Fault Seal Integrity and Hydrocarbon Column Height Prediction in the Deepwater Niger Delta: An Original Stochastic Framework

Accurate prediction of hydrocarbon column heights supportable by bounding faults in deepwater Niger Delta structures is fundamental to de-risking prospects and avoiding costly drilling failures, yet existing deterministic fault seal analysis methods inadequately capture the geological uncertainty inherent in undrilled structures characterised only by seismic data. This study develops an original stochastic framework for fault seal integrity assessment and hydrocarbon column height prediction applicable to deepwater Niger Delta prospects. The methodology integrates probabilistic characterisation of shale gouge ratio distributions using Monte Carlo simulation of fault throw and host rock shale fraction uncertainties derived from seismic attribute analysis and analogue well statistics. A novel adaptation of the fault seal capacity model accounts for the sub-resolution variability of sand-shale sequences observed in deepwater turbidite systems that conventional shale gouge ratio calculations fail to represent. The framework is calibrated using a training dataset of forty-six drilled fault-bounded accumulations with documented contact levels from the deepwater Niger Delta, enabling empirical adjustment of the seal capacity relationship. Cross-validation using a blind test dataset of twelve drilled prospects demonstrates a statistically significant improvement in column height prediction over conventional deterministic shale gouge ratio methods. The framework is applied to six undrilled prospects to generate probabilistic column height distributions and trap fill factor distributions for integration into resource estimates. Keywords: fault seal, hydrocarbon column height, deepwater Niger Delta, stochastic modelling, shale gouge ratio.