Fishing string optimization study and application for openhole horizontal wells

Fishing work in horizontal wells is a high difficult and high risky operation. The horizontal section has large friction resistance and difficult torque transmission, so the conventional fishing string assembly of jarring, back off, and casing milling is hard to obtain expected results. According the problem above, combined with the lithology of openhole section, some aspects are studied, such as increasing effective drilling pressure, decreasing wellbore friction resistance, revering jarring assembly, and operimizing fishing and milling tools, resulting in optimization of the conventional fishing string. The fishing operation on Well NB35-2-B29hst1 proved that the optimized fishing string increased sharply the fishing efficiency of openhole horizontal wells and decreased operation risk, which could be a reference for fishing operations on similar wells.