R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms, and x and y each have a value in the range of from 0 to about 10 but both x and y are not 0;
said ethoxylated fatty amine is present in said gelling agent in an amount in the range of from about 10~ to about 80% by weight of said gelling agent; combining additional aqueous solution of acid other than hydrofluoric acid with said polyme~ized alkali metal silicate gel-gelling agent llOQ3QO
mixture in an amount sufficient to obtain a mixture con-taining excess acid in the range of from about 1~ to dbout 28% by weight of said mixture; and shearing said mixture to thereby obtain a highly viscous thixotropic treating fluid.
Other aspects of this application are claimed in a divisional application.
A variety of alkali metal silicates can be utilized in accordance with the present invention, e.g., sodium, potassium, lithium, rubidium and cesium silicate. Of these, sodium silicate is preferred, and of the many forms in which sodium silicate exists, those having an Na20:Si02 ~eight ratio in the range of from about 1:2 to about 1:4 are most preferred. A specifically preferred material for use in accordance with the method of the present invention is a commercially available aqueous sodium silicate solution having a density of 11.67 pounds per gallon, an Na20:Si02 weight ratio of about 1:3.22 (Grade 40) and having the following approximate analysis:
Component% by Weight Na20 9.1 Si02 29.2 Water 61.7 TOTAL 100.00 A variety of acids can also be used, either organic or inorganic as well as acid producing materials.
Examples of inor~anic acids which can be used are hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. Examples of organic acids which can be used are formic acid and acetic acid. An example of an - 4a -'~, ~ ~.
11003~0 acid forming material which can be used is benzotrichloride.
Of the acids and acid forming materials which can be used, hydrochloric acid, sulfuricacid, phosphoric acid and mixtures of such acids are preferîed with hydrochloric acid being the most preferred. As will be understood by those skilled in the art, hydrofluoric acid cannot be utilized in that its reaction with silicates has an adverse affect on the formation of polymerized silicat~ gel.
In preparing a highly viscous fluid having thixotropic pro-perties and a low pH for treating a subterranean well formation, an aqueous alkali metal silicate solution having a pH of;greàter than about 11 is first prepared. Such a solution using Grade 40 sodium ~ilicate solution starting material is prepared by mixing about 5 parts by volume Grade 40 sodium silicate solution with about g5 parts by volume water. The resultlng solution has a pH
in the range of from about 11 to about 12, and a viscosity of about 1 centipoise. To this solution is added an aqueous acid solution, such as a 20 Bé aqueous hydrochloric acid solution, while agi-tating the mixture, to lower the p~ of the mixture to a value in the range of from about 7.5 to about 8.5 whereby ~he alkali metai silicate polymerizes to form a hi~hly viscous rigid gel. While a polymerized silicate qel will form at pH ~evels other than from about 7.5 to about 8.5, the rate of formation of the gel is ~reatest in such range.
Upon polymerization of the alkali metal silicate in the manner 110~3~0 described above, a highly crosslink~d risid gel structure is formed which is not soluble in water, but wnich is gelatinous due to water being entrapped in the polymer structure. In order to~impart thixotropic properties to the polymerized silicate gel, it is sheared by mixing or agitation, preferably while the polymerization reaction is taking place. It is believed the shearing of the gel divides it into fine particles carrying static charges which will not agglomerate into a ~ass and which exhibit thixotropic proper-ties, i.e., a low viscosity in turbulent flow but a high viscosity when at rest or at low shear rates.
Additional aqueous acid solution is added to the gel to ob-tain a low pH treating fluid of desired acia strength. For example, additional acid solution can be added to the gel in an amount sufficient to o~tain a mixture containing excess acid in a quantity in the range of from about 1 percent to about 5 percent by weight of the mixture. However, the addition of excess acid to the poly-merized silicate gel causes ~he gel to thin out and lose its thixotropic properties to some degree. This is believed to be due to the fact that the sheared gel particles have negative static charges ~hich cause the particles to repel each other which in turn gives the gel its thixotropic properties. When excess acid is added to the gel, the negative charges are at least partially neutralized which decreases the thixotropic properties. In order to overcome tnis problem and to increase the viscosity of the gel mixture containlng excess acid, a viscosity increasing ~1~03~0 chemical wnich also ~unctions as a surfactant, hereinafter referr~
to as a "gelling agent", is combined with the polymerized sodium silicate gel prior -to adding the excess acid therewi~h. It is believed the surface active properties ol the gelling agent pre-Yent the c~arged particles from agglomerating in the presence of acid and thereby prevent the corresponding thinning out and loss of thixotropic properties.
