RU1773101C - Method for development of oil fields - Google Patents

Abstract

FIELD: gas oil producing industry. SUBSTANCE: method consists in displacement of oil from formation in producing wells due to injection of alternating water fringes thickened with ash or mixture of ash with polymer, or mixture of ash with aqueous solution of surfactant. It is also recommended to additionally inject fringes of gas, oxidizer or heat carrier. EFFECT: higher final oil recovery from oil reservoir. 2 cl, 2 tbl

Description

 The invention relates to the oil industry, and in particular to methods for developing oil deposits.

 A known method of plugging cracks in formations, providing for injection into the cracks of a suspension of finely ground non-settling solid materials, namely fly ash, amorphous silicon and finely ground limestone.

 The disadvantage of this method is its low efficiency.

 There is also known a method of developing an oil reservoir by in-situ combustion, involving the injection of water thickened with peat.

 The disadvantage of this method is the need for injection into the reservoir of an oxidizing agent to achieve high efficiency.

 Closest to this method is a method of developing an oil reservoir, involving the injection of clay-thickened water.

 This method involves the selection of oil by producing wells and the injection into the injection wells of the rim of clay-thickened water, as well as the rim of the oxidizing agent or coolant, followed by injection of water. As a result of injecting the rims of clay-thickened water, the coverage of formations by the impact is significantly increased.

 The disadvantage of this method is the insufficient increase in the degree of oil displacement.

 The aim of the invention is to increase the final oil recovery from oil deposits.

 This is achieved by the fact that in a method involving the extraction of oil through production wells and injection of water and water rims with a thickener through injection wells, ash or a mixture of ash with nonionic surface-active substances (nonionic surfactants) or a mixture of ash with polymers are used as a water thickener. .

 In order to increase the efficiency of the process, it is recommended to additionally pump gas or oxidizer rims or coolant.

 As ash, it is recommended to use the remnants of the combustion products generated during the burning of peat or coal at a thermal power plant or in boiler rooms.

 The proposed method is as follows. The deposit is drilled with producing and injection wells, for example, in an area system. After drilling into injection wells, water rims and thickened water are pumped in. The amount and volume of thickened water rims is determined during technical and economic calculations and they depend on the properties of the reservoir oil (in particular viscosity) and the properties of oil-saturated rock: permeability, heterogeneity, percentage of clays, etc. After the termination of the injection, thickened water rims pass for subsequent flooding.

EXAMPLES EXAMPLE 1 To deposit layer ₈ BV (viscosity 1.1 mPa˙s oil reservoir, permeability 0.136 ² microns, a porosity of 22%, formation temperature 75 ° ^C) recommended the following embodiment. Initially, waterflooding is carried out. After injection of water in an amount of 0.2 pore volume, the injection of alternating rims of water and thickened ash (3%) of water with a total volume of thickened water up to 0.1 pore volume begins. Then they switch to flooding. Thickened with ash water is prepared as follows. Ash is loaded into the USP-50 sand mixing plant, and a water conduit is connected to the hydraulic mixing device of the 2СМН-20 machine. A metered amount of ash enters the mixing device and a working mixture is prepared. The prepared water thickened with ash is fed to the cementing unit ЦА-320 for injection into an injection well.

EXAMPLE 2. For a field (reservoir oil viscosity 0.41 mPa˙s, density 691 kg / m ³ ), the permeability ratio between a number of overlying formations is about 100. As a result, the following exposure technique is recommended for leveling the displacement front. Initially, alternating rims of water and a thickened mixture of ash (2-4%) and carboxymethyl cellulose (polymer), 0.05-1.5% water are pumped into the reservoir. After the injection of thickened water in an amount of 0.01 pore volume of the plot, alternating rims of water and thickened ash are pumped to a total volume of thickened water of 0.1 pore volume. Then they switch to flooding.

EXAMPLE EXAMPLE 3 To deposit formation AC ₁₁ (viscosity 3.67 mPa˙s reservoir oil density 815 kg / m ^3, permeability, 0.064 mm ^2, formation temperature 100 ° ^C), the recommended version. Initially, alternating rims of water and a thickened mixture of ash (0.5-2.6%) and AF _9-12 (2-6%) water are pumped into the reservoir to a total injection of thickened water of 0.02 pore volume of the site. Then, alternating rims of water and thickened ash are pumped to the injection of thickened water in an amount of 0.1 pore volume of the site. Then they switch to flooding.

PRI me R 4. For a field, BS ₁₀ ² formation (reservoir oil viscosity 1.7 mPa˙s, density 782 kg / m ³ , permeability 0.3 μm ² , initial oil saturation 0.5), the following option is recommended . Initially, rims of water and thickened ash (up to 3%) of water with a total volume of thickened water up to 0.05 pore volume of the site are pumped into injection wells. Then, alternating rims of water, an oxidizing agent (air) and thickened ash (1-3%) of water are pumped with a water-air ratio of 0.01, with a total volume of thickened water up to 0.2 pore volume of the site. The process is carried out before burning 0.3 volume of the site, after which they switch to water flooding.

EXAMPLE EXAMPLE 5 To deposit (reservoir oil viscosity mPa˙s 225, density 906 kg / m ^3, the reservoir temperature of 18 ^{° C,} the permeability of 1.6 m ²⁾ recommended the following embodiment. Initially, alternating coolant rims (steam, hot water) and thickened ash (2-4%) of hot water are pumped into the reservoir to a total coolant injection of 0.5 pore volume of the plot, thickened water 10.3 pore volume of the plot. Then, alternating rims of water and thickened water ash are pumped to the injection of thickened water in an amount of about 0.1 of the threshold volume of the site, and then waterflooding is carried out.

