Implementation of Coupled 3D Geomechanics and Discrete Fracture Network (DFN) Models in Field Development Optimisation: A Case Study from Carbonate Reservoir, Abu Dhabi

摘要

An onshore oilfield in Abu Dhabi has complex faulted structure of early Cretaceous carbonate reservoir. The porosity in these reservoirs ranges up to 25%. These reservoirs are overlaid by dense carbonate which acts as a cap rock. The field has been produced for 35 years with peripheral water and gas injection scheme to maintain the reservoir pressure. The objectives of this geomechanical study were to verify the impact of in-situ stresses and rock mechanical properties on reservoir performance during production/injection activities, as well as to evaluate the mechanical and hydraulic responses of natural fractures and faults to fluid flow within the reservoir. In addition, evaluation of cap rock integrity and fault seal analyses are also considered as necessary risk assessment inputs for field development program. Extensive rock mechanics testing program has been carried out on reservoir, the interlay dense and cap rock to quantify the contrast in mechanical rock properties and their response to in-situ stresses. Diverse set of data have been integrated including geological, geophysical, petrophysical, reservoir and drilling data to build robust ID and 3D Geomechanical models. Natural fractures were characterized using core inspection, image logs and CT-Scans which have been calibrated to production logging (PLT) and well tests. Multi-attribute analysis with inputs from petrophysical, structural and geophysical data has been used to build and calibrate the 3D DFN model.