A gelling agent suitable for use in accordance with this invention is comprised of a solution of a water soluble organic solvent and an ethoxylated fatty amine-having the general formula:
~(CH2CH20) xH
R - N
(CH2CH2O) yH
wherein:
~ is selected from saturated and unsaturated aliphatic gxoups having in the range of from about 8 to about 22 carbon atoms, and mixtures thereof, and x and y each have a value in the range of from 0 to about lO.
- ~he preferred ethoxylated fatty amines and mixtures thereof useful herein are those wherein the average sum of the values of x and y in the amines used is in the range of from about 1.8 to about 2.2.
Mixtures of ethoxylated terti.ary fatty amines derived from fats and oils such as coconut oil, soy ~ean oil, and tallow are particularly suitable for use in accordance with the present invention.
A preferred mixtllre of ethoxylated fatty amines is a mixture of amines of the general formula:
' . ~(C,H2CH20) XH
R N\
~ CH2CH20)yH
wherein:
is selected from the group consisting of saturated and unsaturated chains of aliphatic groups having in the range of from about 14 to about 18 carbon atoms ar,d mixtures of such groups; and wherein the average sum of the values of x and y in the mixture of ethoxylated amines is equal to 2.
In the most preferred embodiment, x and y each have a value of l (one).
Examples of such amines are those derived from fatty acids o~ the type hexadecyl, tallow, soya and oleyl, either saturated or unsaturated and as pure components or mixtures.
_ A variety of organic solvents can be utilized in the gelling agent so long as such solvents are capable of dissolving the ethoxylated fatty amines and are water soluble. Examples of such water soluble organic solvents include al~anols having in the range of about 1 to 5 carbon atoms per molecule, such as methanol, ethanol, sopropanol and t-butanol; ~etones having in the range of about 3 to 6 carbon atoms per molecule, such as acetone and ~10~3@0 methylethyl ketone; polyhydroxy compounds having in the range of about 2 to o cax~on atoms per molecule, such as et~ylene glycol and glycerine; ethers having in the ranye of about 2 to 6 carbon atoms per molecule, such as dioxane and tetrahydrofuran; com-- pounds containing both ether and alcohol functions having in the range of a~out 4 to 8 carbon atoms per molecule, such as diethylene glycol and triethylene glycol; organic acids having in the range of about l to lO carbon atoms per molecule, such as formic acid, malonic acid, acetic acid, gluconic acid, levu-linic acid and propionic acid; esters having in the range of about 2 to 6 carbon atoms per molecule, such as methyl ~ormate, dimethyl oxylate and dimethyl malonate; and lactones having in the range of about 3 to 5 carbon atoms per molecule, such as beta-propyl lactone and gamma-butyl lactone. Due to the desirably low freezing point and/or high flash point ~tag closed cup) of the resulting gelling agent, the organic acids are preferred with acetic acid being the most preferxed.
The water soluble organic solvent useful herein is preferably ~ in liquid phase at the temperature at which it is mixed with the ethoxylated fatty amines. Furthermore, mixtures of the organic solvents can be used. An example is a mixture o~ methanol and gluconic acid.
The gellin~ agents useful herein can ~e prepared ~y mixin~
the water solub~e organic solvents with the ethoxylated fatty
2~ ctmines ~or a period of time sufficient to completely dissolve 110~3QO
the amines in the solvent. The quantity of ethoxylated amines dissolved in the organic solvent range in an amount of from about 10 percent to about 80 percent by weight, preferably from about SQ percent to about 60 percent amine by weight of the gelling agent.
As mentioned above, the org~nic solvents can be used sin~ly, or in mixtures of solvents of the same chemical class (acids with acids, ketones with ketones and the like) or in mixtures of sol-vents of different chemical classes (acids with alcohols, ethers ~ith ketones and the like). A preferred organic solvent is a mixture of chemicals of different chemical classes wherein at ~east one of the classes is an organic acid.
Ethoxylated fatty amines of the type described above are very difficult to dissolve directly in aqueous acid solutions.
However, the amines are easily dissolved in the above-mentioned water soluble organic solvents, and the resultant solution is rea~ily dissolved in an aqueous acid solution and immediately increases the viscosity of the solution.
~ A gelling agent comprised of an ethoxylated fatty amine or mixture of such amines of the type described above dissolved in a water soluble organic solvent, preferably acetic acid, is com-bined with the polymerized silicate gel in an amount of from about 0.01 percent to about 5.0 percent by volume of the gel.
Excess acid is then added to the gel to obtain a low p~l treating fluid of desired acid strensth, and the mixture is sheared to lloo3~o impart thixotropic properties thereto.
