关键词: 近钻头, 随钻测量, 下座键式, 方位伽马, 井斜, 电磁波

Abstract: At present, most of the downhole systems of the main stream near-bit measurement systems at home and abroad adopt the upper suspension connection mode and the turbine engine provides the power for the systems. The system structure is relatively complex, and the connection is relatively stable and not easy to out of the key. However, when the drilling tool is buried by the formation collapse in the drilling operation, the whole string of instruments cannot be salvaged, which will cause great property losses to the operator. Therefore, a near-bit MWD with lower seat key is designed and developed. The system adopts lower seat key connection mode and battery pack power supply mode, and uses electromagnetic wave wireless short transmission technology to transmit the azimuth gamma and inclination data measured near the bit across the screw to the near-bit receiving sub, which is connected to the MWD downhole system. The data is sent to the MWD master control unit by bus. Finally, the MWD measurement data and near-bit measurement data are sent to the surface processing system through drilling fluid pulse transmission technology to guide subsequent drilling operations. The application shows that the MWD system with lower seat key is accurate in measurement, and it overcomes the disadvantage caused by the uneasily disconnecting key in the operation of the main stream near-bit measurement system, and greatly reduces the risk in directional drilling operation.

Key words: near bit, measurement while drilling, lower seat key type, azimuth gamma, inclination, electromagnetic wave