CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and benefit of United States Provisional Patent Application No. 63/269,813, entitled “Single Phase Retarded Acid Based on a Cationic Surfactant”, filed on March 23, 2022, which is incorporated herein by reference.

TECHNICAL FIELD

[0002] This disclosure relates to compositions of single-phase retarded acids and methods of preparation and use thereof.

BACKGROUND

[0003] This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.

[0004] Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, commonly referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed to control and enhance the efficiency of producing the various fluids from the reservoir. Well treatment methods often are used to increase hydrocarbon production by using a chemical composition, such as a treatment fluid.

[0005] Stimulation operations may be performed to facilitate production of fluids from subsurface formations by increasing the net permeability of a reservoir. There are two main stimulation techniques: matrix stimulation and fracturing. Matrix stimulation is accomplished by injecting a fluid (e.g., acid or solvent) to dissolve and/or disperse materials that impair well production. Specifically, matrix stimulation may be performed (1 ) by injecting chemicals into the wellbore to react with and dissolve damage or (2) by injecting chemicals through the wellbore and into the formation to react with and dissolve small portions of the formation, thereby creating alternative flow paths for the hydrocarbon (i.e., instead of removing the damage, redirecting flow around the damage). Fracturing is a technique whereby a treatment fluid is injected through the wellbore and into the formation at pressures higher than the fracture initiation pressure of the formation. The resulting fracture creates a large flow channel through which hydrocarbons can more readily flow from the formation and into the wellbore.

[0006] In carbonate formations (e.g., formations composed of calcite, limestone, dolomite or a combination thereof), the goal of matrix stimulation is to create new, unimpaired flow channels from the formation to the wellbore. Matrix stimulation, typically called matrix acidizing when the stimulation fluid is an acid, is generally used to treat the near-wellbore region. The near-wellbore region may be defined as the formation that surrounds the wellbore within a distance shorter than about 50 feet. In a matrix acidizing treatment, the acid (e.g., hydrochloric acid for carbonates) is injected at a rate and pressure lower than the fracture initiation pressure. During injection the acid may form conductive “wormholes” that extend radially from the wellbore. Acids may also be injected into subterranean formation at rates and pressures higher than the fracture initiation pressure. In this case, the acid unevenly dissolves the walls of the fracture, so that when the injection is stopped and the fracture closes, conductive channels to the wellbore remain.

[0007] In carbonate reservoirs, one problem that may be associated with the application of inorganic acids at elevated temperatures (e.g., 200°F and above), is their excessive reaction rate owing to a lack of restriction to the mobility of the protons. For example, HCI is very reactive, and higher temperatures and/or low injection rates may favor facial dissolution over wormhole formation. As a result, penetration of acid into the near-wellbore region may reach no further than a few inches. For this reason, less reactive acid formulations have been pursued. One approach is to use organic acids such as lactic, formic and acetic acid. Organic acids have higher pKa’s than HCI, but may not completely spend in the reservoir. A second approach is to suspend the acid as a water-in-oil emulsion, which restricts aqueous acid contact with the reservoir and thus slows the reaction rate. SUMMARY

[0008] Certain embodiments commensurate in scope with the originally claimed disclosure are summarized below. These embodiments are not intended to limit the scope of the claimed disclosure, but rather these embodiments are intended only to provide a brief summary of possible forms of the disclosure. Indeed, embodiments may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0009] The present disclosure proposes a single-phase retarded acid based on a cationic surfactant.

[0010] In a first aspect of the disclosure, embodiments relate to composition(s) that include water, an acid, and an acid retarding agent that includes an alkyl dimethyl benzyl ammonium chloride.

[0011] In another aspect of the disclosure, embodiments relate to method(s) that include preparing a composition including water, an acid, and an acid retarding agent. The acid retarding agent includes an alkyl dimethyl benzyl ammonium chloride. The method also includes injecting the composition into a wellbore penetrating a subterranean formation.

[0012] However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0014] Figure 1 presents a schematic diagram of the dissolution of a calcite rock surface by an acid, according to an embodiment of the disclosure;

[0015] Figure 2 presents the results of limestone dissolution tests conducted in 20% HCI solutions, with and without the presence of the alkyl dimethyl benzyl ammonium chloride surfactant; and [0016] Figure 3 presents the results of limestone dissolution tests conducted in 20% HCI solutions containing alkyl dimethyl benzyl ammonium chloride surfactant.