An alternate procedure for forming a highly viscous thixo-tropic acidic treating ~luid is to combine an a~ueous alkali metal silicate solution having a pH greater than about ll with a concen-trated aqueous acid solution in a quantity whereby excess acid is present in the resulting mixture in an amount in the range of from about 1 percent by weight to about 28 percent by weight while mixing or agitating the resultant mixture. A polymerized alkali metal silicate gel is formed in the mixture at a rapid rate re-sulting in a highly viscous acidic fluid. The gelling agent described above is combined with the fluid to increase the visco-sity thereof and impart stability thereto, and in order to impart thixotropic proper.ies to the fluid, it is sheared in the manner described above.
In fracturing and/or acidizing a subterranean well formation in accordance with the method of the present invention, an aqueous acid solution, preferably 30 to 35 percent by weight hydrochloric acid, is comhined with an alkali metal silicate solution, preferably sodium silicate, having a pH of greater than about 11, in an amount sufficient to lower the pH of the resulting mixture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized al~ali metal silicate gel. The gelling agent de-scribed above is combined with the polymerized silicate gel in an amount in the range of 0.01 percen~ to about 5.0 percent by Z5 volume of the gel and the mixture is agitated or mixed while the 110~3~0 polymerized silicate gel is being formed to thereby shear the gel and impart th xotropic prope~-ties thereto. Additional aqueous acid solution is added to the mixture so that the resulting treating fluid contains excess acid, preferably in an amount in the range of from about 1 percent to about 5 percent by weight of the fluid. Other conventional well treating additives and propping agent, if used, are also added to the fluid while it is being agitated and the resulting low p~ treating fluid is intro-duced into a subterranean formation at a flow rate and pressure sufficient to produce a fracture therein and simultaneously acidizing the formation, i.e., dissolve minerals in the formation whereby the pore spaces are opene& or enlarged and the permeability of the formation increased.
Where it is desired to fracture and/or acidize a subterranean well formation with a treating fluid having a higher concentration o~ excess acid, the aqueous alkali metal silicate solution having a pH of greater than about 11 is combined with a concentrated aqueous acid solution ~30 to 35 percent by weight acid) in a _ quantity whereby excess acid is present in the resulting mixture in a desired amount, preferably in an amount in the range of from about 1 percent by weight to about 28 percent by weight. The gelling agent described above is combined with the mixtu.e in an amount in the range of from about 0.01 percent to about 5.0 percent by volume of the mixture and the resultant mixture is agitated so that as the polymerized silicate gel is formed it ll0~3~o is sheared and thixotropic properties are imparted thereto.
Conventional well treating additives and propping agent, if used, are added to tne treating f~uid followed by introducing the treating fluid into a formaticn to be treated.
The low pH polymerized silicate treating fluids can be pre-pared in batch or they can be prepared continuously while being pumped or otherwise introduced into a subterranean well formation.
After being introduced into ~he formation, the polymerized sili-cate gel dehydrates at a relatively rapid rate, and consequently it is not necessary to include a chemical for breaking the sodium.
silicate gel in the fluids. The time required for the gel to dehydrate depends on the rate of water loss to the formation and other factors, but generally such time is within the range of from about 4 hours to a~out 24 hours. Upon dehydrating, some powdered i5 silicate remains in the treated formation which can readily be removed by contacting the formation with hydrofluoric acid. Prior to the dehydration of the polymerized silicate gel, it has excel-lent stability, i.e., retains its high viscosity over a wide ~ temperature range (up to about 500F). The treating fluids are particularly suitable for treating subterranean well formations of low permeability in that they are relatively non-damaging to such formations as compared to conventional high viscosity fluicls, i.e., do not appreciably reduce the permeability thereof.
The following e~amples are presented to further illustrate the invention.
3Q`O
Example l Several polymerized sodium silicate gels are prepared in the laboratory uslng a Grade 40 sodium silicate so]ution. The quanti-ties of Grace 40 sodium silicate solution, ~ap water containing 2 percent potassium chloride and 20 Bé hydrochloric acid (appro-ximately 31.45 percent by weight hydrochloric acid) shown in . Tab~e I below are used. Except for those gels which are prepared by directly combining the acid and sodium silicate solutions, several drops of phenophthalein indicator are added to the diluted sodium silicate solution followed by the addition of hydrochloric acid solution in the amol~t required to reach an end point, i.e., a pH in the range of from about 8 to about 8.5. Following the addition of the acid and while the polymerized sodium silicate gel forms, the mixture is sheared for lO minutes using a 3absco pump.
