First Potential Demonstrations and Assessments of Monitoring Offshore Oil Rigs States Using GNSS Technologies

Abstract

To guarantee safe and stable operation of the offshore oil rigs, it is important to monitor the status of the oil rigs and the marine hydrological environment around the oil rig. This work first demonstrates and evaluates the potential use of global navigation satellite system (GNSS) technologies in the oil rigs. GNSS real-time kinematic (RTK) is used to monitor the quasi-static displacements and the dynamic responses of the oil rigs. In an 11-month experiment, GNSS-RTK successfully measures the quasi-static displacements with horizontal and vertical changes of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 10$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 15$ </tex-math></inline-formula> mm, respectively, when the temperature changes from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-10^{\circ} \text{C}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30~^{\circ} \text{C}$ </tex-math></inline-formula> . This suggests that GNSS-RTK can be used to monitor tiny quasi-static displacements of the oil rigs. For the dynamic response, the experimental results show that the vibration of the oil rigs has no correlation with significant wave height (SWH) and wind speed, respectively, below 1.0 m and 8.0 m/s, and the dominant frequency and vibration amplitude are, respectively, around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 0.35$ </tex-math></inline-formula> Hz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 5$ </tex-math></inline-formula> mm. However, when SWH and wind speed, respectively, are over 1.0 m and 8.0 m/s, the dominant frequency and vibration amplitude of the oil rigs show strong correlations with SWH and wind speed and, respectively, decreases and increases with SWH and wind speed increase. These variations agree with the physical truths so that it is potential to use GNSS-RTK to monitor the dynamic responses. To provide the SWH and wind speed around the oil rigs, a real-time GNSS-reflectometry (GNSS-R) system is developed and experimentally tested. In a 24-day experiment, the retrieved SWH and wind speed are in agreement with the in situ data with root mean square errors (RMSEs) of 0.37 m and 1.40 m/s, respectively. Finally, an integrated and monitoring scheme of GNSS-RTK and reflectometry for the oil rigs is discussed.