AU2004203288B2 - Methods and compositions for treating subterranean formations with gelled hydrocarbon fluids - Google Patents

Description

P/00/Ol Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL TO BE COMPLETED BY APPLICANT Name of Applicant: HALLIBURTON ENERGY SERVICES, INC. Actual Inventors: Robert S. Taylor, Gary P. Funkhouser, Michael A. McCabe and B. Raghava Reddy Address for Service: CALLINAN LAWRIE, 711 High Street, Kew, Victoria 3101, Australia Invention Title: METHODS AND COMPOSITIONS FOR TREATING SUBTERRANEAN FORMATIONS WITH GELLED HYDROCARBON FLUIDS The following statement is a full description of this invention, including the best method of performing it known to us:- -2 METHODS AND COMPOSITIONS FOR TREATING SUBTERRANEAN FORMATIONS WITH GELLED HYDROCARBON FLUIDS BACKGROUND OF THE INVENTION This invention relates to gelled liquid hydrocarbon treatment fluids and methods of their use and preparation. Gelled liquid hydrocarbon fluids have been utilized in treating subterranean formations penetrated by well bores, e.g., for stimulation or sand control treatments such as fracturing or gravel packing, respectively. In fracturing treatments, a gelled liquid hydrocarbon fracturing fluid that may comprise particulate material, often referred to as proppant, e.g., sand, suspended therein is pumped through a well bore into a subterranean formation at a rate and pressure such that one or more fractures are formed or enhanced in a portion of the formation. Proppant material may be deposited in the fractures, inter alia, to prevent the formed fractures from closing, thereby maintaining conductive channels remain through which produced fluids can flow to the well bore. At a desired time, the viscosity of the gelled liquid hydrocarbon fluid may be reduced, or "broken," and the fluid may be recovered. Similarly, sand control operations, such as gravel packing, use gelled liquid hydrocarbon fluids, often referred to as gravel pack fluids. Gravel pack fluids usually are used to suspend gravel particles for delivery to a desired area in a well bore, e.g., near unconsolidated or weakly consolidated formation particulates, to form a gravel pack to enhance sand control. One common type of gravel packing operation involves placing a gravel pack screen in the well bore and packing the annulus between the screen and the well bore with gravel of a specific size designed to prevent the passage of formation sand. The gravel, inter alia, acts to prevent the particulates from occluding the screen or migrating with the produced fluids, and the screen, inter alia, acts to prevent the gravel from entering the production tubing. Once the gravel pack is substantially in place, the viscosity of the gravel pack fluid often is reduced to allow it to be recovered or produced back from the well bore. Polyvalent metal salts of orthophosphoric acid esters have been utilized as gelling agents for forming high-viscosity gelled liquid hydrocarbon treatment fluids. Such gelled liquid hydrocarbon treatment fluids often have included particulate materials such as proppant or gravel, and oftentimes delayed breakers for causing the treatment fluids to break into relatively thin fluids so that the treatment fluids may be produced back. Descriptions of 20/07/04. eh14270.snc. 2 -3 such high-viscosity gelled liquid hydrocarbon treatment fluids and methods of their use are set forth at least in part in U.S. Patent No. 4,622,155 issued to Harris et al. on November 11, 1986, and U.S. Patent No. 5,846,915 issued to Smith et al. on December 8, 1998. While high-viscosity gelled liquid hydrocarbon treatment fluids and methods have been used successfully in some instances, problems in downstream processes have been encountered as a result of the use of the phosphoric acid ester gelling agent. For example, in recent years, plugging of refinery towers (which often process hydrocarbons produced from formations treated with gelled liquid hydrocarbon fracturing fluids) has caused many expensive, unplanned shut-downs of those towers. The plugging material is high in phosphorus and has been attributed to the phosphoric acid esters used as gelling agents in conventional gelled liquid hydrocarbon treatment fluids used during production of the hydrocarbons from a subterranean formation. The phosphoric acid esters are thought to contribute volatile phosphorus, which may condense on distillation tower trays, resulting in plugging of such trays, which may result in shut-downs of the towers. The volatile phosphorus also may carry over the tops of the distillation towers causing contamination of the hydrocarbon products produced. SUMMARY OF THE INVENTION This invention relates to gelled liquid hydrocarbon treatment fluids and methods of their use and preparation. In one embodiment, the present invention provides a method of treating a subterranean formation comprising the steps of providing a gelled liquid hydrocarbon treatment fluid comprising a liquid hydrocarbon and a gelling agent that comprises a polyvalent metal salt- of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid, and treating the subterranean formation with the gelled liquid hydrocarbon treatment fluid. In another embodiment, the present invention provides a method of fracturing a portion of a subterranean formation comprising the steps of providing a gelled liquid hydrocarbon fracturing fluid comprising a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid, and contacting the portion of the subterranean formation with the gelled liquid hydrocarbon fracturing fluid under conditions effective to create or enhance at least one fracture in the subterranean formation. 20/07/04 eh 14270 nc I -4 In another embodiment, the present invention provides a method of providing sand control to a portion of a subterranean formation comprising: providing a gelled liquid hydrocarbon gravel pack fluid that comprises gravel particulates and a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid; and contacting the portion of the subterranean formation with the gelled liquid hydrocarbon gravel pack fluid so as to form a gravel pack near the portion of the subterranean formation. In another embodiment, the present invention provides a method of preparing a gelled liquid hydrocarbon treatment fluid comprising adding polyvalent metal organophosphonic acid ester or organophosphinic acid salt particulates to a liquid hydrocarbon to form a gelled liquid hydrocarbon treatment fluid. In another embodiment, the present invention provides a method of preparing a gelled liquid hydrocarbon treatment fluid comprising the steps of forming an initial liquid hydrocarbon gel that comprises a liquid hydrocarbon and a first gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid; and adding a second gelling agent to the initial liquid hydrocarbon gel at a desired time to form a viscous gel. In another embodiment, the present invention provides a method of preparing a gelled liquid hydrocarbon treatment fluid comprising the steps of preparing a concentrated gelled liquid hydrocarbon fluid; diluting the concentrated gelled liquid hydrocarbon fluid with a hydrocarbon to prepare a gelled liquid hydrocarbon treatment fluid. In another embodiment, the present invention provides a method of preparing a gelled liquid hydrocarbon fluid comprising the steps of adding an organophosphinic acid having the formula: 0 II

HO-P-CH

2

-CH

2

-CH

2 -R R' where R represents a hydrocarbon group having the general formula CnH 2 ne+, where n is from about 3 to about 21 and R' is either methyl or ethyl; adding an activator composition comprising a source of polyvalent metal ions that react with the organophosphinic acid to form a suitable polyvalent metal salt thereof; and allowing the liquid hydrocarbon to gel. 20/07/04 ehl4770ne 4 -5 In another embodiment, the present invention provides a method of preparing a gelled liquid hydrocarbon fluid comprising the steps of adding an organophosphonic acid ester having the formula: 0 II

