RU2088753C1 - Method of oil pool development - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: method includes withdrawal of oil from producing wells and injection through injection wells into oil pool outline of water and acid fringes. Novelty in the offered method is injection of acid with thickening agent, in form of peat or coal. To increase efficiency of the method, it is practicable to additionally inject fringes of oxidizer or gas. In case of high degree of formation nonuniformity, it is recommended to additionally inject fringes of water thickened with peat. To reduce corrosion activity of acid, it is recommended to add alcohol or nonionic surfactant, and for removal of asphalt-resin and wax deposits, fringe of aqueous solution on nonionic surfactant or fringe of green oil is injected after injection of acid fringe with thickening agent. EFFECT: higher efficiency. 5 cl, 3 tbl

Description

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

 A known method of developing an oil reservoir, involving the selection of oil by producing wells and pumping water into injection wells [1] The disadvantage of this method is its low efficiency.

The closest technical solution, taken as a prototype, is a method of developing an oil reservoir, involving the injection into the reservoir of water and acid [2]
This method involves the selection of oil by production wells and injection of water into the injection wells, as well as acid rims. The disadvantage of this method is the low efficiency in granular reservoirs, especially with increasing water cut in wells and in heterogeneous reservoirs.

 The purpose of the invention is to increase the effectiveness of the impact on the reservoir and increase the final oil recovery from the oil reservoir.

 This goal is achieved by the fact that in the known method, which includes the alternate injection of water and acid into the formation, acid with a thickener, which is used as peat or coal, with a concentration of thickener from 0.001 to 10 wt.

 In order to increase the efficiency of the process, it is recommended to additionally finish the fringes of the oxidizer or gas.

 As coal use crushed charcoal or coal.

 To increase the efficiency of the method with a high degree of heterogeneity of the layers, it is recommended to additionally pump rims of water thickened with peat.

 In order to reduce the corrosive activity of the acid, it is recommended to add alcohol or untreated surfactants to the acid rim with a thickener.

 To remove asphalt-resinous and paraffin deposits, it is recommended to pump an aqueous solution of nonionic surfactants or green oil after acid injection with a thickener.

 In the case of using ground or coarse grinding of peat or coal, it is recommended to filter the prepared mixture before pumping it into the formation.

 As the acid, it is recommended to use hydrochloric, sulfuric, hydrofluoric, clay, or a mixture thereof.

 The proposed method is as follows.

 The deposit is drilled by producing and injection wells. After drilling into the deposits, the formation is flooded with periodic injection of acid rims into the formation. Before the acid is injected, a thickener is added to it, in which peat or coal is used. The amount, volume of injected acid rims with a thickener, their concentration depend on the properties of the reservoir oil and oil-saturated rock, namely permeability, heterogeneity, lithological composition and others, and is determined during technological and feasibility studies.

 The thickened acid may be prepared as follows.

 The quantity of flour prepared from peat or coal is recorded in the hopper of the cemented aggregate CA-320, and the acid is added, after which the components are circulated for mixing. Subsequently, the acid is injected with the thickener simultaneously using the CA-320 aggregate and the acid carrier or the second CA-320 aggregate, while the ratio of the acid supply by the acid carrier and the thickened acid by the aggregate is determined in accordance with the required concentration of the thickener in the acid. In the case of using additional injection of rims of oxidizing agent or gas, it is recommended to pump them after the rims of acid and additional injection of water for washing downhole equipment. In the case of using ground peat or coal, large unreacted particles are recommended to be filtered by a filter installed at the pump inlet or at the outlet of the unit.

Example 1. For a field, reservoir ₁ (reservoir oil viscosity 0.7 MPa • s, density 820 kg / m ³ , permeability 0.05 μm ² , oil saturation 65% reservoir temperature 90 ^o C), the following option is recommended. The reservoir is flooded with periodic injection into the reservoir through injection wells of concentrated hydrochloric acid thickened with peat (0.5%) in an amount of 15-70 m ³ per 1 m of oil-saturated power.

Example 2. For a field (reservoir oil viscosity 0.41 mPa • s, density 691 kGn / m ³ , the permeability ratio between a number of overlying formations is about 100), the following option is recommended. Initially, a rim of water is completed in injection wells, then they are transferred to pumping alternating rims of water, concentrated hydrochloric acid thickened with peat (2.5%) in an amount of 20-50 m ³ per 1 m oil-saturated capacity, water thickened with peat (1%) in the amount of 10-70 m ³ per 1 m of oil-saturated power, and hydrocarbon gas in an amount of up to 0.1 pore volume of the site In the future, water flooding is carried out.

