RU2507386C2 - Method of increasing oil recovery of fractured and porous beds with induced fractures after breakdown - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: in compliance with proposed method, water solution is forced in artificially created fractures which contains 3-10 wt % of suspended mix of bentonite clay powder modified with quartz sand at their ratio of 10:1 - 1:2 and containing 0.01-0.30 wt % of partially hydrolysed polyacrylamide and 0.1-0.6 wt % of cross-linking agent, that is, chromium-containing compound.

EFFECT: higher recovery.

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Description

The invention relates to the oil industry and can be used in the development by flooding of fractured and porous formations with artificially created cracks after hydraulic fracturing - hydraulic fracturing. The proposed method provides uniform displacement of oil from the reservoir, which helps to increase oil recovery for heterogeneous oil reservoirs with channels (cracks) with low filtration resistance and limiting the production of associated produced water.

There is a method of increasing oil recovery in fractured and porous formations with artificially created cracks after hydraulic fracturing (US No. 2007/0267191, 11/27/2007, 6 pp.) Including the injection of an aqueous (with a concentration of up to 0.3%) polymer solution - polyacrylamide, both linear and with a crosslinker including chromium compounds, with the introduction of bentonite clay powder and silica sand in portions.

The closest technical solution, taken as an analogue and prototype, is a method of increasing oil recovery of fractured and porous formations with artificially created cracks after hydraulic fracturing (RF Patent No. 2398102, 2010), including the injection of an aqueous solution of polyacrylamide with a crosslinker - a chromium compound, using additives bentonite clay powder and quartz sand, characterized in that use modified bentonite clay powder and in the form of a mixture of it with quartz sand, is carried out at the beginning of the injection of an aqueous solution containing 0.01-0.30 wt.% of partially hydrolyzed polymer-polyacrylamide and 0.1-0.6 wt.% of a crosslinker - chromium-containing compound, squeezed with water, then - injection of an aqueous solution of polyacrylamide (0.005 wt.%) with a viscosity (0.55 cP) by 10% higher viscosity of produced water (0.5 cP), in which 3-10 wt.% of a mixture of modified bentonite clay powder and silica sand with their initial ratio of 10: 1 are suspended with a subsequent increase in the concentration of sand to a ratio of 1: 2.

The proposed method of increasing oil recovery in fractured and porous formations with artificially created cracks after hydraulic fracturing - hydraulic fracturing, is more effective for increasing oil recovery than the prototype.

A method of increasing oil recovery in fractured and porous formations with artificially created cracks after hydraulic fracturing - hydraulic fracturing, which includes injecting an aqueous solution of polyacrylamide with a crosslinker - a combination of chromium, bentonite clay powder and silica sand, characterized in that they inject an aqueous solution in which 3-10 are suspended wt.% a mixture of bentonite clay powder modified with quartz sand, their ratio from 10: 1 to a ratio of 1: 2. and containing 0.01-0.30 wt.% partially hydrolyzed polyacrylamide and 0.1-0.6 wt.% a crosslinker, a chromium-containing compound (SPHKS).

For the modification of bentonite clay powder, chemical reagents Na ₂ CO ₃ , M-14 BB, metas are used. The degree of hydrolysis of polycrylamide is 5-15%. As the cross-linking agent introduced into the mixture, chromium potassium alum is used in accordance with GOST 4162-79, chromium acetate in accordance with TU 6-09-5380-88, potassium dichromate in accordance with GOST 2652-78, sodium dichromate in accordance with GOST 2651-88, technical calcium chloride in accordance with GOST 450-77.

The technical result for various concentrations of the mixture and the components of the mixture with water are given in tables No. 1, 2.

Table number 1 SPGKS,% Water% Dynamic viscosity, MPa · s Swelling *,% 3 97 300 thirty 5 95 700 fifty 10 90 1900 95

Table number 2 PAA
% Stapler,% GP,% (ratio to sand) KP,% (ratio to clay) Water% Dynamic viscosity, MPa · s Nabuha-
bridge *,% 0.1 0.1 3 (10) 0.3 (1) 96.5 300 thirty 0.2 0.3 4 (4) 1 (1) 94.5 700 fifty 0.3 0.6 5 (1) 5 (1) 89.1 1900 95 * Swelling is equal to the ratio of the volume of the swollen gel-like precipitate (suspension) to the initial volume of water.

The amount of polyacrylamide, clay slurry, silica sand and a crosslinking agent is taken depending on the specific injectivity of the wells and the thickness of the formation. By selecting the concentrations of the reagents, it is possible to control the gelation time and redistribute the flows in any zone of the heterogeneous formation.

As a result of injection, particles of a mixture of clay slurry and silica sand entering the formation begin to interact with the free functional groups of the polyacrylamide with a crosslinker; as a result, the crosslinked polymer-clay-quartz system (SPGKS) flocculates in the washed and fractured zones of the formation and increases the filtration resistance of the flocculant with the formation of swollen eroded sediment, leads to a redistribution of filtration flows. Subsequent injection of the displacing agent (water), and (or) the selection of fluid from the reservoir helps to extract oil from low-permeability, not covered by the displacement zones of the reservoir.

In the process of searching for known solutions, the above proposed technical solution was not found in the development of oil fractured and porous formations with artificially created fractures after hydraulic fracturing - hydraulic fracturing covered by water flooding. This allows us to conclude that the claimed method as an invention.

To prove compliance with the claimed invention, we give specific examples of the method. Experimental work was carried out at one of the fields in Western Siberia, at well No. 30257.

The proposed set of features of the developed method provides an effective redistribution of filtration flows in the reservoir volume due to the increased viscosity of the injected suspensions with the formation of a swollen eroded sediment. The impact on the reservoir in order to regulate the development of the oil field is carried out as a result of the following processes. With the joint injection of an aqueous polymer solution and mixed dispersed clay-sand particles, a significant increase in the stability of the suspension and a significant increase in its viscosity occur. A polymer-stabilized, more stable suspension of a mixture of dispersed particles can be filtered into the reservoir volume only through washed channels and fractures, including those formed after hydraulic fracturing — hydraulic fracturing, without precipitating at the bottom of the well, as the process of sedimentation and swelling takes 12-24 hours after the start of the download. At the same time, due to the overlapping of the washed channels and cracks of the polymer stabilized suspension, the redistribution of filtration flows and the formation of stagnant and weakly drained formation zones occur.

Using the developed method allows you to effectively regulate the development of oil fields in order to increase oil recovery.

The proposed method can be used to act on formations with different reservoir properties, including primarily fractured and (or) porous with artificially created cracks after hydraulic fracturing - hydraulic fracturing, due to this a more uniform displacement of oil from the reservoir is achieved, which increases oil recovery .

Claims (1)

A method of increasing oil recovery in fractured and porous formations with artificially created cracks after hydraulic fracturing - hydraulic fracturing, which includes injecting an aqueous solution of polyacrylamide with a crosslinker - a combination of chromium, bentonite clay powder and silica sand, characterized in that they inject an aqueous solution in which 3-10 are suspended wt.% a mixture of bentonite clay powder modified with quartz sand with a ratio of 10: 1 to 1: 2 and containing 0.01-0.30 wt.% partially hydrolyzed polyacrylamide . 0.1-0.6 wt% crosslinker - chromium compound.