HO-P-CH

2

-CH

2

-CH

2 -R OR' where R represents a hydrocarbon group having the general formula CH 2 ne+, where n is from about 3 to about 21 and R' is either methyl or ethyl; adding an activator composition comprising a source of polyvalent metal ions that react with the organophosphinic acid to form a suitable polyvalent metal salt; and allowing the liquid hydrocarbon to gel. In another embodiment, the present invention provides a gelled liquid hydrocarbon treatment fluid comprising: a liquid hydrocarbon; and a gelling agent that comprises a polyvalent metal salt of a phosphonic acid ester or a polyvalent metal salt of an organophosphinic acid. Other features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows. DESCRIPTION OF PREFERRED EMBODIMENTS This invention relates to gelled liquid hydrocarbon treatment fluids and methods of their use and preparation. The gelled liquid hydrocarbon treatment fluids of the present invention are suitable for use in subterranean treatment operations, such as subterranean stimulation and sand control treatments, such as fracturing and gravel packing, that may be carried out in subterranean formations. The compositions and methods of the present invention also may be suitable, for example, to be used as plugging agents, well bore cleanup fluids, viscous sweep fluids, or insulating fluids to be used in associated methods. The gelled liquid hydrocarbon compositions of the present invention comprise a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid. The term "salt" as used herein and in related applications refers to polyvalent metal ion salts that can be formed directly from an organophosphonic acid ester (or an organophosphinic acid) by a metathesis reaction comprising an alkali metal or ammonium salt of the organophosphonic acid ester (or the organophosphinic acid), or by a metathesis reaction comprising an organophosphonic acid 20/07/04 eh14770 ene 5 -6 dialkyl ester (or organophosphinic acid alkyl ester). Unlike the phosphoric acid esters utilized heretofore, the polyvalent metal salts of the gelling agents of the present invention, inter alia, do not decompose or disassociate as readily as conventional phosphoric acid ester gelling agents. Thus, they may not pose as large of a potential problem for downstream processing. Optionally, the gelling agents of the present invention may comprise water and/or a base if desired. In certain embodiments, the gelled liquid hydrocarbons of the present invention comprise a polyvalent metal salt of an organophosphonic acid ester or polyvalent metal salt of an organophosphinic acid. Suitable organophosphonic acid esters have the formula: 0 II R -P - O-R' OH wherein R comprises a hydrocarbon group having from about 1 to about 30 carbon atoms that, for example, may comprise a linear or branched alkyl, alkenyl, aryl, alkylaryl, arylalkyl, cycloalkyl, alkyl ether, aryl ether, alkyl aryl ether, or a mixture thereof; and R' comprises a hydrocarbon group having from about 1 to about 6 carbon atoms. If R is a relatively small group, then R' may comprise a larger hydrocarbon group similar to that listed above with respect to R such as linear or branched alkyl, alkenyl, aryl, alkylaryl, arylalkyl, cycloalkyl, alkyl ether, aryl ether, alkyl aryl ether group, or a mixture thereof that may have about 1 to about 30 carbon atoms. In choosing a suitable R and R', one should be mindful that if R and R' are both relatively bulky groups (e.g., if R and R' are both 2-ethylhexyl groups), then an adequate gelled liquid hydrocarbon may not form. Techniques that can be utilized for the preparation of organophosphonic acid esters useful in accordance with this invention include, for example, those described in U.S. Patent No. 3,798,162 issued to Dickert, Jr. on March 19, 1974, the relevant disclosure of which is incorporated herein by reference. Suitable organophosphinic acids have the formula: 0 R' -P-OH 1 2 R wherein R' may comprise a linear or branched hydrocarbon group having from about 1 to 30 carbon atoms that, for example, may comprise a linear or branched alkyl, alkenyl, aryl, 20/07/04 eh14770 ene A -7 alkylaryl, arylalkyl, cycloalkyl, alkyl ether, aryl ether, alkyl aryl ether, or a mixture thereof; and R2 may comprise a linear or branched hydrocarbon or aromatic group having from about 1 to about 6 carbon atoms. In choosing a suitable R' and R 2 , one should be mindful that if R' and R 2 are both relatively bulky groups, then an adequate gelled liquid hydrocarbon may not form. Techniques which can be used for the preparation of an organophosphinic acid useful in accordance with this invention are well known. For example, the organophosphinic acid can be prepared from the reaction of alkylphosphonic dichloride with a Grignard reagent as reported by Crofts and Fox in "Unsymmetrical Dialkylphosphinic Acids" J. Chem. Soc. 1958, 2995-2997, the relevant disclosure of which is incorporated herein by reference. An exemplary reaction sequence is illustrated below: 0 0 11 1) 2 eq Me 2 NH || R- P - Cl N R -P-OH 1 2) R2MgBr, Et 2 0 2 Cl 3) HCl, aq R Alternatively, unsymmetrical organophosphinic acids can be prepared in a one-pot synthesis using the method of Boyd et al. in "Synthesis of y-keto-substituted phosphinic acids from bis(trimethylsilyl)phosphonite and c, P-unsaturated ketones," Tetrahedron Lett., 1992, 33, 813-816 and Boyd, E.A.; Regan, A.C.; James, K. "Synthesis of Alkyl Phosphinic Acids from Silyl Phosphonites and Alkyl Halides," Tetrahedron Lett., 1994, 35, 4223-4226, the relevant disclosures of which are incorporated herein by reference. An exemplary reaction sequence is shown below: 0 OSiMe 3 (Me 3 Si) 2 NH P 1. R' I, CH7C1 2 ,0 0 C-RT

N

2 , 1 10"C,1-2 hr \ 2. (Me 3 Si) 2 NH H Me 3 SiO H 3. R 2 1 H 4. MeOH 0 RI -p- OH R2 20/07/04, eh14270.svc, 7 -8 Suitable activator compositions comprise a source of polyvalent metal ions suitable for forming the polyvalent metal salts of organophosphonic acid esters or organophosphinic acids of the gelling agents of the present invention. Examples of such suitable ions include, but are not limited to, aluminum ions, gallium ions, lanthanum ions, ruthenium ions, iron ions, or lanthanide rare earth series ions. Preferred polyvalent metal ions have a +3 oxidation state. When ferric iron is utilized to form the gelling agent, the source of the ions is preferably ferric sulfate or ferric chloride, ferric sulfate being preferred. The ferric iron salt is typically mixed with amines, surfactants and water to form a liquid activator composition. An example of a commercially available ferric iron activator composition is "EA-3TM"1 sold by Ethox Chemicals, Inc. of Greenville, South Carolina. When an aluminum compound is utilized, it is preferably selected from aluminum chloride, sodium aluminate, or aluminum isopropoxide. In certain embodiments, the ratio of metal to phosphorus in a gelled liquid hydrocarbon treatment fluid should be about 1:3; in other embodiments, the metal to phosphorus ratio may be about 2:3. Activator compositions also may comprise amines, surfactants, water, or other suitable components. The polyvalent metal salts of organophosphonic acid esters or. organophosphinic acids of the gelling agents of the present invention may be formed by any suitable method, which will be apparent to those ordinarily skilled in the art upon reading this disclosure. The liquid hydrocarbon utilized to form the gelled liquid hydrocarbon treatment fluids of the present invention can comprise any suitable liquid hydrocarbon including, but not limited to, a-olefins, internal olefins, alkanes, aromatic solvents, cycloalkanes, liquefied petroleum gas, kerosene, diesel oil, gas oil (also known as gas condensate), fuel oil, other petroleum distillates, certain mixtures of crude oil, or mixtures thereof. Liquid hydrocarbons that may be specifically designed for use with CO 2 are generally preferred in some instances, e.g., a dry gas well. An example of a suitable liquid hydrocarbon is commercially available from the Trysol Corporation of Sundre, Alberta, Canada under the trade name

"FRACSOL

TM

." If desired, enhancers may be added, inter alia, to provide alkalinity, improve the stability of the polyvalent metal ions in the activator composition, and/or improve the dispersability of the metal ions in the hydrocarbon liquid so as to facilitate the formation of the gelled liquid hydrocarbon treatment fluid. Preferred enhancers should provide alkalinity and should facilitate the gellation of the liquid hydrocarbon. Suitable enhancers may be 20/07/04 eh 14270 ne R -9 defined by the general formula CnHmOxNy, wherein n is from about 1 to about 50, m is from about 0 to about the number of hydrogens necessary to satisfy the valence requirements of the enhancer compound, x is from about 1 to about 10 (preferably around 2), and y is from about 0 to about 10 (preferably under 3). Suitable examples would be where the ratio of C to N in the enhancer ranges from about 1:1 to about 50:1, and C to 0 from about 1:1 to about 20:1. Specific examples include ethoxylated amines, like triethanolamines, NN-dibutyl ethanol amines, and oxyalkylated di-C 2

