RU2201500C2 - Method of development of flooded deposit of liquid or gaseous hydrocarbons - Google Patents

Abstract

FIELD: oil and gas production, processes developing oil and gas fields making it possible to enhance oil and gas output of flooded deposits. SUBSTANCE: method of development of flooded deposit of liquid or gaseous hydrocarbons includes injection of insulating compositions through production or injections wells into watered intervals. Insulating compositions are prepared from chemical reagents which, interacting, form sediment which index of product of solubility is equal to or exceeds 7. Insulating screens are formed in formations with permeability up to 20×100^-15 sq m with use of aqueous solutions with content of starting chemical reagents 2.5-5.0 per cent by mass. Aqueous solutions with concentration of starting reagent 6.0-15.0 per cent by mass are utilized to form insulating screen in formations with permeability exceeding 20×100^-15 sq m. EFFECT: increased oil and gas output from formation, reduced water cutting of production wells thanks to raised stability of insulating screen mounted in washed-through zones of deposit to effect of stratal or flood water, expanded assortment of utilized chemical reagents. 1 dwg, 3 tbl

Description

 The invention relates to the oil and gas industry, in particular to methods for the development of oil and gas fields, allowing to increase oil and gas recovery of flooded deposits.

 A known method of developing a heterogeneous oil reservoir [Instructions for the use of polyacrylamide with clay slurry in flooded wells to increase oil production and limit the flow of water. RD 39-5765678-213-87P, 1987], which includes sequentially alternating injection into the flooded layer of an aqueous solution of partially hydrolyzed polyacrylamide and a clay suspension and subsequent injection of the displacing agent.

 The disadvantage of this method is its low efficiency due to the rapid erosion of the insulating material due to the destruction of polyacrylamide.

 The closest technical solution, taken as a prototype, is a method of isolating the influx of water into the well (RF patent 1700199, E 21 B 33/12, 43/32, 1991), including the sequential injection of aqueous solutions of calcium chloride and salt with an equivalent ratio of gypsum-forming ions. Preliminarily, sodium tripolyphosphate is introduced into the calcium chloride solution in an amount of 0.05-0.25% by weight of the calcium sulfate forming, and solutions of 6-10% concentration are used as the aqueous solution of the sulfuric acid salt.

 The disadvantage of this method is that the precipitate formed as a result of the reaction, calcium sulfate, is a finely dispersed suspension and is partially soluble in water, which is why premature erosion occurs on the insulating screen of injected or produced water. In addition, the implementation of the method is limited to the use of specific chemicals in its implementation. In this case, calcium chloride and sulfuric acid salts. In the absence of these reagents (for example, ran out), it is impossible to implement the method. The use of other components of the method does not provide.

 These circumstances significantly reduce the effectiveness of the method.

 The technical result of the invention is to increase the oil and gas recovery of the formation and to reduce the water cut of producing wells by increasing the stability of the insulating screen installed in the washed areas of the reservoir to the action of formation or injection water, as well as by expanding the range of chemicals used.

In a method for developing an irrigated reservoir of liquid or gaseous hydrocarbons, which comprises injecting insulating compositions through production or injection wells into irrigated intervals of the invention, the insulating compositions are prepared from chemicals that, when interacting with each other, form a precipitate whose solubility index is equal to or greater than 7, wherein to create insulating screens in formations having a permeability of 200 • 10 ^-15 m ² using aqueous solutions with a content of ref dnyh chemicals 2.5-6.0 wt.%, to create insulating layers screens with permeability greater than 200 • 10 ^-15 m ^2, using aqueous solutions of a concentration of the initial reactants, 6.0 -15.0 wt. %

 The drawing shows a graphical dependence of the actual solubility of some substances on the value of their solubility index.

