BRPI0604762B1 - methods of treating underground formation and facilitating runoff through a conduit - Google Patents

Abstract

Methods of treating an underground formation and facilitating flow through an underground conduit, composition and treatment fluid are provided treatment fluids comprising a base fluid and an orthoester-based surfactant. In some circumstances, the treatment fluid may have a pH of about 8.5 or above. Also provided are emulsified treatment fluids comprising an oleaginous phase, an aqueous phase having a pH of about 8.5 or above, and an orthoester-based surfactant. Also provided are methods for using the treatment fluid and methods for facilitating flow through a conduit.

Description

"Methods of Treating Underground Formation and Facilitating Flow Through a Conduct" BACKGROUND The present invention relates to orthoester-based surfactants. More particularly, the present invention relates to treatment fluids comprising orthoester-based surfactants and associated methods.

Surfactants can be used in a wide variety of applications. These applications may be above or below ground, for example in an underground formation penetrated by a wellbore. When used in above-ground applications, surfactants may be used, for example, to emulsify an oilseed fluid (eg, a heavy oil) to facilitate transport in an oil pipeline. Surfactants can also be used in underground applications such as drilling operations, stimulus treatments (eg fracture treatment), well hole cleaning, viscous sweeping, and complementing operations (eg treatment for sand control, gravel compaction). In such applications, surfactants may be used for numerous purposes, including use as emulsifying agents, non-emulsifying agents, foaming agents, foaming agents, dispersants, wetting agents, and the like.

Although a wide variety of surfactants have been used in underground applications, problems have been associated with their use. For example, certain surfactants used to date may have undesirable environmental characteristics and / or may be limited by strict environmental restrictions in certain areas of the world. Therefore, biodegradable surfactants have been used to reduce the potential for bioaccumulation and / or persistence of these surfactants in the environment. Currently available biodegradable surfactants, such as esters, amides, and acetals, have characteristics that may limit their utility in underground applications. For example, esters and amides may not degrade as desired under conditions that may be encountered within the bore. Moreover, the degradation of esters and wetlands is slower at the pHs found in the underground environment and may thus result in unacceptably long persistence times. Similarly, problems may also be encountered with the use of acetals in underground applications. Although acetals are usually stable at high pH values (eg,> about 6), low pH values (e.g., about 1-4) may be required for their degradation to occur at desirable ratios. This typically requires exposure of the surfactant to an acid to facilitate its degradation after introduction into underground formation, which may add undesirable expense and complexities to underground application.

SUMMARY The present invention relates to orthoester based surfactants. More particularly, the present invention relates to treatment fluids comprising orthoester-based surfactants, and associated methods. As used herein, the term "orthoester-based surfactant" refers to amphiphilic compounds containing one or more orthoester functional groups.

In one embodiment, the present invention provides a method comprising: providing a treatment fluid comprising a base fluid and an orthoester-based surfactant; and introduce the treatment fluid into an underground formation.

Another embodiment of the present invention provides a method comprising: providing an emulsified treatment fluid comprising an oleaginous phase, an aqueous phase having a pH of about 8.5 or more, and an orthoester-based surfactant; and introducing the emulsified treatment fluid into an underground formation.

Another embodiment of the present invention provides a method for facilitating flow through a conduit, which method comprises: providing an emulsified treatment fluid comprising an orthoester-based surfactant, an oleaginous phase, and an aqueous phase which has a pH of about 8.5 or more; flowing the emulsified treatment fluid through the conduit; and reducing the pH of the aqueous phase to facilitate degradation of at least a portion of the orthoester-based surfactant, thereby facilitating the separation of the oil phase from the aqueous phase.

Still another embodiment of the present invention provides a method for synthesizing an orthoester-based surfactant, which method comprises: providing an acetal diketene or acetal multicetene, and reacting acetal diketene or acetal multicetene with one or more hydrophobic alcohols and one or more hydrophilic alcohols.

In another embodiment, the present invention provides an underground treatment fluid comprising a base fluid and an orthoester-based surfactant.

Another embodiment of the present invention provides an emulsified underground treatment fluid comprising an oleaginous phase, an aqueous phase having a pH of about 8.5 or more, and an orthoester-based surfactant. Yet another embodiment of the present invention provides a composition comprising a 3'-orthoester based surfactant synthesized from an acetal diketene or acetal multicetene by the addition of one or more hydrophobic alcohols and one or more hydrophilic alcohols.

Aspects and advantages of the present invention will be readily apparent to those skilled in the art upon reading the description of the following preferred embodiments. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to orthoester-based surfactants. More particularly, the present invention relates to treatment fluids comprising orthoester-based surfactants and associated methods. These treatment fluids may be suitable for use in a variety of underground applications, including, but not limited to, drilling operations, stimulus treatments (eg treatment of an invoicing), well hole cleaning, viscous sweeping, and operations. (eg sand control treatments, gravel compaction). Such treatment fluids may also be used above ground, for example to facilitate the transport of an oleaginous fluid. As used herein, the term "treating" or "treating" refers to any operation that utilizes a fluid in conjunction with a desired function and / or for a desired purpose. The term "treating" or "treating" does not imply any "particular action by the fluid. I. Treatment Fluids of the Present Invention Treatment fluids of the present invention generally comprise a base fluid and a base surfactant. Such treatment fluids may include aqueous fluids, aqueous gels, viscoelastic surfactant gels, oil gels, foam gels, and emulsions (for example, water-in-oil or oil-in-water). orthoesters are generally degradable, where degradation of orthoester bonds therein will generally result in the destruction, or reduction, of surfactant surface activity. The degradation ratios of orthoester-based surfactants should increase with decreasing However, these orthoester-based surfactants are generally stable at a pH of about 8.5 or above. However, orthoester-based surfactants may be included in the treatment fluids of the present invention for any of a number of purposes, including emulsifying agents, non-emulsifying agents, foaming agents, foaming agents, dispersants, wetting agents, combinations of the same. same, and similar.