-C

8 alkyl amines; NN-di-loweralkyl fatty amines; oxyalkylated fatty amine; monoammonium citrate; bis(hydroxyethyl) tallowamine; and ethoxylated dehydroabietylamine. Mixtures of such suitable enhancers also are suitable. An example of a suitable enhancer is a surfactant. Surfactants may be added to facilitate the formation of a gelled liquid hydrocarbon treatment fluid. Surfactants may decrease the gellation time of the gelled liquid hydrocarbon because they may allow for a better dispersion of the metal ions in the hydrocarbon fluid. Suitable surfactants that may be used include basic surfactants, especially those that may comprise an amine group. Use of about 0.1% to about 10.0% of a suitable surfactant based on the amount of the gelling agent may be beneficial, inter alia, to help speed formation of the gelled liquid hydrocarbon fluid or to impart desirable rheological characteristics. Some specific examples of suitable surfactants include imidazoline, a fatty acid soap, a fatty acid, dioctyl sulphosuccinate, sodium alkyl benzene sulphonate, fatty acid esters, fatty acid alkanolamides, and amido betaines. In certain embodiments, the gelled hydrocarbon treatment fluids of the present invention may comprise particulate materials like proppant or gravel that can be utilized in, for example, fracturing or gravel packing operations. Suitable particulate materials include, but are not limited to, graded walnut or other nut shells, resin-coated walnut or other nut shells, graded sand, resin-coated sand, sintered bauxite, various particulate ceramic materials, glass beads, various particulate polymeric materials and the like. The particular size of the particulate material employed may depend on the particular application for which the particulate materials are being used, characteristics of the subterranean formation, characteristics of the particular gelled liquid hydrocarbon treatment fluid being used, as well as other variables. Generally, the particulate sizes may vary in the range of from about 2 to about 200 mesh, U.S. Sieve Series scale. One of ordinary skill in the art with the benefit of this disclosure will be able to choose an appropriate particulate material for a given application. 20/07/A4 PhIA70 ne 0 -10 In addition, in a preferred embodiment, if water is not already contained in the hydrocarbon liquid, or added thereto as a component of a component, e.g., in an activator composition or an enhancer, water may be added in an amount, for example, of about 0.05% or greater by the total treatment fluid volume. The presence of the water, inter alia, may be used beneficially in the compositions and methods of the present invention, for example, to allow for slowly water soluble or encapsulated breakers to be dissolved or released that may be used to reduce the viscosity of the gelled liquid hydrocarbon treatment fluid of the present invention when desired. See, for example, Smith et al. U.S. Patent No. 5,846,915 issued on December 8, 1995, the relevant disclosure of which is incorporated herein by reference. If a gelled liquid hydrocarbon treatment fluid of the present invention is being used in an application wherein it may be desirable to eventually reduce the viscosity of the treatment fluid, for example, to recover it from the subterranean formation at a desired time, then a suitable breaker may be included in or added to the fluid. Any breaker that is able to reduce the viscosity of the gelled liquid hydrocarbon treatment fluid when desired is suitable for use in the compositions and methods of the present invention. In certain preferred embodiments, delayed gel breakers that will react with the treatment fluid after a desired delay period may be used. Suitable delayed gel breakers can be materials that are slowly soluble in water, those that are encapsulated, or those that are otherwise designed to slowly solubilize in the fluid. In certain preferred embodiments wherein these types of breakers are used, the breaking of the gel does not take place until the slowly soluble breakers are at least partially dissolved in the water. Examples of such slowly soluble breakers are given in U.S. Patent No. 5,846,915 issued to Smith et al. on December 8, 1998. Hard-burned magnesium oxide, especially that having a particle size which will pass through a 200 mesh Tyler screen, is a preferred delayed gel breaker. Other breakers such as alkali metal carbonates, alkali metal bicarbonates, alkali metal acetates, other alkaline earth metal oxides, alkali metal hydroxides, amines, weak acids and the like can be encapsulated with slowly water soluble or other similar encapsulating materials so as to make them act after a desired delay period. Such materials are well known to those skilled in the art and function to delay the breaking of the gelled liquid hydrocarbon for a required period of time. Examples of water soluble and other similar encapsulating materials that may be suitable include, but are not limited to, porous solid materials such as precipitated silica, elastomers, polyvinylidene chloride (PVDC), nylon, waxes, polyurethanes, polyesters, cross-linked partially hydrolyzed acrylics and the 20/07/04. eh14270.SDC. 10 - 11 like. Of the slowly soluble or encapsulated breakers mentioned, hard-burned magnesium oxide, which may be commercially available from Clearwater Inc. of Pittsburgh, Pennsylvania, is preferred. In certain embodiments, when a polyvalent metal salt of an organophosphonic acid ester and an alkaline breaker are utilized, e.g., magnesium oxide, an initial increase in the viscosity of the gelled hydrocarbon liquid may be achieved, after which the gel is broken. If used, the delayed gel breaker may be present in the gelled hydrocarbon liquids of the present invention in an amount in the range of from about 0.01% to about 3% w/v, more preferably in an amount in the range of from about 0.05% to about 1% w/v. "Percent w/v" as used herein refers to the weight of the component based on the volume of the liquid hydrocarbon that is present in the treatment fluid (i.e. g/100 ml expressed as %). Another type of breaker which can be utilized when the gelling agent is a ferric iron polyvalent metal salt of an organophosphonic acid ester or a ferric iron polyvalent metal salt of the organophosphinic acid is a reducing agent that reduces ferric iron to ferrous iron. Of the various oxidation states of iron, ferric iron is capable of forming a viscosifying coordination salt with an organophosphonic acid ester or organophosphinic acid, therefore the salt may be disassociated by reducing the ferric iron to the ferrous state. The disassociation may cause the gelled liquid hydrocarbon treatment fluid to break. Examples of reducing agents which can be utilized include, but are not limited to, stannous chloride, thioglycolic acid, hydrazine sulfate, sodium diethyldithiocarbamate, sodium dimethyldithiocarbamate, sodium hypophosphite, potassium iodide, hydroxylamine hydrochloride, 2-mercaptoethanol, ascorbic acid, sodium thiosulfate, sodium dithionite, and sodium sulfite. Of these, the preferred reducing agents for use at a temperature of about 90*C are stannous chloride, thioglycolic acid, hydrazine sulfate, sodium diethyldithiocarbamate, and sodium dimethyldithiocarbamate. The most preferred reducing agent is thioglycolic acid, which may be delayed by salt formation or encapsulation. As mentioned above in connection with other breakers that can be used, the reducing agent utilized also can be delayed by encapsulating it with a slowly water soluble or other similar encapsulating material. If used, the gel breaker is generally present therein in an amount in the range of from about 0.01% to about 3% w/v, more preferably in an amount in the range of from about 0.05% to about 1% w/v. Gelled liquid hydrocarbon treatment fluids of the present invention may be prepared by any suitable method. For instance, a gelled liquid hydrocarbon treatment fluid comprising a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or an 70/07/Md Phl70Aenc 11 - 12 organophosphinic acid may be produced at the well site. In an example of such an on-site method, an organophosphonic acid ester or an organophosphinic acid may be added to a suitable amount of an activator composition that comprises a source of polyvalent metal ions so as to form a gelling agent comprising polyvalent metal salt of an organophosponic acid ester or a polyvalent metal salt of an organophosphinic acid. This may be done in a liquid hydrocarbon fluid so that the resultant gelling agent may gel the liquid hydrocarbon fluid. In certain embodiments, the ratio of metal to phosphorus in the gelled liquid hydrocarbon treatment fluid should be about 1:3; in other embodiments, the metal to phosphorus ratio may be about 2:3. A gelling agent of the present invention that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid may be formed off-site and then added to the liquid hydrocarbon at the well site so as to form a gelled liquid hydrocarbon treatment fluid. In an example of such a method, the polyvalent metal salt may be prepared by any method that is suitable for forming solid salt particulates (e.g., flakes, pellets, or other particulates) that later can be introduced to a liquid hydrocarbon fluid. The polyvalent metal salt particulates may be transported to the well site where they can be added to a liquid hydrocarbon fluid. In some embodiments of such methods, the liquid hydrocarbon fluid may be pre-gelled or partially gelled using any suitable technique. In one embodiment of such a technique, after the salt particulates are added to the liquid hydrocarbon fluid, no significant increase in the viscosity of the liquid hydrocarbon fluid may be realized until the temperature of the fluid is sufficient to enable the salt particulates to dissolve in the liquid hydrocarbon fluid to eventually increase its viscosity. Another method of preparing a gelled liquid hydrocarbon treatment fluid of the present invention comprises forming an initial liquid hydrocarbon gel by adding a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid to a liquid hydrocarbon fluid to form an initial gel. At a desired time, an additional quantity of a gelling agent that may comprise a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid may be added to the initial gel, for example, as it is pumped into a well bore penetrating a subterranean formation, to form a more viscous gel. Another example of a method for forming the gelled liquid hydrocarbon treatment fluids of the present invention involves preparing a liquid hydrocarbon gel having a high 20/07/04. ehl4270snc 12 - 13 concentration of a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid. This gel may be highly viscous. This highly viscous gel may be prepared off-site and then delivered to the location of use at a desired time. At the location, the highly viscous gel may be diluted with a hydrocarbon if desired for use (for instance, if the gel is to be used in a fracturing or sand control treatment method). Although certain methodologies of making a gelled liquid hydrocarbon treatment fluid of the present invention have been discussed in detail, one should note that the order of addition of each component is not critical, and therefore, other methods are suitable as well. A preferred method of preparing a gelled liquid hydrocarbon fluid of this invention comprises adding an activator composition comprising a source of polyvalent metal ions and an organophosphonic acid ester to a liquid hydrocarbon, the organophosphonic acid ester having the formula: 0 II