Table 1 presents data on core permeability and blockage coefficient after exposure to insulating compositions, including AlCl ₃ and Na ₂ CO ₃ according to the proposed technical solution. Table 2 presents data on core permeability and plugging coefficient after exposure to insulating compositions, including Na ₂ SiO ₃ and Hcl according to the proposed technical solution.

 Table 3 presents comparative data on core permeability and blockage coefficient after exposure to insulating compositions of the prototype and the proposed technical solution.

The product of solubility (PR) is understood to mean the product of the activities of the cation and anion, which decomposes in a solvent (in water) into electrolyte ions [General chemistry. / Ed. Sokolovskoy E.N. - M .: Moscow State University, 1980]:
PR = a _To ^m • a _A ⁿ , (1)
where a _K is the cation activity;
and _A is the activity of the anion;
m, n are stoichiometric coefficients.

 The smaller the value (PR), the less soluble the substance in water. For practical convenience, when comparing and evaluating the solubility of substances, the value of the solubility product index (pPR) is used, which is equal to the logarithm of PR taken with the opposite sign: pPR = -lg (Pp). Moreover, the larger the RPR value, the less soluble is the substance in water.

 From the graph shown in the drawing it can be seen that when the solubility of the precipitate exceeds 7, the actual solubility of the precipitate in water is practically zero. When the solubility index is up to 7, the actual solubility of the precipitate in water increases sharply with decreasing solubility.

 Based on the fact that one of the main conditions for the effectiveness of an insulating screen is its resistance to formation or injection water, the sediment solubility index of 7 is taken as a criterion when choosing the initial chemical reagents for insulating compositions. The starting chemicals must have the ability to dissolve well in fresh and saline water.

 Inorganic salts (chlorides of 2- and 3-valence metals, nitrates of 2- and 3-valence metals, sulfates and sulfites of alkali and alkaline earth metals, for example, can be used as starting chemicals for the preparation of insulating compositions satisfying these conditions) , nitric acid salts, ammonium salts, etc.) in combination with alkalis (caustic soda, potassium hydroxide, sodium silicates, potassium silicates, soda ash, etc.) or acids (hydrochloric, nitric, sulfuric, oxalic, acetic etc.).

 In the experiments, linear models of the formation (core) were used with a length of 1 m and a diameter of 0.03 m of various permeabilities. Quartz sand was used as a porous medium.

Example 1. (Table 1, experiment 2). At the beginning of the experiment, the initial water permeability of the core was determined. It was equal to 110 • 10 ^-15 m ² . As the starting reagents for the preparation of an aqueous solution of the insulation composition according to the proposed method, the available aluminum chloride and soda ash were used.

образовался осадок Аl(ОН)₃. По справочным данным определили показатель произведения растворимости образовавшегося в результате реакции осадка Аl(ОН)₃ - он равнялся 33. Так как величина показателя растворимости осадка при выборе исходных химических реагентов для изоляционных композиций должна быть от 7 и более, то данные реагенты подходили для приготовления этих композиций.In the interaction of these reagents

precipitate Al (OH) _{3 was formed} . According to the reference data, we determined the solubility product of the precipitate Al (OH) ₃ formed as a result of the reaction — it was 33. Since the value of the solubility index of the precipitate when choosing the initial chemical reagents for insulation compositions should be 7 or more, these reagents were suitable for preparing these compositions.

Prepared aqueous solution of the insulating composition with the starting reagents taken with a concentration, wt.%:
AlCl ₃ - 2.5
Na ₂ CO ₃ - 2.5
pumped into a porous medium. After 24 hours, the water permeability of the core was determined. It was equal to 4.4 • 10 ^-15 m ² . The blockage ratio was 96%. Further, water was injected into the cores at a pressure of 12.0 MPa for ten days with the subsequent determination of core permeability. It was equal to 8.8 • 10 ^-15 m ² . The blockage rate after exposure was 92%.

 The prepared aqueous solution of the insulating composition with a content of each reagent of 2.5 wt.% Created a resistant insulating screen.

