CO2 drive technological limit well spacing determination method for low-permeability oil reservoir

Abstract

The invention provides a CO2 drive technological limit well spacing determination method for a low-permeability oil reservoir. The method comprises the steps that the minimum miscible pressure of CO2 and crude oil is determined through a long-thin pipe displacement test; through a rock core displacement test, with the combination of the minimum miscible pressure of the crude oil, the relational expression of the change of starting pressure gradient along with fluidity under the miscible phase and immiscible phase conditions is determined; a calculation formula of a CO2 drive technological limit oil supply radius is established through an oil reservoir engineering method; through a site test method or an oil reservoir numerical simulation method, stratum pressure distribution conditions are obtained, a miscible phase area and an immiscible phase area are determined, and the proportionality coefficient of the miscible phase area and the immiscible phase area is calculated; and through a calculation formula of CO2 drive technological limit well spacing, stratum technological limit well spacing under the current condition is obtained through calculation. According to the CO2 drive technological limit well spacing determination method for the low-permeability oil reservoir, oil field potential is further exploited, economically recoverable reserves are increased greatly, the resource exploitation basis is enhanced, and the crude oil recovery ratio is further increased.

Description

technical field [0001] The invention relates to a calculation method for injection-production well spacing in oilfield development, in particular to a low-permeability reservoir CO 2 Method for determining the limit well spacing of flooding technology. Background technique [0002] With the continuous improvement of exploration and development technology, the important position of low-permeability reservoirs in my country's oil development has become increasingly obvious regardless of their reserves and production. However, due to the limitation of reservoir conditions, the development effect is relatively poor. Oil agent, used for oil displacement can greatly increase the production rate and recovery rate of this type of oil reservoir, and its development effect has been significantly improved. [0003] Well pattern and well spacing are the key to the design of carbon dioxide flooding schemes, especially the injection-production well spacing has an important impact on the d...

AI Technical Summary

Problems solved by technology

Laboratory experiments have shown that due to the low permeability of low-permeability reservoirs, there is a start-up pressure gradient in carbon dioxide flooding, and effective displacement can only be achieved if the displacement pressure gradient between injection and production wells is greater than the start-up pressure gradient, so there is a limit injection-production well spacing

If the injection-production well spacing is too small, it is easy to cause premature gas channeling and affect the development effect; if the injection-production well spacing is too large, the displacement between injection-production wells cannot be realized, and the production wells are elastically developed, with low recovery

At the same time, carbon dioxide is affected by pressure between injection and production wells, and there will be three states: miscible, miscible and immiscible engineering, and immiscible. There is a large gap between the start-up pressure gradient and the technical limit well spacing of these three states

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