Harmonic Analysis of Tides at Bonga Oil Field, Nigeria

Abstract

Oil exploration and exploitation activities are being moved from swamp and shallow waters to deep offshore locations in Nigeria, and therefore, there is a need to provide predicted tides to support oil and gas operations in deep offshore environment. In this work, 51 days' water level observations derived from water pressure data recorded by AANDERAA Water Level Recorder WLR 7 at a depth of 1,000 m at Bonga field were analysed and used to carry out tidal harmonic analysis. Eleven tidal constituents were used for the harmonic analysis. Astronomical arguments (v + u) and the nodal factor (f) were computed for each tidal constituent with a programme written in Matlab environment. The amplitudes and the phase
lags for each constituent were calculated and tidal predictions beginning from the initial time of tidal observation in September 11, 2010 to January 2019 were done at 10 minutes' intervals. Statistical analysis of predicted tides and observed tidal data was done. The highest deviation of the predicted tides from the observed tidal data is 0.0008 m, while the Root Mean Square Error is 0.0003 m. Autocorrelation at lags 1 to 30 for the residuals of observed and predicted tidal data shows that there is no significant correlation in the series of the 30 lags. The series of residuals of observed and predicted data is white noise. The accuracy of this work is high enough for offshore operations in Bonga Field.