HO-P-CH

2

-CH

2

-CH

2 -R OR' where R represents a hydrocarbon group having the general formula CnH 2 n+ 1 , where n is from about 3 to about 21 and R' preferably comprises a methyl or ethyl group, or adding an organophosphinic acid having the formula: 0

HO-P-CH

2

-CH

2

-CH

2 -R R' where R represents a hydrocarbon group having the general formula CnH 2 n+ 1 , where n is from about 3 to about 21 and R' preferably is either methyl or ethyl, so as to form a suitable polyvalent metal salt thereof that will gel the liquid hydrocarbon. In a preferred embodiment, the source of polyvalent metal ions comprises aluminum or iron. The resultant polyvalent metal salt of the organophosphonic acid ester or the polyvalent metal salt of the organophosphinic acid may be present in an amount in the range of from about 0.1% to about 10.0% w/v, more preferably in an amount in the range of from about 0.2% to about 2% w/v. Optionally, a breaker may be added to the gelled liquid hydrocarbon fluid. If a delayed gel breaker is used, the delayed gel breaker may be present in the hydrocarbon liquid in an 20/07104 eh14270sne 13 - 14 amount in the range of from about 0.01% to about 3% by weight of the hydrocarbon liquid, more preferably in an amount in the range of from about 0.05% to about 1%. A preferred gelled liquid hydrocarbon composition of this invention comprises a hydrocarbon liquid and a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid. The gelled liquid hydrocarbon composition may comprise water and/or a base. The gelled liquid hydrocarbon composition optionally may comprise an enhancer and/or a breaker. In certain embodiments, the enhancer comprises a surfactant. In certain embodiments, the breaker is a delayed gel breaker. The delayed gel breaker may comprise a reducing agent that is capable of reducing ferric iron to ferrous iron, and it may be encapsulated with a slowly water soluble or other similar encapsulating material. A preferred hydrocarbon liquid gelling agent of this invention comprises a ferric iron or aluminum polyvalent metal salt of an organophosphonic acid ester, the organophosphonic acid ester having the formula: 0 II

HO-P-CH

2

-CH

2

-CH

2 -R OR' where R represents a hydrocarbon group having the general formula CnH 2 n+ 1 , where n is from about 3 to about 21 and R' preferably is methyl or ethyl, or an organophosphinic acid having the formula: 0 II HO -P -CH 2

-CH

2

-CH

2 -R R' where R represents a linear or branched alkyl chain having the general formula CnH 2 n+, where n is from about 1 to about 21, and R' preferably is a methyl or ethyl. A preferred hydrocarbon liquid gelling agent comprises a ferric iron polyvalent metal salt of an organophosphonic acid ester, the ester having the formula: 20/07/04. eh14270.soc. 14 - 15 0 II

HO-P-CH

2

-CH

2

-CH

2 -R OR' where R represents a linear or branched alkyl chain having the general formula CnH 2 n+ 1 , where n is from about 1 to about 21 and R' preferably is a methyl or ethyl group, or an organophosphinic acid having the formula: 0 II

HO-P-CH

2

-CH

2

-CH

2 -R R' where R represents a linear or branched alkyl chain having the general formula CnH 2 n+ 1 , where n is from about 1 to about 21 and R' preferably is a methyl or ethyl group. In a treatment fluid embodiment, a gelling agent comprising an organophosphonic acid ester or an organophosphinic acid may be added to the liquid hydrocarbon along with an activator composition that comprises a source of polyvalent metal ions to gel the liquid hydrocarbon. An exemplary method of the present invention of treating a subterranean formation comprises the steps of: providing a gelled liquid hydrocarbon treatment fluid comprising a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid, and treating the subterranean formation with the gelled liquid hydrocarbon treatment fluid. Treating the subterranean formation may involve fracturing the subterranean formation, performing a sand control treatment (e.g., gravel packing), providing a plugging agent (e.g., pill), providing a well bore cleanup fluid, performing a viscous sweep, or providing an insulating fluid. U.S. Patent No. 5,271,464 assigned to Halliburton Company, the relevant disclosure of which is incorporated by reference, describes providing a plugging agent with a gel. U.S. Patent Nos. 4,473,408 and 4,003,393, both assigned to The Dow Chemical Company, the relevant disclosures of which are incorporated by reference, describe the use of organic gels for cleaning the interior of a pipeline. U.S. Patent No. 5,034,139 assigned to Nalco Chemical Company, the relevant disclosure of which is incorporated by reference, describes the use of a thixotropic gel as a viscous sweep. U.S. Patent No. 6,283,215 assigned to Institut Francais Du Petrole, the relevant disclosure of which is incorporated by reference, describes insulation of tubings placed in a well bore. In certain of such embodiments, the gelling agent that 20/07/04, eh14270.spc, 15 -16 comprises a polyvalent metal salt of the organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid may be present in the treatment fluid in an amount in the range of from about 0.1% to about 10.0% w/v. In a fracturing treatment fluid embodiment, a gelling agent comprising a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid may be added to the liquid hydrocarbon along with an activator composition that comprises a source of polyvalent metal ions to gel the liquid hydrocarbon. In certain embodiments, the polyvalent metal salt of the organophosphonic acid ester or the polyvalent metal salt of the organophosphinic acid may be added in an amount in the range of from about 0.1% to about 10% w/v. Optionally, a fracturing fluid of the present invention may comprise water and/or a base to achieve a desired gel. A fracturing fluid of the present invention also may comprise proppant. A preferred method of fracturing a subterranean formation in accordance with the present invention comprises the steps of: (a) providing a gelled liquid hydrocarbon treatment fluid comprising a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester, the organophosphonic acid ester having the formula: 0 II

HO-P-CH

2

-CH

2

-CH

2 -R

OCH

3 where R represents a hydrocarbon group having the general formula CnH 2 n+l, where n is from about 3 to about 21, or a polyvalent metal salt of an organophosphinic acid, organophosphinic acid having the formula: 0 HO - P - CH 2 - CH 2 - CH 2 - R

CH

3 where R represents a linear or branched alkyl chain having the general formula CnH 2 n+, where n is from about 3 to about 21; and (b) contacting the subterranean formation with the gelled liquid hydrocarbon treatment fluid under conditions effective to create or enhance at least one fracture in the subterranean formation. In certain embodiments, the gelling agent may be present in the treatment fluid in an amount in the range of from about 0.1% to about 5.0% w/v, more preferably in an amount in the range of from about 0.2% to about 2.5% w/v. )AI7/AA h1A27A) e If -17 In certain embodiments, the gelled liquid hydrocarbon treatment fluid may comprise a proppant material. In certain embodiments, the proppant material may be present in the fluid in an amount in the range of from about 1 to about 32 pounds of proppant material per gallon of liquid hydrocarbon, more preferably in the range of about 1 to about 22 pounds per gallon. As mentioned, if desired, water may be added if not otherwise present in the gelled liquid hydrocarbon treatment fluid, so that, e.g., a delayed gel breaker may be utilized. A suitable delayed gel breaker may be present in the treatment fluid in an amount in the range of from about 0.01% to about 3% w/v, more preferably in an amount in the range of from about 0.05% to about 1% w/v. In a gravel pack treatment fluid embodiment, a gelling agent comprising a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid may be added to the liquid hydrocarbon in an amount in the range of from about 0.1% to about 10% w/v with a portion of gravel particulates. Optionally, a gravel pack treatment fluid of the present invention may comprise water and or a base to achieve a desired gel. A method of the present invention of providing sand control to a subterranean formation comprises the steps of contacting a portion of the subterranean formation with a gelled liquid hydrocarbon gravel pack fluid of the present invention that comprises gravel and a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid so as to create a gravel pack neighboring that portion of the subterranean formation. In certain embodiments, the gelling agent may be present in the gelled liquid hydrocarbon gravel pack fluid in an amount in the range of from about 0.1% to about 5.0% w/v, more preferably in an amount in the range of from about 0.2% to about 2.5% w/v. In certain embodiments, the gravel particulates may be present in the fluid in an amount in the range of from about 1 to about 32 pounds of proppant material per gallon of liquid hydrocarbon, more preferably in the range of about 1 to about 22 pounds per gallon. As mentioned, if desired, water may be added, if not otherwise present in gelled liquid hydrocarbon gravel pack fluid, so that, e.g., a delayed gel breaker may be utilized. A suitable delayed gel breaker may be present in the gelled liquid hydrocarbon gravel pack fluid in an amount in the range of from about 0.01% to about 10% w/v, more preferably in an amount in the range of from about 0.05% to about 3% w/v. 20/07/04 eh1427Osne 17 - 18 In order to further illustrate the methods and composition of the present invention, the following examples are given. In no way should such examples be read to limit or define the scope of the invention. EXAMPLES Example 1 A number of monoesters of alkylphosphonic acids were prepared in the laboratory as follows: solid dodecylphosphonic acid monomethyl ester, solid tetradecylphosphonic acid monomethyl ester, solid hexadecylphosphonic acid monomethyl ester, solid octadecylphosphonic acid monomethyl ester, solid C 2 0

