From Design to Experimental Validation of the Fully Mechanical Gravity Tool Face Measurement-While-Drilling System

Summary Exploiting geothermal resources such as hot dry rocks (HDRs) requires directional drilling technology. Measurement-while-drilling (MWD) technology plays a crucial role in directional measurement. However, its high temperature and environment limit downhole measurement instruments in application. For this research, we designed an MWD system with a mechanical gravity tool face, and the fully mechanical structure was used to overcome the high-temperature constraints. The bias stabilization platform, gravity tool face coding method, and mud pulse generation structure were designed. The eccentric stable model and pulse generation structure model were established through numerical analysis, and a gravity tool face angle coding and identification method was also established. The experimental prototype testing system was built on theoretical analysis and hydrodynamics. The feasibility of the tool functions and the recognition algorithm were verified experimentally, with a maximum measurement error of 6° and an average measurement error of 2.6°. The average measurement error of the system in the well test is 6°, which verifies the reliability of the system.