Print this pageThe Role of Geologic Risk Analysis in Maximizing Field Value during Development Planning: Gobe Fields, Papua New Guinea
FRANKLIN, STAN P., and S. A. AZIZI
An integrated program of structural, stratigraphic, and geostatistical reservoir modelling combined with reservoir simulation was used to provide a basis for development planning within the recently delineated Gobe Fields of Papua New Guinea. By coupling reservoir engineering, drilling, and economic analysis, with a sound geologic foundation, team members designed a development plan to incorporate the impact of geologic risk.
Complex thrust belt geology, structural uncertainty, and thin oil bands combine to create a significant risk of sidetracking or non-optimum wellbore trajectories. To assess the impact of structural uncertainty on development drilling, a decision risk analysis was created by combining economic parameters with reservoir simulation and geologic risk analysis. Geosteering using Logging While Drilling (LWD) technology and forward dip modelling has proven highly successful in managing structural risk as the wells are drilled.
The primary reservoir in the greater Gobe area is the lagifu Sandstone member of the Jurassic Imburn Formation. Facies change along strike from shoreface to deltaic/distributary mouth bar deposits within an overall wave-dominated delta environment. Reservoir quality is primarily controlled by grain-size and sorting, which are a function of depositional facies. The higher energy deltaic/distributary mouth bar facies show superior reservoir properties relative to the shoreface sandstones.
Parasequence scale flooding surfaces identified on log and core were used to form an initial hydraulic zonation that serve as the basis for geostatistical reservoir characterization. Capillary pressure data were used to refine the hydraulic zonation in terms of pore-throat radii, permeability, and saturation profiles. Porosity models were created using kriging and Gaussian Sequential Simulation techniques. Permeability models were constructed using a probabilistic cloud transform technique.