Abstract
This research introduces a low cost, small size directional solution for the rotary steerable system installed directly behind the drilling bit. The proposed solution employs a reduced inertial sensor system (RISS) to provide the 3-D navigation solution for wellbore continuous surveying while horizontal drilling. The RISS consists of one micro-electromechanical systems (MEMS) gyroscope and three-axis MEMS accelerometers. The azimuth angle is obtained using a single gyro. The inclination and the toolface angle are derived from the measurements of the three-axis accelerometers together with an accurate earth gravity model. With the attitude information, velocities of the drilling bit are determined by the penetration rate of the drill bit, which is continuously available by using the information of the drill pipe length and drilling time. To limit the long-term growth of the surveying errors, a Kalman filter relying on the minimum curvature method position was developed to estimate the position errors. The proposed method is examined by conducting a drilling simulation experiment in a laboratory using the three-axis rate table. Two different MEMS systems were tested during the experiment. Results showed that the proposed technique could significantly limit the long-term growth of the position errors. The experiments were performed for almost 2 h and demonstrated no significant divergence of the RISS algorithm.