Method for determining gas diffusion coefficient under heavy oil thermal recovery condition

Abstract

The invention belongs to the technical field of oil and gas field development engineering, and particularly relates to a method for determining a gas diffusion coefficient under a heavy oil thermal recovery condition, which is used for determining the diffusion coefficient of gas in a saturated heavy oil core under a one-dimensional heat transfer condition. The method includes: obtaining an experimental pressure curve in the diffusion process through a pressure drop method; on the basis of determining the temperature field, considering the influence of temperature change on crude oil and rock physical property parameters; calculating theoretical pressure in the diffusion process through a PR state equation; and fitting the actually measured pressure curve and the calculated theoretical pressure curve through a genetic algorithm to obtain the diffusion coefficient of the gas in the saturated heavy oil rock core under the one-dimensional heat transfer condition. According to the method for determining the gas diffusion coefficient under the heavy oil thermal recovery condition, the change of oil reservoir physical property parameters in the heat transfer process is considered, the calculated gas diffusion coefficient is closer to reality, more accurate reference is provided for a heavy oil thermal recovery scheme, the predicted recovery rate is more accurate, and the recovery cost and risk are reduced.

Description

technical field [0001] The invention relates to a method for determining the gas diffusion coefficient under the thermal recovery condition of heavy oil, and belongs to the technical field of oil and gas field development engineering. Background technique [0002] Heavy oil has the characteristics of high viscosity, poor fluidity and high difficulty in extraction under reservoir conditions, making thermal oil recovery an effective way to extract heavy oil. On the basis of steam injection, auxiliary gas (N 2 , CO 2 , flue gas, etc.) can effectively supplement formation energy, reduce heavy oil viscosity and expand steam heating range, which can improve thermal recovery effect. In the stage of steam huff and puff, the fluid in the reservoir cannot seep, and diffusion is the main migration mode. The gas diffusion coefficient is the main parameter to describe the diffusion, which determines the concentration and migration distance of gas diffusion at different times in the re...

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Problems solved by technology

[0004] However, in the actual thermal recovery process of heavy oil, the change of temperature field greatly affects the physical parameters of the reservoir, which in turn affects the recovery factor.

Chinese patent documents CN106840973B, CN106872594B and CN112198093A disclose methods for measuring the diffusion coefficient of gas in saturated oil cores under constant temperature conditions, but do not involve changes in the temperature field. The diffusion coefficient calculated by the method of the above patent documents is consistent with the actual heavy oil thermal recovery process inconsistency in

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