RU2821497C1 - Method for development of oil deposit located under gas deposit - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: method of developing an oil deposit located under a gas deposit includes opening of productive formation and underlying water-bearing formations by injection wells, opening of productive formation with horizontal production wells, flooding of productive formation by downhole pumping in injection wells from water-bearing formations to oil-bearing formation, extraction of product from productive formation through production wells. Injection wells are drilled along the oil-bearing contour of the deposit. Shafts of horizontal production wells with length of 300 m are placed at distance of 200–250 m from injection wells across the displacement front. At that, injection into productive formation on deposit is carried out from the very beginning of deposit development due to downhole pumping from water-bearing formations in injection wells with formation water injection volume, equal to 1.1–1.3 of the volume of production from horizontal production wells, and maintaining formation pressure in the horizontal production well at the initial level to exclude gas breakthrough into the oil-saturated part from the gas cap.

EFFECT: higher oil displacement coefficient and increased production of oil reserves, as well as exclusion of gas breakthrough into oil-saturated part of the deposit.

1 cl

Description

The invention relates to the oil industry and can be used in the development of an oil deposit located under a gas deposit.

There is a known method for developing a section of an oil deposit (patent RU No. 2807319, MPK E21B 43/20, publ. November 14, 2023, Bulletin No. 32), including opening the productive formation and underlying aquifers with injection wells, opening the productive formation with production wells, waterflooding productive formation by in-well pumping in injection wells from aquifers into oil-bearing formations, selection of products from the productive formation through production wells. Waterflooding of the productive formation in the deposit area is carried out by in-well pumping of formation water in injection wells from the underlying aquifer-donor formation to the overlying oil-bearing reservoir-acceptor with a pressure 15% higher than the initial formation pressure and not exceeding the threshold for the formation of auto-hydraulic fracturing cracks, and the volume of formation water for pumping is 1.1 of the volume of produced products from surrounding production wells, and the cycle of pumping formation water in injection wells is 25 calendar days, while over the next 3 days the injection wells are idle, then a high-yield well is identified on the site and one day before the injection is stopped wells are stopped for 5 days to redistribute the injected formation water into nearby production wells in the area with deteriorated filtration and capacitance properties.

There is a known method for developing oil deposits in carbonate reservoirs (patent RU No. 2515741, MPK E21B 43/20, published May 20, 2014, Bulletin No. 14), including opening the productive formation and underlying aquifers with injection wells, followed by construction and secondary opening formations, opening of the productive formation by production wells with subsequent construction and opening of the productive formation, waterflooding of the productive formation by in-well pumping in injection wells from aquifers to the oil-bearing formation, selection of products from the productive formation through production wells. Waterflooding of the productive formation is carried out with constant pressure with alternating technological downtime of injection wells for no more than 4 days, and pressure compensation by waterflooding during downtime of injection wells is carried out at the expense of nearby injection wells.

The disadvantages of these methods are the low oil displacement coefficient, the possibility of gas breakthrough into the oil-saturated part of the deposit, and uneven production of oil reserves.

The technical objectives of the proposed method are to increase the oil displacement coefficient by using its own formation water, to eliminate gas breakthrough into the oil-saturated part of the reservoir, and to increase the production of oil reserves.

A method for developing an oil reservoir located under a gas reservoir, including opening up a productive formation and underlying aquifers with injection wells, opening up a productive formation with horizontal production wells, flooding a productive formation by in-well pumping in injection wells from aquifers to an oil-bearing formation, withdrawing products from the productive formation through production wells.

What is new is that injection wells are drilled along the oil-bearing contour of the deposit, and the trunks of horizontal production wells 300 m long are placed at a distance of 200-250 m from the injection wells across the displacement front, while injection into the productive formation of the deposit is carried out from the very beginning of the development of the deposit after account of in-well pumping from an aquifer in an injection well with a volume of formation water injection equal to 1.1–1.3 of the volume of produced products from horizontal production wells and maintaining reservoir pressure in a horizontal production well at the initial level to prevent gas breakthrough into the oil-saturated part of the gas cap .

The method is implemented in the following sequence.

Injection wells are drilled along the oil-bearing contour of the deposit, and the trunks of horizontal production wells 300 m long are placed at a distance of 200-250 m from the injection wells across the displacement front. Products are selected from the productive formation through production wells.

Waterflooding of the productive formation in the deposit area is carried out by in-well pumping of formation water in injection wells from aquifers into the oil-bearing formation. In this case, injection into the productive formation of the deposits is carried out from the very beginning of the development of the deposit due to in-well pumping from the aquifer in the injection well with the volume of injection of formation water equal to 1.1–1.3 of the volume of produced products from horizontal production wells and maintaining formation pressure in the production horizontal well at the initial level to prevent gas breakthrough into the oil-saturated part of the gas cap.

An example of a specific implementation of the method

A gas-oil multilayer reservoir is drilled with horizontal production wells along a uniform triangular grid with a distance between wells of 400 m. Injection wells are drilled along the oil-bearing contour of the deposit, and equipment is lowered for downhole pumping. Horizontal wells with a trunk length of 300 m are drilled across the displacement front at a distance of 220 m from the injection wells.

To monitor the depletion of the aquifer, MIG downhole pressure gauges are installed in injection wells. Based on the results of core studies and geophysical studies of wells, the following values were obtained: porosity 13%, permeability 139 mD, oil saturation 76%, average oil-saturated thickness 1.8 m, initial reservoir pressure 9.8 MPa.

They carry out hydrodynamic studies, measurements of the current reservoir pressure of the productive formation, and geological and hydrodynamic modeling.

Horizontal production wells are put into operation with a liquid flow rate of 89 m ³ /day and, at the same time, injection wells with equipment for downhole pumping (ISP), water is taken from the aquifer and pumped into the oil-bearing reservoir with a volume of 1.2 of the volume of the produced liquid, which will be 106 .8 m ³ /day. Reservoir pressure is kept at the initial value of 9.7 MPa.

Thanks to the use of the proposed method, the oil displacement coefficient increases due to the use of its own formation water, gas breakthrough into the oil-saturated part of the deposit does not occur, and the production of oil reserves increases.

Claims (1)

A method for developing an oil deposit located under a gas reservoir, including opening up a productive formation and underlying aquifers with injection wells, opening up a productive formation with horizontal production wells, flooding a productive formation by in-well pumping in injection wells from aquifers into an oil-bearing formation, withdrawing products from the productive formation through production wells, characterized in that injection wells are drilled along the oil-bearing contour of the deposit, the trunks of horizontal production wells 300 m long are placed at a distance of 200-250 m from the injection wells across the displacement front, while injection into the productive formation of the deposit is carried out from the very beginning of the development of the deposit after account of in-well pumping from aquifers in injection wells with a volume of formation water injection equal to 1.1-1.3 of the volume of produced products from horizontal production wells, and maintaining reservoir pressure in the horizontal production well at the initial level to prevent gas breakthrough into the oil-saturated part from gas cap.