Base fluids included in the treatment fluids of the present invention may include any fluid that may be used to prepare an appropriate treatment fluid. Examples of suitable base fluids include, but are not limited to, aqueous fluids, oleaginous fluids and combinations thereof. Examples of oleaginous fluids include, but are not limited to, olefins, internal olefins, alkanes, aromatic solvents, cycloalkanes, liquefied petroleum gas, kerosene, diesel oils, crude oils, heavy oils, gas oils, fuel oils, paraffin oils, oils minerals, low toxicity mineral oils, olefins, esters, amides, synthetic oils (eg polyolefins), polydiorganosyloxanes, siloxanes, organosiloxanes, ethers, acetals, dialkylcarbonates, hydrocarbons, diesel, crude oil, organic solvents, oil and combinations of these. same. Since orthoester-based surfactants generally degrade at low pH, treatment with an aqueous based fluid should, in most embodiments, have a pH of about 8.5 or more. Suitable aqueous liquids may include, but are not limited to, freshwater, seawater, saltwater, brines (e.g., natural or formulated brines), and combinations thereof. The aqueous liquid may be of any source, provided that it contains an excess of compounds that will adversely affect the emulsified treatment fluid. In some embodiments, non-aqueous fluids may also be used as the base fluid. In certain embodiments, the aqueous liquid may comprise a gelling agent (e.g. viscoelastic surfactants, natural or synthetic polymers, etc.) to gel the aqueous liquid and increase its viscosity, and optionally a crosslinking agent to crosslink. the gelling agent, further increasing the viscosity of the liquid. The orthoester-based surfactants useful in the present invention may generally be any appropriate orthoester-based surfactants. In certain embodiments, at least a portion of the orthoester-based surfactants are of Formula I: Formula I wherein R is hydrogen or an alkyl group having from 1 to 4 1 Λ 1 carbon atoms, R is a hydrophobic group, R is a hydrophilic group, R is CH 1, C 2 H 5, C 3 H 7 or C 4 H 9, x is an integer from 1 to 2, y is an integer from 0 to 2, and z is an integer from 0 to 2, where the sum of x, y and z is equal to 3. Preferably R3 is CH3 or C2H5.

In certain embodiments, appropriate orthoester-based surfactants may be synthesized from diketene acetals or multicetene acetals. In certain embodiments, appropriate nonionic or cationic orthoester based surfactants containing an amine may be synthesized by the transesterification of an alkanolamine and a hydrophobic alcohol with a low molecular weight orthoester, or by the reaction of an aminolamine and a hydrophobiciethyl alcohol. acetal or acetal multicetene. Suitable orthoester-based surfactants and synthesis methods are described in US Patent No. 6653395, the relevant disclosure thereof being incorporated herein by reference. Other suitable orthoester-based surfactants and synthesis methods are described in WO 03/018534 and PG Pub. US No. 2004/0039235, the relevant disclosures thereof being incorporated herein by reference.

The hydrophobic groups contained in the orthoester-based surfactants may be any hydrophobic groups derived from hydrophobic alcohols that are capable of undergoing an orthoester transesterification reaction. In certain embodiments the hydrophobic groups may comprise fatty alcohols mono-alcohols, fatty alcohol ethoxylates, poly (alkylene oxides), poly (tetrahydrofiirane) and polybutadiene, chain-capped and hydroxyl-terminated hydrophobes. Examples of suitable hydrophobic poly (alkylene oxides) include, for example, chain capped poly (butylene oxide) and chain capped poly (propylene oxide). Suitable hydrophobic groups include, for example, alkyl groups of 8 or more carbon atoms. Suitable examples of alkyl groups of 8 or more carbons include, but are not limited to, 2-ethylhexyl, octyl, decyl, coconut alkyl, lauryl, oleyl, alkyl rape, and alkyl tallow. Those of ordinary skill in the art will, with the benefit of this disclosure, be able to determine appropriate hydrophobic groups based, among other things, on the hydrophilic-lipophilic balance and the particular function that the surfactant will perform.

Hydrophilic groups contained in the orthoester-based surfactants may be derived from hydrophilic alcohols. Suitable hydrophilic alcohols include, for example, chain-capped poly (ethylene oxide) and alkanolamines. Examples of suitable alkanolamines include, but are not limited to, α, β-dimethylethanolamine; N, N-diethylethanolamine; N-methyldiethanolamine; N-methylhydroxyethyl piperazine; 1,4-bis (2-hydroxyethyl) piperazine; N, N-dimethyl-N ', N'-bis (2-hydroxyethyl) propylenediamine; N, N-diethyl-N ', N, -bis (2-hydroxyethyl) propylenediamine; 3-dimethylamino-1-propanol; 3-diethylamino-1-propanol; and triethanolamine. In certain embodiments, hydrophilic groups may be derived from tertiary amines. Hydrophilic groups derived from tertiary amines may be appropriate in certain embodiments, as tertiary amine may be less likely to cause undesirable side reactions in orthoester-based surfactant synthesis. In some embodiments, the tertiary amine-containing orthoester-based surfactant may be quaternized by alkylation to form a quaternary ammonium compound or a cationic orthoester-based surfactant.

