非达西渗流效应对考虑原油压缩系数低渗透油藏直井产能的影响

Impact of non-darcy flow on vertical well productivity of low-permeability reservoirs considering oil compressibility

低渗透油藏普遍具有低孔、低渗特征,导致其油水渗流存在非线性和流态的多变性,使得流体的渗流不再符合经典的达西定律。考虑启动压力梯度、原油压缩系数和基于岩石本体有效应力理论的应力敏感效应的综合影响,推导出修正的低渗透油藏直井产能方程。以某低渗透油藏为例,研究启动压力梯度、原油压缩系数应力敏感效应对其产能的影响。结果表明低渗透油井中启动压力梯度比应力敏感和原油压缩系数对产能的影响更为强烈,建议低渗透油藏直井产能预测时必须充分考虑启动压力梯度的影响。

There are nonlinearity of water/oil percolation and multi - variability of flow regime in low - permeability oil reservoirs due to the reservoirslow porosity and low permeability. As a result,the fluid percolation is inconsistent with the traditional Darcy law. Considering the comprehensive influences of start - up pressure gradient, oil compressibility and stress sensitivity based on the theory of rock primary effective stress, an improved equation of vertical well productivity of low permeability reservoir is deduced. The effects of start - up pressure gradient, oil compressibility and stress sensitivity are studied by real data from a low - permeability reservoir. Results indicate the impact of start - up pressure gradient on the productivity is much stronger than that of stress sensitivity and oil compressibility. It suggests that start - up pressure gradient effect should be taken into consideration to predict the productivity of vertical well of low permeability reservoirs.