水平井地层破裂压力的解析公式

Analytical Formula of Formation Breakdown Pressure for Horizontal Well

分析了正断层地层任意偏离角水平井在裸眼完井和射孔完井两种完井方式下,井筒和孔眼的应力状态,以垂直井地层破裂压力公式为基础,利用替代方法,给出了水平井地层破裂压力的解析公式,并进行了算例研究.结果表明,地层破裂压力与完井方式及偏离角密切相关.由于射孔完井孔眼和裸眼完井井筒的应力状态完全不同,所以,两者破裂压力通常并不相等.不论是裸眼完井还是射孔完井,其破裂压力都是偏离角的单调递增函数.当偏离角为0°时,破裂压力最低;而当偏离角为90°时,破裂压力最高.

Stress states of the wellbore and the perforation hole for the horizontal well with any deviation angle under open-hole completion and perforation hole completion in normal faults were investigated.Based on the formation breakdown pressure（FBP） formula of vertical wells,the corresponding analytical formula for horizontal wells were derived with the substituting method,and one numerical example was studied.The result shows that the FBP is dependent on the completion method and the deviation angle.The FBP for perforation completion was quite different from that of open-hole completion since both of the stress states were distinct.Whether for open-hole or perforation completions,the FBP is the monotonically increasing function of the deviation angle which arrives at the minimum value and the maximum value at angles of 0 degree and 90 degrees respectively.