Example 3. For the field, reservoir BS ₈ (viscosity of reservoir oil 2.4 MPa • s, density 800 kg / m ³ , permeability 0.24 μm ² ) the following option is recommended. The reservoir is flooded with periodic injection of concentrated sulfuric acid, thickened with coal flour (1%), in an amount of 10-80 m ³ per 1 m of oil-saturated power. After injection into the formation of the rim of acid with a thickener, an additional rim of green oil is pumped in an amount of 2-7 m ³ per 1 m of oil-saturated power.

Example 4. For a field, reservoir A _7-8 (reservoir oil viscosity 10 mPa • s, density 849 kg / m ³ , reservoir temperature 56 ^o C, permeability 0.054 μm ² , initial oil saturation 57%), the following option is recommended. Initially finish the rim of water in an amount of about 0.1 pore volume of the plot. Subsequently, they switch to the injection of alternating rims of water and air with a water-air ratio of 0.01. After injection of every eighth air rim, a rim of concentrated hydrochloric acid with a thickener is completed, which is used peat (0.5%) containing 1% butyl alcohol in an amount of 5-40 m ³ per 1 m of oil-saturated formation thickness. The process is carried out before air injection in an amount of about 28% of the pore volume of the site. Subsequently, flooding is carried out.

Example 5. For the field, reservoir BV ₈ (viscosity of reservoir oil 1.1 MPa • s, permeability 0.136 μm ² , porosity 22% reservoir temperature 75 ^o C) the following option is recommended. The reservoir is flooded with periodic injection of concentrated hydrochloric acid with a thickener, which is used as peat (0.5%), and containing 2% AF _9-12 , in an amount of 10-50 m ³ per 1 m of oil-saturated power. After the acid rim with a thickener, the rim of the aqueous solution of AF _9-12 5% concentration in the amount of 5-20 m ³ per 1 m of oil-saturated power is pumped.

 To compare this method with known methods (water flooding with an acid rim, wet in-situ combustion with peat-thickened water, water-gas treatment), a series of experiments was carried out.

To compare this method with waterflooding with an acid rim, experiments were carried out on a reservoir model as applied to field conditions. The permeability of the reservoir model was 0.23 μm ² , the porosity was 22%. The experiments were carried out at a temperature of 75 ^o C. The oil viscosity at this temperature was 1.1 MPa • s. To maintain similarity, the rate of water and acid supply was maintained so that the filtration rate did not exceed 5 cm / h.

 In water flooding experiments with a rim of acid, the rim of water was initially finished in an amount of 0.5 pore volume, then a rim of concentrated acid (for hydrochloric acid of 24% concentration in an amount of 0.5 pore volume, for sulfuric acid of 94% concentration 0, 15 pore volume of the model) and then three more pore volumes of water were filtered through the model.

 Waterflooding experiments with the injection of an acid rim with a thickener, which is used as peat or coal, were carried out similarly. The acid with a thickener was prepared as follows. The day before the experiments, dried and ground peat or coal was added to the acid. When injected into the model, the acid with the thickener was continuously mixed.

In experiments N 6-8, butyl alcohol or AF _9-12 was additionally introduced into acid rims with a thickener.

 The experimental results are shown in table 1.

To compare this method with a method involving wet in-situ combustion (VVG) with the injection of peat-thickened water, laboratory experiments were carried out in relation to the conditions of the field, BS ₁₀ reservoir (reservoir oil viscosity 1.7 MPa • s, density 782 kg / m ³ , reservoir temperature 82 ^o C). A cylindrical core holder with a diameter of 0.046 m and a length of 0.40 m was used as a reservoir model. The experiments were carried out at a pressure of 21.0 MPa.

When conducting the VVG experiment with the injection of water thickened with peat initially at the reservoir temperature and increasing the temperature in the reservoir model to 280 ^o C, two threshold volumes of water were filtered through the model. Then they switched to the injection of alternating rims of air and peat-thickened water (1.5%). The volume of the rim of thickened water was 0.15, the volume of the rim of air was 0.075 of the pore volume of the model. The total volume of peat-thickened water was 1.05 of the pore volume of the model. Subsequently, alternating rims of water and air were pumped.

