Microwave Radar Wave and Current Measurement Analysis in the Gulf of Mexico

Abstract

Accurate measurement and characterization of the wave environment is an integral part of planning, design, and operations for offshore facilities. Remote sensing with new wave radar systems allows remote wave and current field observation, reducing data contamination associated with traditional submerged upward/horizontal-looking acoustic meters. These instruments are relatively new to the industry and are participating in ongoing validation studies to gain further acceptance within the industry. Shell Exploration and Production Corporation (Shell E&P) operates a network of offshore oil and gas installations in the north and central Gulf of Mexico that have maintained a variety of oceanographic sensors for many years in support of operations. Shell E&P has recently expanded their Metocean observation capacity, to include both LiDAR wind profilers and microwave wave radars, in addition to existing ocean current profilers. To date more than a year's worth of LiDAR and radar wave and current data has been collected at tension leg platforms (TLP) Ursa and Olympus, observing a full range of meteorological and oceanographic conditions, representative of the region, including the passage hurricanes Harvey and Nate. In addition, an upward looking near surface Acoustic Wave and Current profiler (AWAC) has simultaneously been collecting data at the nearby Mars TLP. The present study evaluates the variability in the wave system response, the comparison between the three stations, the correlation between the radar current observations and wave signals, and the ability of the measurement systems to successfully capture normal as well as extreme conditions. The observations showed a good correlation between the three stations, showing a transition from wind sea to swell as the peak of hurricane Nate passes. The data also showed the presence of orthogonal wind sea and swell wave systems after the storm peak at both Ursa and Olympus, although the Mars AWAC had been pulled for the storm. All three wave and current meters were deployed during the passage of more remote hurricane Harvey however. Surface currents showed a clear response to the wind speed and direction but were temporally offset from the near-surface currents. Wave data analysis successfully resolved spatially and temporally coherent wave systems that are consistent with expected hurricane conditions, showing a 10 m significant wave height and a maximum wave height of 15 m at Olympus, with 8 m and 13 m at Ursa, respectively.