,from which leakage sections appearing during drilling can be determined,density of mud in hole during underbalanced drilling can be calculated;and information about leakage and sealing,and for analyzing the efficiency of underbalanced drilling can be provided.

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.

Inverse transient analysis-based numerical simulation of leakage in water distribution systems;

Judging leakage in well testing string has become a noticeable problem.

The primary causes which make the oil pump efficiency low were analysed from the influences of pump filling degree,stroke loss and dropout.

The paper starts with an introduction to the research state of the monitor technology of oil pipeline dropout in the past 15 years, followed by the analysis of monitor principles, merits and defects of different monitor technologies.