Development of an Integrated Reservoir Simulation and Uncertainty Quantification Framework for Gas Field Development Optimisation in the Niger Delta

Optimal development planning for Niger Delta gas fields requires robust frameworks that explicitly incorporate subsurface uncertainty into production forecasting and infrastructure sizing decisions, yet current practice relies predominantly on deterministic scenario analyses that underrepresent the full range of outcomes. This study develops and validates an integrated reservoir simulation and uncertainty quantification framework specifically designed for Niger Delta gas field development optimisation. The framework combines geostatistical geological uncertainty modelling using multiple-point statistics, ensemble-based history matching algorithms, and stochastic production forecast generation with a probabilistic surface facility sizing methodology. The research methodology involves application of the framework to a real Niger Delta gas field dataset under confidentiality agreement, including seismic interpretation, well logs, production history, and PVT data. The framework is implemented through a workflow linking Petrel geological modelling, ECLIPSE reservoir simulation, and a Monte Carlo-based economic decision tree. The study's original contributions include: a novel ensemble smoother with multiple data assimilation (ES-MDA) parameterisation adapted for Niger Delta stratigraphic complexity, an uncertainty-aware well location optimisation algorithm, and a P10-P50-P90 facility sizing methodology that explicitly accounts for correlated geological uncertainties. Validation against held-out production history demonstrates superior predictive accuracy compared to conventional deterministic approaches. The framework enables development planners to identify high-regret decisions sensitive to geological uncertainty and design flexible development strategies preserving option value. Recommendations include industry adoption of the framework through a collaborative NNPC-academia research consortium and mandatory uncertainty quantification reporting in Niger Delta development plans submitted for NUPRC approval. Keywords: reservoir simulation, uncertainty quantification, Niger Delta, gas field development, history matching.