The gels contain 5 percent, 7-1~? percent and lO percent by volume Grade 40 sodium silicate and the last three gels shown in Table I contain excess acid in the amounts given. Viscosities of the gels are~apparent viscosities measured on a Model 35 FANN
~iscometer, No. 1 spring, standard bob and sleeve at room tem-perature and at 300 rpm.
llOQ3~0 , ~ o o o U~ CO
a dP
tn E~ O~ ooooo o ~ U ~ el~
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. _ 11003~0 - Example 2 Ethoxylated soya (mixture of chains having 14, 16 and 18 ~arbon atoms) amines having an average of 2 moles of e~hylene oxide per mole of amine are tested in the laboratory for increasing the vi~cosity and stabilizing acidic polymerized sodium sili.cate gel. The procedure for testing the amines is to first prepare a polymerized sodium silicate gel containing 5 percent excess acid in accordance with the procedure set forth in Example 1. The amines are diluted in equal volumes of acetic acid and added to the sodium 1~ silicate gel in the quantity indicated in Table II below while agitating the mixture. Viscosities are measured using a Model 35 FANN viscometer, No. 1 spring, standard bob and sleeve at 300 rpm.
TABLE II - VISCOSITIES OF POLYMERIZED SODIUM SILICATE
GELS CONTAINING EXCESS ACID AND GELLING AGENT
Quantity of Gelling Agent Combined with Sodium Silicate Gel, Gallons Viscosity of Gelling Agent/ Viscosity of Sodium Sili-1000 Gallons Sodium Silicate cate Gel with Gelling Agent Sodium Silicate Gel WithoutGelling Agent Used Gel Gelling Agent cp c~
_ Ethoxylated soya a~e-acetic acid 5 7 34 E*hoxylated soya ~ne-~cetic acid 3 7 29 Ethoxylated soya ~e-acetic acid 1 7 20 -As shown in Table II, the ethoxylated soya amine gelling a~ent lloa3~0 improves the overall viscosity of a sodium silicate gel containing excess aci2. Observations of the gel indicate that the gel is consistent and thick with little water separation. In addition, the gelling agent stabilizes the gel and prevents loss of tisco-sity and thixotropic properties.
Example 3 A gelling agent is prepared by dissolving 3 grams of ethoxy-lated soya amines having an average of 2 moles of ethylene oxide per mole of amine in 6 mls. of glacial acetic acid. The approxi-mate composition of the soya fatty acids from which the soya aminè
is derived is as follows:
Acid ~ by Weight myristic (C14) 0 to 1%
palmitic (C16) 6 to 10 stearic (C18) 2 to 4 ~
21 to 29%
linoleic (C18) 50 to 59%
linolenic ~C18) 4 to 8%
Tne gelling agent is combined with 125 mls. of an aqueous hydrochloric acid solution containing 15 percent by weight hydro-chloric acid. The gelling agent is readily mixed with the aqueous acid solution, and after mixing, the aqueous acid solution has an apparent viscosity of 95 centipoises measured on a Model 35 FANN viscometer, No. 1 spring, standard bob and sleeve at room temperature and 300 rpmO
. -17-llOQ330 Æxample 4 Liquid permeability tests a~e carxied out in the laboratory using ~erea sandstone (high permeability), Bandera sandstone (medium permeability) and Ohio sandstone ~low permeability). Tap water containing 2 percent by weight potassium chloride is first caused to flow through the test cores at an upstream pressure of approximately 120 psig and the liquid permeability of the cores calculated from the average 10w rate of liquid flowing through the cores, the liquid viscosity, the core length, liquid pressure, and core area. The cores are next treated with a 5 percent poly merized sodium silicate gel prepared as described in Example 1 by flowing the gel through the cores followed by immersion of the cores in the gel for from about 15 to about 24 hours during which time the gel is caused to break. The cores are then re-verse flowed with tap water containing 2 percent by weight potas-sium chloride and the liquid permeability calculated. Additional cores are tested in the same manner, but the cores are treated with a highly viscous gel formed from water and hydroxypropyl guar gum (40 pounds hydroxypropyl guar gum per 1000 gallons of water) instead of the sodium silicate gel. The results of tnese tests are given in Table IV below.
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the amines in the solvent. The quantity of ethoxylated amines dissolved in the organic solvent range in an amount of from about 10 percent to about 80 percent by weight, preferably from about SQ percent to about 60 percent amine by weight of the gelling agent.
As mentioned above, the org~nic solvents can be used sin~ly, or in mixtures of solvents of the same chemical class (acids with acids, ketones with ketones and the like) or in mixtures of sol-vents of different chemical classes (acids with alcohols, ethers ~ith ketones and the like). A preferred organic solvent is a mixture of chemicals of different chemical classes wherein at ~east one of the classes is an organic acid.
Ethoxylated fatty amines of the type described above are very difficult to dissolve directly in aqueous acid solutions.
