New measurement-while-drilling surveying technique utilizing sets of fiber optic rotation sensors

Horizontal drilling processes in the oil industry utilize directional measurement-while-drilling (MWD) instruments to monitor the position and the orientation of the bottom hole assembly (BHA). The present directional monitoring equipment includes three accelerometers and three magnetometers mounted in three mutually orthogonal directions. At some predetermined surveying stations, the accelerometers measure the Earth gravity components to determine the BHA inclination and tool face angles while the magnetometers measure the Earth's magnetic field to determine the BHA azimuth.; The massive amount of ferrous and steel materials around the drilling rig, the presence of downhole ore deposits, the drill string-induced interference and the geomagnetic influences can all have a deleterious impact on the magnetometer measurements. Therefore, this research proposes the use of fiber optic gyroscopes (FOGs) to replace the magnetometers. A quantitative feasibility study has shown that the FOG has excellent immunity to the severe downhole shock and vibration forces.; This thesis aims at developing new MWD surveying methodologies based on the inertial navigation techniques for integrating the FOG technology with the three-axis accelerometers to provide complete surveying solution downhole.; Inertial navigation systems (INS) determine the position and the orientation of a moving platform using three-axis accelerometers and three-axis gyroscopes forming what is known as inertial measurement unit (IMU). Since the BHA cannot accommodate a complete IMU, this research utilizes some specific conditions related to horizontal drilling operations to minimize the number of gyroscopes so that only one or two high-accuracy FOGs would be sufficient to provide full surveying solution downhole. In addition, some adaptive filtering techniques are utilized to enhance the FOG performance in order to reduce its output uncertainty. Moreover, applied optimal estimation techniques based on Kalman filtering methods are employed to improve the surveying accuracy.; The suggested FOG-based MWD surveying techniques eliminate the costly non-magnetic drill collars in which the presently used magnetometers are installed, survey the borehole continuously without interrupting the drilling process and improve the overall accuracy by utilizing some real-time digital signal processing techniques.