页岩气水平井生产压降计算新模型

New Production Pressure Drop Calculation Model for Shale Gas Horizontal Well

页岩气水平井井筒流动规律复杂,常规井筒压降模型适应性各不相同。为了提高水平井井筒压力和流态分布预测准确度,通过国内外大量实验数据优化了井筒压降模型的流型转换界限,并在泡状流、段塞流条件下使用M-B模型持液率和无滑脱摩阻系数,环雾流条件下使用B-B模型持液率和滑脱摩阻系数,分层流条件下考虑液滴夹带的持液率和滑脱摩阻系数,建立了页岩气水平井生产压降计算新模型。通过与15口井实测压力分布数据对比,结果表明新模型在小水量大气量下的误差为4.03%,相比于B-B模型降低了6.05%;大水量下的误差为5.96%,相比于M-B模型降低了13.12%;平均相对误差为4.34%,相比于M-B模型降低了31.65%,相比于B-B模型降低了73.14%,新模型准确度更高,适用范围更广。采用新模型对N209H15-2页岩气水平井井筒压力与流态进行了实例应用,计算得到的压力分布与测压数据吻合度很高,并且可得到该井不同气水比下包含分层流的井筒流态变化特征。可见新模型扩展了对页岩气水平井井筒流动规律的认识,为排水采气工艺措施的制定提供了理论支撑。

Complicated wellbore flow law of shale gas horizontal wells urged variable adaptability of conventional wellbore pressure drop models. In order to improve the prediction accuracy of wellbore pressure and flow pattern distribution in horizontal wells, the flow pattern boundary equation of wellbore pressure drop model was optimized through a large number of experimental data at home and abroad, a new pressure drop calculation model of shale gas horizontal well is established based on the conditions of bubble flow and slug flow in which the liquid holdup and non slip friction coefficient of M-B model are used, and under the condition of annular fog flow in which the liquid holdup and slip friction coefficient of BB model are used, and under the condition of stratified flow in which the liquid holdup and slippage friction coefficient of droplet entrainment is considered. Compared with the pressure distribution data of 15 wells, the results show that the error of the new model under small water amount and large gas volume is 4.03%, which is 6.05% lower than B-B model. The error under large water volume is 5.96%, which is 13.12% lower than M-B model. The average relative error is 4.34%, which is 31.65% lower than M-B model and 73.14% lower than B-B model. The new model has higher accuracy and wider application scope. The new model was applied to the wellbore pressure and flow pattern of N209 h15-2 shale gas horizontal well, and the changes of wellbore flow pattern include stratified flow under different gas water ratio were obtained and the calculated pressure distribution is in good agreement with the pressure measurement data. The new model expands the understanding of wellbore flow law of shale gas horizontal wells and provides theoretical support for the formulation of drainage and gas production process measures.