However, the amines are easily dissolved in the above-mentioned water soluble organic solvents, and the resultant solution is rea~ily dissolved in an aqueous acid solution and immediately increases the viscosity of the solution.
~ A gelling agent comprised of an ethoxylated fatty amine or mixture of such amines of the type described above dissolved in a water soluble organic solvent, preferably acetic acid, is com-bined with the polymerized silicate gel in an amount of from about 0.01 percent to about 5.0 percent by volume of the gel.
Excess acid is then added to the gel to obtain a low p~l treating fluid of desired acid strensth, and the mixture is sheared to lloo3~o impart thixotropic properties thereto.
An alternate procedure for forming a highly viscous thixo-tropic acidic treating ~luid is to combine an a~ueous alkali metal silicate solution having a pH greater than about ll with a concen-trated aqueous acid solution in a quantity whereby excess acid is present in the resulting mixture in an amount in the range of from about 1 percent by weight to about 28 percent by weight while mixing or agitating the resultant mixture. A polymerized alkali metal silicate gel is formed in the mixture at a rapid rate re-sulting in a highly viscous acidic fluid. The gelling agent described above is combined with the fluid to increase the visco-sity thereof and impart stability thereto, and in order to impart thixotropic proper.ies to the fluid, it is sheared in the manner described above.
In fracturing and/or acidizing a subterranean well formation in accordance with the method of the present invention, an aqueous acid solution, preferably 30 to 35 percent by weight hydrochloric acid, is comhined with an alkali metal silicate solution, preferably sodium silicate, having a pH of greater than about 11, in an amount sufficient to lower the pH of the resulting mixture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized al~ali metal silicate gel. The gelling agent de-scribed above is combined with the polymerized silicate gel in an amount in the range of 0.01 percen~ to about 5.0 percent by Z5 volume of the gel and the mixture is agitated or mixed while the 110~3~0 polymerized silicate gel is being formed to thereby shear the gel and impart th xotropic prope~-ties thereto. Additional aqueous acid solution is added to the mixture so that the resulting treating fluid contains excess acid, preferably in an amount in the range of from about 1 percent to about 5 percent by weight of the fluid. Other conventional well treating additives and propping agent, if used, are also added to the fluid while it is being agitated and the resulting low p~ treating fluid is intro-duced into a subterranean formation at a flow rate and pressure sufficient to produce a fracture therein and simultaneously acidizing the formation, i.e., dissolve minerals in the formation whereby the pore spaces are opene& or enlarged and the permeability of the formation increased.
Where it is desired to fracture and/or acidize a subterranean well formation with a treating fluid having a higher concentration o~ excess acid, the aqueous alkali metal silicate solution having a pH of greater than about 11 is combined with a concentrated aqueous acid solution ~30 to 35 percent by weight acid) in a _ quantity whereby excess acid is present in the resulting mixture in a desired amount, preferably in an amount in the range of from about 1 percent by weight to about 28 percent by weight. The gelling agent described above is combined with the mixtu.e in an amount in the range of from about 0.01 percent to about 5.0 percent by volume of the mixture and the resultant mixture is agitated so that as the polymerized silicate gel is formed it ll0~3~o is sheared and thixotropic properties are imparted thereto.
Conventional well treating additives and propping agent, if used, are added to tne treating f~uid followed by introducing the treating fluid into a formaticn to be treated.
The low pH polymerized silicate treating fluids can be pre-pared in batch or they can be prepared continuously while being pumped or otherwise introduced into a subterranean well formation.
After being introduced into ~he formation, the polymerized sili-cate gel dehydrates at a relatively rapid rate, and consequently it is not necessary to include a chemical for breaking the sodium.
silicate gel in the fluids. The time required for the gel to dehydrate depends on the rate of water loss to the formation and other factors, but generally such time is within the range of from about 4 hours to a~out 24 hours. Upon dehydrating, some powdered i5 silicate remains in the treated formation which can readily be removed by contacting the formation with hydrofluoric acid. Prior to the dehydration of the polymerized silicate gel, it has excel-lent stability, i.e., retains its high viscosity over a wide ~ temperature range (up to about 500F). The treating fluids are particularly suitable for treating subterranean well formations of low permeability in that they are relatively non-damaging to such formations as compared to conventional high viscosity fluicls, i.e., do not appreciably reduce the permeability thereof.
The following e~amples are presented to further illustrate the invention.