 During the VVG experiment with the injection of peat-thickened water and acid with a thickener, which is used as peat, in contrast to the previous one, in the process of pumping alternating rims of air and thickened water, instead of two rims of air, two rims of concentrated sulfuric acid with a thickener were pumped, as used peat (1.5%), 0.01 each of the pore volume of the model (third and sixth rims). The experimental results are given in table. 2.

To compare this method with the known method, water-gas exposure, experiments were conducted on a reservoir model in relation to the conditions of the field. The permeability of the reservoir models ranged from 0.26 to 0.28 μm ² , porosity 24%. The experiments were carried out at a pressure of 7.0 MPa and a temperature of 70 ^o C. The viscosity of the oil was 1.2 MPa • s.

 In a water-gas experiment, four threshold volumes of water and twenty gas rims with a total volume of 0.4 pore volumes were pumped through the model.

 In the experiment on injecting water, gas, and acid with a thickener, a rim of water with a volume of 0.5 pore volume was initially filtered through the model, followed by 21 alternating rims of water, concentrated hydrochloric acid, thickened with peat (1.5%), and hydrocarbon gas in accordance with 6: 1: 6 in terms of experience. Subsequently, another 2.5 pore volumes of water were filtered through the model. At the same time, 3.4 pore volumes of water, 0.4 pore volumes of gas and 0.06 pores of acid with a thickener were pumped through the model.

 The main experimental results are given in table.3.

 From the data given in table. 1-3, it is seen that when applying the proposed development method, the displacement coefficient increases in comparison with known methods.

Laboratory studies have also shown that as a result of the addition of a thickener to the acid, which is used as peat or coal, the corrosive activity of acids is significantly reduced. Thus, the addition of 1.0% peat to a 50% sulfuric acid solution at a temperature of 20 ^o C reduces the dissolution rate of steel by 2.6 times, at 60 ^o C by 2.2 times; the addition of 0.5% peat to a 12% hydrochloric acid solution at a temperature of 20 ^o C reduces the dissolution rate of steel 3.1 times, at 60 ^o C 2.7 times; the addition of 1.0% coal (milled) to a 12% hydrochloric acid solution at a temperature of 20 ^o C reduces the dissolution rate of steel by 2.3 times, at a temperature of 60 ^o C by 2.0 times. This decrease in acid corrosion activity in relation to oilfield equipment allows increasing the amount of acid injected with one thickener during one well operation, which significantly reduces labor costs.

 As shown by studies, when applying this method, compared with the known new properties are manifested. This is due to the fact that an additional, more viscous displacing agent is pumped into the formation, contributing to an increase in exposure and the degree of oil displacement. As a result of adsorption on the rock and the calcination of the thickener, as well as the reaction of the acid with the thickener and the rock, the acid redistributes over the interlayers with lower permeability. In addition, the reaction products of the acid with a thickener, which is used as peat or coal, as laboratory experiments show, are an effective displacing agent, and also contribute to the formation of stable oil-water emulsions and foam systems. This is due to the fact that during the reaction of the acid with the thickeners of the proposed type, a wide range of surfactants is formed, which determines the increase in the effectiveness of the proposed technology. As a result of the interaction of the acid with the rock, carbon dioxide is formed, which, together with the reaction products of the acid and thickener, increases the washing out of the oil. The salts and finely divided material formed during the reaction of the acid with the rock are part of the oil-water emulsions, increasing their viscosity and resistance, thereby contributing to the alignment of fronts and increase the degree of displacement.

 The use of this development method compared to the well-known one, which involves the alternate injection of water and acid into the formation, increases the impact coverage, alignment of the displacement fronts and increase the degree of displacement, resulting in an increase in the effectiveness of the impact on the formation and an increase in the final oil recovery from the oil reservoir.

Claims (5)

 1. A method of developing an oil deposit, which includes alternately injecting water and acid into the formation, characterized in that, in order to increase the effectiveness of the effect on the formation and increase the final oil recovery, acid with a thickening agent is pumped into the formation, using peat or coal with a concentration of thickening agent 0.001 to 10 wt.  2. The method according to claim 1, characterized in that the oxidant or gas is additionally pumped.  3. The method according to claim 1, characterized in that it further injected water thickened with peat.  4. The method according to p. 1, characterized in that the acid with a thickener is additionally introduced alcohol or nonionic surfactants.  5. The method according to claim 1, characterized in that after the injection of the acid with a thickener, an aqueous solution of nonionic surfactants or green oil is pumped.

Images