RU2166621C1 - Method of treating bottom-hole formation zone and regulation of permeability of water-oil-saturated reservoir - Google Patents

Abstract

FIELD: oil producing industry, particularly, methods of increase of injectivity of water-injection wells and coverage of formation by treatment. SUBSTANCE: method includes injection of chemical reagents to bottom-hole zone of injection wells with subsequent process interval. Method is distinguished by the fact that chemical reagents are used in the form of mixture of liquid spent hydrocarbon - waste of isoprene production after its separation and purification and bactericide SNPKh-1004. After process interval, reaction products are forced with sewage water into formation. Said liquid spent hydrocarbon is injected in amount of 0.5-1.0 cu.m/m of oil-saturated thickness of formation, and said bactericide is injected in amount of 100-200 g/cu. m of said liquid spent hydrocarbon. EFFECT: restored permeability of medium- and low-permeability oil-saturated zones and reduced permeability of highly permeable zones of water-saturated reservoirs. 2 cl, 1 tbl, 2 ex

Description

 The invention relates to the oil industry, in particular to methods for increasing the injectivity of water injection wells and increasing the coverage of the formation by exposure.

 A known method of developing an oil field, including sequential injection before and after injection of the cross-linked polymer composition into the injection wells of the bactericide (RF patent N 2136867).

 The disadvantage of this method is its low efficiency by reducing the injectivity of wells.

 The closest analogue to the proposed method is a method of treating the bottom-hole zone of the formation and regulating the permeability of the water-saturated reservoir by injecting chemicals into the bottom-hole zone of the injection wells — a water-insulating agent with a bactericide, and in the medium and low permeability intervals of the intensifying agent followed by a technological break (RF patent No. 214 )

This method is also not effective enough, since when processing the bottom-hole zone, injection wells must have an injection rate of at least 100 m ³ / day, which limits the application of the development method. Together with the injected waste water, mechanical particles, oxidized oil, asphaltenes, resins and paraffins enter the reservoir. In addition, anaerobic bacteria multiply in the perforated zone of the formation, as well as in the bottomhole zone of the injection wells, and their waste products are deposited. The sizes of these particles are commensurate with the pore sizes of low- and medium-permeable zones of the formation. As a result, as these particles accumulate in the perforated zone of the injection well formation and in the bottomhole zone, the injectivity can decrease to almost zero. Moreover, in the first place, the injectivity of low- and medium-permeable reservoirs decreases, the oil saturation of which is very high. The injectivity of highly permeable collectors, mainly washed with water, decreases in most cases slightly.

 The objective of the invention is to provide an effective method for processing the bottom-hole formation zone with the aim of restoring the permeability of medium and low permeability oil-saturated zones and reducing the permeability of highly permeable zones of a water-saturated reservoir.

The problem is solved in that in the method of processing the bottom-hole zone of the formation and regulating the permeability of the water-saturated reservoir by injecting chemicals into the bottom-hole zone of the injection wells followed by a technological break, a mixture of liquid spent hydrocarbon JOU - isoprene production waste after its isolation and purification is used as chemical reagents and bactericide SNPCH-1004, and after a technological break the reaction products are forced through sewage into the reservoir. Moreover, the specified JOU is injected in an amount of 0.5-1.0 m ³ per 1 m of oil-saturated thickness of the reservoir, and the specified bactericide is in quantities of 100-200 g / m ^{3 of the} specified JOU.

 The essence of the method is to dissolve and remove sediments based on oxidized oil, asphalt tar and paraffin deposits, as well as deactivated bacterial cells that are formed under the action of the bactericide SNPCH-1004 on the bacterial community based on the processes of biogenic destruction of residual oil in the wellbore and bottom-hole zone of injection wells and subsequent pushing the reaction products into the formation by injected water, regulating the permeability of the water-washed zones of the formation, increasing the coverage of the formation by water flooding and th increasing oil recovery. The largest number of microorganisms is characteristic of the bottom-hole zone of injection wells, where, under the conditions of favorable factors, a bacterial community is formed based on the processes of biogenic destruction of residual oil. When injected into oil reservoirs, microorganisms contained in the injected fluids are sorbed on the surface of its channels, forming colonies of various types of microorganisms and their metabolic products (mucus, biofilm, microbial bodies, etc.). This leads to a decrease in the diameter of the formation channels, primarily to clogging of oil-saturated pores of the formation. In general, this process reduces the permeability of the reservoir, injectivity of injection wells and, as a result, reduces oil recovery.