In certain embodiments, the appropriate Formula 1 orthoester-based surfactants may be synthesized by reacting, in one or more steps, a low molecular weight orthoester of Formula II as illustrated below with hydrophilic alcohols. and hydrophobic alcohols, in the presence of an acid catalyst: Formula II where R has the same meaning as Formula I and R4 is an alkyl group having from 1 to 6 carbon atoms. Examples of suitable acid catalysts include methanesulfonic acid, p-toluenesulfonic acid and citric acid. Examples of suitable low molecular weight orthoesters of Formula II include trimethyl orthoformate, trimethyl orthoacetate, triethyl orthoformate, triethyl orthoacetate, tripropyl orthoformate and tripropyl orthoacetate. The orthoesters-4e-bako weight-loss-may be used due to the ease of transesterification of such molecules with high molecular weight alcohols. Examples of suitable hydrophobic alcohols and hydrophilic alcohols are described above. In one embodiment , an appropriate Formula I orthoester-based surfactant can be synthesized by reacting trimethyl orthoformate with a mixture of hydrophilic and hydrophobic alcohols in the presence of an acid catalyst as illustrated in Reaction Scheme I: Reaction Scheme I where R has the same meaning as in Formula I, R 5 is a hydrophobic group, R 6 is a hydrophilic group, r is an integer from 1 to 2, p is an integer from 0 to 2, and any integer from 0 to 2, and where the sum of r, p and q is 3. Since the trimethyl orthoformate molecule has three positions that can be replaced by the reactants, the reaction product shown in Reaction Scheme I is a mixture of several different reaction products. Some molecules will have a hydrophobic substituent group and a hydrophilic substituent group. Some molecules will have two hydrophobic substituent groups. And some molecules will have two substituent hydrophilic groups. The surface activity of the reaction products will depend, among other things, on substituents, such as molecules containing a hydrophobic group and a hydrophilic group in the same molecule should exhibit surface activity. In general, reaction products containing Only hydrophilic groups or hydrophobic groups will exhibit negligible surface activity or even no activity at all.

In certain embodiments, the appropriate orthoester-based surfactants may be synthesized by reacting in one or more steps an acetal diketene or multicetene with one or more hydrophobic alcohols and one or more hydrophilic alcohols. Examples of hydrophobic alcohols of hydrophilic alcohols which may be used in the synthesis of an orthoester-based surfactant from a diketene or acetal multicetene are described above. Suitable examples of acetal diketene or multicetene may be synthesized as described in US Patent No. 4,304,767, the relevant disclosures thereof being incorporated herein by reference. In one embodiment, as illustrated below in Reaction Scheme II, an acetal diketene may be synthesized by reacting pentaerythritol and chloroacetaldehyde dimethyl acetal in the presence of p-toluenesulfonic acid or methanesulfonic acid to produce 2, which by dehydrogenation in t-butoxide in t-butanol yields acetal diketene 3, and an appropriate orthoester-based surfactant 4 can be synthesized by reacting the resulting acetal diketene with a mol equivalent of hydrophobic and hydrophilic alcohols each in the presence of a small amount of iodine dissolved in pyridine. In some embodiments, the orthoester-based surfactant may be synthesized by mixing hydrophobic and hydrophilic alcohols with acetal diketene without the aid of an iodine / pyridine catalyst, provided that the acetal alcohols and diketene are extremely pure.

Reaction Scheme II wherein R7 is a hydrophobic group and R8 is a hydrophilic group. As those of ordinary skill in this technology will observe, the reaction product shown in Reaction Scheme II is a mixture of several different reaction products. Some molecules will have a hydrophobic substituent group and a hydrophilic substituent group. Some molecules will have two hydrophobic substituent groups. And some molecules will have two substituent hydrophilic groups. The surface activity of the reaction products will depend, among other things, on substituents, such as molecules containing a hydrophobic group and a hydrophilic group in the same molecule should exhibit surface activity. In general, reaction products containing only hydrophilic groups or only hydrophobic groups should have negligible surface activity or no activity at all.

In certain embodiments, an appropriate amine-containing orthoester-based surfactant may be synthesized by a transesterification reaction of an alkanolamine and a hydrophobic alcohol with a low molecular weight orthoester of the above listed Formula II, or by the reaction of an alkanolamine and a hydrophobic alcohol with an acetal diketene or an acetal multicetene. In certain embodiments, the amine-containing orthoester-based surfactant may be synthesized from a tertiary amine. In some embodiments, the tertiary amine-containing orthoester-based surfactant may be quaternized by alkylation to form a quaternary ammonium compound, such as a cationic orthoester-based surfactant.

