The movement of plunger piston,the compressibility of the liquid and the leakage in the clearance between the plunger piston and pump barrel were comprehensively considered,and a new continuous flow equation of the fluid in the pump cylinder was setup.

By the analysis of the situation of sealant rubber ring application to the worksites of Xiaowa Oilfield, the main reasons re- sulting in the frequent leakage of sealant rubber rings are found out, thus providing the reference for the spot management of the same oilfields with viscous crude.

The Block Su-25 in Changqing Oilfield has heaving formations into which mud losses frequently take place and from which water production is high.

Leak resisting toughening agent F27A solves lost circulation in fractured formation.;

In Qianfoya Group and Xujiahe Group, there are very low formation fracture pressure layers or faults existed, which leads to lost circulation during drilling and cementing operations.