Bottom Hole Pressure Measurement Technology And Application In Underbalanced Drilling

The key of successful underbalanced drilling lies in the research and application of bottomhole pressure control technology. This research and application is the core and an important subject of underbalanced drilling technology. Although underbalanced drilling technology has applied in many oilfields in domestic, but it still has greater distance from foreign countries technology. Some people in foreign countries have developed the bottomhole pressure while drilling wired and wireless measuring instrument (PWD). It has high precision in bottomhole negative pressure control. But in domestic, this technology is comparatively backward. And the error of bottomhole pressure is very great. In underbalanced drilling, to maintain a reasonable accurate bottomhole negative value is a key technology. In order to solve the problem of bottomhole pressure measurement technology in underbalanced drilling, based on former research, with bottomhole pressure measurement technology, this paper analyzed the problem of the existing model.According to underbalanced multiphase flow basic equation and the existing research results, we established the new formula of bottomhole pressure distribution in underbalanced drilling. The new model fully considered the effect on bottomhole pressure inflicted by the solid phase of debris. We derived the formula of multiphase flow effect on acceleration pressure drop. Its error is in the range of 3%. The bottomhole pressure met the designed negative pressure value. It can guide the bottomhole pressure design in underbalanced drilling and the actual bottomhole pressure calculation. At the same time we developed the bottomhole pressure measuring instruments in underbalanced drilling. The instrument applied to measure high temperature and high pressure deep underbalanced drilling. And it can measure and store while drilling and playback after tripping out. Although it cannot read the data while drilling, it will be able to overcome the influence of well depth restriction using by electromagnetic wave measuring equipment while drilling and the drilling fluid performance using by pulse measuring equipment. It can be applied to not only the flow underbalanced drilling, but the deep well, gasified fluid drilling, air drilling and foam drilling. It has applied on underbalanced drilling and gasified fluid drilling and achieved good results.