образовался осадок Аl(ОН)₃. По справочным данным определили показатель произведения растворимости образовавшегося в результате реакции осадка Аl(ОН)₃ - он равнялся 33. Так как величина показателя растворимости осадка при выборе исходных химических реагентов для изоляционных композиций должна быть от 7 и более, то данные реагенты подходили для приготовления этих композиций.Example 2. (Table 1, experiment 3). At the beginning of the experiment, the initial water permeability of the core was determined. It was equal to 115 • 10 ^-15 m ² . As the starting reagents for the preparation of an aqueous solution of the insulation composition according to the proposed method, the available aluminum chloride and soda ash were used. In the interaction of these reagents

precipitate Al (OH) _{3 was formed} . According to the reference data, we determined the solubility product of the precipitate Al (OH) ₃ formed as a result of the reaction — it was 33. Since the value of the solubility index of the precipitate when choosing the initial chemical reagents for insulation compositions should be 7 or more, these reagents were suitable for preparing these compositions.

Prepared aqueous solution of the insulating composition with the starting reagents taken with a concentration, wt.%:
AlCl ₃ - 4.0
Na ₂ CO ₃ - 4.0
pumped into a porous medium. After 24 hours, the water permeability of the core was determined. It was equal to 5.6 • 10 ^-15 m ² . The blockage ratio was 95%. Further, water was injected into the cores at a pressure of 12.0 MPa for ten days with the subsequent determination of core permeability. It was equal to 8.05 • 10 ^-15 m ² . The blockage rate after exposure was 93%.

 The prepared aqueous solution of the insulating composition with a content of 4.0 wt.% Of each reagent created a resistant insulating screen.

образовался осадок Аl(ОН)₃. По справочным данным определили показатель произведения растворимости образовавшегося в результате реакции осадка Аl(ОН)₃ - он равнялся 33. Так как величина показателя растворимости осадка при выборе исходных химических реагентов для изоляционных композиций должна быть от 7 и более, то данные реагенты подходили для приготовления этих композиций.Example 3. (Table 1, experiment 4). At the beginning of the experiment, the initial water permeability of the core was determined. It was equal to 140 • 10 ^-15 m ² . As the starting reagents for the preparation of an aqueous solution of the insulation composition according to the proposed method, the available aluminum chloride and soda ash were used. In the interaction of these reagents

precipitate Al (OH) _{3 was formed} . According to the reference data, we determined the solubility product of the precipitate Al (OH) ₃ formed as a result of the reaction — it was 33. Since the value of the solubility index of the precipitate when choosing the initial chemical reagents for insulation compositions should be 7 or more, these reagents were suitable for preparing these compositions.

Prepared aqueous solution of the insulating composition with the starting reagents taken with a concentration, wt.%:
AlCl ₃ - 5.0
Na ₂ CO ₃ - 5.0
pumped into a porous medium. After 24 hours, the water permeability of the core was determined. It was equal to 8.2 • 10 ^-15 m ² . The blockage ratio was 94%. Further, water was injected into the cores at a pressure of 12.0 MPa for ten days with the subsequent determination of core permeability. It was equal to 8.4 • 10 ^-15 m ² . The blockage rate after exposure was 94%.

 The prepared aqueous solution of the insulating composition with a content of each reagent of 5.0 wt.% Created a resistant insulating screen.

When exposed to a core with an aqueous solution of an insulating composition with a content of each reagent of 6.0 wt. % or more (see table. 1, experiments 5 and 6), almost the same results are obtained as with their content = 5.0 wt.%. However, their consumption increases. Therefore, the maximum boundary value of the content of reagents was taken 5.0 wt.%. The minimum boundary value of the reagent content was taken 2.5 wt.%, Since when the content of the reagents is 1.5 wt. % (see Table 1, experiment 1) the permeability after exposure to the core with water for 10 hours and a discharge pressure of 12 MPa was 55.2 • 10 ^-15 m ² , and the blocking coefficient was 54%.

