考虑启动压力梯度的面积井网极限井距计算

低渗透储层具有低孔、低渗特征，其孔隙结构异常复杂，表现出非达西渗流，存在启动压力梯度现象。本文在归纳总结启动压力梯度的表现形式基础上，得出启动压力梯度应综合反应储层和流体特性，即应与流度存在相应的关系。并选取某油田盐膏层间低渗透致密岩心，通过实验研究，得出了启动压力梯度与流度之间的关系式。在考虑启动压力梯度情况下，推导出直井、水平井极限井距计算公式，研究直井极限井距与渗透率、生产压差之间的关系。并通过控制变量法，研究了水平井长度、岩石渗透率、流体粘度、生产压差对水平井极限井距的影响，得出相应的图版。且在研究单口直井、水平井极限井距的基础上，扩展到不同类型井网组合井距的计算。最后通过实例结果验证，此方法简单、实用，对确定低渗透储层合理井网井距具有重要的指导意义。

Calculating the limit well spacing of area well pattern considering threshold pressure gradient

The low permeable reservoirs have unusually complex pore structure with low porosity and permeability. And it shows that the non-Darcy flow and existing threshold pressure gradient. In this paper, we conclude that the threshold pressure gradient should comprehensively reflect the features of reservoir fluid property, which should exist corresponding relationship with mobility, by summing up the form of threshold pressure gradient. We choose the dense core of low permeability between the salt-gypsum layers in certain oilfield and obtain the relational expression between the threshold pressure gradient and the mobility by experiment researching. We elicit the computational formula of limit well spacing for the vertical well and horizontal well, studying the relationship between the limit spacing of vertical well and the permeability, production pressure. We also study the impact of the horizontal well length, the rock permeability, fluid viscosity, production pressure on the horizontal well limit spacing by using control variable method, draw the corresponding chart, and extend to calculating the combination spacing of different well patterns based on the researching one vertical well, horizontal well limit well spacing. This method is simple and practical through example results and has important guiding significance for deciding the reasonable well pattern and well spacing.