DETAILED DESCRIPTION

[0017] In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it may be understood by those skilled in the art that the methods of the present disclosure may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0018] At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation — specific decisions are made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the composition used/disclosed herein can also comprise some components other than those cited. In the summary of the disclosure and this detailed description, each numerical value should be read once as modified by the term "about" (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. The term about should be understood as any amount or range within 10% of the recited amount or range (for example, a range from about 1 to about 10 encompasses a range from 0.9 to 11 ). Also, in the summary and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any concentration within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each possible number along the continuum between about 1 and about 10. Furthermore, one or more of the data points in the present examples may be combined together, or may be combined with one of the data points in the specification to create a range, and thus include each possible value or number within this range. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to a few specific, it is to be understood that inventors appreciate and understand that any data points within the range are to be considered to have been specified, and that inventors possessed knowledge of the entire range and the points within the range.

[0019] Unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0020] In addition, use of the "a" or "an" are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of concepts according to the disclosure. This description should be read to include one or at least one and the singular also includes the plural unless otherwise stated.

[0021] The terminology and phraseology used herein is for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited.

[0022] As used herein, “embodiments” refers to non-limiting examples disclosed herein, whether claimed or not, which may be employed or present alone or in any combination or permutation with one or more other embodiments. Each embodiment disclosed herein should be regarded both as an added feature to be used with one or more other embodiments, as well as an alternative to be used separately or in lieu of one or more other embodiments. It should be understood that no limitation of the scope of the claimed subject matter is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the application as illustrated therein as would normally occur to one skilled in the art to which the disclosure relates are contemplated herein.

[0023] Moreover, the schematic illustrations and descriptions provided herein are understood to be examples only, and components and operations may be combined or divided, and added or removed, as well as re-ordered in whole or part, unless stated explicitly to the contrary herein. Certain operations illustrated may be implemented by a computer executing a computer program product on a computer readable medium, where the computer program comprises instructions causing the computer to execute one or more of the operations, or to issue commands to other devices to execute one or more of the operations.

[0024] The terms “formation” or “subterranean formation” as utilized herein should be understood broadly, and are used interchangeably. A formation includes any underground fluidly porous formation, and can include without limitation any oil, gas, condensate, mixed hydrocarbons, paraffin, kerogen, water, and/or CO2 accepting or providing formations. A formation can be fluidly coupled to a wellbore, which may be an injector well, a producer well, and/or a fluid storage well. The wellbore may penetrate the formation vertically, horizontally, in a deviated orientation, or combinations of these. The formation may include any geology, including at least a sandstone, limestone, dolomite, shale, tar sand, and/or unconsolidated formation. The wellbore may be an individual wellbore and/or a part of a set of wellbores directionally deviated from a number of close proximity surface wellbores (e.g. off a pad or rig) or single initiating wellbore that divides into multiple wellbores below the surface.

[0025] The term “oilfield treatment fluid” as utilized herein should be understood broadly. In certain embodiments, an oilfield treatment fluid includes any fluid having utility in an oilfield type application, including a gas, oil, geothermal, or injector well. In certain embodiments, an oilfield treatment fluid includes any fluid having utility in any formation or wellbore described herein. In certain embodiments, an oilfield treatment fluid includes a matrix acidizing fluid, a wellbore cleanup fluid, a pickling fluid, a near wellbore damage cleanup fluid, a surfactant treatment fluid, an unviscosified fracture fluid (e.g. slick water fracture fluid), and/or any other fluid consistent with the fluids otherwise described herein. An oilfield treatment fluid may include any type of additive known in the art, which are not listed herein for purposes of clarity of the present description, but which may include at least friction reducers, inhibitors, surfactants and/or wetting agents, fluid diverting agents, particulates, acid retarders (except where otherwise provided herein), organic acids, chelating agents, energizing agents (e.g. CO2 or N2), gas generating agents, solvents, emulsifying agents, flowback control agents, resins, breakers, and/or non-polysaccharide based viscosifying agents.

