摘要
在对油井储层实施爆燃气体压裂过程中,地层参数会对裂缝扩展形态产生影响。建立爆燃气体在裂缝内的流动方程,通过设定与时间相关的气体压力分布函数,实现了爆燃气体沿裂缝压力梯度的求解。应用线弹性断裂力学、弹性力学理论模拟在爆燃气体驱动下裂缝的张开与闭合,得到了裂缝尖端应力强度因子、裂缝扩展速度及裂缝几何形态与气体载荷及地层特性之间的关系方程。模型分析结果表明:在离散时间域内,在特定气体压力作用下,裂缝起裂后,首先迅速以稳定速度传播,后期速度逐渐衰减,且在裂缝扩展过程中显示出相应的动态效果;与裂缝断裂韧性相比,地应力对裂缝形态影响更为明显,是裂缝扩展的主要阻力,地应力越大,裂缝起裂越晚,且裂缝传播速度越小;高弹性模量的岩层有利于裂缝的延伸,可以获得更长的裂缝长度,有利于压裂效果的改善。
During the process of deflagration gas fracturing on oil reservoir,the formation parameters will affect the geometric shape of fracture.By establishing the theoretic model of deflagration gas flow in preliminary fracture,a function describing gas pressure distribution is also proposed herein to realize the resolution of gas pressure gradient along the fracture.Based on the elasticity and line—elasticity fracture mechanics theory,the relation equations about stress strength of fracture top,crack growth velocity,fracture geometric shape,gas loading and formation parameters are derived to stimulate the opening and closing process of fracture.In discrete time—domain and under certain borehole gas pressure,the modeling results show that,after initiation,the fracture extends with stable velocity and decreases gradually in later stage.The process of fracture propagation has the characteristic of dynamic response.Compared to the fracture elasticity,the tectonic stress has more significant effect on fracture shape,and is the main resistance of fracture propagation.The greater tectonic stress is,the smaller fracture growth velocity and relatively later fracture initiation.The information with higher elastic modulus is favorable for fracture extension and can give rise to longer fracture that is beneficial to fracturing performance.
出处
《油气地质与采收率》
CAS
CSCD
北大核心
2011年第1期101-104,118,共4页
Petroleum Geology and Recovery Efficiency
基金
国家科技重大专项专题"海相碳酸盐岩储层改造技术研究"(2008ZX05005-006-05)
关键词
地层参数
爆燃气体
压裂
裂缝扩展
数值分析
formation parameter
deflagration gas
fracturing
fracture propagation
numerical analysis
