Abstract
Hydrocarbon column height is one of the most important parameters that affects the volumetric calculation. Previous prospect volumetric calculations were done using statistics built from the existing database of column heights of hydrocarbon discoveries of deeply buried carbonate pinnacles in Central Luconia. A re-look of the discoveries revealed that not all of the data in the existing database are applicable for a given prospect due to the different geological settings. As it is a common practice to update the database from time to time, a refresh was done after new multi-PSC 3D seismic acquisition and interpretation was completed and more published well information from adjacent PSC's were made available. A more scientific approach was taken this time around; the effective sealing unit of the deeply buried pinnacles was compared against our prospect. All the deeply buried pinnacles in the statistics were effectively sealed by the clastic 5.8mya depositional sequence. The percentage of hydrocarbon fill for each buildup was plotted on the existing paleogeographic map of the overlaying sealing strata. Given sufficient charge, multiple factors remain that can negatively affect hydrocarbon accumulation in Luconia carbonate buildups. These include high aquifer overpressure, crestal faulting, and channels which can impinge on the reservoir and act as thief beds. Some channels may clearly be seen in the seismic, while some appear to be pinched-out, and others may be sub-seismic. In the area of carbonate build-ups that were used in the statistical database, lower percentage of hydrocarbon fill coincides with the presence of a regional channel complex, interpreted to act as theif zones. However for our prospect, within this overall channel complex, several large buildups seem to act as baffles or barriers to the channels, deflecting them away from our prospective carbonate build-up. Thus, by comparing with our prospect, we realized that the regional statistics might not always be applicable, depending on several geological variables. Our prospect has no thieving channel at top seal level and is further protected by the updip channel belt by another carbonate platform. We should not use statistics generated from discovery wells that are affected by the thief beds. Statistics are always favoured whenever we have little knowledge about a basin or subject. By showing how geoscience can drive the statistics, we will be reminded on how using it without interpretation may be misleading.
