RU2802645C1 - Method for increasing oil recovery of reservoir - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: used to increase the rate of hydrocarbon recovery from reservoirs during surfactant-polymer flooding. The method for increasing oil recovery includes determining the injectivity of an injection well, preparing and pumping a mixture of surfactant with a polymer through the injection well, and withdrawing oil through production wells. At the same time, a section of an oil deposit is selected with a ratio of injection wells to production wells of 1:3-1:5. After that, oil is sampled through production wells to measure production rates, interfacial tension between oil and water, and water viscosity. Next, the arrival of the shaft of oil to one of the production wells is determined by the increase in production rates, a 2-fold decrease in the value of interfacial tension between oil and water, and an increase in 1.5 times the value of water viscosity. Then, after a decrease in the oil production rate from the maximum value by 12.5%, hydraulic fracturing is carried out in this production well. After the hydraulic fracturing of the reservoir, the production well is put into operation and the set of works is repeated on another production well that has responded to the injection of a mixture of surfactant with a polymer. The development is carried out before the development of a section of an oil deposit.

EFFECT: increased oil recovery of the formation is provided with simultaneous impact on production and injection wells due to hydraulic fracturing of the formation on production wells during the arrival of the oil shaft formed as a result of surfactant-polymer treatment.

1 cl, 1 dwg

Description

The invention relates to the oil and gas industry, and can be used to increase the rate of hydrocarbon extraction from formations during surfactant-polymer flooding.

There is a known method for developing an oil reservoir (patent RU No. 2244812, IPC E21B 43/22, C09K 8/584, publ. 01/20/2005, Bulletin No. 2), including injection of a slug of Sulphacell aqueous dispersion into the reservoir through an injection well and oil production through a production well. This dispersion additionally contains a nonionic surfactant (NSAS) AF9-12 in the following ratio of reagents, wt. %: SC 0.5 - 1, AF9-12 0.01 - 0.1, water the rest.

The disadvantage of this method is the lack of impact on the drainage radius of production wells, i.e. injection of this slug will form a shaft of oil, which will go towards the production wells, but will not be fully recovered due to the small drainage radius of the production wells.

There is a known method for increasing oil recovery (patent RU No. 2483202, MPK E21B 43/22, published May 27, 2013, Bulletin No. 15), including determining the injectivity of an injection well, preparing and pumping a silicate gel suspension through the injection well and extracting oil through production wells. A surfactant, or a polymer, or a mixture of a surfactant and a polymer, is additionally pumped into the injection well. Injection is carried out in alternating slugs of a silicate gel suspension at a concentration of 0.01-15 wt. % and surfactant or polymer or a mixture of surfactant and polymer. A slug of silicate gel suspension is pumped in volume ratio to a slug of surfactant, or polymer, or a mixture of surfactant and polymer from (1÷5) to (5÷1), starting with the maximum concentration of the slugs at the minimum injection pressure with a gradual decrease in concentration until the permissible pressure is reached on the production string or productive formations. The slug concentrations are adjusted depending on changes in injection pressure.

The disadvantage of this method is that a large number of channels are blocked, including those with residual oil and silicate gel rims, which does not contribute to increased oil recovery.

To maintain the same fluid flow rates during surfactant-polymer flooding, it is necessary to lower the bottomhole pressure and increase the depression, which is physically natural, since water with a lower viscosity moves faster than the polymer solution at an equal pressure difference. In addition, the oil displacement front during surfactant-polymer flooding has a radial flow from the injection well; accordingly, in order to extract more oil, it is necessary to increase the drainage radius.

The technical objective of the invention is to increase oil recovery from the formation while simultaneously influencing production and injection wells, namely, carrying out hydraulic fracturing of the formation at production wells during the arrival of a shaft of oil formed as a result of surfactant-polymer action.

The technical problem is solved by a method of increasing oil recovery from a reservoir, including determining the injectivity of an injection well, preparing and pumping a mixture of surfactants with a polymer through an injection well, and withdrawing oil through production wells.

What is new is that they select an area of an oil deposit with a ratio of injection wells to production wells of 1:3-1:5, then carry out oil sampling through production wells to measure the flow rates, interfacial tension between oil and water, water viscosity, and determine the flow of oil to one of the production wells by increasing the flow rate, reducing by 2 times the value of interfacial tension between oil and water and increasing the viscosity of water by 1.5 times, then after reducing the oil flow rate from the maximum value by 12.5%, hydraulic fracturing of the formation is carried out in this production well, after hydraulic fracturing, the production well is put into operation and the set of works is repeated at another reacted production well to pump a mixture of surfactant and polymer, development is carried out until the oil deposit section is developed.

In fig. shows the change in oil flow rates of a producing well in the surfactant-polymer flooding section with hydraulic fracturing (red line) and without hydraulic fracturing (yellow line).

The method is carried out in the following sequence. Select an area of an oil deposit with a ratio of injection wells to production wells of 1:3-1:5.

The injectivity of the injection well is determined.

