Utilising Stratigraphic Driven Approaches and Simulations to Build Robust 3-D Geologic Models for Miocene Reservoirs, “Josh” Field, Niger Delta

Abstract

Reservoir properties models that are constrained to facies models and upscaled for dynamic simulation and volumetric estimation are often marred with spurious reservoir properties models which either underestimate or overestimate the reserves base. Realistic facies models were built for “Josh” field, coastal swamp Depobelt, Niger delta by using integrated core description, 3D seismic, wireline logs, sedimentological and biostratigraphic dataset. Lithofacies identified include shallow shelf sandstones and mudstones, lower to middle Shoreface sandstones, tidal channel sandstones and transgressive marine mudstones while the depositional environment is delta front (inner neritic to middle neritic) as revealed from supervised classification of cored well, biostratigraphic and sedimentological analysis. The depositional units were identified by mapping Maximum flooding Surfaces, Sequence Boundaries and Transgressive Surfaces. For each parasequence, flooding surfaces were correlated; isopach, sandstone-quality trend maps, and mudstone-quality trend maps were constructed to capture the reservoir lithofacies heterogeneities; flow and baffle facies and petrophysical variations within the depositional units. These were upscaled and modeled using modeling algorithms: Truncated Gaussian with Trends (TGT), Truncated Gaussian Simulation (TGS) and Sequential Gaussian Simulation (SGS). Results revealed that the sequence stratigraphic driven approach generated the most geologically reasonable facies model and showed favorable reservoir quality values with the potential for substantial hydrocarbon storage for many lithofacies. This sequence stratigraphic facies model predicted significant vertical compartmentalization identified by the flooding surface mudstones. Petrophysical ranges associated with each facie, as deduced from core and log data, appeared to be clearly related to their respective reservoir qualities. It revealed that this approach to facies model remains a key driver to the understanding of these reservoirs. This will help in placing infill development wells, aiding history-matching and fluid-flow simulations in verifying both the infill targets and reservoir compartments.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017