致密气藏不对称裂缝偏心直井半解析模型及其渗流特征

doi:10.7657/XJPG20220407

摘要/Abstract

摘要：

针对致密气藏不对称裂缝偏心直井渗流问题,根据质量守恒方程建立了不对称裂缝偏心直井数学模型。采用拉普拉斯变换和数值离散方法,得到拉普拉斯空间偏心直井的井底拟压力;利用Stehfest数值反演方法,获得压力和产量分布,并讨论了裂缝角度、裂缝无因次导流能力和偏心距对井底拟压力和产量的影响。借助Saphir试井分析软件,建立了气井的数值模型并进行数值离散计算,将计算结果与半解析解进行对比,验证了数学模型的正确性。同时,根据无因次井底拟压力变化特征,将偏心直井流体流动划分为储集层与裂缝双线性流阶段、储集层线性流阶段、裂缝椭圆流阶段、平面径向流阶段、距离裂缝较近边界控制流阶段和圆形封闭边界控制流阶段。

关键词: 致密气藏, 水力压裂井, 偏心直井, 不对称裂缝, 不对称因子, 井底拟压力, 渗流特征

Abstract:

To understand the flow regime of asymmetrically fractured off-center vertical wells in tight gas reservoirs,a mathematical model for asymmetrically fractured off-center vertical wells was established according to the mass conservation equation. The bottom-hole pseudo pressure of off-center vertical well in Laplace space was obtained by using Laplace transform and numerical discretization. The time-space distribution of pressure and production were determined by using the Stehfest numerical inversion method,and the impacts of fracture angle,dimensionless fracture conductivity and eccentric distance on bottom-hole pseudo pressure and production were discussed. With the help of Saphir well test interpretation software,the numerical model of gas well was built and the numerical calculation for discretization was performed. The calculated results were compared with the semi-analytical solution to verify the mathematical model. Furthermore,according to the variation characteristics of the dimensionless bottom-hole pseudo pressure,the fluid flow in asymmetrically fractured off-center vertical wells was divided into six stages: bilinear flow stage in reservoir and fracture,linear flow stage in reservoir,elliptical flow stage in fracture,plane radial flow stage,near-fracture boundary-dominated flow stage,and circular closed boundary-dominated flow stage.

Key words: tight gas reservoir, hydraulic fractured well, off-center vertical well, asymmetric fracture, asymmetry factor, bottom-hole pseudo pressure, flow characteristic

中图分类号:

TE312

王玉风, 姬安召, 张光生, 陈占军. 致密气藏不对称裂缝偏心直井半解析模型及其渗流特征[J]. 新疆石油地质, 2022, 43(4): 425-432.

WANG Yufeng, JI Anzhao, ZHANG Guangsheng, CHEN Zhanjun. Semi-Analytical Model and Flow Characteristics of Asymmetrically Fractured Off-Center Vertical Wells in Tight Gas Reservoirs[J]. Xinjiang Petroleum Geology, 2022, 43(4): 425-432.

图/表 5

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