образовался осадок Аl(ОН)₃. По справочным данным определили показатель произведения растворимости образовавшегося в результате реакции осадка Аl(ОН)₃ - он равнялся 33. Так как величина показателя растворимости осадка при выборе исходных химических реагентов для изоляционных композиций должна быть от 7 и более, то данные реагенты подходили для приготовления этих композиций.Example 4. (Table 1, experiment 8). At the beginning of the experiment, the initial water permeability of the cores was determined. It was equal to 230 • 10 ^-15 m ² . As the starting reagents for the preparation of an aqueous solution of the insulation composition according to the proposed method, the available aluminum chloride and soda ash were used. In the interaction of these reagents

precipitate Al (OH) _{3 was formed} . According to the reference data, we determined the solubility product of the precipitate Al (OH) ₃ formed as a result of the reaction — it was 33. Since the value of the solubility index of the precipitate when choosing the initial chemical reagents for insulation compositions should be 7 or more, these reagents were suitable for preparing these compositions.

Prepared aqueous solution of the insulating composition with the starting reagents taken with a concentration, wt.%:
AlCl ₃ - 6.0
Na ₂ CO ₃ - 6.0
pumped into a porous medium. After 24 hours, the water permeability of the core was determined. It was equal to 11.5 • 10 ^-15 m ² . The blockage ratio was 95%. Further, water was injected into the cores at a pressure of 12.0 MPa for ten days with the subsequent determination of core permeability. It was equal to 18.4 • 10 ^-15 m ² . The blockage rate after exposure was 92%.

 The prepared aqueous solution of the insulating composition with a reagent content of 6.0 wt.% Created a resistant insulating screen.

образовался осадок Аl(ОН)₃. По справочным данным определили показатель произведения растворимости образовавшегося в результате реакции осадка Аl(ОН)₃ - он равнялся 33. Так как величина показателя растворимости осадка при выборе исходных химических реагентов для изоляционных композиций должна быть от 7 и более, то данные реагенты подходили для приготовления этих композиций.Example 5 (Table 1, experiment 9). At the beginning of the experiment, the initial water permeability of the cores was determined. It was equal to 300 • 10 ^-15 m ² . As the starting reagents for the preparation of an aqueous solution of the insulation composition according to the proposed method, the available aluminum chloride and soda ash were used. In the interaction of these reagents

precipitate Al (OH) _{3 was formed} . According to the reference data, we determined the solubility product of the precipitate Al (OH) ₃ formed as a result of the reaction — it was 33. Since the value of the solubility index of the precipitate when choosing the initial chemical reagents for insulation compositions should be 7 or more, these reagents were suitable for preparing these compositions.

Prepared aqueous solution of the insulating composition with the starting reagents taken with a concentration, wt.%:
AlCl ₃ - 10.0
Na ₂ CO ₃ - 10.0
pumped into a porous medium. After 24 hours, the water permeability of the core was determined. It was equal to 12 • 10 ^-15 m ² . Clogging ratio was 96%. Further, water was injected into the cores at a pressure of 12.0 MPa for ten days with the subsequent determination of core permeability. It was equal to 21 • 10 ^-15 m ² . The blockage rate after exposure was 93%.

 The prepared aqueous solution of the insulating composition with a content of each reagent of 10.0 wt.% Created a resistant insulating screen.

образовался осадок Аl(ОН)₃. По справочным данным определили показатель произведения растворимости образовавшегося в результате реакции осадка Аl(ОН)₃ - он равнялся 33. Так как величина показателя растворимости осадка при выборе исходных химических реагентов для изоляционных композиций должна быть от 7 и более, то данные реагенты подходили для приготовления этих композиций.Example 6 (Table 1, experiment 10). At the beginning of the experiment, the initial water permeability of the cores was determined. It was equal to 280 • 10 ^-15 m ² . As the starting reagents for the preparation of an aqueous solution of the insulation composition according to the proposed method, the available aluminum chloride and soda ash were used. In the interaction of these reagents

precipitate Al (OH) _{3 was formed} . According to the reference data, we determined the solubility product of the precipitate Al (OH) ₃ formed as a result of the reaction — it was 33. Since the value of the solubility index of the precipitate when choosing the initial chemical reagents for insulation compositions should be 7 or more, these reagents were suitable for preparing these compositions.

