In recent years, due to increased energy demand, energy companies have increased the focus on the basement reservoirs following proven hydrocarbon discoveries in these complex reservoirs. Mumbai High field in western offshore, India is one of the budding fields to attest the potential of basement hydrocarbon accumulations with its proven hydrocarbon reserves. However, understanding and characterizing these complex basement plays of Mumbai High field are complicated by the distinctiveness of fracture properties, lithology, mineralo-facies, petrophysical properties and stress regimes.
Basement reservoirs are usually very dense, porosity is mainly secondary, and distribution of porosity and permeability is sporadic. Hence productivity of these reservoirs is inconsistent. Primarily the basement rocks have poor reservoir quality. The pore space in the basement reservoirs is mainly formed through fracturing and diagenetic processes. Hence, the development of an effective fracture network can lead to a potential reservoir for the hydrocarbon in basement.
Conventional well-log approaches are well defined for clastic and carbonate reservoirs, but these approaches are not adequate for fractured basement characterization. This paper emphasizes an integrated comprehensive approach for understanding the reservoir quality of basement reservoirs in terms of complex mineralogical and lithological variations, fracture properties, the tendency of fractures to slide and dilate and fracture distribution near and far away from the borehole using advanced logging techniques. A synergistic advanced well log evaluation methodology has been adopted to address the challenges of reservoir characterization in fractured basement with the help of multiple advanced well-log measurement. As more wells are drilled, this technique has proven robust giving consistent results validated with production data.
