多段压裂水平井不均匀产油试井模型

A pressure transient analysis model of multi-fractured horizontal well in consideration of unequal production of each fracture

针对某条或多条裂缝产油量较小或不产油这一问题,运用Green函数、Newman乘积方法和叠加原理,建立多段压裂水平井不均匀产油试井模型,将裂缝内流动划分为远离井筒的变质量线性流和靠近井筒的径向流表征裂缝有限导流,利用Stehfest数值反演得到考虑井筒存储和表皮效应的实空间井底压力解,绘制典型图版,并分析不均匀产油和裂缝参数对井底压力的影响。结果表明:多段压裂水平井均匀产油和不均匀产油的压力和压力导数特征差异明显;两端裂缝产油量越大,压裂裂缝间距越大,裂缝半长越小,裂缝呈纺锤形分布时,缝间干扰越小,早期径向流越明显,在系统拟径向流之前出现一个新平台。与试井软件Saphir中的经典多级压裂水平井数值模型对比,结果证明了提出的模型的正确性。

In this study, the effect of unequal production of each fracture （ UPEF） on well testing behavior was considered in order to develop a pressure transient analysis （PTA） model for multi-fractured horizontal wells （MFHW） , and semi-analytical solutions were given based on the Green＇s function, the Newman＇s product method and superposition principles. The flow in a hydraulic fracture is divided into two flow regimes （ i. e. a variable-mass linear flow far from the horizontal wellbore and a radial flow near the horizontal wellbore） to characterize the finite conductivity flow within the fractures. Then, characteristic pressure curves wee obtained using a numerical Stehfest inversion algorithm,and sensitivity analysis （e. g. UPEF, fracture and parameters） was further conducted. The analysis results indicate that there are obvious differences among the type curves obtained via assuming an equal production of each fracture （EPEF） and the UPEF. The early-radial flow behaves as a horizontal line in the pressure derivative curves when the fractures located at the ends of wellbore contribute much more to total oil production than those at the middle section, or when the fractures are wide-spaced and short, or when the fractures behave as spindle shape. In comparison with the classic PTA model of the MFHW in Saphir software, the accuracy and reliability of the newly proposed model has been proven.