地下储气库井管柱沿程流体状态数值模拟

Numerical simulation on the state of fluids along the string of gas storage well

确定注采过程中天然气在油管柱内的运动状态是分析储气库井管柱受力、确定冲蚀位置的关键。根据井身结构和运行参数建立天然气流经储气库定向井油管柱过程的物理模型,通过数值试验研究造斜段管柱内沿程速度、涡量和近壁压力分布;分析注采压差、井斜角及油管内径对管柱近壁压力的影响规律。结果表明:油管柱内流体状态受注采压差和井身结构影响,天然气流速和近壁压力在流入流出造斜段时发生波动;管柱沿程速度和动压随井深增大而减小,冲蚀点位置出现在造斜段流入端和流出端管柱中心线与最大狗腿角位置径向线的连线上;随着注采压差增大,流入端和流出端弯曲外侧和内侧平均压程比均明显增大;随着井斜角增大,流入端弯曲外侧和内侧的平均压程比增大,流出端弯曲外侧和内侧的平均压程比减小;随着油管内径增大,流入端弯曲外侧和内侧的平均压程比减小,流出端弯曲外侧和内侧的平均压程比增大。

To analyze the force applied on the string of gas storage well and determine the erosion position,it is crucial to figure out the motion state of natural gas in the tubing string in the process of gas injection and production.In this paper,a physical model used to simulate the flowing process of natural gas along the tubing string of directional gas storage well was established on the basis of casing program and operation parameters.Then,the velocity and vorticity along the string and the distribution of pressure close to the wall in the deflecting section were researched by means of numerical experiment.And finally,the influential laws of injection-production pressure difference,hole deviation angle and tubing ID on the pressure close to the wall of string were analyzed.It is indicated that the state of fluids inside the tubing string is affected by injection-production pressure difference and casing program,and the flow velocity of natural gas and its pressure close to the wall fluctuate the moment it flows into and out of the deflecting section.The velocity and dynamic pressure along the string decrease as the well gets deep.Erosion point is located at the connection line between the radial line at the maximum dogleg angle and the central line of string from the inflow end to the outflow end of deflecting section.As the injection-production pressure difference increases,the average pressure range ratio between the outside and the inside of the bend at inflow and outflow ends increases obviously.With the increasing of hole deviation angle,the average pressure range ratio between the outside and the inside of the bend at the inflow end increases while that at the outflow end decreases.And with the increasing of tubing ID,the average pressure range ratio between the outside and the inside of the bend at the inflow end decreases while that at the outflow end increases.