-

24 phosphonic acid monomethyl ester, solid octadecylphosphonic acid monobutyl ester, liquid octylphosphonic acid monomethyl ester and liquid decylphosphonic acid monomethyl ester. The following laboratory procedure was utilized in the preparation of the above listed esters. Alkylphosphonic acid dimethyl (or dibutyl) esters were first prepared by charging a 250 milliliter three-necked round bottom flask with 0.2 mole of 1-alkene and 0.5 mole of dimethyl or dibutyl phosphite. The flask was fitted with a reflux condenser, thermometer, temperature controller, septum stopper and nitrogen purge. The mixture was magnetically stirred and heated to 150*C or the boiling point of the 1-alkene, whichever was lower. 2.5 milliliters of t-butyl peroxide was slowly added with a syringe over the course of 1 hour. The mixture was heated at 150'C for another 1.5 hours. The excess dialkyl phosphite was removed using vacuum distillation. The following laboratory procedure was utilized in the preparation of monomethyl (or monobutyl) esters that are liquids at room temperature. That is, alkylphosphonic acid monomethyl (or monobutyl) esters were prepared using the alkylphosphonic acid dimethyl (or dibutyl) esters prepared in accordance with the above described procedure as follows. 0.045 mole of alkylphosphonic acid dimethyl (or dibutyl) ester was charged to a 100 milliliter round bottom flask. A solution of 1.9 grams (0.048 mole) of sodium hydroxide in 38 milliliters of methanol was added to the flask and the flask was fitted with a reflux condenser. The mixture was stirred magnetically and heated to reflux for 3 hours. 10 milliliters of water and 50 milliliters of hexane were added, and the resulting mixture was shaken. The phases were separated, and the hexane layer containing the unreacted dimethyl (or dibutyl) ester was discarded. The aqueous layer was washed twice with 20 milliliter portions of hexane, and the hexane layer was discarded. 3.6 milliliters of 38% hydrochloric acid (0.045 mole) was added 70/0714 eh14770ene 12 -19 to the aqueous phase followed by 40 milliliters of water. The mixture was extracted 3 times with 20 milliliter portions of hexane. The combined organic fractions were washed with water and dried over anhydrous magnesium sulfate. The solvent was removed using a rotary evaporator. The alkylphosphonic acid monomethyl (or monobutyl) esters produced were liquids at room temperature. Alkylphosphonic acid monoesters which are solids at room temperature also were prepared. These were the C 1 2 to C 24 alkyl phosphonic acid mono methyl esters. The following laboratory procedure was utilized. A 100 milliliter round bottom flask was charged with 0.05 mole of alkylphosphonic acid dimethyl ester, and the flask was warmed to melt the solid. A solution of 2.5 g (0.063 mole) of sodium hydroxide in 38 milliliters of methanol was added, and the flask was fitted with a reflux condenser. The mixture was stirred magnetically and heated to reflux for 3 hours. The flask was cooled, and 5 milliliters 38% hydrochloric acid (0.062 mole) was added, followed by the addition of 125 milliliters of water. The slurry was extracted into hexane. The hexane solution was washed with water, dried over anhydrous magnesium sulfate, and concentrated on a rotary evaporator. The product was allowed to recrystallize, then it was collected on a buchner funnel, washed with hexane, and air dried. Example 2 A commercially available octylphosphonic acid monomethyl ester was obtained which contained 55-65% octylphosphonic acid monomethyl ester, 20-30% octylphosphonic acid and 10-20% octylphosphonic acid dimethyl ester. 2 milliliters of the commercial octylphosphonic acid monomethyl ester and 2 milliliters of a ferric iron activator commercially available from Clearwater Inc. of Pittsburgh, Pennsylvania under the trade designation "HGA-65TM" were added to 200 milliliters of kerosene. Initial cross-linking was observed after 20 seconds of stirring with an overhead stirrer. A strong cross-linked gel was observed after 1 minute. This test shows that the organophosphonic acid ester may comprise portions of the phosphonic acid and the phosphonic acid dialkyl ester. Example 3 2 milliliters of the commercially available octylphosphonic acid monomethyl ester described in Example 2 were added to 200 milliliters of kerosene along with a ferric iron 20/07/04. eh14270.snc 19 -20 activator composition. The ferric iron activator composition comprised 240 grams of deionized water, 60 grams of ferric sulfate pentahydrate and 33.3 grams of triethanolamine. Upon mixing, the cross-linking reaction was slower than that observed in Example 2, but good cross-linking was observed after 2 to 3 minutes. Example 4 The commercially available octylphosphonic acid monomethyl ester described in Example 2 was added to No. 2 off-road diesel oil along with a commercially available ferric iron cross-linking composition obtained from Ethox Chemicals, Inc. of Greenville, S.C. sold under the trade designation "EA-3TM" (see U.S. Patent No. 6,149,693 issued to Geib on November 21, 2000). Three different mixtures were prepared having the quantities of components shown in Table I below. After mixing, each of the mixtures was placed in a Model 50 viscometer at 68'C and the viscosities of the mixtures were observed over time. The results of these tests are given in Table I below. 20/07/04 eh14270 sne 20 -21 TABLE I Viscosities of Gelled Diesel Oil Using Commercially Available Gelling Agent Components at 68*C Time, Viscosity, cp. @ 170/sec Minutes Mixture A' Mixture B 2 Mixture C 3 30 297 169 197 60 243 172 210 90 218 187 212 120 205 209 204 150 193 217 199 180 184 218 193 210 175 218 188 240 167 217 184 270 158 216 182 300 152 217 Mixture A comprised 6 milliliters of commercially available Albright & Wilson "ITCTM-996" octylphosphonic acid monomethyl ester per liter of diesel oil and 5 milliliters of "ETHOXTM EA-3" ferric iron activator composition per liter of diesel oil. 2 Mixture B comprised 5 milliliters of commercially available Albright & Wilson "ITCTM996" octylphosphonic acid monomethyl ester per liter of diesel oil and 5 milliliters of "ETHOXTM EA-3" ferric iron activator composition per liter of diesel oil. 3 Mixture C comprised 5 milliliters of commercially available Albright & Wilson "ITCTM-996" octylphosphonic acid monomethyl ester per liter of diesel oil and 6 milliliters of "ETHOXTM EA-3" ferric iron activator composition per liter of diesel oil. From Table I, it can be seen that the commercially available octylphosphonic acid monomethyl ester and activator produced viscous fluids. Example 5 The procedure of Example 4 was repeated except that the octylphosphonic acid monomethyl ester was synthesized in accordance with the procedure set forth in Example 1 and the third mixture tested, i.e., mixture F, included magnesium oxide breaker. The results of these tests are given in Table II below. 20/07/04. ehI4270.snc. 21 - 22 TABLE II Viscosities of Gelled Diesel Oil Using Synthesized Octylphosphonic Acid Monomethyl Ester and Commercial Ferric Iron Activator Composition at 68 0 C Time, Viscosity, cp. @ 170/sec Minutes Mixture D' Mixture E 2 Mixture F 3 4 299 388 395 30 131 143 85 60 135 146 47 90 140 151 34 120 146 156 25 150 149 160 17 180 - 162 10 210 163 240 164 I Mixture D comprised 5 milliliters of synthesized octylphosphonic acid monomethyl ester per liter of diesel oil and 5 milliliters of "ETHOXTM EA-3" ferric iron activator composition per liter of diesel oil. 2 Mixture E comprised 5 milliliters of synthesized octylphosphonic acid monomethyl ester per liter of diesel oil and 6 milliliters of "ETHOXTM EA-3" ferric iron activator composition per liter of diesel oil. Mixture F comprised 5 milliliters of synthesized octylphosphonic acid monomethyl ester per liter of diesel oil, 5 milliliters of "ETHOXTM EA-3" ferric iron activator composition per liter of diesel oil and 1.2 grams magnesium oxide breaker per liter of diesel oil. From Table II, it can be seen that the synthesized octylphosphonic acid monomethyl ester produced gels. In addition, mixture F including magnesium oxide gel breaker showed an increased viscosity as a result of neutralization of the organophosphonic acid ester by the magnesium oxide breaker therein, after which the gel was broken. Example 6 The procedure of Example 4 was repeated except that the organophosphonic acid ester used was synthesized hexadecylphosphonic acid monomethyl ester. The results of these tests are given in Table III set forth below. )AIn'7/AA ah1AV1 , e n C) ~ C) . -en -E E. 42 2 42 4 000 00 ~ ~ ~ ~ 4 00r- . r-r- 0 4 0 0 0 0 W)Ci a -r- 00 - CA- ~0 r 0 0 0 - 0 0 '0~ -i r- a) 0)0j 040 0 ~ ~ 0 0 0 o 0 0 0 U -T -u I-.m W m0 a) a) 00 a*, C-. aN) a ) a)) a) a) a- a-. (71 C) ---- 0 --- -l\ -o -d -o c c 4-' - - -, - - C a) ) 4 . q) 4, 'A -1 CI r- 00 2* C >0 0 0 o o o -N 01 N 01 2t i2 -a 0 0 02 - .2 22 22 C 2 E E2 2 En( A D E - - n ( 06 06 0 C> o o4c. o 0 o r- 004lNIlIN 00 C) C - 0 0n 0 O -C: 0C 0 CA-- 0 0 E0. o 0 E E 0 E 0 . - 0 0 0- L ) 0 > ~ > >C)> > >- a) a) u) Q) u) ) u) 0- Cd co Cd C m c)~a a) k-) 00 ( C oco~oo -~'0 0 00~0 0 0 c~0 0 - 24 From Table III, it can be seen that synthesized hexadecylphosphonic acid monomethyl ester and the ferric iron activator utilized form gels in diesel oil at 68'C. Example 7 The test procedure of Example 4 was repeated except that synthesized octadecylphosphonic acid monomethyl ester was utilized, the temperature of the gelled diesel oil was increased over time and two of the four gelled mixtures tested contained a magnesium oxide breaker. The results of these tests are given in Table IV below. 20/07/04 eh 1427) snn 24 4.) w) 00k o r-o -~' W)J 00 _A 0 C-4 04 4 0 0 0 r - a2 - 0 Q H E E CO 0i co 0 0 000O ecE 0c E' 0 Cw t cii 0, b) 0 C0i) - 0 020 2 (N 0 0. C>l En 0- -0 = 000 o Mj IC "o ) c0 0 ClE 0 0 Cd 0 M 2e E H~ 2 -2 - ~ ~ ~ o 0 - 01 C1 C4 o +5 - 26 As can be seen from Table IV, synthesized octadecylphosphonic acid monomethyl ester and the ferric iron activator utilized form gels in diesel oil over a broad temperature range. Further, the magnesium oxide breaker neutralized the acid ester which increased the viscosity attained over a broad range of temperatures. 5 Example 8 The test procedure of Example 4 was repeated except that a Tempco Rheo-15 rheometer was utilized to measure apparent viscosities at various temperatures with fluids containing 40% CO 2 by volume. One of the test mixtures was formed with a #2 Off Road Diesel hydrocarbon fluid, and another test mixture included magnesium oxide. The results 10 of these tests are set forth in Table V below. TABLE V Viscosities of Gelled Diesel Using Commercially Available Gelling Agent Components 15 and 40% Carbon Dioxide by Volume at Various Temperatures Mixture S' Mixture T 2 Mixture U 3 Time, Temp., C Viscosity, cp. Temp., C Viscosity, cp. Temp. C Viscosity, cp. minutes T @ 170/sec @ 170/sec ' @ 170/sec 0 10 120 7 120 7 100 10 66 155 52 195 60 295 20 85 115 66 205 63 330 30 85 95 68 195 66 340 40 85 85 71 190 68 345 50 85 85 74 175 71 350 60 85 85 77 165 72 350 70 - - 82 145 74 340 80 - - 85 130 77 335 90 - - 88 110 79 320 100 - - 91 90 85 315 110 - - 93 80 88 300 120 - - 96 65 90 285 130 - - 99 45 91 265 140 - - 102 35 93 240 150 - - 104 20 96 210 ' Mixture S comprised 5 milliliters of commercially available Albright & Wilson "ITCTM-966" octylphosphonic acid monomethyl ester per liter of #2 Off Road Diesel Fuel containing 40% by volume carbon dioxide and 5 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of #2 Off Road Diesel Fuel containing 40% by volume carbon dioxide. 20 2 Mixture T comprised 7 milliliters of commercially available Albright & Wilson "ITCTM-966" octylphosphonic acid monomethyl ester per liter of diesel oil containing 40% by volume carbon dioxide and 7 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of diesel oil containing 40% by volume carbon dioxide. 3 Mixture U comprised 7 milliliters of commercially available Albright & Wilson "ITCTM-966" 25 octylphosphonic acid monomethyl ester per liter of #2 Off Road Diesel Fuel containing 40% by volume carbon dioxide, 7 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of #2 Off Road Diesel Fuel containing 40% by volume carbon dioxide and 0.240 grams of magnesium oxide breaker per liter of diesel oil containing 40% by volume carbon dioxide.