3Q`O
Example l Several polymerized sodium silicate gels are prepared in the laboratory uslng a Grade 40 sodium silicate so]ution. The quanti-ties of Grace 40 sodium silicate solution, ~ap water containing 2 percent potassium chloride and 20 Bé hydrochloric acid (appro-ximately 31.45 percent by weight hydrochloric acid) shown in . Tab~e I below are used. Except for those gels which are prepared by directly combining the acid and sodium silicate solutions, several drops of phenophthalein indicator are added to the diluted sodium silicate solution followed by the addition of hydrochloric acid solution in the amol~t required to reach an end point, i.e., a pH in the range of from about 8 to about 8.5. Following the addition of the acid and while the polymerized sodium silicate gel forms, the mixture is sheared for lO minutes using a 3absco pump.
The gels contain 5 percent, 7-1~? percent and lO percent by volume Grade 40 sodium silicate and the last three gels shown in Table I contain excess acid in the amounts given. Viscosities of the gels are~apparent viscosities measured on a Model 35 FANN
~iscometer, No. 1 spring, standard bob and sleeve at room tem-perature and at 300 rpm.
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. _ 11003~0 - Example 2 Ethoxylated soya (mixture of chains having 14, 16 and 18 ~arbon atoms) amines having an average of 2 moles of e~hylene oxide per mole of amine are tested in the laboratory for increasing the vi~cosity and stabilizing acidic polymerized sodium sili.cate gel. The procedure for testing the amines is to first prepare a polymerized sodium silicate gel containing 5 percent excess acid in accordance with the procedure set forth in Example 1. The amines are diluted in equal volumes of acetic acid and added to the sodium 1~ silicate gel in the quantity indicated in Table II below while agitating the mixture. Viscosities are measured using a Model 35 FANN viscometer, No. 1 spring, standard bob and sleeve at 300 rpm.
TABLE II - VISCOSITIES OF POLYMERIZED SODIUM SILICATE
GELS CONTAINING EXCESS ACID AND GELLING AGENT
Quantity of Gelling Agent Combined with Sodium Silicate Gel, Gallons Viscosity of Gelling Agent/ Viscosity of Sodium Sili-1000 Gallons Sodium Silicate cate Gel with Gelling Agent Sodium Silicate Gel WithoutGelling Agent Used Gel Gelling Agent cp c~
_ Ethoxylated soya a~e-acetic acid 5 7 34 E*hoxylated soya ~ne-~cetic acid 3 7 29 Ethoxylated soya ~e-acetic acid 1 7 20 -As shown in Table II, the ethoxylated soya amine gelling a~ent lloa3~0 improves the overall viscosity of a sodium silicate gel containing excess aci2. Observations of the gel indicate that the gel is consistent and thick with little water separation. In addition, the gelling agent stabilizes the gel and prevents loss of tisco-sity and thixotropic properties.
Example 3 A gelling agent is prepared by dissolving 3 grams of ethoxy-lated soya amines having an average of 2 moles of ethylene oxide per mole of amine in 6 mls. of glacial acetic acid. The approxi-mate composition of the soya fatty acids from which the soya aminè
is derived is as follows:
Acid ~ by Weight myristic (C14) 0 to 1%
palmitic (C16) 6 to 10 stearic (C18) 2 to 4 ~
21 to 29%
linoleic (C18) 50 to 59%
linolenic ~C18) 4 to 8%
Tne gelling agent is combined with 125 mls. of an aqueous hydrochloric acid solution containing 15 percent by weight hydro-chloric acid. The gelling agent is readily mixed with the aqueous acid solution, and after mixing, the aqueous acid solution has an apparent viscosity of 95 centipoises measured on a Model 35 FANN viscometer, No. 1 spring, standard bob and sleeve at room temperature and 300 rpmO
. -17-llOQ330 Æxample 4 Liquid permeability tests a~e carxied out in the laboratory using ~erea sandstone (high permeability), Bandera sandstone (medium permeability) and Ohio sandstone ~low permeability). Tap water containing 2 percent by weight potassium chloride is first caused to flow through the test cores at an upstream pressure of approximately 120 psig and the liquid permeability of the cores calculated from the average 10w rate of liquid flowing through the cores, the liquid viscosity, the core length, liquid pressure, and core area. The cores are next treated with a 5 percent poly merized sodium silicate gel prepared as described in Example 1 by flowing the gel through the cores followed by immersion of the cores in the gel for from about 15 to about 24 hours during which time the gel is caused to break. The cores are then re-verse flowed with tap water containing 2 percent by weight potas-sium chloride and the liquid permeability calculated. Additional cores are tested in the same manner, but the cores are treated with a highly viscous gel formed from water and hydroxypropyl guar gum (40 pounds hydroxypropyl guar gum per 1000 gallons of water) instead of the sodium silicate gel. The results of tnese tests are given in Table IV below.
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3Qo E'rom Table IV it can be seen that the pcly~erized sodium silicate gel is relatively non-damaging to formation permeability and is considerably less damaging to formation permeability than hydroxypropyl guar gum gel.