Prepared aqueous solution of the insulating composition with the starting reagents taken with a concentration, wt.%:
AlCl ₃ - 15.0
Na ₂ CO ₃ - 15.0
pumped into a porous medium. After 24 hours, the water permeability of the core was determined. It was equal to 5.6 • 10 ^-15 m ² . Clogging ratio was 98%. Further, water was injected into the cores at a pressure of 12.0 MPa for ten days with the subsequent determination of core permeability. It was equal to 16.8 • 10 ^-15 m ² . The blockage rate after exposure was 94%.

 The prepared aqueous solution of the insulating composition with a content of each reagent of 15.0 wt.% Created a resistant insulating screen.

When the core is exposed to an aqueous solution of an insulating composition with each reagent content of 18 wt.% (See table 1, experiment 11), almost the same result is obtained as with their content of 15.0 wt.%. However, their consumption increases. Therefore, the maximum boundary value of the content of reagents was taken 15.0 wt.%. The minimum boundary value of the reagent content was taken 6.0 wt.%, Since with a reagent content of 5.0 wt.% (See table 1, experiment 7), the permeability after exposure to the core with water for 10 hours and a discharge pressure of 12 MPa amounted to 159.6 • 10 ^-15 m ² , and the blocking coefficient - 43%.

Образовавшийся в результате реакции осадок Si(OH)₄ имел показатель произведения растворимости 42. Поэтому данные реагенты подходили для приготовления изоляционной композиции. Данные эксперимента описаны в таблице 2, они аналогичны результатам опытов в таблице 1.In the following experiment (table 2), the available sodium silicate and hydrochloric acid were used as starting reagents for preparing an aqueous solution of the insulating composition according to the proposed method

The precipitate Si (OH) ₄ formed as a result of the reaction had a solubility product 42. Therefore, these reagents were suitable for preparing the insulating composition. The experimental data are described in table 2, they are similar to the results of the experiments in table 1.

Thus, based on the data presented, the principle of choosing the concentration of the initial chemical reagents depending on the permeability of the insulated reservoir is determined:
- to create insulating screens in formations with a permeability of up to 200 • 10 ^-15 m ² use aqueous solutions with a content of the original chemical reagents 2.5-5.0 wt.%;
- to create insulating screens in formations with a permeability of more than 200 • 10 ^-15 m ² using solutions with a concentration of initial reagents 6.0-15.0 wt.%.

 To compare the effectiveness of the effects of insulating compositions according to the prototype and the proposed method, experiments were carried out (see table 3).

 At the beginning of the experiments, the indicator of the product of the solubility of the precipitate was determined according to the prototype and the proposed method.

In the insulating composition of the prototype, aluminum sulfate - Al ₂ (SO ₄ ) _{3 was} used as the sulfuric acid salt.

Показатель произведения растворимости осадка, сульфата кальция (СаSO₄), равен 5.The precipitate formation reaction in this case has the form:

The product solubility index of the precipitate, calcium sulfate (CaSO ₄ ), is 5.

For insulating compositions according to the proposed method, aluminum chloride and soda ash, sodium silicate and hydrochloric acid were used. The precipitates formed as a result of the reaction between the starting reagents, Al (OH) ₃ and Si (OH) _4, have a solubility product index of 33 and 42, respectively.

 The table shows that in experiment 1 (prototype) the initial permeability of the core after injection of the insulation composition decreased by an average of 75%.

