Study On Downlink System Technology For Rotary Steering Drilling System

With the increasing demand for long-range wells,long horizontal wells and other drilling requirements in drilling technology,rotary steering,geosteering has been greatly developed.A key part of these technologies is the ability that can remotely control downhole tools on the ground.The key challenge is how to transmit control information to downhole tools from the surface("downlink telemetry").At present,there are few researches on downlink telemetry,such as,the propagation characteristics of downlink telemetry and the design methods of downlink telemetry system.The research on its key technology has very important theoretical and practical significance.According to the existing problem of downlink telemetry technology of rotary steering system,a downlink method with drilling fluid negative discharge pulse mode is proposed to achieve downlink telemetry of downhole rotary steering drilling tool in this thesis.The method is achieved by changing periodic flow of the drilling fluid flowing into drillstring,which can generate drilling fluid negative flow pulse,and then the turbine generator is used to sense the changes of the flow and acquire negative flow pulses,and then downlink information will be sent and received downhole.After that,the basic principle of this method is clarified,its implementation is pointed out,its system structure is constructed and the key problems in the method are described.In this paper,the design method of the bypass downlink surface with reconfigurable structure is proposed based on the principle of the drilling fluid negative discharge pulse downlink mode.The design method uses the new throttle switch valve and the reconfigurable step-down module to construct the downlink surface,and the basic design theory of the method is constructed.The downlink surface device is designed with the actual drilling conditions,and the flow field characteristics are analyzed.And then the control system of the downlink surface device of the communication system is built based on PLC free port communication.According to the drilling demand,the composition of the downlink information is analyzed and the coding scheme of the downlink information is established.To solve the problem of downhole signal reception of negative discharge pulses and meet the requirement of downhole power supply for rotary steering tool,a new structure scheme of downhole turbine generator is proposed.The rotating magnetic field generator with the structure of an external rotating magnet and an internal fixed coil is presented,and the design of the downhole generator is given,including permanent magnet design,winding design,electromagnetic performance analysis and multi-field coupling analysis.The turbine structure is designed based on univariate flow theory,and the load and mechanical characteristics of the turbine is analyzed.Then the relationship between the flow rate and the turbine output speed,the generator output voltage and the power efficiency of the turbine is analyzed,and the relationship between the output efficiency of the turbine generator and turbine discharge is analyzed.Finally,the downlink surface device and downhole turbine generator are developed,and the laboratory experiment platform is built.The experiment in the laboratory is carried out to test the design method of downlink surface device and the effectiveness of downhole turbine generator design.Moreover,the complexity of the real drilling is considered,and the drilling experiment is carried out in the field to verify the validity of the transmission model of the proposed downlink communication method and the feasibility of the integration of the whole downlink communication system composed of the downlink surface device and downhole turbine generator.It is also verified that the developed downlink telemetry system has certain engineering value.The research results of this paper have been successfully applied in the field test of the rotary steering drilling system,and have achieved good results,which fully validates the correctness and validity of the research results.