| Extended reach well drilling technology has become an important mean to explore the oil and gas on offshore, drill fluid technologies directly result in the success or failure of extended reach well drilling. Field application shows that many complicated conditions such as tripping stuck, bouncing torque, loss of circulation and so on are existed in the process of well drilling in T platform of DS oilfield. So it is necessary to research the drill fluid technology of extended reach well in T platform.The drill fluid technology of extended reach well in T platform is researched based on the data of completed extended reach wells, the content of studies completed and the results obtained are as follows:(1) The existence of clay minerals, coal-bearing interlayer and igneous rock interlayer are the main cause of complicated conditions on the basis of research for drill fluid systems and complicated conditions of completed wells. Meanwhile, technical requirements of the drilling fluid system are presented.(2) Calculation models of collapse pressure and fracture pressure are established on the basis of analysis of the stress state of rock wall and the strength of the rock failure criteria, which provides a theoretical basis to determine the safe window of drilling fluid density for extended reach wells in T platform.(3) Performance evaluations on collapse prevention, seal, rheology and lubricity of standby drilling fluid system are conducted on the basis of laboratory tests, the results show that the low free water drilling fluid system is suitable for Longjing formation and Huagang formation.(4) The best added amount of treating agents such as inhibitors, blocking agent, lubricant, and agent related to the rheology are recommended on the basis of laboratory tests.(5) Field tests of drill fluid system are conducted; field application shows that the drilling fluid system can inhibit the underground complex conditions effectively. |
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