Under the mucus layer, favorable conditions are created for the functioning of bacteria, including anaerobic ones, in particular sulfate-reducing (SBA). These bacteria, as well as their vital products, are able to clog the pores of the formation not only due to mucus, but also due to the deposition of iron sulfide formed as a result of the interaction of hydrogen sulfide released by bacteria with iron ions contained in the formation water. In order to prevent the development of the sulfate reduction process in the production reservoirs, in the wellbore and in the bottomhole zone of the well, it is proposed to inject liquid spent hydrocarbon containing the bactericide SNPCH-1004 in an amount of 100-200 g / m ^{3 of} ZhOU solvent.

 The hydrocarbon part of the sediment as a result of the dissolution of its JOU, mechanical particles (deactivated bacterial cells-products of biocidal action) are forced into the reservoir by subsequent injection of injected water, which reduces the permeability of the water supply channels of the reservoir. Thus, low- and medium-permeable oil-saturated layers not previously covered by waterflooding are connected to the filtration process. This leads to an increase in reservoir coverage by the effect of displacing water - an increase in oil recovery, and an increase in the rate of oil recovery, i.e. reduction of the terms of field development.

The effectiveness of this method is the sum of the effects:
- firstly, from the effect of increasing the injectivity of injection wells.

 - secondly, from increasing the coverage of the formation by water flooding.

 Liquid spent hydrocarbon (ZhOU) according to TU 38.303-05-27-92, waste from the production of isoprene of two-stage dehydrogenation after its isolation and purification. Designed for dewaxing wells, dissolving hetero-organic heavy hydrocarbon compounds, as well as fuel. The composition of liquid spent hydrocarbons includes the following components: piperylene, toluene, absorbent A-2. Launches the Sterlitamak synthetic rubber plant, Sterlitamak.

 The inhibitor-bactericide SNPCH-1004 is a product of the interaction of alkylphosphorous acid with a mixture of primary aliphatic amines of normal structure, dissolved in hydrocarbon solvents. Inhibitor-bactericide SNPCH-1004 is a complex reagent. This makes it possible to use it simultaneously to reduce hydrogen sulfide corrosion and suppress sulfate-reducing bacteria in oilfield pipelines. The inhibitor bactericide SNPCH-1004 belongs to the 4th class of low-hazard substances.

 The effectiveness of the composition was determined by laboratory and field studies.

 Laboratory research.

 The experimental procedure is as follows.

Two columns of organic glass were filled with disintegrated sandstone of the Kushkul field. In each column, air and water permeabilities were determined (k ₁ ). Then, a paraffin solution in benzene is poured into 1 column, benzene is evaporated under vacuum, and the permeability of the porous medium in the column is again determined. Columns with a porous medium were connected in series for subsequent filtration. Water saturation of porous media was created by filtration of 3-5 pore volumes of water through porous media. Then, 3 cm ^{3 of a} solution containing SSC was introduced into column No. 1. The experiment is stopped for 1 day for the reproduction of bacteria. After a technological pause, the permeability values in the column (k ₂ ) were determined. Then, the proposed composition was pumped into the porous medium in column 1. After exposure (for 1 day), water filtration and permeability measurements were continued (k ₃ ).

 Example 1

Column No. 1; 2 from organic glass with a diameter of 18 mm and a length of 300 mm, disintegrated sand obtained from cores of sandstone of the terrigenous Devonian of the Kushkul deposit is placed. The water permeability of the porous medium in column 1 was 0.54 μm ² , in column 2 - 0.52 μm ² .

