Research On Key Process Technology Of Horizontal Well Drilling In Western Sichuan

Drilling practices indicate that drilling techniques of horizontal wells are the main technical measures to improve single completion productivity and reduce the cost of reservoir development. With the development of horizontal well technology, especially the horizontal well trajectory control technology, departments of petroleum exploration and development put forward higher requirements on the construction of horizontal wells in order to get the best development effect with the least investment. There are various problems of engineering technology in the process of drilling wells, such as the design difficulties of well-bore configuration, low ROP, long drilling cycle, poor borehole stability, big liability of collapse, great friction torque of drill string, serious striking of horizontal section, difficulties of running casing and ensuring the quality of cementing wells. Further more, the complex formation of western Sichuan area and the anomalous pressure of multiple gas layers on vertical level have also increasingly hampered the exploration and development of the western Sichuan area. With the accelerated development of western Sichuan area, the study on drilling techniques of horizontal wells has become one of the most important tasks.With the reference of present state of horizontal well technology development, the thesis studied the borehole stability of horizontal wells, theory of drag and torque, theory of casing safety according to above problems encountered in the process of drilling horizontal wells in western Sichuan area. On the basis of pore pressure prediction, basic stress, rock mechanics parameters, the thesis built a calculation model of horizontal well borehole stress, predicted the formation fracture pressure and collapse pressure of horizontal wells with the combination of rock failure criteria, analyzed the influence of hole deviation angle and azimuth to the formation fracture pressure and collapse pressure of horizontal wells, and determined the density window for safety drilling mud by the adoption of elasticity theory. The thesis also deduced the prediction model of drag and torque in three-dimensional borehole, analyzed hook load and torque of typical horizontal wellhead under different conditions in western Sichuan area, and verified the strength of the drill string in different conditions with the application of elasticity theory. In addition, the thesis calculated the maximum well-bore curvature of casing string with a plurality of rigid centralizers in a curved well bore, and discussed the possible impact of borehole diameter, rigid centralizer diameter, casing size, casing string structures and other factors on feasibility of casing running.Based on the researches of throry, the author made a tracking analysis on XC-structure horizontal wells in western Sichuan area. The thesis analyzed the influence of hole deviation angle and azimuth on caving pressure and formation fracture pressure of XC-structure. providing support for the choice of drilling fluids density and horizontal section direction. Well-bore trajectory of typical XC-structure horizontal well is also designed in the thesis to optimize the structure of the drill string by adopting the analysis of torque and drag. The thesis also made feasibility analysis of running production casing in X21-1H well, and verified the results according to the practical drilling data.The research results of the thesis will provide a significant reference for the optimal design of horizontal well and improvement of the whole drilling technology in western Sichuan area.