投球分压的理论验证及实例分析

THE THEORY VERIFICATION AND EXAMPLES ANALYSIS OF STEEING BALL SEPARATE-LAYER FRACTURING

本文从理论上论证了尼龙堵球在分层压裂时的三种受力状态：当惯性力小于拖拽力时使堵球偏离中心流线而趋向孔眼；当使球保持在孔眼口的持力大于由于流动而使之脱落的冲击力时，堵球将坐牢在孔眼上而保证压裂施工顺利进行；压裂停泵后，持力为零，地层流压对球有一个作用力，使堵球从孔眼脱落而回落井底。从实际压裂施工的井温曲线、施工曲线分析中，论证了投球分压的可行性，以及不同种类投球分压的效果差异分析，为采油厂选择投球分压提供了较充足的理论和实际应用依据。

This paper discusses theorectically the three stress states of the nylon ball in the separale- layerfracturing: the ball will deviate from the centre flowline and tend to the pore when the inertia force issmaller than the drag force: the ball will set on the pore and ensure the successful operation in fracturing when the force keeping the ball on the pore is larger than the impact force caused by the liquid flow;after pumping off, the holding force is zero, the force prchced by the formation pressure `will drop theball into the bottom hole from the pore. According to the practical well temperature log and the recordedoperation curves in fracturing, this paper discusses the feasibility of setting ball separate1ayer fracturing, analyses the resu1ts of different fracturing schemes, and provides the full application basis in theory and practice for the selection of setting ball fracturing of seprate layers