- 27 From Table V, it can be seen that gels were formed even though the gels contained 40% by volume carbon dioxide. Also, a significant increase in viscosity was realized when the gel included only enough magnesium oxide breaker to partially neutralize the octylphosphonic acid monomethyl ester. 5 Example 9 The procedure described in Example 4 was repeated except that magnesium oxide breaker was included in the three mixtures that were tested. In addition, one of the gels was produced utilizing a hydrocarbon liquid commercially available from Trysol Corp. of Sundre, Alberta, Canada under the trade name "FRACSOLTM" to which was added 40% by 10 total volume carbon dioxide. The results of the tests are given in VII below.

-28 TABLE VI Break Times of Various Gels with Magnesium Oxide Mixture VI Mixture W 2 Mixture X 3 Time, Temp., C Viscosity, cp. Temp., *C Viscosity, cp. Temp., "C Viscosity, cp. minutes @ 170/sec170/se @170/sec 5 31 366 33 375 39 370 10 46 365 48 307 68 365 15 54 365 55 240 85 360 20 59 364 58 173 85 200 25 62 363 61 105 85 70 30 64 360 62 83 85 30 35 65 357 64 76 85 15 40 66 353 65 67 85 13 45 67 335 65 62 85 10 50 67 318 66 56 85 9 55 67 302 66 51 85 5 60 68 293 66 47 85 2 90 68 185 66 34 120 68 97 67 25 150 68 74 67 17 180 68 67 67 11 210 68 60 240 68 54 270 68 47 300 68 35 330 68 25 360 68 18 390 68 14 420 68 12 5 1 Mixture V comprised 5 milliliters of commercially available Albright & Wilson "lTCTM-966" octylphosphonic acid monomethyl ester per liter of off-road diesel oil, 5 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of off-road diesel oil and 2.4 grams of magnesium oxide breaker per liter of off-road diesel oil. The off-road diesel oil contained water. 2 Mixture W comprised 5 milliliters of synthesized octylphosphonic acid monomethyl ester per liter of off 10 road diesel oil, 5 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of off-road diesel oil and 1.2 grams of magnesium oxide breaker per liter of off-road diesel oil. The off-road diesel oil contained water. 3 Mixture X comprised 7 milliliters of commercially available Albright & Wilson "ITC T M -966" octylphosphonic acid monomethyl ester per liter of "FRACSOLTM" hydrocarbon liquid mixed with 40% 15 by volume carbon dioxide, 7 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of "FRACSOLTM" hydrocarbon liquid mixed with 40% by volume carbon dioxide and 1.1 grams of magnesium oxide breaker per liter of "FRACSOLTM" hydrocarbon liquid mixed with 40% by volume carbon dioxide. Mixture X also contained water. From Table VII, it can be seen that progressive breaks were obtained by the 20 presence of the magnesium oxide. The synthesized organophosphonic acid ester required significantly less breaker and still showed a faster break rate than the commercial organophosphonic acid ester. The gel containing 60% by volume "FRACSOLTM" hydrocarbon liquid and 40% by volume carbon dioxide also achieved a progressive and complete break as a result of the presence of the magnesium oxide.

