Estimating Storm Surge And Reservoir Subsidence Of Offshore Platforms Using WaveRadar REX SAAB Sensors

Abstract

WaveRadar REX (SAAB) instruments are widely used in the offshore oil and gas industry for wave, tide and air gap observations. This study extends the application of WaveRadar REX to the estimation of storm surge and reservoir subsidence from long-term water level measurements. AirGap data from several offshore fixed steel platforms offshore Borneo island (South China Sea) were analysed, yielding waves, astronomical tides, Sea Surface Anomalies (SLAs), which included storm surge and changes to water level due to long-term climate variability. Vertical platform movements, which can be attributed to reservoir subsidence and Vertical Land movements, were also derived. The storm surge estimates were consistent with values reported for the region, with positive storm surge (+0.3m) peaking in November and December, at the onset of winter western North Pacific Monsoon and northeasterly winds; negative storm surges (-0.2m) were recorded from March to July, coinciding with the boreal summer East Asian Summer Monsoon and southwesterly winds. Locations further offshore showed marginally lower storm surge compared to the coastal stations. Along the coast of Borneo, there was a shift in the timing of the positive storm surge arrival offshore Sabah, with establishment of positive storm surge shifted forward by about a month. Lastly, trends of SLAs derived from WaveRadar REX AirGap can be used to monitor long-term Vertical Land Movements and offshore platform subsidence. The comparison of AirGap subsidence estimates against independent dGPS measurements of vertical platform movement showed excellent agreement for several offshore platforms, all results within 0.05m accuracy. The new technique offers a cheap and reliable method of continuous vertical subsidence monitoring of fixed offshore platforms using instrumentation routinely installed offshore, thus offering an alternative to dGPS subsidence monitoring.

Advancing digital healthcare engineering for aging ships and offshore structures: an in-depth review and feasibility analysis

“…However, for large areas such as wind farms, wave buoys are not suitable due to their measurements being confined to a single point. Alternatively, air gap sensors can be employed for fixed and/or floating offshore platforms to estimate wave height and period by measuring the elevation of the water surface (Anokhin and Ewans, 2018). Although air gap sensors cannot directly measure wave direction as they are installed on the structure, they can provide information on ocean waves distorted by the column.…”

A Review of Subsidence Monitoring Techniques in Offshore Environments

“…Direct measurement techniques Section 3.1 Hydrostatic leveling Section 3.1.1 [24][25][26][27] Casing collar deformation analysis Section 3.1.2 [28,29] Hydrographic techniques Section 3.2 Bathymetry Section 3.2.1 [30][31][32][33] Air gap measurements Section 3.2.2 [33][34][35] Radar water-level measurements Section 3.2.3 [33,36] Radioactive marker technique (RMT) Section 3.3 [8,[37][38][39][40] Well logging Section 3.4 Electric log data Section 3.4.1 [41] Formation-compaction monitoring tool (FCMT) Section 3.4.2 [42] Tiltmeters Section 3.5 [43][44][45][46][47] Fiber optic cables Section 3.6 [48] Fugro-proposed tools Section 3.6.1 [43] Fiber Bragg grating (FBG) strain sensor Section 3.6.2 [43,49] Time-lapse gravimetry and pressure Section 3.7 [43,[50][51][52][53][54][55][56] Agisco compensator Section 3.8 [43] Microelectromechanical systems (MEMSs) Section 3.9 [57][58][59] Remote sensing Section 3.10 InSAR (interferometric synthetic aperture RADAR) Section 3.10.1…”

“…This strategic intervention serves a dual purpose: it reduces the effects of compaction while boosting the productivity of the reservoir [23]. Casing collar deformation analysis Section 3.1.2 [28,29] Hydrographic techniques Section 3.2 Bathymetry Section 3.2.1 [30][31][32][33] Air gap measurements Section 3.2.2 [33][34][35] Radar water-level measurements Section 3.2.3 [33,36] Radioactive marker technique (RMT) Section 3.3 [8,[37][38][39][40] Well logging Section 3.4…”

“…have gained extensive usage in the offshore oil and gas sector. These measurements serve as a means to deduce vertical movements of platforms, which can be attributed to both reservoir subsidence and vertical land shifts [34,35].…”

Spatial and Seasonal Variability of Metocean Design Criteria in the Southern South China Sea From Covariate Extreme Value Analysis

“…Weather patterns in the SCS region are governed by the seasonal monsoons: the East Asian Summer Monsoon ( [2], [3], [4], [5]) observed from May to September and characterised by southwesterly winds; and the western North Pacific Monsoon (North-East Monsoon), with strong northeasterly winds recorded from mid-November to early March across the entire region. The transitional inter-monsoonal periods are observed from April to May and from September to October when the winds are light and variable in direction.…”