[0026] The term “high pressure pump” as utilized herein should be understood broadly. In certain embodiments, a high pressure pump includes a positive displacement pump that provides an oilfield relevant pumping rate - for example at least 0.5 barrels per minute (bpm), although the specific example is not limiting. A high pressure pump includes a pump capable of pumping fluids at an oilfield relevant pressure, including at least 500 psi, at least 1 ,000 psi, at least 2,000 psi, at least 5,000 psi, at least 10,000 psi, up to 15,000 psi, and/or at even greater pressures. Pumps suitable for oilfield cementing, matrix acidizing, and/or hydraulic fracturing treatments are available as high pressure pumps, although other pumps may be utilized.

[0027] The term “treatment concentration” as utilized herein should be understood broadly. A treatment concentration in the context of an HCI concentration is a final concentration of the fluid before the fluid is positioned in the wellbore and/or the formation for the treatment, and can be any concentration necessary to provide sufficient acidic function. The treatment concentration may be the mix concentration available from the HCI containing fluid at the wellsite or other location where the fluid is provided from. The treatment concentration may be modified by dilution before the treating and/or during the treating. Additionally, the treatment concentration may be modified by the provision of additives to the fluid. In certain embodiments, a treatment concentration is determined upstream of additives delivery (e.g. at a blender, hopper, or mixing tub) and the concentration change from the addition of the additives is ignored. In certain embodiments, the treatment concentration is a liquid phase or acid phase concentration of a portion of the final fluid.

[0028] As mentioned above, hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, commonly referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed to control and enhance the efficiency of producing the various fluids from the reservoir. Well treatment methods often are used to increase hydrocarbon production by using a chemical composition, such as a treatment fluid. [0029] Stimulation operations may be performed to facilitate production of fluids from subsurface formations by increasing the net permeability of a reservoir. There are two main stimulation techniques: matrix stimulation and fracturing. Matrix stimulation is accomplished by injecting a fluid (e.g., acid or solvent) to dissolve and/or disperse materials that impair well production. Specifically, matrix stimulation may be performed (1 ) by injecting chemicals into the wellbore to react with and dissolve damage or (2) by injecting chemicals through the wellbore and into the formation to react with and dissolve small portions of the formation, thereby creating alternative flow paths for the hydrocarbon (i.e. , instead of removing the damage, redirecting flow around the damage). Fracturing is a technique whereby a treatment fluid is injected through the wellbore and into the formation at pressures higher than the fracture initiation pressure of the formation. The resulting fracture creates a large flow channel through which hydrocarbons can more readily flow from the formation and into the wellbore.

[0030] In carbonate formations (e.g., formations composed of calcite, limestone, dolomite or a combination thereof), the goal of matrix stimulation is to create new, unimpaired flow channels from the formation to the wellbore. Matrix stimulation, typically called matrix acidizing when the stimulation fluid is an acid, is generally used to treat the near-wellbore region. The near-wellbore region may be defined as the formation that surrounds the wellbore within a distance shorter than about 50 feet. In a matrix acidizing treatment, the acid (e.g., hydrochloric acid for carbonates) is injected at a rate and pressure lower than the fracture initiation pressure. During injection the acid may form conductive “wormholes” that extend radially from the wellbore. Acids may also be injected into subterranean formation at rates and pressures higher than the fracture initiation pressure. In this case, the acid unevenly dissolves the walls of the fracture, so that when the injection is stopped and the fracture closes, conductive channels to the wellbore remain.

[0031] In carbonate reservoirs, one problem that may be associated with the application of inorganic acids at elevated temperatures (e.g., 200°F and above), is their excessive reaction rate owing to a lack of restriction to the mobility of the protons. For example, HCI is very reactive, and higher temperatures and/or low injection rates may favor facial dissolution over wormhole formation. As a result, penetration of acid into the near-wellbore region may reach no further than a few inches. For this reason, less reactive acid formulations have been pursued. One approach is to use organic acids such as lactic, formic and acetic acid. Organic acids have higher pKa’s than HCI, but may not completely spend in the reservoir. A second approach is to suspend the acid as a water-in-oil emulsion, which restricts aqueous acid contact with the reservoir and thus slows the reaction rate.