- 29 Example 10 Gelled hydrocarbon liquid test samples were prepared by combining 0.02M (6.4 g/L) of hexadecylphosphonic acid monomethyl ester and 5 milliliters per liter of Ethox "EA-3TM" ferric iron activator composition. Various reducing agents for reducing ferric 5 iron to ferrous iron and thereby breaking the gels were added to the test samples. Thereafter, the viscosities of the test samples over time were measured to determine the effectiveness of the reducing agents in breaking the gels. The results of these tests are given in Table VIII below. TABLE VII 10 Break Times of Diesel Oil Gel' Containing Various Reducing Agents @ 90 0 C Reducing Viscosity, cp. @ 170/sec At Time Agent Used 0 2 hrs. 21 hrs. 45 hrs. 242 hrs. Blank - No Reducing Agent 60 66 66 66 66 Stannous 7 3 - - Chloride dihydrate Thioglycolic Acid 45 3 - Sodium 141 18 3 Diethyldithiocarbamate Sodium 123 42 30 3 Dimethyldithiocarbamate Hydrazine Sulfate 45 96 57 33 3 Hydroxylamine Hydrochloride 75 69 15 3 15 '0.02M (0.64 wt%) hexadecyl phosphonic acid monomethyl ester per liter of off-road diesel oil, 5 milliliters of Ethox "EA-3TM" ferric iron activator composition per liter of off-road diesel oil and 0.01 M reducing agent per liter of off-road diesel oil. [0.1 Molar for stannous chloride dihydrate = 22.56 g/L; 0.1 M for thioglycolic acid (mercaptoacetic acid) = 9.21 g/L; 0.1 M for sodium diethyldithiocarbamate = 22.53 g/L; 0.1 M for sodium dimethyldithiocarbamate = 14.32 g/L; 0.1 m hydroxylamine hydrochloride = 6.95 g/L] The off-road 20 diesel oil gels contained water. From Table VIII, it can be seen that reducing agents comprised of stannous chloride, thioglycolic acid, sodium diethyldithiocarbamate, sodium dimethyldithiocarbamate and hydrazine sulfate can be utilized as efficient reducing agent breakers for the hydrocarbon gels of this invention, at 90'C. 25 Additional reducing agents could be the preferred reducing agents at higher temperatures where a slower rate of reaction is required. The additional reducing agents include, but are not limited to, sodium hypophosphite, potassium iodide, 2 mercaptoethanol (thioglycol), ascorbic acid, sodium thiosulfate, sodium dithionite, sodium sulfite and salts thereof. 30 -30 Example 11 To demonstrate an improved synthesis procedure using octadecylphosphonic acid, monomethyl ester as a specific example, a 500 ml round bottom flask was charged with 0.3 moles of octadecylphosphonic acid, dimethyl ester, 225 ml of methanol, and 15 g of 5 sodium hydroxide. The flask was fitted with a reflux condenser and stirred magnetically while heating to reflux for 30 hours. The mixture was transferred to a 1 liter beaker and allowed to cool. While stirring, 31 ml of concentrated hydrochloric acid was added, followed immediately by 500 ml of water. The mixture was heated to fuse the solid and then cooled to ambient temperature. The solid product was removed from the beaker, 10 dissolved in 250 ml of hexanes, and dried over anhydrous magnesium sulfate. The solvent was removed using a rotary evaporator to give the crude product in a 97% yield (94% monoester by 31 P NMR). If desired, the crude product could be further purified by recrystallization from hexanes. For esters other than methyl, a similar procedure may be used with the methanol 15 replaced with the alcohol consistent with the ester (e.g., n-butanol with the dibutyl ester, isopropanol with the diisopropyl ester, etc.). Due to the high boiling points of these alcohols as compared to methanol, the reaction times may be reduced. By using the appropriate alcohol, product purity may be improved possibly by avoiding transesterification with the methanol solvent. 20 Example 12 This example demonstrates the effect of a base on gelation performance. In this example, tris(methyl hexadecylphosphonate) iron(III) was synthesized from hexadecylphosphonic acid, dimethyl ester with a procedure similar to that described in: J.J. Kokalas, D.N. Kramer, F. Block, R. Levin, "The Infrared Spectra of Tris(methyl 25 methylphosphonate) iron(III), tris(ethyl ethylphosphonate) iron(III), and tris(isopropyl methylphosphonate) iron(III)," Spectroscopy Letters, 1969, 2, 273-281. Without isolating the tris(methyl hexadecylphosphonate) iron(III) from the reaction mixture, the crude product was added to Norpar 12 (alkane mixture, predominately C12) to give a 15 mM concentration of the iron complex. Rheology was determined using a constant frequency 30 (1 Hz) oscillatory stress sweep on a Haake Rheostress RS150 rheometer fitted with a 60 mm diameter, 2" cone and plate. The rheology was then measured after adding 0.4% v/v water to the solution. The rheology was again measured after adding 0.4% v/v of 25% w/w sodium hydroxide. According to the measurements taken, the storage modulus, G', is -31 low (which indicates a weak gel) until the sodium hydroxide is added. The large increase in G' is consistent with a strong gel. Table VIII Effect of Water and Base on G' G'(Pa) Stress (Pa) No Water 0.4% Water 0.4% Water + 0.4% 25% NaOH 1.0 6.7 7.3 87 10.7 6.5 7.5 87 5 Thus, the present invention is well adapted to carry out the objects and attain the benefits and advantages mentioned as well as those which are inherent therein. While numerous changes to the methods and compositions can be made by those skilled in the art, such changes are encompassed within the spirit of this invention as defined by the 10 appended claims. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or IS steps. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form or suggestion that the prior art forms part of the common general knowledge in Australia.

Claims (46)

1. A method of treating a subterranean formation comprising: providing a gelled liquid hydrocarbon treatment fluid (gelled fluid) comprising a liquid hydrocarbon and a gelling agent that comprises a polyvalent 5 metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid, and treating the subterranean formation with the gelled fluid.

2. A method of fracturing a portion of a subterranean formation comprising: providing a gelled liquid hydrocarbon fracturing fluid (gelled fluid) 10 comprising a gelling agent that comprises a polyvalent metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid, and contacting the portion of the subterranean formation with the gelled fluid under conditions effective to create or enhance at least one fracture in the 15 subterranean formation.

3. A method of providing sand control to a portion of a subterranean formation comprising: providing a gelled liquid hydrocarbon gravel pack fluid (gelled fluid) that comprises gravel particulates and a gelling agent that comprises a polyvalent 20 metal salt of an organophosphonic acid ester or a polyvalent metal salt of an organophosphinic acid; and contacting the portion of the subterranean formation with the gelled fluid so as to form a gravel pack near the portion of the subterranean formation.

4. The method of any one of claims I to 3 wherein the gelled fluid 25 comprises water and/or a base.

5. The method of any one of claims I to 4 wherein the liquid hydrocarbon of the gelled fluid comprises at least one liquid hydrocarbon selected from the group consisting of an ax-olefin, an internal olefin, an alkane, an aromatic solvent, a cycloalkane, liquefied petroleum gas, kerosene, diesel oil, gas oil, fuel oil, a 30 petroleum distillate, a crude oil mixture, or a mixture thereof.

6. The method of any one of claims I to 5 wherein the liquid hydrocarbon is designed for use with CO 2 . 19/03/1Ock 4270claimsaccepted.doc,32 - 33

7. The method of any one of claims 1 to 6 wherein the polyvalent metal salt of an organophosphonic acid ester is formed by a metathesis reaction comprising an alkali metal or an ammonium salt of the organophosphonic acid ester.

8. The method of any one of claims I to 6 wherein the polyvalent metal salt 5 of an organophosphonic acid ester is formed by a metathesis reaction comprising an organophosphonic acid dialkyl ester.

