Asynchronous co2 injection recovery method in different wells with symmetrical fractures

Abstract

The invention relates to a different-well asynchronous CO2-injecting oil extracting method adopting symmetric-type crack distributing. The different-well asynchronous CO2-injecting oil extracting method comprises the following steps that a well opening oil extracting valve of a horizontal well I is closed, and CO2 is injected into an oil sleeve annular space I and enters an odd stage crack; a well opening of the horizontal well I is closed, and two horizontal wells are simultaneously stewed; a well opening of a horizontal well II is opened to extract oil, and crude oil is generated from an even stage crack and pumped into an oil sleeve annular space II; a well opening oil extracting valve of a horizontal well II is closed, and CO2 is injected into an oil pipe II and enters an annular space formed by a flow guiding pipe II, a casing pipe II and the oil pipe II through a perforating hole II and then enters the odd stage crack; the well opening of the horizontal well II is closed, and the two horizontal wells are simultaneously stewed; and the well opening of the horizontal well I is opened to extract the oil, and the crude oil is generated from the even stage crack and enters an annular space formed by a flow guiding pipe I, a casing pipe I and an oil pipe I and then enters the oil pipe I through a perforating hole I. The different-well asynchronous injecting and extracting method can effectively displace residual oil between the wells, between the cracks and in a dead oil area.

Description

technical field [0001] The invention belongs to the technical field of oil and gas reservoir development, and in particular relates to asynchronous injection of CO in different wells with symmetrical fracture layout 2 Oil recovery method. Background technique [0002] In recent years, due to the drastic reduction in the recoverable resources of conventional oil and gas, the exploration and development of unconventional oil and gas has become a new focus, and tight oil is one of them. Tight oil reservoirs are usually developed by depletion at the initial stage of development, but the natural energy of tight oil reservoirs in my country is generally insufficient, and the depletion recovery method alone will cause a rapid drop in reservoir pressure and a rapid decline in production, so energy supplementation is required after a period of development , such as water injection development, CO injection 2 development etc. [0003] Due to the low porosity and permeability of tigh...

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Problems solved by technology

[0003] Due to the low porosity and permeability of tight reservoirs, poor formation connectivity, large seepage resistance, and high heterogeneity, a series of problems may occur when using conventional water injection methods and injection-production well patterns: the injection pressure of water injection wells Usually large, injection is difficult; water channeling is easy to form; and because the seepage resistance of the formation is relatively large, and the flow capacity of the injected water in the formation is poor, resulting in a relatively small swept volume and a relatively limited increase in production of a single well, etc.

Although this invention patent can increase the oil recovery rate, due to the single-well injection and production, for oil and gas reservoirs with a large oil layer area, the swept volume, sweep efficiency and recovery degree will be limited, thereby reducing the oil recovery. Realize the displacement of the dead oil zone in the formation

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