Uncertainty Analysis of Reservoir Static Modelling: A Case Study of KMJ Oil Field

Abstract

This case study explains the uncertainty of Original Oil in Place (OOIP) calculations in reservoir static modeling of KMJ Oil Field. This field consists of 4 (four) wells in an area of ± 600 acres with high heterogeneity, so in building a 3D Model, it is necessary to analyze the sensitivity and uncertainty of geological concepts, calculations of petrophysical properties, and fluid contact. The OOIP calculation uses a probabilistic method and determines reserves related to field development. The uncertainty analysis study begins by identifying the parameters with the most significant influence (Sensitivity Analysis) in calculating OOIP in the static reservoir model. To determine the ranking of reservoir uncertainty parameters, several geological, geophysical, and petrophysical factors in building a static model must be tested according to the method used in each parameter. The OOIP calculation in the static model is calculated into three scenario categories, namely low estimate (P10), base estimate (P50), and high estimate (P90). The combination of determining facies (shale volume) porosity, fluid contact, and the cut-off is a variable/parameter that is very influential in volumetric multi-scenario calculations (probabilistic method) in the KMJ Oil Field. The results of the uncertainty analysis of the KMJ Oil Field have a low OOIP estimate (P10) of 10.86 MMSTB, a base estimate (P50) of 11.49 MMSTB, and a high estimate (P90) of 12.01 MMSTB. Furthermore, the static model used for reservoir simulation (dynamic model) in the KMJ Oil Field is the base estimate model (P50) of 11.49 MMSTB.