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3Qo E'rom Table IV it can be seen that the pcly~erized sodium silicate gel is relatively non-damaging to formation permeability and is considerably less damaging to formation permeability than hydroxypropyl guar gum gel.
Claims (19)
1. A method of forming a low pH highly viscous thixotropic fluid for use in treating a subterranean well formation comprising the steps of:
combining an aqueous solution of acid other than hydrofluoric acid with an aqueous alkali metal silicate solution having a pH
of greater than about 11 in an amount sufficient to lower the pH of the resulting mixture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized alkali metal silicate gel;
combining a gelling agent with said polymerized alkali metal silicate gel, said gelling agent consisting of a solution of a water soluble organic solvent and a mixture of ethoxylated fatty amines having the general formula:
wherein:
R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms, and x and y each have a value in the range of from 0 to about 10 but both x and y are not 0;
said ethoxylated fatty amine is present in said gelling agent in an amount in the range of from about 1% to about 80% by weight of said gelling agent;
combining additional aqueous solution of acid other than hydrofluoric acid with said polymerized alkali metal silicate gel-gelling agent mixture in an amount sufficient to obtain a mixture containing excess acid in the range of from about 1% to about 28% by weight of said mixture; and shearing said mixture to thereby obtain a highly viscous thixotropic treating fluid.
combining an aqueous solution of acid other than hydrofluoric acid with an aqueous alkali metal silicate solution having a pH
of greater than about 11 in an amount sufficient to lower the pH of the resulting mixture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized alkali metal silicate gel;
combining a gelling agent with said polymerized alkali metal silicate gel, said gelling agent consisting of a solution of a water soluble organic solvent and a mixture of ethoxylated fatty amines having the general formula:
wherein:
R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms, and x and y each have a value in the range of from 0 to about 10 but both x and y are not 0;
said ethoxylated fatty amine is present in said gelling agent in an amount in the range of from about 1% to about 80% by weight of said gelling agent;
combining additional aqueous solution of acid other than hydrofluoric acid with said polymerized alkali metal silicate gel-gelling agent mixture in an amount sufficient to obtain a mixture containing excess acid in the range of from about 1% to about 28% by weight of said mixture; and shearing said mixture to thereby obtain a highly viscous thixotropic treating fluid.
2. The method of claim 1 wherein the average sum of the values of x and y in said mixture is in the range of from about 1.8 to about 2.2.
3. The method of claim 1 wherein said alkali metal silicate is sodium silicate.
4. The method of claim 1 wherein said aqueous sodium silicate solution is Grade 40 sodium silicate solution diluted with water.
5. The method of claim 3 wherein said acid is selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid and mixtures thereof.
6. The method of claim 5 wherein said acid is hydrochloric acid.
7. The method of claim 1 wherein R is selected from the group consisting of saturated and unsaturated aliphatic groups having in the range of from about 14 to about 18 carbon atoms and mixtures of such groups, and wherein the average sum of the values of x and y in said mixture of ethoxylated amines is equal to 2.
8. The method of claim 7 wherein said organic solvent is an organic acid.
9. The method of claim 8 wherein said organic acid is acetic acid.
10. The method of claim 7 wherein said organic solvent in said gelling agent is acetic acid and said ethoxylated fatty amines are present in said gelling agent in an amount of about 50% by weight of said gelling agent.
11. The method of claim 1 wherein said gelling agent includes an ethoxylated fatty amine having the general formula:
wherein:
R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms.
wherein:
R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms.
12. A method of fracturing and simultaneously acidizing a subterranean well formation comprising the steps of:
combining an aqueous solution of acid other than hydrofluoric acid with an aqueous alkali metal silicate solution having a pH of greater than about 11 in an amount sufficient to lower the pH of the resulting mixture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized alkali metal silicate gel;
combining a gelling agent with said polymerized alkali metal silicate gel, said gelling agent consisting of a solution of a water soluble organic solvent and a mixture of ethoxylated fatty amines having the general formula:
wherein:
R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms and mixtures thereof, and x and y each have a value in the range of from 0 to about 10, with the average sum of the values of x and y in said mixture being in the range of from about 1.8 to about 2.2;
said ethoxylated fatty amine is present in said gelling agent in an amount in the range of from about 10%
to about 80% by weight of said gelling agent;
combining additional aqueous solution of acid other than hydrofluoric acid with said polymerized alkali metal silicate gel-gelling agent mixture in an amount sufficient to obtain a mixture containing excess acid in the range of about 1% to about 28%
by weight of said mixture;
shearing said mixture to thereby obtain a highly viscous thixotropic acidic treating fluid; and introducing said treating fluid into said subterranean formation at a flow rate and pressure sufficient to produce a fracture therein.
