RU2398102C1 - Method for increase of oil recovery of cracked and porous beds with artificially created cracks after hydraulic bed rupture - hbr - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to oil industry and may be used for waterflooding of cracked and porous beds, non-uniform in permeability, with artificially created cracks after HBR. In method for increase of oil recovery from cracked and porous beds with artificially created cracks after hydraulic bed rupture - HBR, including pumping aqueous solution of polyacrylamide with crosslinker - chrome compound, using additive of bentonite clay powder and quartz sand, modified bentonite clay powder is used, as well as in mixture with quartz sand, at first aqueous solution is pumped, containing 0.01-0.30 wt % of partially hydrolyzed polyacrylamide and 0.1-0.6 wt % of crosslinker - chrome-containing compound, driving with water, then pumping of aqueous solution of polyacrylamide with viscosity that is 10% more than viscosity of formation water, where 3-10 wt % of modified bentonite clay powder and quartz sand mixture is suspended with their initial ratio of 10:1 with further increase of sand concentration up to ratio of 1:2.

EFFECT: improved oil recovery.

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 ensures the alignment of the injectivity profile of injection wells with heterogeneous oil reservoirs with channels (cracks) with low filtration resistances and the limitation of 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. 2002/0169085, 11/14/2002, 11 pp.), Including the injection of an aqueous (with a concentration of up to 1%) polymer solution — polyacrylamide, both linear and co a stapler, including chromium compounds, with the introduction of quartz sand in portions of it.

The closest technical solution, taken as an analogue and prototype, is a way to increase oil recovery of fractured and porous formations with artificially created cracks after hydraulic fracturing (US No. 2007/0267191, 11/27/2007, 6 pp.), Including the injection of water (with a concentration of up to 0.3% ) polymer solution - polyacrylamide both linear and with a crosslinker, incl. chromium compounds, with the introduction of bentonite clay powder and silica sand in portions.

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 fractures after hydraulic fracturing - hydraulic fracturing, which includes injecting an aqueous solution of polyacrylamide with a crosslinker - a chromium compound, using an additive of bentonite clay powder and silica sand, characterized in that they use modified bentonite clay powder and in the form of a mixture it with quartz sand, first carry out the injection of an aqueous solution containing 0.01-0.30 wt.% partially hydrolyzed polyacrylamide and 0.1-0.6 wt.% a crosslinker - a chromium-containing compound, pumped with water, then - injection of an aqueous solution of polyacrylamide with a viscosity 10% higher than the viscosity of produced water, in which 3-10 wt.% of a mixture of modified bentonite clay powder and silica sand with an initial ratio of 10: 1 are suspended with a subsequent increase sand concentration to a ratio of 1: 2.

As a result of injection, particles of clay slurry and silica sand entering the formation begin to interact with the free functional groups of polyacrylamide with a crosslinker; as a result, the crosslinked polymer-clay-quartz system (PHC) flocculates in highly permeable zones of the formation and an increase in the filtration resistance of the flocculant leads to a redistribution of filtration streams. Subsequent injection of the displacing agent (water) helps to extract oil from low-permeability unplanned areas of the formation.

As a cross-linking agent introduced into PHC, chromium potassium alum is used according to GOST 4162-79, chromium acetate according to TU 6-09-5380-88, potassium dichromate according to GOST 2652-78, sodium dichromate according to GOST 2651-88 with a concentration of 0, 1% to 0.6%. The amount of partially hydrolyzed 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 clay powder, a modified bentonite clay powder of the PMBA brand is used. Before the injection, the well is tested in three modes with the construction of an indicator curve to assess the nature of the washed zones and cracks. The volume, concentration of components and the rate of injection is selected depending on the studies. 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. 713.

At the beginning, a mixture of a 0.30% aqueous solution of polyacrylamide and a 0.6% crosslinker, potassium dichromate, not higher than the injection pressure, is pumped, squeezed by the rim of the water in the tubing and an additional 5 m ³ into the formation. The second stage injects a 10% mixture of modified bentonite clay powder and quartz sand in a 0.005% aqueous solution of polyacrylamide with a viscosity 10% higher than the viscosity of produced water - 0.55 cP (solution) and 0.5 cP (water), respectively, at pressure above discharge pressure by 30%. The suspension of clay and quartz sand is injected according to the scheme - first, the clay concentration and sand concentration are in a ratio of 10: 1, followed by an increase in sand concentration to a ratio of 1: 2, depending on the change in injectivity and injection pressure during the injection process. Next is the sale of water rims in the amount of one tubing volume and an additional 5 m ³ into the reservoir. The number of subsequent alternating cycles depends on the results of studies of the indicator curve, changes in injectivity and discharge pressure during the injection process.

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

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. 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 an increase in its viscosity occur. A polymer-stabilized, more stable suspension of a mixture of dispersed particles is able to filter into the reservoir volume at the most permeable water-washed intervals and fractures, including those formed after hydraulic fracturing, without being deposited on the bottom of the well. At the same time, due to the deeper penetration of dispersed particles into the formation and the viscous properties of the polymer stabilized suspension, redistribution of filtration flows occurs and the formation of stagnant and slightly drained zones of the formation is connected.

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

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

Claims (1)

A method of increasing oil recovery in fractured and porous formations with artificially created fractures after hydraulic fracturing - hydraulic fracturing, which includes injecting an aqueous solution of polyacrylamide with a crosslinker - a chromium compound, using an additive of bentonite clay powder and silica sand, characterized in that they use modified bentonite clay powder and in the form of a mixture it with quartz sand, first carry out the injection of an aqueous solution containing 0.01-0.30 wt.% partially hydrolyzed polyacrylamide and 0.1-0.6 wt.% a crosslinker - a chromium-containing compound, pumped with water, then - injection of an aqueous solution of polyacrylamide with a viscosity 10% higher than the viscosity of produced water, in which 3-10 wt.% of a mixture of modified bentonite clay powder and silica sand with an initial ratio of 10: 1 are suspended with a subsequent increase sand concentration to a ratio of 1: 2.