In some embodiments, the amine may be a tertiary amine or a quaternary ammonium salt. For example, a tertiary amine may be quaternized by reacting the orthoester-based surfactant containing a tertiary amine with an alkylating agent (e.g. methyl chloride or dimethylsulfate) to obtain a cationic orthoester-based surfactant. Low molecular weight alkanolamines and orthoesters, and diketene acetals are described above. The particular function that orthoester-based surfactants useful in the present invention will perform will depend on a variety of factors. These factors may include, but are not limited to, the choice of hydrophobic and hydrophilic groups, the relative amounts of these hydrophobic and hydrophilic groups, and temperature. For example, if an oil-in-water (“o / w”) emulsion or a water-in-oil (“w / o”) emulsion is to be formed, it can be determined by the hydrophobicity of the surfactant end and the hydrophilicity of the Head group. The hydrophilic / lipophilic balance (“HLB”) of the surfactant may provide a quantitative prediction of whether the surfactant will facilitate the formation of an o / w emulsion or a w / o emulsion. HLB can be determined from the surfactant chemical formula using empirically determined numbers of ~ gms. Even the HLB method is only semi-empirical and other factors (such as the relative volumes of the oil and water phases) may have considerable influence on the type of emulsion formed.

By varying the factors listed above, specific properties of the orthoester-based surfactant, such as solubility, wetting, emulsification, foaming, foaming, misting, gelling, detergency, and the like, may be varied. For example, when used as an emulsifying agent, an orthoester-based surfactant having an HLB of from about 3 to about 6 may be suitable for stabilizing a w / o emulsion. In other embodiments, to stabilize an o / w emulsion, an orthoester-based surfactant having an HLB of from about 8 to about 18 may be appropriate. Those of ordinary skill in the art with the benefit of this disclosure will be able to determine the appropriate orthoester-based surfactant for use in a particular application. The amount of orthoester-based surfactants useful in the present invention to include in the treatment fluids of the present invention will vary depending upon, among other things, the particular application. In certain embodiments, orthoester-based surfactants should be present in an amount in the range of from about 0.01% to about 5% by weight of the fluid. In certain embodiments, orthoester-based surfactants should be present in an amount ranging from about 0.05% to about 2% by weight of the fluid.

In some embodiments, when an aqueous based fluid is used, the pH of the treatment fluids of the present invention may, among other things, affect the degradation of orthoester based surfactants. The orthoester-based surfactants useful in the present invention are generally stable at a pH of about 8.5 or more. However, degradation of the orthoester bond should generally result in the destruction of surfactant surface activity. At a pH of about 8 or less, orthoester-based surfactants should degrade on reasonable grounds. Generally, a reduction in pH to a neutral value (about pH 7) should allow the orthoester-based surfactant to degrade relatively quickly. Degradation ratios should increase with decreasing pH and increasing temperature. In underground applications, the buffering action of formation together with temperature may in some embodiments provide the desired degradation of the orthoester-based surfactant. In general the pH of a particular treatment fluid of the present invention may be maintained at about 8.5 or more. In embodiments where a non-aqueous base fluid is used, the surfactant is. The orthoester base present in the treatment fluid should start to degrade by interaction with the formation fluids (eg formation brines).

To maintain the pH of the treatment fluids of the present invention within a desired range, if necessary, the fluids may optionally comprise a pH buffer and / or a strong base. The pH buffer and / or strong base may be included in the treatment fluids to adjust the pH to and / or maintain the pH within a desired range, among other things for the stability of degradable orthoester based surfactants. In some embodiments, a pH buffer may be used, such as when an acid is used to lower the pH of the treatment fluid at a desired time. Examples of suitable pH buffers include, but are not limited to, sodium carbonate, potassium carbonate, sodium or potassium diacetate, sodium or potassium phosphate, sodium or potassium hydrogen phosphate, and combinations thereof. In some embodiments, a strong base may be used, for example, when the buffering effect of the formation is used to bleach the β-pW-of treatment fluid. Examples of suitable strong bases include, but are not limited to, sodium hydroxide, potassium hydroxide, and combinations thereof. The pH buffer and / or strong base may be present in the treatment fluids of the present invention in an amount sufficient to maintain the pH of the treatment fluid at or above about 8.5 as desired. A person of ordinary skill in this technology, with the benefit of this disclosure, will recognize the appropriate pH buffer and / or strong base, and the amount thereof, for use in a selected application.

Although the orthoester-based surfactants included in the treatment fluids of the present invention are generally degradable, or cleavable, in some embodiments, faster degradation may be desired. Accordingly, in some embodiments, to facilitate degradation of orthoester-based surfactants and thus generally destroy or reduce their surface activities, the pH of the treatment fluid may be decreased at the desired time. Generally, at a pH of about 8 or less, orthoester-based surfactants should degrade on reasonable grounds. In underground applications, buffering action of formation together with temperature may, in some embodiments, provide the desired degradation. In some embodiments, orthoester-based surfactants may be included in the treatment fluid to facilitate the formation of an emulsion. At a desired time, the emulsion may be broken by decreasing the pH of the aqueous phase of the treatment fluid sufficiently to allow degradation of the orthoester-based surfactant. By degrading orthoester bonds, reducing the surface activity of the orthoester-based surfactant will facilitate breakdown of the emulsion. Separation of the two phases of an emulsion is commonly referred to as "breaking" the emulsion.

