考虑压力敏感效应和启动压力梯度的低渗透气藏水平井产能研究

低渗透气藏由于普遍具有低孔、低渗的特征,导致其气水渗流具有非线性特征和流态的多变形,进而储层流体的渗流不再遵循经典的达西定律。结合岩石本体有效应力相关理论,在前人的基础上,推导了低渗透气藏水平井产能公式,该公式综合考虑了压力敏感效应和启动压力梯度的影响,更加接近于实际气藏,更能准确的对低渗透气藏水平井产能进行评价。实例计算表明:在低渗透气藏水平井产能分析中,必须考虑压力敏感效应和启动压力梯度;且随着压力敏感系数和启动压力梯度的增大,水平井产量降低。水平井产能随着生产压差的增大而增大,但气井产能指数却是先快速上升,然后再缓慢降低。因此对于低渗透气井而言,存在一个生产压差的最优值。

The study on horizontal well productivity in low permeability gas reservoir by considering pressure sensitive effect and kickoff pressure gradient

:As the low permeability gas reservoir generally has the characteristic of low porosity and low permeability, it makes the gas water seepage has nonlinear characteristics and flow pattern of deformation, and also the seepage of reservoir fluid no longer follow the classic Darcy law. In combination with primary effective stress related theory, basing on the basis of the predecessors, well productivity formula of the low permeability gas reservoir horizontal is deduced. It considers the pressure sensitive effect and the influence of starting pressure gradient, and it is more close to the actual gas reservoir, and it can more accurately evaluate the horizontal wells productivity in low permeability gas reservoir. Example calculation shows that: in the horizontal well productivity analysis of low permeability gas reservoir, pressure sensitive effect and the start-up pressure gradient must be considered, and with the increase of the pressure sensitive coefficient and start-up pressure gradient, the horizontal well production is reduced. Horizontal well production increases with the increase of production pressure difference, but the gas well productivity index is rising fast first, and then slow down. For low permeability gas well, there is a optimal value of the production pressure difference.