非达西渗流效应对低渗气藏水平井产能的影响

Impact of non-Dacy seepage effect on deliverability of horizontal wells
in low permeability gas reservoirs

唐林 郭肖 苗彦平 刘玉奎 陈晨

西南石油大学油气藏地质及开发工程国家重点实验室，四川 成都 610500

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

低渗气藏普遍具有低孔、低渗、高含水的特征，气体渗流时表现出明显的非达西渗流效应，如启动压力梯度、应力敏感及滑脱效应。目前已有的考虑应力敏感的低渗气藏产能模型均基于Terzaghi有效应力理论，但该理论并不适用于描述岩石的应力敏感性，引入新的拟压力函数，综合考虑启动压力梯度、滑脱效应及基于本体有效应力理论的应力敏感的影响，推导出了修正的低渗气藏水平井产能方程。以某低渗气藏为例，分别研究这些效应对产能的影响程度。结果表明：基于Terzaghi有效应力理论的应力敏感使得水平井产气量平均降幅为13.28%，而基于本体有效应力理论（实际）的平均降幅仅为1.80%。因此，在低渗气藏开发中应采用基于岩石本体有效应力理论的关系式。

The low permeability gas reservoirs are generally characterized by low porosity, low permeability and high water cut, resulting in the obvious non-Darcy seepage effect of gas percolation, such as start-up pressure gradient, stress sensitivity and slippage effect. Current studies on low permeability gas reservoirs are all based on Terzaghi effective stress theory, which can not be applied in describing the stress sensitivity. Therefore, introducing a novel pseudo-pressure function, a modified deliverability model for horizontal wells in low permeability gas reservoirs has been derived by taking into consideration of threshold pressure gradient, stress sensitivity based on the theory of primary effective stress and slippage effect. Those effects mentioned above are studied based on a real low permeability gas reservoir. The study results show that the stress sensitivity based on Terzaghi effective theory makes the gas flow of horizontal well decrease by 13.28% on the average. The gas well production based on the theory of primary effective stress decreases by 1.80% on the average. Therefore, the relational expression based on the theory of primary effective stress can be used in the process of low permeability gas reservoir development.

10.6056/DKYT201305015