To reduce the pH of the treatment fluid at a desired time, numerous methods can be employed. In some embodiments, the treatment fluid may be contacted with an acid upon introduction of the treatment fluid into the underground formation. Examples of suitable acids include, but are not limited to, hydrochloric acid, hydrofluoric acid, formic acid, phosphoric acid, sulfamic acid, acetic acid, derivatives thereof and mixtures thereof.

In other embodiments, a delayed release acid such as an acid releasing degradable material or an encapsulated acid may be included in the treatment fluid to reduce the pH of the treatment fluid at a desired time, such as for example after the introduction of the treatment fluid into the underground formation. Suitable encapsulated acids which may be included in the treatment fluids of the present invention include, but are not limited to, fumaric acid, formic acid, acetic acid, acetic anhydride, anhydrides, hydrochloric acid, hydrofluoric acid, hydroxyfluoroboric acid, combinations thereof, and the like. Examples of encapsulation methodology are described in US Pat. 5,373,901; 6444316; 6527051; and 6554071, the relevant disclosures thereof being incorporated herein by reference. Degradable acid-releasing materials may also be included in the treatment fluids of the present invention to lower the pH of the fluid. Suitable acid-releasing degradable materials which may be used in conjunction with the present invention are those materials which are substantially insoluble in water such that they degrade over time rather than instantaneously in an aqueous environment. , to produce an acid. Examples of suitable acid-releasing degradable materials include esters, polyesters, orthoesters, polyorthoesters, lactides, polylactides, glycolides, polyglycolides, substituted lactides where the substituted group comprises hydrogen, alkyl, aryl, alkylaryl, acetyl heteroatoms and mixtures thereof, substantially insoluble anhydrides in water. The hydrocarbons were capolymers thereof. Materials suitable for use as an acid releasing degradable material of the present invention may be considered degradable if the degradation is due, inter alia, to chemical processes such as hydrolysis, oxidation or enzymatic decomposition. The appropriate pH adjusting agent or acid releasing material, and the amount thereof, may depend upon the characteristics and conditions of the formation, the particular orthoester-based surfactant selected, and other factors known to those skilled in the art, such as the benefit of this disclosure.

Depending on the particular application, the treatment fluids of the present invention may further comprise any of a variety of additional additives. Examples of suitable additives include, but are not limited to, anchor particles, gravel particles, weighting agents, organophilic clays, bridging agents, fluid loss control agents, wetting agents, corrosion inhibitors. , scale inhibitors, fluid loss control additives, gases, paraffin inhibitors, asphaltenes inhibitors, catalysts, hydrate inhibitors, iron control agents, clay control agents, biocides, friction reducers, combinations thereof and the like. Particular additives included in treatment fluids should not adversely affect the other components of the treatment fluid or the orthoester-based surfactant. Individuals skilled in this technology, with the benefit of this disclosure, will recognize the types of additives to be included for a particular application.

The treatment fluids of the present invention may be used in any suitable underground application. These applications may include, but are not limited to, drilling operations, stimulus treatments (eg, fracturing treatments), and complementing operations (eg —treatments _________ for sand control, gravel compaction, etc.). An example method of the present invention comprises: providing a treatment fluid of the present invention comprising a base fluid and an orthoester-based surfactant, introducing the treatment fluid into an underground formation. Introduction of the treatment fluid into the underground fluid may include introducing the treatment fluid into a wellbore that penetrates the underground formation. In some embodiments, the method may further comprise allowing at least one orthoester-based surfactant to degrade. As discussed above, at a desired time, the pH of the treatment fluid may be reduced to facilitate degradation of the orthoester-based surfactant, thereby destroying or reducing surface activity of the surfactant.

In drilling embodiments, treatment fluids may be used to drill at least a portion of the wellbore that penetrates the underground formation. For example, treatment fluids may be used as a drilling fluid or a drilling fluid. In another embodiment, the treatment fluids of the present invention may be used in a sand control treatment (e.g., as a gravel compaction fluid). In sand control embodiments, treatment fluids may also comprise gravel particulates, where at least a portion of the gravel particulates may be deposited within or adjacent to a portion of the underground formation to form a gravel compact. As referred to herein, the term "gravel compaction" refers to gravel particulates that have been deposited in a wellbore to provide some degree of sand control, such as compacting the annular space between the wellbore and a screen arranged in the wellbore with gravel particulates of a specific size designed to prevent the passage of "gravel". In some embodiments the screenless gravel compaction may be employed as well. In the billing embodiments, the treatment fluid may be introduced into the underground formation at or above a pressure sufficient to create or accentuate one or more underground formation fractures. II. Emulsified Embodiments of the Treatment Fluids of the Invention For emulsion embodiment, the treatment fluids of the present invention may be an emulsified treatment fluid comprising an oil phase, an aqueous phase having a pH about 8.5 or more, and an orthoester-based surfactant. As referred to herein, the term "emulsified treatment fluid" refers to any emulsified fluid that has a continuous phase and a discontinuous phase, either a w / o emulsion or an o / w emulsion. In an o / w emulsion, the aqueous phase is the continuous (or external) phase and the oilseed phase is the discontinuous (or internal) phase. In a w / o emulsion (or inverted emulsion), the aqueous phase is the discontinuous phase and the oil phase is the continuous phase.

