Abstract

We carried out an integrated reservoir characterization to model a heavy oil reservoir called Balol located in the heavy oil belt of Mehsana in the western state of Gujarat in India. The Oil and Natural Gas Corporation of India was the field operator. The operator adopted in situ combustion process in northern part of Balol because of high-mobility contrast between oil and water. However, the performance review carried out by the operator found that oil recovery from this field was not as per prediction. Hence, serious attempts were made to interpret 3D seismic data to map the reservoir efficiently. We integrated the information derived from 3D time-lapse seismic data with the well logs provided by the operator to explain the movement of thermal front tracked using time-lapse seismic data. To model the reservoir, flow unit and electrofacies characterization was also carried out, and four to five FUs with conduits and baffles to flow were identified. Electrofacies analysis identified three major reservoir facies. These analyses also revealed that Balol reservoir was layered and heterogeneous with depth. Further, in addition to 3D seismic data, well logs and empirical equations were used to generate porosity, water saturation, and permeability models for the entire reservoir. Thus, a reservoir model with heterogeneous distribution of petrophysical properties was generated. We observed a high permeability trend in the northwest direction at injection wells, which could be governing the movement of thermal fronts in the reservoir.

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