Development an‎d modeling of an inertial navigation system based on fiber optic gyroscopes for measuring parameters during deep-sea drilling

8/20/2025 12:00:00 AM

Directional drilling processes in the oil industry use measurement while drilling (MWD) systems to indicate the position an‎d orientation of the BHA downhole tools. The general structure of the directional system includes 3 accelerometers an‎d 3 magnetometers in 3 bidirectional an‎d orthogonal directions, one temperature sensor an‎d 2 shock an‎d vibration sensors. The accelerometers measure the components of the Earthʹs gravity to determine the BHA deflection angle an‎d orientation angles, while the magnetometers measure the Earthʹs magnetic field to determine the BHAʹs orientation.Large amounts of iron compounds an‎d steel objects around the drilling rig, the presence of bottomhole ore deposits, the effect of induced magnetic interference from the drill string, the effects of geomagnetic penetration (dependent on gravity), the effect of bending an‎d curving of the drilling assembly at high angles, an‎d the coaxiality error between the measuring tool an‎d the downhole assembly can all have detrimental effects on magnetometer measurements. In this thesis, as a solution, the use of fiber optic gyroscopes (FOG) with amplified optical feedback along with three-axis accelerometers is proposed to be independent of the magnetometers. For this purpose, a suitable model for a fiber optic gyroscope with amplified optical feedback is presented, then it is simulated using Optisystem software an‎d the outputs proportional to the sample rotation rates are shown.This structure allows for direct measurement of the rotation rate, thereby enabling more accurate estimation of the BHA position an‎d orientation. Simulation results show that changing key parameters such as fiber loop length an‎d feedback gain have a significant impact on the quality of the gyroscope response. Based on the simulation analyses in this thesis, at a wavelength of 1535 to 1550 nm, a loop length of 0.56 km an‎d a feedback gain of about 9.2 dB, it produces an optimal output that is about 13.1% more sensitive an‎d 19.3% more stable an‎d accurate compared to the latest recorded results at a wavelength of 1525 to 1565 nm, a loop length of 0.496 km an‎d a feedback gain of 9.32 dB.

ژيروسكوپ فيبر نوري , اثر سايناك , شيفت فاز , بهره فيدبك , نرخ چرخش , جهت ابزار , زاويه انحراف , آزيموت

Fiber optic gyroscope , Saynakʹs work , Phase shift , Feedback gain , Rotation rate , Toolface , Angle of deviation , Azimuth

Reza Ganjavi

Dr. Sattar Mirzakouchaki