Generally, the emulsified treatment fluids of the present invention are suitable for use in a variety of applications where an o / w emulsion or a w / o emulsion is appropriate. For example, orthoester-based surfactants may be useful in facilitating the formation of emulsions w / o which may be used in a variety of underground operations including drilling operations (for example, a drilling fluid or a drilling fluid). , fracture treatment (eg as fracturing fluid), well hole cleaning, viscous sweeping and sand control treatments (eg as a gravel compaction fluid). A drilling fluid is a fluid in the reservoir portion of an underground formation. In addition, orthoester-based surfactants may be useful in facilitating the formation of an o / w emulsion that can be used for a variety of underground applications, including well-hole cleaning, such as paraffin removal, asphaltenes, and / or scale. In another embodiment, the orthoester-based surfactant may be used to form an emulsified treatment fluid which may be used to facilitate transport of the oil phase, such as to facilitate the flow of a heavy oil through an oil pipeline. As used herein, the term "heavy oil" refers to any petroleum with an API gravity of less than 28 degrees or a high specific gravity. The oleaginous phase of the emulsified treatment fluids of the present invention may comprise any oleaginous fluid suitable for use in an emulsion used in underground applications. Oil fluid can be from natural or synthetic sources. Examples of suitable oleaginous fluids include, but are not limited to, α-olefins, internal oils, alkanes, aromatic solvents, cycloalkanes, liquefied petroleum gas, kerosene, diesel oils, crude oils, heavy oils, gas oils, fuel oils, oils paraffinics, mineral oils, low toxicity mineral oils, olefins, esters, amides, synthetic oils (e.g. polyolefins), polydiorganosiloxanes, siloxanes, organosiloxanes, ethers, ketals, dialkylcarbonates, hydrocarbons, and combinations thereof. The amount of oil phase to be included in the emulsified treatment fluid depends on a number of factors, including the particular orthoester-based surfactant used, the type of emulsion (eg o / w or w / o), the desired application and rheology. . For example, in certain embodiments, such as stimulation, the emulsified treatment fluid should have a viscosity sufficient to carry (T) anchor material. In some embodiments, for an o / w emulsion, the oil phase may be present in an amount in the range of from about 10% to about 65% by volume of the emulsified treatment fluid. In some embodiments, for a w / o emulsion, the oil phase may be present in an amount in the range of from about 20% to about 90% by volume of the emulsified treatment fluid.

For emulsified embodiments, the emulsified treatment fluids of the present invention may also comprise an aqueous phase. In general, the aqueous phase may comprise an aqueous liquid. Suitable aqueous liquids may include, but are not limited to, freshwater, seawater, saltwater, brines (e.g., natural or formulated brines), and combinations thereof. The aqueous liquid may be from any source as long as it does not contain an excess of compounds that may adversely affect the emulsified treatment fluid. The amount of aqueous phase to be included in the emulsified treatment fluid depends on numerous factors including the particular orthoester-based surfactant used, the type of emulsion (e.g. o / w or w / o), the desired application and rheology. In some embodiments, for an o / w emulsion, the aqueous phase may be present in an amount in the range of from about 35% to about 90% by volume of the emulsified treatment fluid. In some embodiments, for a w / o emulsion, the phasase may generally be present in an amount in the range of from about 10% to about 80% by volume of the emulsified treatment fluid.

In general, the orthoester-based surfactant should be included in the emulsified treatment fluids of the present invention in order to reduce the surface tension between the oil phase and the aqueous phase, and in order to facilitate the formation and stabilization of emulsified treatments of the present invention. As previously discussed, the orthoester-based surfactant may be tailored to facilitate the formation of an o / w or w / o emulsion. The orthoester-based surfactant may be present in the emulsified treatment fluids of the present invention in an amount ranging from about 0.01% to about 5% by weight of the emulsified treatment fluids. In another embodiment, the orthoester-based surfactant may be present in the emulsified treatment fluids of the present invention in an amount ranging from about 1% to about 3% by weight of the emulsified treatment fluids.

As previously discussed, orthoester-based surfactants included in the emulsified treatment fluids of the present invention are generally stable at a pH of about 8.5 or more. As a result, for stabilization of orthoester-based surfactants, the aqueous phase of the emulsified treatment fluids of the present invention should have a pH of about 8.5 or greater. To maintain the pH of the treatment fluids of the present invention within a desired range, the aqueous phase may optionally comprise a pH buffer and / or a strong base. The pH buffer and / or strong base may be included in the aqueous phase to adjust the pH, and / or maintain the pH within a desired range, among other things, for the stability of the degradable orthoester based surfactants. In some embodiments, a pH buffer may be used, such as when an acid is used to lower the pH of the treatment fluid at a desired time. In some embodiments, a strong base may be used, such as when the buffering effect of the formation is used to lower the pH of the treatment fluid. PH buffers and strong bases may include those previously described. The pH buffer and / or strong base may be present in the aqueous phase of the present invention in an amount sufficient to maintain the pH of the treatment fluid at 8.5 or above as desired. A person of ordinary skill in this technology, with the benefit of this disclosure, will recognize Joem's strong proprietary and / or base-based pH buffer as the amounts thereof for use in a selected application.

