RU2205946C1 - Method of development of oil pool - Google Patents

Abstract

FIELD: oil producing industry; applicable in development of oil formations by waterflooding. SUBSTANCE: method includes displacement of oil by fringe formed by successive injection into formation through injection wells of aqueous suspension based on mixture of bentonite clay and polyacrylamide and reagent, pushing it over formation by displacing fluid. Reagent is used in form of aqueous suspension based on mixture of wood flour, condensed spent sulfite-alcohol liquor and potassium bichromate. Added to aqueous suspension based on mixture of bentonite clay and polyacrylamide may be chromium acetate or bichromate of potassium or sodium. Pushing may be effected after injection of each suspension. In a variety of cases, operations of injection and pushing are repeated. EFFECT: increased coverage by waterflooding for long period of time, involving into active development of slightly drained or nondrained oil reserves, and increased oil mobility due to reduction of its viscosity. 4 cl, 1 tbl

Description

 The invention relates to the oil industry and can be used in the development of oil reservoirs by flooding.

 The closest method to the proposed one is a method of developing an oil reservoir, including displacing oil by a rim created by sequentially injecting into the formation through injection wells an aqueous suspension based on a mixture of bentonite clay and polyacrylamide, an aqueous surfactant solution, followed by pushing the reservoir with a buffer liquid - water (see ed. St. RF 1566820, E 21 B 43/22, 1996).

 The objective of the invention is to align the injectivity profile of the formation, increase coverage by water flooding for a long period, involve in the active development of weakly drained and underexposed oil reserves, as well as increase the mobility of oil by reducing its viscosity.

 The problem is solved in that in the method of developing an oil reservoir, including displacing oil by a rim created by sequentially injecting an aqueous suspension through injection wells of a mixture of bentonite clay and polyacrylamide and a reagent, pushing the reservoir with a buffer liquid, an aqueous suspension is used as a reagent based on a mixture of wood flour, condensed sulphite-alcohol stillage and potassium dichromate.

 Chromate acetate or potassium or sodium dichromate can be added to the aqueous suspension based on a mixture of bentonite clay and polyacrylamide.

 The pushing is carried out after pumping each suspension.

 In some cases, the pumping and pushing operations are repeated.

 The essence of the technology consists in pumping two aqueous suspensions into the well, one of which is polymer dispersed based on polyacrylamide and bentonite clay powder, and the other based on wood flour, condensed sulphite-alcohol stillage and potassium dichromate, which has the properties of a viscoelastic gel.

 A barrier is gradually pumped into the formation, consisting of a dispersed system based on bentonite clay powder and a support composition containing an acrylic polymer.

 This supporting composition increases the stability and strength of the disperse system due to the swelling of the bentonite clay powder, injected in an aqueous polymer solution. In this case, the swelling of the powder present in the polymer solution occurs only in reservoir conditions when it comes into contact with water injected into the reservoir, which leads to a sharp decrease in the permeability of the pore space of the highly permeable formation zone, thereby preventing the washing out of the injected dispersed system formed under reservoir conditions.

 To enhance the crosslinking effect between the disperse system and the polymer system, chromium acetate or potassium or sodium dichromate is used.

 Subsequent injection of a suspension based on a mixture of wood flour, condensed sulfite-alcohol stillage and potassium dichromate due to the formation of a gel system allows to increase the coefficient of coverage by water flooding for a rather long period of 8-18 months. Part of the gas with injected water produces the Jamen effect, which creates additional filtration resistance and increases the duration of the gel system. The other part of the gas segregates into the bedside, where it involves in the active development of weakly drained and non-drained oil reserves. In this case, gas-exposed oil reduces its viscosity and increases mobility.

 The method is implemented as follows.

 The following materials were used for processing the oil deposit in accordance with the present invention: bentonite clay according to GOST 39-202-86, polyacrylamide DKS-40, POLIDIA, condensed sulphite-alcohol stillage (waste from the production of cellulose by the sulfate method) according to TU-84-39-68 as well as wood flour, potassium dichromate, chromium acetate or sodium dichromate in accordance with the “List of chemical products agreed and approved for use in the oil industry” dated 04.15.2000.

 To carry out the technological process, waterflooding systems operating on deposits (water pipes, pumps, tanks for reagents, etc.), as well as cementing unit ЦА- = 320, ejector, etc. are used.

 Before starting work, the injectivity of the formation was determined.

 Working solutions were prepared immediately before injection.

The table shows the consumption of materials per well with an injectivity of up to 500 m ³ .

 An aqueous suspension was prepared from a measured amount of polyacrylamide, bentonite clay and chromium acetate (or potassium or sodium dichromate). Then, an aqueous suspension was prepared based on wood flour, condensed sulphite-alcohol stillage and potassium dichromate.

 The mixture through the casting head mounted on the wellhead was injected into the well. After the introduction of each of the suspensions was carried out pushing with a buffer liquid.

 When using the present invention, the following technical result is achieved: the injectivity profile of the formation is equalized, formations are involved in the development, which under other conditions could not be flooded and, thereby, the coverage of the reservoir by water flooding increases.

Claims (4)

 1. A method of developing an oil deposit, including the displacement of oil by a rim created by sequentially injecting an aqueous suspension into the formation through injection wells based on a mixture of bentonite clay and polyacrylamide and a reagent, pushing the formation through a buffer liquid, characterized in that the aqueous suspension is used as a reagent based on a mixture of wood flour, condensed sulphite-alcohol stillage and potassium dichromate.  2. The method according to p. 1, characterized in that in an aqueous suspension based on a mixture of bentonite clay and polyacrylamide, chromium acetate or potassium or sodium dichromate is added.  3. The method according to claim 1 or 2, characterized in that the pushing is carried out after pumping each suspension.  4. The method according to any one of claims 1 to 3, characterized in that the operation of pumping and pushing is repeated.

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