Static and dynamic modeling integrating the FZI approach with stochastic modeling for characterizing heterogeneous shale-sand reservoirs

Abstract

Reservoir simulation is essential for optimal field development and recovery process planning. The present work aims at developing an integrated static to dynamic approach for modeling heterogeneous and shaly-sand Nahr Omr Formation in Subba oil field of Iraq. An updated dataset of production rates and PVT data from Dhi Qar Oil Company were used in constructing a high-resolution static model in Petrel involving 10 wells, sonic logs for assessing porosity, and 2D seismic data for structural modeling. In order to incorporate heterogeneities within the reservoir, the Flow Zone Indicator (FZI) technique was employed to classify intervals into 7 Hydraulic Flow Units (HFUs). According to petrophysical analysis, S21 and S22 are identified as the main reservoir units with a high proportion of clean sands, high effective porosity, and low water saturation levels. The static model was subsequently upscaled into a dynamic reservoir simulator (CMG IMEX), using lab measurements of fluid properties and multi-phase relative permeabilities. In addition, OOIP of 2.07 billion STB and an OWC at 2533m (SSTVD) were estimated based on volumetric calculations. As a result, an excellent history match, with R2 = 0.957, was achieved for all fields while for Well A it was R2 = 0.981.