Improvement and application for casing cutting technology in Qinghai Oilfield

The operation of freeing the stuck pipe above the sticking point by back-off and taking the casing during casing replacing will take a long time and a lot of money, and the extent of retrieved casing is not certain, so the operation is quite passive. Using cutting tool to cut off the free string above the sticking point in the hole and retrieving the cut-off string out of hole at one time can greatly speed up the operation and can realize manual control over the cutting location. In a number of wells at site, the internal structure of mechanical inside cutters has been improved, and hydraulic force is exerted to cutting head instead of mechanical force, which has solved the problems of difficulty in determining the cutting location of the mechanical inside cutting, uneven force exerted on the cutting head, as well as being unable to cut normally due to failure to exert pull force in advance due to the fish head not being at the wellhead. Also, the string assembly to be cut off has been improved and tested on site, which has solved the problems of cutting and fishing to be finished in two times, low efficiency and easy damage to the cutters, realizing integrated operation of cutting and fishing, effectively protecting the cutting head, extending the service life of cutters and improving the job efficiency. At present, the cutting technology in Qinghai Oilfield has gradually replaced the traditional well servicing technology which addresses stuck pipe by back-off and fishing. This cutting technology has become one of the preferred downhole service technologies to quickly remove stuckpipe accident and rapidly retrieve the casing string in retrieving and casing replacing operations.