Column No. 1 is filled with a benzene paraffin solution with the following content of heavy components: asphaltenes — 10.3%; resins - 19.8%; paraffins - 28.7%. The benzene is evaporated under vacuum to a constant column weight. Then 5 pore volumes of wastewater are filtered and 3 cm ^{3 of a} solution containing 6.0 • 10 ³ cells / cm ^{3 of} sulfate-reducing bacteria is introduced. The experiment is interrupted for 1 day for the growth of bacteria in a porous medium (column 1). The permeability of the first column to water was 0.37 μm ² (k ₂ ). Then, in the column No. 1, the proposed ZhOU is introduced into the porous medium in an amount of 30% of the pore volume of the porous medium and a bactericide at the rate of 150 mg / dm ^{3 of the} solvent. After 1 day, this composition is pushed with sewage pumped water into the porous medium of column 2. The success of our assumption is determined by the change in the permeability of porous media in the 1st and 2nd columns. The results of the experiments are shown in the table. In the experience of testing the proposed method, the permeability of the porous medium was restored in the 1st column by 35.1%, and in the 2nd column decreased by 40.4% (experiment 6, table), which implies that the goal was achieved.

 Example 2

Two columns filled with disintegrated sandstone from cores of the Kushkul field with water permeability I - 0.58 μm ² ; II - 0.40 μm ² . The speakers were connected in series. In the first column, a solution of a benzene mixture of asphalt-resin-paraffin substances in an amount of 30% of the pore volume and 3 cm ^{3 of a} solution containing 6.0 • 10 ³ cells / dm ^{3 of} SVB was applied. The permeability of the porous medium after a daily break in column 1 was 0.25 μm ² . After a day, the proposed solvent of the JOC in the amount of 30% of the pore volume of the porous medium is introduced into column No. 1 in a porous medium. The experiment is stopped for a day. Then continue the filtration of wastewater. The permeability in the 1st column recovered slightly, k ₁ = 0.30 μm ² , the permeability of the porous medium in the column N 2 k ₃ = 0.36 μm ² (experiment 4, table).

 Thus, laboratory studies show the effectiveness of the proposed method: as a result of dissolution and removal of sediment, consisting of mechanical particles, paraffin deposits, oxidized oil, microorganisms and their waste products, low- and medium-permeable layers are involved in the filtering process. As a result of the subsequent pushing of sediments into the formation by water, the permeability of the water-washed part of the formation decreases. Waterflood coverage increases and both oil recovery and oil recovery rates increase.

 An example of a test method in the field.

To test the method, the injection well N 518 of the Kushkul field of the Ufaneft NGDU was selected. The injectivity of the well before work was 20 m ³ / day at a pressure of 190 MPa. In accordance with the proposed method, 2.5 m ^{3 of the} aforementioned composition of chemicals (350 g SNPCH in 2.5 m ^{3 of} JOU solvent) was pumped into the well. Then the composition was squeezed into the bottomhole formation zone with sewage in a volume of 5.5 m ³ . The well was stopped for response within 24 hours. After that, the injection of water from the PPD system was continued. After the work, pressure and injectivity were measured. The pick-up was 180 m ³ per day at a pressure of 140 atm. Thus, the throttle response has increased.

 The technology of applying the proposed method is simple and consists in pumping into an injection well and selling the composition from the wellbore to the formation with water and holding for 24 hours. Then the PPD system water is injected.

Claims (2)

 1. The method of processing the bottom-hole zone of the formation and regulating the permeability of the water-saturated reservoir by injecting chemicals into the bottom-hole zone of the injection wells followed by a technological break, characterized in that the mixture of liquid spent hydrocarbon JOU - waste from isoprene production after its isolation and purification is used as chemical reagents bactericide SNPCH-1004, and after a technological break the reaction products are forced through sewage into the reservoir. 2. The method according to claim 1, characterized in that the specified JOU is injected in an amount of 0.5 - 1.0 m ³ per 1 m of oil-saturated thickness of the reservoir, and the specified bactericide is in an amount of 100 - 200 g / m ^{3 of the} specified JOU.

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