Since orthoester-based surfactants act to stabilize the emulsified treatment fluids of the present invention, the emulsified treatment fluids should break down due to the degradation of the surfactants therein without the need for inclusion of breaker breakers therein. conventional emulsion (e.g. acid precursors). In underground applications, the formation buffer action together with the temperature may in some embodiments provide the desired degradation. However, in some embodiments, a faster break may be desired such that a delayed release acid such as an acid releasing degradable material or an encapsulated acid may be included in the emulsified treatment fluids. Suitable delayed release acids may include those described above. In some embodiments, the emulsified treatment fluids of the present invention may be contacted with an acid upon introduction of the emulsified treatment fluid into the well bore. Examples of suitable acids include, but are not limited to, hydrochloric acid, hydrofluoric acid, formic acid, phosphoric acid, sulfamic acid, acetic acid, derivatives thereof and mixtures thereof.

Depending on the particular application the emulsified treatment fluids of the present invention may also comprise a variety of additional additives. Examples of suitable additives include, but are not limited to, anchor material particulates, gravel particulates, weight-forming agents, organophilic clays, bridging agents, fluid loss control agents, wetting agents, corrosion, fouling inhibitors, fluid loss control additives, gases, paraffin inhibitors, catalysts, catalysts, hydrate bulbs, iron control agents, clay control agents, biocides, reducerstriite, combinations thereof and the like . Particular additives included in treatment fluids should not adversely affect other components of the emulsified treatment fluid. Individuals skilled in this technology, with the benefit of this disclosure, will recognize the types of additives to be included for a particular application.

The emulsified treatment fluids of the present invention may be used in any suitable underground application where an emulsion may be used, including, but not limited to, drilling operations (for example, a drilling fluid or a drilling fluid), treatment for fracturing (eg as fracturing fluid), well hole cleaning, viscous sweeping and sand control treatments (eg as a gravel compaction fluid). An example method of the present invention comprises: providing an emulsified treatment fluid of the present invention comprising an orthoester-based surfactant, an oleaginous phase, and an aqueous phase having a pH of about 8.5 or more; and introducing the emulsified treatment fluid into an underground formation. Introducing the emulsified treatment fluid into an underground formation includes introducing the emulsified treatment fluid into a well borehole that penetrates an underground formation. As discussed above, the emulsified treatment fluid may be an o / w or w / o emulsion.

In drilling embodiments, emulsified treatment fluids may be used to drill at least a portion of a wellbore that penetrates underground formation. For example, emulsified treatment fluids may be used as drilling fluid or drilling fluid. In another embodiment, the emulsified treatment fluids of the present invention may be used in a sand control treatment (e.g., as a gravel compaction fluid). In the sand control embodiments, the emulsified treatment fluids may further comprise gravel particulates, where at least a portion of the gravel particulates may be deposited within or adjacent to a portion of the underground formation to form a gravel compact. In embodiments for fracturing, the emulsified treatment fluid may be introduced into the underground formation at or above sufficient pressure to create or accentuate one or more underground formation fractures. Another exemplary method of the present invention comprises utilizing the fluids. Emulsified treatment plants of the present invention to facilitate the flow of the oil phase through a conduit, such as to facilitate the flow of a heavy oil through an oil pipeline. An example of such a method may comprise: providing an emulsified treatment fluid of the present invention comprising an orthoester-based surfactant, an oleaginous phase, and an aqueous phase having a pH of about 8.5 or more; flowing emulsified treatment fluid through the conduit; reducing the pH of the aqueous phase to facilitate the degradation of at least a portion of the orthoester-based surfactant, thereby facilitating the separation of the oil phase from the aqueous phase. Since emulsified treatment fluid can be broken down by degradation of the orthoester-based surfactant, when the pH of the aqueous phase is reduced, the oil phase and the aqueous phase must separate. Among other things, this may allow recovery. In most embodiments, the pH of the aqueous phase may be reduced at the receiving end of the pipeline where it is desired to recover the oleaginous fluid. In certain embodiments, the oil phase may be an oil. When a heavy oil is used, the emulsified treatment medium may be used to facilitate the flow of the heavy oil through the duct, such as to facilitate a better understanding of the present invention, the following examples of embodiments In no way should the following examples be read as limiting or defining the scope of the invention. 75/25 o / w was prepared according to the following procedure. First, 2 grams (g) of an orthoester-based surfactant according to Formula I (R1 = octadecyl, R2 = MFEG-35Q ”and R3 = CH3) were dissolved in 50 milliliters (ml) of a solution comprising 0, 05% sodium hydroxide by weight of the solution. To the resulting solution, 150 ml of mineral oil (HDF-2000) was added while stirring in a mixer to form an o / w emulsion. The rheology of the o / w emulsion prepared according to the above procedure was measured on a FANN® 35 viscometer adapted with yield strength adapter. Flow voltage adapters are described in US Patent No. 6874353, the relevant disclosures of which are incorporated herein by reference. Data analysis was performed using the Casson model to determine that: yield stress = 13 Pascals; viscosity due to infinite drag = 97 centipoise; and r2 = 0.99, where r is the correlation coefficient. EXAMPLE 2 A 75/25 w / o emulsion was prepared according to the following procedure. First, 4 grams (g) of an orthoester-based surfactant according to Formula I (R1 = PPO-2500 with butyl capping, R2 - MPEG-350, and R3 = CH3) were dissolved in 50 ml of a mineral oil (HDF-2000) containing 10% by volume ACCOLADE ™ drilling fluid base oil. ACC0LADE-T-M_se drilling fluid base oil is commercially available from Halliburton Energy Services, Inc., Duncan, Oklahoma. To the resulting solution was added while stirring in a mixer to form a w / o emulsion. The rheology of the w / o emulsion prepared according to the above procedure was measured on an adapter-adapted FANN® 35 viscometer. The yield stress adapters are described in US Patent No. 6874353, the relevant disclosures of which are incorporated herein by reference.The data analysis was performed with the Casson model to determine that: yield stress = 40 Pascals; in infinite drag ratio = 153 centipõisere r2 = 0.99, where r is the correlation coefficient.

