Research On Optimum Fast Drilling Technology For Circum-mahu Depression Of Xinjiang Oilfield

Circum-mahu area is located in the northwestern margin of Junggar basin, and it is recognized as the most hydrocarbon abundant depression. In recent years, several exploration wells have access to high-yield industrial oil and gas flow in the slope area, showing a good exploration prospect in this area. Circum-mahu area is the the main field increasing reserve and production to build "Xinjiang Daqing".The generalized sequence of geology in Circum-mahu area is as follows: Cretaceous Period of Tugulu Group, Jurassic Period (Qigu Group, Toutunhe Group, Xishanyao Group, Sangonghe Group, Badaowan Group), Triassic Period (Baijiantan Group, Kelamayi Group, Baikouquan Group), Permian Period (Wuerhe Group, Xiazijie Group, Fengcheng Group, Jiamuhe Group).The rock drillability of upper formation is good, but conglomerates have grown at base of Badaowan Formation with a thickness of 100-350m and poor drillability, leading to low ROP, long drilling period, high cost and difficulty in bit selection, which greatly hinders the exploration progress in Circum-mahu area.To promote the drilling speed and fast drilling in conglomerates grown at base of Badaowan Formation, solve the long drilling period of deep Permian Period formation and decrease drilling cost in Circum-mahu area, the study combined on-site data analysis, laboratory rock mechanical testing with mathematical statistics methods. Based on the analysis of rock mechanical parameters testing, mechanical parameters profile of rock samples can be built. The study also contains bit selection, individualized PDC bit selection and special drilling tools optimization, and the main research contents and results are as follows:(1) The geological characteristics of Circum-mahu area are analyzed and summarized. Drilling difficulties are found out by analyzing the data of completed wells. Poisson ratio, elastic modulus, compressive strength and other parameters were measured by carrying out the core experiment.(2) The mechanical specific energy theory and field application effect analysis are used to select bits. The drilling bit effect data of completed wells was evaluated, the individualized PDC bit was optimized. The preferred bit solution and the bit sequence of Circum-mahu area were given.(3) Working principle and characteristics of different special drilling tools is analyzed and the tools are optimized through the test and application of circum Mahu area, showing good results of using "torsion impact generator + PDC bit". And the cost is also analyzed, which provides the reference for the improvement of ROP and drilling efficiency.(4) According to the poor drillability in deep formation of Circum-mahu area, underbalanced gas based fluid drilling technology is optimized, and the work of mechanism and capacity to carry water during gas based fluid UBD is studied. Specific measures to deal with the formation water are put forward, and the principle and technology of gas-liquid conversion is also analyzed.Through the researches above, based on rock mechanics character studies and well logging data, bit selection, special drilling tools and underbalanced gas based fluid drilling are analyzed. The study provides a theoretical basis and technical support for increasing drilling speed and efficiency, speeding up the process of exploration and development of Circum-mahu area.