Integrated Geo-Statistical Modeling – An Effective Tool to Meet the Exploration Challenge of Low Porosity Carbonate Reservoir within Najmah-Sargelu Formation, Kuwait

Abstract

The emergence of low porosity carbonate lithofacies of Najmah-Sargelu Formation as a commercial hydrocarbon play has led to change the exploration perspective of these formations. Several wells from different structures in Kuwait has shown the production potential of light oil@ 1000–4000 BOPD and natural gas 3.8–19.0 MMSCFD. The production has been obtained from bituminous mudstone, wackestone and algal limestone from Najmah-Sargelu Formation. Understanding the geometry and distribution of carbonate lithofacies of Najmah-Sargelu Formation is a major exploration challenge. Geo-statistical 3D model is a dynamic tool, which has been utilized to quantify the geometry and spatial distribution of carbonate lithofacies vis-a-vis its continuity. A careful geo-statistical workflow was evolved to address the major challenges of these reservoirs. An artificial intelligence, neural network was trained against cored section and subsequently applied in the noncored sections for lithofacies prediction. Sequence Stratigraphic framework, seismic grid and 3D geo-statistical modeling were integrated to create a geological model. Core-measured rock property data were analyzed to illustrate the distributions of core porosity and permeability of Najmah-Sargelu lithofacies. The distribution of internal properties and heterogeneity has been quantitatively described as the relationship of a reservoir facies within a sequence stratigraphic framework. Spatial estimation of lithofacies and reservoir properties provides insight into the deposition and diagenetic process of the reservoir units. The depositional pattern and connectivity analysis suggests a ramp setting in inner shelf environment of deposition with three major alternate transgressive and regressive sequences. An integrated geo-statistical modeling has resulted in depicting the internal geometry and connectivity of low porosity carbonate lithofacies thereby reducing the uncertainty in volumetric assessment in the delineation phase of Najmah-Sargelu Formation.