combining an aqueous solution of acid other than hydrofluoric acid with an aqueous alkali metal silicate solution having a pH of greater than about 11 in an amount sufficient to lower the pH of the resulting mixture to a level in the range of from about 7.5 to about 8.5 thereby forming a polymerized alkali metal silicate gel;
combining a gelling agent with said polymerized alkali metal silicate gel, said gelling agent consisting of a solution of a water soluble organic solvent and a mixture of ethoxylated fatty amines having the general formula:
wherein:
R is selected from saturated and unsaturated aliphatic groups having in the range of from about 8 to about 22 carbon atoms and mixtures thereof, and x and y each have a value in the range of from 0 to about 10, with the average sum of the values of x and y in said mixture being in the range of from about 1.8 to about 2.2;
said ethoxylated fatty amine is present in said gelling agent in an amount in the range of from about 10%
to about 80% by weight of said gelling agent;
combining additional aqueous solution of acid other than hydrofluoric acid with said polymerized alkali metal silicate gel-gelling agent mixture in an amount sufficient to obtain a mixture containing excess acid in the range of about 1% to about 28%
by weight of said mixture;
shearing said mixture to thereby obtain a highly viscous thixotropic acidic treating fluid; and introducing said treating fluid into said subterranean formation at a flow rate and pressure sufficient to produce a fracture therein.
13. The method of claim 12 wherein said aqueous alkali metal silicate solution is Grade 40 sodium silicate diluted with water.
14. The method of claim 13 wherein said acid is hydro-chloric acid.
15. The method of claim 12 wherein R is selected from the group consisting of saturated and unsaturated aliphatic groups having in the range of from about 14 to about 18 carbon atoms and mixtures of such groups, and wherein the average sum of the values of x and y in said mixture of ethoxylated amines is equal to 2.
16. The method of claim 15 wherein said organic solvent in said gelling agent is acetic acid and said ethoxylated fatty amines are present in said gelling agent in an amount of about 50% by weight of said gelling agent.
17. The method of claim 16 which is further characterized to include the step of combining a propping agent with said mixture prior to introducing said mixture into said subterranean formation.
18. The method of claim 1 wherein said mixture of addit-ional aqueous solution of acid other than hydrofluoric acid and said polymerized alkali metal silicate gel-gelling agent mixture contains excess acid in the range of from about 1% to about 5% of said mixture.
19. The method of claim 12 wherein said mixture of addit-ional aqueous solution of acid other than hydrofluoric acid and said polymerized alkali metal silicate gel-gelling agent mixture contains excess acid in the range of from about 1% to about 5% of said mixture.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA365,476A CA1109244A (en) | 1978-01-23 | 1980-11-25 | Treating subterranean well formations |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87173578A | 1978-01-23 | 1978-01-23 | |
| US871,735 | 1978-01-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1100300A true CA1100300A (en) | 1981-05-05 |
Family
ID=25358013
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA318,724A Expired CA1100300A (en) | 1978-01-23 | 1978-12-28 | Treating subterranean well formations |
Country Status (6)
| Country | Link |
|---|---|
| AU (1) | AU525097B2 (en) |
| BR (1) | BR7900134A (en) |
| CA (1) | CA1100300A (en) |
| GB (1) | GB2012839B (en) |
| IT (1) | IT1109767B (en) |
| NO (1) | NO790212L (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4324669A (en) * | 1979-11-19 | 1982-04-13 | Halliburton Company | Foamed high viscosity aqueous inorganic acid solutions and methods of using the same |
| US5981446A (en) * | 1997-07-09 | 1999-11-09 | Schlumberger Technology Corporation | Apparatus, compositions, and methods of employing particulates as fracturing fluid compositions in subterranean formations |
-
1978
- 1978-12-28 CA CA318,724A patent/CA1100300A/en not_active Expired
-
1979
- 1979-01-10 BR BR7900134A patent/BR7900134A/en unknown
- 1979-01-22 NO NO790212A patent/NO790212L/en unknown
- 1979-01-22 AU AU43528/79A patent/AU525097B2/en not_active Ceased
- 1979-01-22 GB GB792228A patent/GB2012839B/en not_active Expired
- 1979-01-23 IT IT19542/79A patent/IT1109767B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| NO790212L (en) | 1979-07-24 |
| GB2012839A (en) | 1979-08-01 |
| GB2012839B (en) | 1982-04-28 |
| IT7919542A0 (en) | 1979-01-23 |
| AU525097B2 (en) | 1982-10-21 |
| AU4352879A (en) | 1979-08-02 |
| BR7900134A (en) | 1979-08-14 |
| IT1109767B (en) | 1985-12-23 |
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