The Case Study of the Effect of Fault Transmissibility on the Oil Reservoir Production in the Onshore Field, United Arab Emirates

Abstract

Abstract A study was conducted to improve the history match of oil production from an onshore field, hereinafter referred to as the OS field, by applying realistic fault transmissibility multipliers (TMs) with or without an integrated discrete fracture network (DFN) based model. Analysis of pressure before and after the start of production, production rate, injectivity tests and geomechanical studies were used to improve the knowledge of fault behaviour. These studies indicate that faults are discontinuous and potentially cut by open fractures; the data indicates that faults act as conduits and not as barriers to fluid flow. The fault TMs used to gain a history match were higher than predicted by the fault permeability and thickness data obtained from samples collected from UAE outcrops. Three scenarios were examined in which the fault transmissibility was given various values: (i) a fixed value, (ii) approximated based on fault rock properties from UAE outcrops combined with the DFN model or (iii) a fixed value combined with DFN. The results from these models were compared with historical production data. Applying a fault TM of 5 with a dual-porosity and permeability model produced the best match to production data. Oil production was predicted to be 13% higher using this model than for the base case in which faults did not impact flow. This is because faults enhanced fluid flow within this field. The fault analysis was consistent with geomechanical studies, which led to increasing the TM of the fault above one and integrating it with the DFN model until history matching was achieved. The history matching of the model is non-unique, and one could almost certainly get the same results by altering other parameters within the model. However, this study focused on integrating all available field data, such as fault properties, porosity and permeability of the matrix, and fractures that provide a history match without changing the petrophysical properties of the reservoir.