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考虑热流固耦合作用的多孔介质孔隙尺度两相流动模拟

PORE-SCALE SIMULATION OF MULTIPHASE FLOW CONSIDERING THERMO-HYDRO-MECHANICAL COUPLING EFFECT IN POROUS MEDIA

  • 摘要: 为了研究深层油气资源在岩石多孔介质内的运移过程, 使用一种基于Darcy-Brinkman-Biot的流固耦合数值方法, 结合传热模型, 完成了Duhamel-Neumann热弹性应力的计算, 实现了在孔隙模拟多孔介质内的考虑热流固耦合作用的两相流动过程. 模型通过求解Navier-Stokes方程完成对孔隙空间内多相流体的计算, 通过求解Darcy方程完成流体在岩石固体颗粒内的计算, 二者通过以动能方式耦合的形式, 计算出岩石固体颗粒质点的位移, 从而实现了流固耦合计算. 在此基础上, 加入传热模型考虑温度场对两相渗流过程的影响. 温度场通过以产生热弹性应力的形式作用于岩石固体颗粒, 总体上实现热流固耦合过程. 基于数值模型, 模拟油水两相流体在二维多孔介质模型内受热流固耦合作用的流动过程. 研究结果表明: 热应力与流固耦合作用产生的应力方向相反, 使得总应力比单独考虑流固耦合作用下的应力小; 温度的增加使得模型孔隙度增加, 但当注入温差达到150 K后, 孔隙度不再有明显增加; 温度的增加使得水相的相对渗流能力增加, 等渗点左移.

     

    Abstract: Researches on the thermo-hydro-mechanical (THM) coupling effect in porous media from the perspective of pore-scale is of great significance for the study of enhanced oil recovery, nuclear storage, and geological sequestration of CO2. In order to study the migration of oil resources in porous media in the deep oil reservoir, we used a combined method to realize the THM process occurring in porous media. The Darcy-Brinkman-Biot method was applied to simulate the THM process and the calculation of thermal stress was achieved by adding the Duhamel-Neumann thermoelastic stress to the model. A water-oil two-phase flow process considering THM coupling effect in porous media was then realized. The model has simulated flow of multiphase fluid in the pore space by solving the Navier-Stokes equations and calculated flow of the fluid in the rock matrix by solving the Darcy equation. The two processes were coupled with a series of momentum exchange equations to obtain the displacement of solid particles, thus realizing the fluid-solid coupling effect. On this basis, a heat transfer model was added to numerical model to consider the influence of temperature field on the two-phase flow process. Temperature field acts on the matrix in the form of thermoelastic stress to realize the THM coupling process. Based on the model, we simulated the flow process of water-oil two-phase fluid in a two-dimensional porous media model. The results have shown that: (1) the direction of thermal stress was opposite to that generated by fluid-structure coupling effect, which made the total stress smaller than that under the fluid-structure coupling effect; (2) the porosity of the model increased with the increase of temperature, however, when the injection temperature difference reached 150 K, the porosity no longer increased significantly; (3) with the increase of temperature, the relative permeability of the water phase increased and the equal-permeability point shifted to the left.

     

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