 After exposure to the insulating screen by injected water, core permeability averaged 83% of the initial core permeability. The data presented indicate that during the pumping process the insulation screen was destroyed, it was eroded, which explains the insignificant clogging coefficient - an average of 17%.

 In experiments 2 and 3 (according to the proposed method), the core permeability after injection of insulating compositions decreased from the initial permeability by 95 and 98%, respectively. After exposure to the insulating screen with injected water, core permeability averaged 8 and 3%, respectively (blockage coefficient 92 and 97%, respectively). It can be seen from the data that the insulating screen practically did not lose its insulating ability in the process of pumping water. Moreover, the clogging coefficient in the proposed method in comparison with the prototype is on average 5.55 times greater.

 An example implementation of the method.

 Before conducting insulation work on the well, a set of studies is carried out: hydrodynamic studies to determine the injectivity profile or studies to determine the place of water entry into the well.

 In the process of hydrodynamic studies determine the injectivity of the reservoir at various injection pressures, followed by the calculation of permeability.

 Further, by any known method (flow measurement, thermometry, etc.), the injectivity profile or the place of water intake is determined, followed by an assessment of the absorption intensity or fluid flow in the selected interval.

In any known way (according to reference data, laboratory experiment, calculation method), the solubility product of the precipitate formed during the interaction of the initial chemical reagents, which the manufacturer has available, is determined. For example, the following chemicals are available at the time of work: aluminum chloride (AlCl ₃ ), sodium sulfate (Na ₂ SO ₄ ), calcium chloride (CaCl ₃ ), caustic soda (NaOH) and sodium carbonate (Na ₂ CO ₃ ) . When interacting with sodium sulfate and sodium hydroxide, calcium chloride forms a precipitate — calcium sulfate (CaSO ₄ ) and calcium hydroxide (Ca [OH] ₂ ), respectively. Aluminum chloride reacts with sodium carbonate to form a precipitate - aluminum hydroxide (Al [OH] ₃ ). The solubility product index for CaSO ₄ is five, for Ca [OH] _{2 it} is six and for Al [OH] _{3 it} is thirty-three. To implement the method, only those reagents are used for which the solubility product of the precipitate formed during their interaction is greater than 7. Therefore, in this case, aluminum chloride and sodium carbonate are selected as the initial chemical reagents for the method.

 Based on a certain permeability, the concentration of solutions necessary to create an insulating screen is selected.

 At the first stage of work in various containers, the calculated amount of aqueous solutions of aluminum chloride and sodium carbonate is prepared with a given concentration depending on the permeability of the insulated collector.

 Next, the pumping unit through the tee injects the solutions into the formation, followed by the sale of the estimated volume of the water “buffer”, after which the well is left for technological uptime for 24 hours

 After technological dwellings in the well, hydrodynamic studies and studies are carried out to determine the injectivity profile (inflow).

 Implementation of the proposed method will allow due to a more durable insulating screen to significantly affect the redistribution of fluid flows in remote zones of the reservoir and involve “stagnant” reservoir zones in the development process and, therefore, increase oil and gas recovery, reduce water cut of produced products, and prevent premature watering of wells.

 In addition, by expanding the range of chemicals used, the time of forced shutdowns of wells associated with waiting for reagents necessary for repair is significantly reduced.

Claims (1)

A method for developing an irrigated reservoir of liquid or gaseous hydrocarbons, comprising injecting insulating compositions through production or injection wells into irrigated intervals, characterized in that the insulating compositions are prepared from chemicals that, when interacting with each other, form a precipitate whose solubility product index is equal to or greater than 7 moreover, to create insulating screens in formations with permeability up to 200 • 10 ^-15 m ² use aqueous solutions with the content of the original th chemical reagents 2.5-5.0 wt. %, to create insulating screens in formations with a permeability exceeding 200 • 10 ^-15 m ² , use aqueous solutions with a concentration of starting reagents 6.0-15.0 wt. %

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