9. The method of any one of claims 1 to 6 wherein the polyvalent metal salt of an organophosphinic acid is formed by a metathesis reaction comprising an organophosphinic acid alkyl ester.

10 10. The method of any one of claims I to 6 wherein the polyvalent metal salt of an organophosphonic acid ester is formed from the reaction of an activator composition that comprises a source of polyvalent metal ions and an organophosphonic acid ester, the organophosphonic acid ester having the formula: 0 15 || R - P - O - R' OH wherein R or R' independently comprises a hydrocarbon group having 1 to 30 20 carbon atoms.

11. The method of any one of claims I to 6 wherein the polyvalent metal salt of an organophosphinic acid is formed from a reaction of an activator composition that comprises a source of polyvalent metal ions and an organophosphinic acid, the organophosphinic acid having the formula: 25 0 R'- P - OH 1 2 R 30 wherein R' or R 2 independently comprises a hydrocarbon group having I to 30 carbon atoms.

12. The method of claim 10 or I1 wherein if present in the formula R, R' or R2 comprise a linear or branched alkyl, alkenyl, aryl, alkylaryl, arylalkyl, cycloalkyl, alkyl ether, aryl ether, alkyl aryl ether, or a mixture thereof. 35

13. The method of claim 12 wherein R, R1 or R 2 independently comprises a hydrocarbon group having from I to 6 carbon atoms. 19/03/10,ck l4270claimsaccepteddoc,33 - 34

14. The method of claim 9 to 13 wherein the source of the polyvalent metal ions comprise aluminum ions, gallium ions, lanthanum ions, ruthenium ions, iron ions, or lanthanide rare earth series ions.

15. The method of any one of claims 9 to 13 wherein the polyvalent metal 5 ions comprise ions having a +3 oxidation state.

16. The method of any one of claims 9 to 13 wherein the activator composition comprises a ferric iron salt, aluminum chloride, sodium aluminate, or aluminum isopropoxide.

17. The method of any one of claims I to 16 wherein the gelled fluid 10 comprises a surfactant.

18. The method of claim 17 wherein the surfactant comprises imidazoline, a fatty acid soap, a fatty acid, dioctyl sulphosuccinate, sodium alkyl benzene sulphonate, a fatty acid ester, a fatty acid alkanolamide, or an amido betaine.

19. The method of claim 17 or 18 wherein the surfactant is present in the 15 gelled fluid in an amount in the range of from 0.1% to 10% based on the gelling agent.

20. The method of any one of claims 1 to 19 wherein the gelled fluid comprises an enhancer.

21. The method of claim 20 wherein the enhancer provides at least some 20 alkalinity to the gelled liquid hydrocarbon treatment fluid.

22. The method of claim 20 wherein the enhancer has the general formula CnHmOxNy, wherein n is from 1 to 50, m is from 0 to the number necessary to satisfy the valence of the enhancer, x is from I to 10, and y is from 0 to 10.

23. The method of claim 20 wherein the enhancer comprises an ethoxylated 25 amine, triethanolamine, NN-dibutyl ethanol amine, an oxyalkylated di-C 2 -Cs-alkyl amine, NN-di-loweralkyl fatty amine, an oxyalkylated fatty amine, monoammonium citrate, bis(hydroxyethyl) tallowamine, ethoxylated dehydroabietylamine, or a mixture thereof.

24. The method of claim I wherein treating the subterranean formation 30 involves fracturing a portion of the subterranean formation.

25. The method of claim 24 wherein the gelled fluid comprises proppant. 19/03/10,ck 4270claimsaccepted.doc,34 - 35

26. The method of claim 1 wherein treating the subterranean formation involves providing sand control to at least a portion of the subterranean formation.

27. The method of claim 26 wherein the gelled fluid comprises gravel.

28. The method of claim 25 or 27 wherein the proppant or gravel comprise 5 nut shells, resin-coated nut shells, graded sand, resin-coated sand, sintered bauxite, particulate ceramic materials, glass beads, or particulate polymeric materials.

29. The method of any one of claims 1 to 5 wherein the gelled fluid comprises water, the water being present in an amount of at least 0.05% by the total fluid volume. 10

30. The method of any one of claims 1 to 5 wherein the gelled fluid further comprises a breaker, the breaker being present in an amount sufficient to reduce the viscosity of the gelled fluid at a desired time.

31. The method of claim 30 wherein the breaker comprises a delayed gel breaker. 15

32. The method of claim 31 wherein the delayed gel breaker comprises an encapsulated delayed gel breaker.

33. The method of any one of claims 30 to 32 wherein the breaker, delayed gel breaker or encapsulated delay gel breaker is present in an amount in the range of from 0.01% to 3% w/v of the gelled fluid. 20

34. The method of claim 30 wherein the breaker comprises hard burned magnesium oxide, an alkali metal carbonate, alkali metal bicarbonate, alkali metal acetate, an alkaline earth metal oxides, an alkali metal hydroxide, an amine, or a weak acid.

35. The method of claim 30 wherein the breaker comprises a reducing agent 25 that is capable of reducing ferric iron to ferrous iron.

36. The method of claim 35 wherein the reducing agent comprises stannous chloride, thioglycolic acid, hydrazine sulfate, sodium diethyldithiocarbamate, sodium dimethyldithiocarbamate, sodium hypophosphite, potassium iodide, hydroxylamine hydrochloride, 2-mercaptoethanol, ascorbic acid, sodium thiosulfate, sodium 30 dithionite, or sodium sulfite.

37. The method of claim I wherein the treating the subterranean formation involves: 19/03/1Ockl4270claimsaccepted.doc,35 - 36 using the gelled liquid hydrocarbon treatment fluid to provide a plugging agent to a portion of the subterranean formation or a portion of a well bore penetrating the subterranean formation; or using the gelled fluid as a well bore cleanup fluid; or 5 using the gelled fluid to perform a viscous sweep of a portion of the subterranean formation or a portion of a well bore penetrating the subterranean formation; or insulating a portion of the subterranean formation, a portion of a well bore penetrating the subterranean formation, or a tubing placed in a well bore penetrating 10 the subterranean formation.

38. The method of claim I further comprising the step of preparing the gelled liquid hydrocarbon treatment fluid at the location of the subterranean formation.

39. The method of claim 1 further comprising the step of preparing the gelled liquid hydrocarbon treatment fluid at a location away from the subterranean 15 formation and transporting the gelled liquid hydrocarbon treatment fluid to the subterranean formation.

40. The method of claim 2 or 3 wherein the polyvalent metal salt of an organophosphonic acid ester or the polyvalent metal salt of an organophosphinic acid is present in an amount in the range of from 0.1% to 10% w/v. 20

41. The method of claim 2 wherein the polyvalent metal salt of an organophosphonic acid ester or the polyvalent metal salt of an organophosphinic acid is present in an amount in the range of from 0.2% to 5% w/v.

42. The method of claim 3 wherein the polyvalent metal salt of an organophosphonic acid ester or the polyvalent metal salt of an organophosphinic acid 25 is present in an amount in the range of from 0.1% to 5% w.v.

43. The method of claim 2 or 3 wherein the polyvalent metal salt of an organophosphonic acid ester is formed from the reaction of an activator composition that comprises a source of polyvalent metal ions and an organophosphonic acid ester, the organophosphonic acid ester having the formula: 19/03/1Ock 14270claimsaccepted.doc,36 - 37 0 || HO - P - CH 2 -CH 2 -CH 2 -R 5 OCH 3 where R represents a hydrocarbon group having the general formula CH 2 n+ 1 , where n is from 3 to 21.

44. The method of claim 2 or 3 wherein the polyvalent metal salt of an organophosphinic acid is formed from a reaction of an activator composition 10 comprising a source of polyvalent metal ions and an organophosphinic acid, the organophosphinic acid having the formula: 0 II HO-P-CH 2 -CH 2 -CH 2 -R 15 1 CH 3 where R represents a linear or branched alkyl chain having the general formula CH 2 ni, where n is from 3 to 21. 20

45. The method of claim 25 wherein the proppant is present in an amount in the range of from I to 32 pounds of proppant per gallon of gelled fluid.

46. The method of claim 3 wherein the gravel is present in an amount in the range of from I to 32 pounds of gravel per gallon of gelled fluid. 19/03/1 Ock 4270claimsacceptcd.doc,37