Accordingly, the present invention is well adapted to obtain the purposes and advantages mentioned, as well as those inherent thereto. The particular embodiments disclosed above are illustrative only since the present invention may be modified and practiced in different but equivalent ways, apparent to those skilled in the art and having the benefits of the teachings herein. In addition, no limitation is intended for construction or design details shown herein other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered to be within the scope and spirit of the present invention. In particular, all value ranges (in the form, "from about a to about b", or equivalently, "from about a, ab", or equivalent, "from about ab") here Disclosed should be understood as referring to the establishment (the establishment of all sub-establishments) of the respective range of values, and establishing all ranges within the broader range of values. Further, the terms in the claims have their normal, simple meanings, unless otherwise explicitly and clearly defined by the applicant.

Claims (18)

A method of treating an underground formation comprising: providing a treatment fluid comprising a base fluid and an orthoester-based surfactant, wherein at least a portion of the orthoester-based surfactant is of the following formula: wherein R1 is a hydrophobic group and R2 is a hydrophilic group; and introducing the treatment fluid into an underground formation. Method according to claim 1, characterized in that the treatment fluid is an emulsion having a pH of 8.5 or above. Method according to claim 1, characterized in that the base fluid is selected from the group consisting of: an aqueous fluid, an oleaginous fluid, and combinations thereof. Method according to claim 1, characterized in that the orthoester-based surfactant is an emulsifying agent, a non-emulsifying agent, a foaming agent, a foam remover, a dispersant, a humectant, or a combination thereof. A method according to claim 1, characterized in that the orthoester-based surfactant is synthesized from an acetal diketene or an acetal mullietetene by the addition of a hydrophobic alcohol and a hydrophobic alcohol, Method according to claim 1, characterized in that the orthoester-based surfactant contains an amine and is synthesized by the reaction of an alkanolamine and a hydrophobic alcohol with an aeetal diketene or an acetal multicetene, or by transesterification of a alkanolamine and a hydrophobic alcohol with a low molecular weight orthoester of the following Formula II: Formula II wherein R is hydrogen or an alkyl group having from 1 to 4 carbons, and R4 is an alkyl group having from I to 6 carbons. Method according to Claim 1, characterized in that the orthoester-based surfactant contains a tertiary amine. Method according to claim 1, characterized in that the orthoester-based surfactant is present in the treatment fluid in an amount in the range 0.01% to 5% by weight of the treatment fluid, A method according to claim 1, further comprising the step of: reducing the pH of the treatment fluid to facilitate degradation of at least a portion of the orthoester-based surfactant. Method according to claim 9, characterized in that the step of reducing the pH of the treatment fluid comprises the step of: contacting the treatment fluid with an acid. A method according to claim 1, characterized in that the treatment fluid is introduced into the underground formation at or above sufficient pressure to create or accentuate one or more fractures in the underground formation. A method according to claim 1, further comprising the step of: drilling at least part of a wellbore that penetrates the underground formation using the treatment fluid. A method of treating an underground formation, characterized in that it comprises: providing an emulsified treatment fluid comprising an oil phase, an aqueous phase having a pH of 8.5 or above, and an orthoester-based surfactant in that the orthoester-based surfactant is synthesized from an acetal diketene or an acetal multicetene by the addition of a hydrophobic alcohol and a hydrophobic alcohol, wherein at least a portion of the orthoester-based surfactant is of the following formula: wherein R1 is a hydrophobic group c R 'is a hydrophilic group; c, introducing the emuisified treatment fluid into an underground formation. A method according to claim 13, characterized in that the emulsifying treatment fluid further comprises gravel particulates, and wherein the method further comprises depositing at least a portion of the gravel particulates within or adjacent to a portion of the formation. underground to form a gravel compact. A method according to claim 13, further comprising the step of: reducing the pH of the aqueous phase to facilitate degradation of at least a portion of the orthoester-based surfactant, thereby facilitating separation of the oil phase of the aqueous phase. The method of claim 13, further comprising the step of: introducing the emulated treatment fluid into the underground formation at or above sufficient pressure to create or accentuate one or more fractures in the underground formation. A method of facilitating flow through a conduit, comprising: providing an emulsified treatment fluid comprising an orthoester-based surfactant, an oleaginous phase and an aqueous phase having a pH of 8.5 or above. wherein at least a portion of the orthoester-based surfactant is of the following formula: wherein R1 is a hydrophobic group and R2 is a hydrophilic group; flowing emulsified treatment fluid through the conduit; and, reducing the pH of the aqueous phase to facilitate degradation of at least a portion of the orthoester-based surfactant, thereby facilitating the separation of the oil phase and the aqueous phase. A method according to claim 17, characterized in that the oil phase comprises a heavy oil.