As a mixture of a surfactant with a polymer, for example, a mixture of a water-soluble or oil-water-soluble surfactant or a complex surfactant and an acrylic polymer is used in the following ratio of components, wt. %: surfactant 0.01-0.2; polymer 0.01-0.5; water - the rest.

A mixture of surfactant and polymer is prepared as follows. At 99.98-99.3 wt. % water with a density of 1.00 to 1.20 g/cm ³ add 0.01-0.2 wt. % surfactant and 0.01-0.5 wt. % polymer and stir on a magnetic stirrer until smooth.

A mixture of surfactant and polymer is injected through an injection well.

Oil is sampled through production wells to measure production well flow rates, interfacial tension and water viscosity.

The arrival of a shaft of oil to one of the production wells is determined by an increase in flow rates, a 2-fold decrease in the value of interfacial tension of water and a 1.5-fold increase in the value of water viscosity.

Then, after the oil flow rate has decreased from the maximum values by 12.5%, hydraulic fracturing is carried out (for example, hydraulic fracturing is carried out according to patent RU No. 2485306, IPC E21B 43/26, published June 20, 2013, Bulletin No. 17) in this production well.

After hydraulic fracturing, the production well is put into operation and the set of works is repeated at another reacted well to inject a mixture of surfactant and polymer. Development is carried out until the oil deposit area is fully economically viable.

An example of a specific implementation.

Select an area of an oil deposit with a ratio of injection wells to production wells of 1:4, = 733 thousand m ³ , = 1000 mD, = 26 mPa s, = 28 mPa s.

The injectivity of an injection well is determined to be 100 m ³ /day at a bottomhole pressure of 90 atm.

As a mixture of surfactant and polymer, a mixture of ethoxylated alkylphenol based on trimers of propylene AF ₉ -6 and polyacrylamide with a molecular weight of (3-15)·10 ⁶ is used in the following ratio of components, wt. %: surfactant 0.01-0.2; polymer 0.01-0.5; water - the rest.

A mixture of surfactant and polymer is prepared as follows. At 99.98-99.3 wt. % water with a density of 1.00 to 1.20 g/cm ³ add 0.01-0.2 wt. % surfactant and 0.01-0.5 wt. % polymer and stir on a magnetic stirrer until smooth.

The surfactant with the polymer is pumped into the injection well.

Oil is sampled through four production wells. The oil flow rate of producing wells is 1.5-4.5 tons/day, the interfacial tension of water is 25-28 mN/m and the viscosity of produced water is 1.6-1.8 mPa s.

With an oil flow rate of 3-6.8 tons/day, with an interfacial tension of 15 mN/m and with a water viscosity of 2.4 mPa·s, it is determined that a shaft of oil has arrived at one of the production wells.

When the oil flow rate is 2.63-5.95 tons/day, hydraulic fracturing is carried out in this production well.

To do this, the walls of the production well are perforated in the formation interval with channels no less than the length of the zone of stress concentration in the rocks from the wellbore. A pipe string with a packer is lowered, the packer is set above the roof of the perforated productive formation, and gelled fracturing fluid is pumped into the subpacker zone. A linear gel with the simultaneous addition of a borate crosslinker and destructor is used as a gelled rupture fluid. After completing the injection of the gelled fracturing fluid with fracture anchorage into the pipe string, they are forced into the formation by the process fluid, held for the time necessary for the injection pressure to decrease by 70-80% of the pressure of the gelled fracturing fluid with the fracture anchorage being pushed into the formation, and the packer is unpacked , remove it and the pipe string to the surface.

The well is put into operation.

The production well mode did not change - liquid flow rate was 15 m ³ /day with a drawdown of 24 atm. The injection well mode also did not change - the injectivity is 100 m ³ /day at a bottomhole pressure of 90 atm. Then the set of works is repeated at another reacted production well to inject a mixture of surfactant and polymer. Development is carried out until a section of the oil deposit is depleted.

An increase in oil flow rate from 3.5 tons/day to 8.5 tons/day (Fig.), which in additional (to the effect of surfactant-polymer flooding) accumulated oil production amounts to 1400 tons in 3 years.

The proposed method for increasing oil recovery allows increasing the sweep and displacement coefficient through an integrated approach to reservoir development with the simultaneous use of intensification using hydraulic fracturing technology in the surfactant-polymer flooding area, which ultimately leads to increased oil recovery.

Claims (1)

A method for increasing oil recovery of a reservoir, including determining the injectivity of an injection well, preparing and pumping a mixture of surfactants with a polymer through the injection well, withdrawing oil through production wells, characterized in that a section of the oil deposit is selected with a ratio of injection wells to production wells of 1:3-1:5, then oil is sampled through production wells to measure flow rates, interfacial tension between oil and water, water viscosity, the arrival of a shaft of oil to one of the production wells is determined by the increase in flow rates, a 2-fold decrease in the value of interfacial tension between oil and water and an increase in 1.5 times the water viscosity value, then after the oil flow rate has decreased from the maximum value by 12.5%, hydraulic fracturing is carried out in this production well, after hydraulic fracturing the production well is put into operation and the set of works is repeated at another reacted production well for injection of a mixture of surfactant and polymer, development is carried out until the development of a section of the oil deposit.