[0032] Other approaches have been applied toward retarding the acid reactivity. For example, the inorganic acid may be encapsulated by shells of polymer gel, thickened by linear or crosslinked gels or viscoelastic surfactants, or mixed with chelating agents. Such acid systems are commonly referred to as “retarded acids.” [0033] More recently, acid retarding agents (RA) based on salt compounds have been introduced. The salt compound used in the RA may be selected from compounds having one or more cations selected from lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, mercury, boron, aluminum, gallium, indium, thallium, tin, ammonium, alkylammonium, dialkylammonium, trialkylammonium and tetraalkylammonium, and one or more anions selected from fluoride, chloride, bromide, iodide, sulfate, bisulfate, sulfite, bisulfite nitrate, alkanesulfonates, arylsulfonates, acetate and formate. The RA may be magnesium chloride. In such systems, the acid may be present at concentrations between about 7.5 wt% and 36 wt%, based on the total weight of the composition.

[0034] Aqueous compositions described below and useful in accordance with the disclosure exhibit a retarded acid reactivity that facilitates greater depth of fracture and/or matrix acidizing. In certain embodiments, a composition includes water, an acid, and an acid retarding agent. In particular, the acid retarding agent includes an alkyl dimethyl benzyl ammonium chloride. Additionally, in certain embodiments, a method includes preparing a composition that includes water, an acid, and an acid retarding agent that includes an alkyl dimethyl benzyl ammonium chloride. After preparing the composition, the method may also include injecting the composition into a wellbore penetrating a subterranean formation.

[0035] The alkyl dimethyl benzyl ammonium chloride (ADBAC) has the following structure:

Formula I wherein n is an integer comprised between 8 and 18.

[0036] The role of the ADBAC surfactant is to attach to the rock surface, occupying sites where protons would normally bind and react. A schematic diagram of the process is shown in Figure 1 . As a bulk acidizing fluid passes over a calcite rock surface at a velocity Q, protons migrate to the surface. Dissolution of the calcite takes place at a rate k _r . The surfactant of the disclosure interacts with the calcite rock surface such that the value of k _r is reduced.

[0037] For all aspects, the acid may comprise hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen fluoride, sulfuric acid, nitric acid, phosphoric acid, alkanesulfonic acids or arylsulfonic acids, or combinations thereof. The acid (e.g., hydrochloric acid) may be present at a concentration between 7.5 wt% and 36 wt%, or between 10.0 wt% and 28 wt%, or between 15.0 wt% and 18.0 wt%.

[0038] For all aspects, the alkyl dimethyl benzyl ammonium chloride may comprise between 14% and 40% C12, 50% and 58% C14 and 10% and 28% C16.

[0039] For all aspects, the alkyl dimethyl benzyl ammonium chloride is present at a concentration between 0.1 wt% and 5.0 wt%, or between 1.0 wt% and 2.0 wt%.

[0040] For all aspects, the composition may further comprise corrosion inhibitors, friction reducers, iron control additives, diverting agents, or fluid-loss control agents, or combinations thereof.

[0041] With regard to the disclosed methods, the temperature of subterranean formation may be between 100°F and 300°F, or between 150°F and 250°F. The subterranean formation may comprise calcite, limestone, or dolomite, or a combination thereof. [0042] The composition may be injected into the wellbore at a pressure lower than the fracture initiation pressure of the subterranean formation. Or, the composition may be injected into the wellbore at a pressure equal to or higher than a fracture initiation pressure of the subterranean formation.

Examples

[0043] In the examples, limestone discs (1 -in. diameter and 0.25-in thickness) were submerged into acid solutions at 160°F. During the test period the limestone discs were periodically removed from the solutions, dried with a paper towel, weighed and then returned to the solutions. Thus, a dissolution rate could be determined.

[0044] Two ADBAC solutions were tested. ADBAC #1 contained the following mix of alkyl groups: 14% C12, 58% C14 and 28% C16. ADBAC #2 contained the following mix of alkyl groups: 40% C12, 50% C14 and 10% C16.

Example 1

[0045] In this example, the limestone discs were submerged in a 20 wt% HCI solution at 160°F.

[0046] As shown in Figure 2, the limestone discs submerged in solutions containing 1 % ADBAC 1 or ADBAC 2 dissolved significantly slower than the disc in the control solution containing no surfactant.

Example 2

[0047] Aging tests were conducted to determine the thermal stability of ADBAC. Solutions of 20% HCI, containing 1 % ADBAC 2 were aged in an oven for 4 hours at 250°F. Following the thermal treatment, limestone dissolution tests were conducted. [0048] As shown in Figure 3, ADBAC 2 is thermally stable at low pH and high temperature.

[0049] The preceding description has been presented with reference to present embodiments. Persons skilled in the art and technology to which this disclosure pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this present disclosure. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.