Seismic Inversion to Map the Hard Streak Layer And Porosity Distribution In Carbonate Reservoir A Case Study From Western Offshore Basin of India.

Basak, P.S. (Oil & Natural Gas Corporation Limited) | Deb, Abhijit (Oil & Natural Gas Corporation Limited) | Dotiwala, Sucheta (Oil & Natural Gas Corporation Limited) | Sanyal, A. (Oil & Natural Gas Corporation Limited) | Pokhriyal, S.K. (Oil & Natural Gas Corporation Limited)



The present study area lies to the West of Bassein field in Western Offshore Basin of India. The exploration for hydrocarbons in this area was initiated in the year 1976 with the acquisition of 2D seismic data. Subsequently, in the years 1984, 1992, and 1993, a close grid 2D seismic data was acquired. Based on the interpretation of the above 2D data, a number of exploratory wells were drilled in the area which have established the middle-late Eocene limestone reservoirs of Bassein Formation (upper & lower) as the principal target for exploration. In addition, the early Oligocene limestone of Mukta Formation has produced gas in commercial quantities. There is also an indication of presence of oil in the early Oligocene limestone of Heera Formation.

The area forms a part of Heera-Panna-Bassein, covering about five structures. Out of these, one structure has been taken for this study. This prospect falls in Bassein West producing oil and gas in commercial quantities from Bassein lower & upper and lower Oligocene Mukta formations. The Bassein lower pays of the well under study, are unique as it is the only well in the area which has produced from Bassein lower formation. In this well the two producing lime stone pays of Bassein lower are separated by an hard streak tight layer of limestone. The objective of present study focuses on First to map the areal extent of hard streak layer and secondly to predict the porosity in and around the well under study, to find out the extension of the reservoir.