Publications

Reservoir modeling of a fractured reservoir provides a unique set of challenges. Two structural domain based approaches have been used to construct geo-models. Each is reconciled with dynamic data which is a critical ingredient in the evaluation.The first model is a structural sub-domain based Net Pore Volume Model (NPV). The model is a probabilistic approach of determining net pore volume from the gross rock volume within a structural domain. The NPV model combines a probabilistic porosity range with a probabilistic net to gross range using the gross rock volume in each structural compartment or domain. Appraisal drilling in various fractured basement fields has verified the fact that lateral seals in the basement exist. These sealing faults when identified are natural domain boundaries. Various analysis such as GOR (Gas Oil Ratios) and chromatographic finger print analysis can enhance the understanding of compartments within the structure. Well information defines the probabilistic range of porosity while mud-gas data or production logging data is used to define the effective hydrocarbon charged fracture as a function of net to gross. All porosity determination methods used to derive fractured basement porosity have inherent weaknesses. Net/gross techniques have been difficult to define in the fractured basement reservoirs. Additional techniques are being developed using modern logging techniques in granitic reservoirs show promise in improving N/G estimation. These uncertainties require a probabilistic approach. The probabilistic ranges of data are also compared to known analog information. A probabilistic resource distribution is generated and reconciled with dynamic data.The Structural “Halo Model (SHM) is a structural based modeling approach that uses seismic faults and/or top basement surface fault information (disruption patterns) to define a porosity network through the rock volume. It is a simple means to describe a discrete fracture network model (DFN) with limited geostatistic information related to the fractures. The “Halo Model is based on vertical and aerial damage around seismically defined faults. The porosity properties are inferred from field analogs, dynamic data, and local well data. Basement fractured reservoirs have porosity that generally decreases with depth. Net porosity values are controlled by a shape factors both vertically and laterally away from the faults. Shape factors are determined by the degree of internal deformation from seismic character, top basement surface expression, local well data, and dynamic data with constraints from analog field history matched data. The Halo model is the ideal model for reservoir simulation because it is a more realistic view of the reservoir.Both techniques require a detailed understanding of the structural elements affecting the reservoir. The two models use uniquely different approaches to arrive at HIIP and are used to compare volumes to each other in order to validate the assumptions that are fraught with large ranges of uncertainty.