摘要
基于分形理论和分数阶微积分,建立具有割理(裂缝)系统应力敏感性的煤层气藏多级压裂水平井半解析模型;采用线源理论、数值离散和叠加原理等方法,求解拉式空间下的井底压力解;利用Stehfest数值反演技术,绘制真实空间下的无因次试井曲线,进行相关参数的敏感性分析。结果表明:根据导数曲线的不同特征,划分为8个不同的流动阶段,即井筒储集效应阶段、表皮效应阶段、第一线性流阶段、第一径向流阶段、第二线性流阶段、割理系统径向流阶段、窜流阶段和整体径向流阶段,拟渗透率模量和反常扩散系数增加,压力和压力导数曲线后期上升;分形维数减小,压力和压力导数曲线上升;水力裂缝半长变大,第一线性流阶段持续时间变长,第一径向流持续时间缩短;水力裂缝间距变短,第二线性流阶段出现时间变早,第一径向流阶段持续时间变短;水力裂缝条数越多,中期压力和压力导数曲线位置越低。该结果为更好地理解煤层气藏压裂水平井的渗流规律提供指导。
Based on the fractal theory and the fractional calculus,a semi-analytical model for MFHWs in the coal bed methane reservoir is established,which also takes the stress sensitivity of the cleat system into consideration.Through line-sink theory element discretization,superposition principle and other series of l methods,the bottom hole pressure in the Laplace domain is obtained.By Stehfest numerical technology,dimensionless well test curves in the real time domain are drawn and sensitivity analysis is made.Relevant results indicate that eight different flow regimes are identified according to different features of the derivative curve,they are the wellbore storage period,the skin effect period,the first linear flow period,the first radial flow period,the second linear flow period,the pseudo-radial flow period of the cleat system,the cross-flow period and the late-radial flow period of the whole system.When the pseudo-permeability modulus and the anomalous diffusion coefficient become bigger,the pressure and pressure derivative curves will increase in the later period.The smaller fractal dimension will cause the higher position of the pressure and pressure derivative curves.The longer the half-length of the hydraulic fracture,the longer the duration of the first linear flow period becomes and the shorter the first radial flow period becomes.The shorter the distance between each hydraulic fracture,the earlier the second linear flow period appears and the duration of the first radial flow period is shorter.The more hydraulic fractures cause the lower position of the pressure and pressure derivative curves in the middle time.The relevant results can provide theoretical guidance for better understanding the seepage of MFHWs in coal bed methane reservoir.
作者
姜瑞忠
王星
王琼
刘秀伟
JIANG Ruizhong;WANG Xing;WANG Qiong;LIU Xiuwei(School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,Shandong 266580,China)
出处
《东北石油大学学报》
CAS
北大核心
2020年第3期97-106,I0007,共11页
Journal of Northeast Petroleum University
基金
国家科技重大专项(2017ZX05013-002)
国家自然科学基金项目(51574265)。
