Drilling trajectory survey technology based on 3D RISS with a single fiber optic gyroscope

Abstract Recently, a complete inertial measurement unit (CIMU) with three-axis Fiber optic gyroscopes (FOG) has replaced the three-axis magnetometers in Measurement While Drilling system (MWDs) to survey the drilling trajectory. However, installing three FOGs into MWDs meets lots of challenges. Firstly, because of the limited space in the downhole, CIMU is too big to accommodate all kinds of well. Secondly, the capacity of the power battery supporting the MWD is limited while CIMU has a high-power consumption. Finally, because of the high cost of FOGs, CIMU increases the drilling tool expense. Thus, on the basis of implementing the survey drilling trajectory function, it is critical to reduce the number of FOGs. Targeting a low-power, low-cost and high-accuracy navigation solution for MWD, this paper proposed a three-dimension (3D) navigation solution using a reduced inertial sensor system (RISS) for MWD. The RISS consists of only one single-axis FOG and three-axis accelerometers. In order to improve the measurement accuracy, the drilling piper length information obtained from a recursive algorithm named as Average Angle Method (AAM) was fused to RISS using the Kalman filter method. To validate the availability and utility of this surveying method, three experiments simulating different drilling process were performed using three-axis rate table under laboratory conditions. The experiment results show that the proposed solution could provide accurate directional and orientation information of the wellbore trajectory while drilling.