PRI me R 6. For a field, reservoir BS ₈ (viscosity of reservoir oil 2.43 mPa˙s, density 800 kg / m ³ , permeability 0.24 μm ² ), the following option can be recommended. Initially, a rim of water is pumped into injection wells. Then they switch to the injection of alternating rims of water, thickened ash (0.5-1.0%) of water and hydrocarbon gas to the total injection of thickened water in the amount of 0.15 pore volume of the site, gas in the amount of 0.3 pore volume of the site. Then carry out flooding.

 To compare this method with known methods (water flooding, water flooding with nonionic surfactants, water flooding with polymers, water-gas treatment, wet in-situ combustion with thickened clay water), a series of experiments was carried out.

To compare the proposed method with waterflooding, experiments were carried out on a reservoir model as applied to field conditions. The permeability of the reservoir model was 0.18 μm ² , porosity 22%. Experiments were carried out at a temperature of 75 ^C. The viscosity of the oil at this temperature was 1.1 mPa˙s. To maintain similarity, the rate of supply of water and thickened water to the reservoir model was maintained so that the velocity of the filtration front did not exceed 5 cm / h.

 In water flooding experiments, 4 pore volumes of water were filtered through a model.

 In experiments with the injection of thickened water rims, a rim of water in an amount of 0.5 pore volume was pumped through the model first, then a rim of thickened water with a volume of 0.2 pore volume, and then 3 more pore volumes of water were filtered through the model. Similarly conducted and experiments on flooding with surfactants and polymers. The experimental results are shown in table 1.

To compare the proposed method with a known method by water-gas treatment, experiments were conducted on a reservoir model as applied to field conditions. The permeability of the reservoir model was 0.26 μm ² , porosity 24.1%. Experiments were carried out at a pressure of 7.0 MPa and a temperature of 70 ^C. The viscosity of the oil at this temperature was 1.2 mPa˙s.

 In experiments on water-gas treatment, 4 pore volumes of water from 20 gas rims with a total volume equal to 0.4 pore volumes were filtered through the model through the model.

 In experiments with the injection of rims of water, gas and thickened ash (2%) of water, a rim of water with a volume of 0.5 pore volume was initially filtered through the model, then 20 alternating rims of thickened water, gas, and water in a ratio of 1: 2: 1.5 under conditions experiments, further through the model another 2.5 pore volumes of water were filtered. At the same time, 0.4 pore volumes of gas and 0.2 pore volumes of thickened water were pumped through the model. Methane was used as the gas during the experiments. The experimental results are shown in table.2.

To compare the proposed method with a method involving wet in-situ combustion with thickened clay water, laboratory experiments were conducted in relation to field conditions, BS ₁₀ ² formation, formation oil viscosity 1.7 mPa˙s, density 782 kg / m ³ , formation temperature 82 ^about C. As a reservoir model, a cylindrical core holder with a diameter of 0.046 m and a length of 0.40 m was used. The permeability of the reservoir model was 0.215 μm ² , porosity 29%, initial oil saturation 0.5. The experiments were carried out at a pressure of 21 MPa.

The experiments on wet in-situ combustion with thickened clay (bentonite) or ash water were carried out according to the following procedure. Initially, a pore volume of water was pumped through a reservoir model at reservoir temperature. Then included heating device on the outer side of the model with a given constant heating rate of 50 ^C per hour, and pumped through one pore volume of water. When the temperature reached in the reservoir model, equal to 280 ^{° C,} switched to download alternating slugs of air and gelled with bentonite or ashes water. The rim volume of the water was 0.15 of the threshold volume of the model, air 0.075. The concentration of bentonite or ash in thickened water was 1.5%. The total volume of water injected with bentonite or ash amounted to one pore volume of the model. After that, we switched to the injection of alternating rims of water and air.

 When applying the proposed development method, the oil displacement coefficient is increased in comparison with known methods. In addition, during the experiments, a decrease in the permeability of the reservoir model was observed during injection of thickened ash with water by 10-15%.

 As shown by studies, when applying this method, compared with the known new properties are manifested. This is due to the fact that rims of thickened ash of water are pumped into the reservoir, which have the ability not only to reduce the filtration ability of water-washed zones, but also to increase oil displacement. When peat or coal ash is placed in water, a chemical reaction is observed with the release of heat and gas. Moreover, the most pronounced effect is observed for coal ash, slightly less for peat ash of a thermal power plant and even less for ash obtained from burning peat in a muffle furnace. When filtering water rims, thickened with ash, through reservoir models containing degassed oil and water, significant gas evolution is observed for all types of ash considered; the acidity (pH) of the produced water varies from 5 to 3-4. A significant increase in the degree of oil displacement during the injection of rims with thickened water ash is associated with the manifestation of the effect of water-gas treatment, with a change in the acidity of water, which contributes to an increase in the degree of capillary impregnation with water, the formation of foam systems, especially when added to the rims of nonionic surfactants. Foam systems as a result are formed even without additional injection of gas or an oxidizing agent. The presence in the ash of a large amount of salts leads to the fact that the properties of the crosslinker are manifested when mixing the ash with polymers, increasing the mechanical stability of structured systems.

 Using the proposed development method in comparison with the well-known involving injection of thickened clay clay water, increases the exposure and the degree of oil displacement, resulting in an increase in the final oil recovery.

Claims (2)

 1. METHOD FOR DEVELOPMENT OF OIL DEPOSITS, including the selection of oil through production wells and injection of water through the injection wells and the rim of the water with a thickener, characterized in that, in order to increase the final oil recovery, ash or a mixture of ash with nonionic surface-active are used as a thickener. substances, or a mixture of ashes with polymers.  2. The method according to claim 1, characterized in that the rims of the gas or oxidizer or coolant are further pumped.

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