Research progress of rotary steerable system and its control methods

Rotary steerable system is a shining pearl in directional drilling technology and an important technical means to realize the low-cost and efficient development of oil and gas resources. First of all, the basic structure of the rotary steerable system was introduced. According to the different steering modes and bias effects, the rotary steerable system is divided into five categories: static push-the-bit type, dynamic push-the-bit type, static pointing type, dynamic point-the-bit type and mixed type, for which the steering principle was analyzed one by one. Secondly, according to the research and application of rotary steerable system technology at home and abroad, the development status of push-the-bit, point-the-bit and mixed types of the rotary steerable systems was systematically analyzed, with the advantages and disadvantages of different technologies summarized. Meanwhile, the basic situation and progress of the development of rotary steerable control system were summarized from the three directions of modern control, intelligent control and compound control. Finally, discussion was performed on the future development direction of rotary steerable technology, as well as the difficulties in the design of rotary steerable control system and their solutions. On this basis, it was pointed out that: (1) The current push-the-bit and point-the-bit type rotary steerable systems of China should be improved to promote the build-up rate, stability, automation and intelligence of the system, and the research on guiding technology, two-way communication, downhole closed-loop control and other supporting technologies should be carried out, so as to further improve the industrial application capability of the system. (2) Theoretical research should be conducted for the four subsystems of surface monitoring, two-way communication, measurement-while-drilling and bottomhole assemble of the mixed type rotary steerable system. (3) In response to the challenges of diversified drilling environment, refined control ability and intelligent control requirements, it was proposed that the research on control technology of rotary steerable system should focus on three directions in the future: comprehensive application of various control methods, adaptive fault tolerance to the complicated environment and unknown challenges, and decision/control integration based on the intelligent technology. In summary, this study can provide a useful reference for the development and improvement of the future rotary steerable system in China. For the control system, a set of control strategies that could effectively cope with future challenges is formed in combination with artificial intelligence technology based on the comprehensive development of various control methods.