Study On Well Boring Technology In Deep Water Horizontal Well

Deep-water petroleum exploration and exploitation is doomed to be an important area for our country with the increasing demand for energy and the difficulties for finding oil and gas in land and shallow water. For oil and gas development in deepwater, the main risk of deepwater drilling is well control due to marine environment.It would bring irreparable damages to platform staff and deepwater environment once blowout accident occurs. In order to ensure the safety of deepwater drilling and completion, it is necessary to do research on safe theory and technology to control overflow once kick occurs and put forward reasonable well killing methods.Therefore, safe and feasible well killing technology in deepwater drilling has great significance to ensure the security of deepwater drilling.This paper established a model to calculate wellbore temperature distribution during well killing process considering heat exchange between killing fluid,casing and formation,choke line and seawater and simulated wellbore temperature distribution along well depth under different killing flow rates and killing time,which can provide basic data for annular pressure calculation.Moreover, according to characteristics of complex wellbore temperature field, long choke line and narrow safety density window,deepwater horizontal well killing models and kick torlerance and critical mud increment calculation models of driller’s method and wait&weight method have been established considering the influences of hydraulic friction within choke line, temperature and gas expansion on choke pressure and standpipe pressure. Furthermore, kick torlerance, critical mud increment and choke pressure and standpipe pressure variation along time for vertical and horizontal well of driller’s method and wait&weight method have been calculated based on geological and engineering characteristics of reservoir in south china sea.Then influences of choke line length, inner diameter of choke line, overflow amounts, killing flow rate and the length of horizontal segment on choke pressure and standpipe pressure variation along time have been analyzed. Finally, differnences between driller’s method and wait&weight method have been comparatively analyzed and inversion of overflow control process in South China Sea oil field has been studied.Simulation results show that circulating temperature differs a lot from static temperature and circulating temperature deviates from the static temperature with the increase of killing flow rate, moreover, the top of temperature appears a certain depth above the bottom hole. Furthermore, kick tolerance and critical mud increment would increase along the increment of killing flow rate and caseing shoe depth, however, kick torlerance would be smaller with larger overflow. Kick torlerance and critical mud increment of engineer’s method is larger than driller’s method. In addition, the peak value of choke pressure is higher with longer choke line, smaller inner diameter of choke line and larger amounts of overflow and standpipe pressure also is higher with longer choke line, smaller inner diameter of choke line and larger killing rate,whereas,length of horizontal segment has little influence on choke pressure and standpipe pressure in killing process. At last, the inversion of overflow control in South China Sea shows that the theoretical results and the measured data error is less than10%.The research results in this paper can be used to predict circulating temperature distribution of annular wellbore and choke pressure and standpipe pressure variation along with time and kick torlerance and critical mud increment during killing process,which can provide theory guidance for killing method selection and plan of killing scheme as well as formulating reasonable killing measurements.