The pattern of surface drilling in development wells of Beibu Gulf Basin

The geological conditions of Beibu Gulf Basin in the western South China Sea are very complex. When drilling the surface layers of development wells, there existed such problems as wellbore instability, difficulty in controlling drilling fluid properties, difficulty in controlling wellbore trajectory, and so no, which led to difficulty in sand carrying in surface drilling hole, large friction and low efficiency in directional slide drilling, and there also existed great risk of borehole collision. Now this Basin is mainly dominated by low quality oil/gas reservoirs or marginal oil/gasfields and the oilfield has low development benefit, so drilling cost must be controlled effectively. This paper presents the technical difficulties in surface drilling in development wells in Beibu Gulf Basin. A set of method which improves surface drilling efficiency in development wells in this Basin and reduces drilling risks has been developed by optimizing the wellbore configuration, using economic and applicable seawater bentonite drilling fluid system, optimizing the design of positive displacement motor assembly and improving the measurement while drilling system. The field application shows that this pattern can increase drilling efficiency and reduce drilling costs while guaranteeing drilling safety and quality. This pattern can also provide technical references for field workers.