Characterization, Modelling and Simulation of the Fractured Najmah-Sargelu Carbonate Reservoir, Umm Gudair Field, West Kuwait

Abstract

AbstractThe Najmah-Sargelu reservoirs of the Umm Gudair field in West Kuwait are tight, oil-bearing carbonate reservoirs in which production is mainly achieved through a well-developed multiscale fracture network. Developing such complex reservoirs implies the building of accurate matrix models, the fine static and dynamic characterization of fractures and the correct representation of both matrix and natural fractures into simulation models. In this paper, we present such a multi-disciplinary approach based on the integration of geological, petrophysical, geophysical, and dynamic data and where state of the art techniques in seismic characterisation, sequence stratigraphy, fracture modeling and simulation have been used.The matrix model of the reservoirs was primarily developed based on the analysis of well data involving a core description and petrophysical interpretation. It was finalized by integrating the results of a detailed sequence stratigraphic analysis and a lithological characterization from seismic. The fracture characterization was based on the analysis of static and dynamic data and built upon the results of a former regional study. Large-scale fractures were identified with the help of seismic attributes and seismic facies map. Three sets of small-scale diffuse fractures were also characterized based on borehole image interpretations. Their occurrence is controlled by the shale content of rocks. Finally, the dynamic characterization of fractures using production data, well test and flowmeter data concludes on the critical impact of fractures on fluid flow in the reservoirs. Based on these results, a 3D Discrete Fracture Network (DFN) model of the reservoirs was built. It was calibrated against well test data in order to assess the hydraulic properties of fractures.Both fine matrix model and fracture model were upscaled and combined to build a dual porosity simulation model. The history matching process enabled to better constrain both fracture network porosity and the matrix-fracture exchanges. It was then used to optimize the future development plan of the Najmah-Sargelu reservoirs. Classical production strategies such as depletion, water or gas injection were first tested. The type, number and position of new wells were then optimized.