致密砂岩储层水平井螺旋射孔参数优化研究

射孔孔眼连接井筒和储层,提供泄油通道、有效降低储层破裂压力和引导裂缝走向。开展大型真三轴物理模拟试验,研究射孔长度、射孔密度、射孔孔径、射孔相位和射孔簇间距对裂缝起裂特征、扩展形态和储层破裂压力的影响规律。试验结果表明:射孔参数的改变本质上是改变射孔孔间距,孔间距决定孔眼之间的连通性,影响近井筒裂缝扩展形态和岩石破裂压力;射孔孔径和射孔密度的增加,减小孔间距,有利于裂缝间相互沟通,降低近井筒裂缝复杂性和岩石破裂压力;射孔相位的增大,增大孔间距,易产生分层复杂裂缝,岩石破裂压力增高;而射孔长度和射孔簇间距的变化对裂缝扩展形态没有影响。根据试验结论,给现场提出了射孔参数优化的理论基础和施工建议。

Parameter optimization of spiral perforations in horizontal well with tight sandstone reservoir

The perforation, a channel connecting wellbore with reservoir, provides the path of oil drainage, reduces the fracturing pressure of reseroir, and determines the direction of fracture propagation. A series of large true tri-axial physical simulation experiments are conducted to study the effects of perforation length, density, diameter, phase and spacing on the characteristics of fracture initiation, behaviors of fracture propagation and fracturing pressure. The experimental results show that the change of perforation parameters affects the perforation spacing, and the distance of two adjacent perforations. It decides the interaction between the two adjacent perforations, and then determines the fracture propagation geometry. The increasing perforation diameter and density reduce the perforation spacing, which is beneficial for fractures to link up with each other and to decrease fracture complexity and fracturing pressure of nearby well bares. The increase of perforation phase, whereas, enlarges the perforation spacing, forming the layered fracture with a high fracturing pressure. In addition, the changes of the perforation length and spacing have no effect on fracture morphology. Thus, according to the experimental results, some theoretical bases and suggestions about the parameter optimization of perforations are put forward for the field operation.