Application of Multi-Attributes Analysis and Spectral Decomposition Techniques to Identify the Reservoir Sands of Kopili Formation (Eocene) of North Assam Shelf, India

Md S. Akhtar, Ram K. Singh, Sujit Roy Moulik, and H. J. Singh
ONGC, Dehradun, India

Kopili Formation of Eocene age has been considered as a major source rock in this part of the basin. Due to its depositional setup this Formation not only contains the source rock but also has several reservoirs that have been a prolific producer in Geleki area of North Assam Shelf. In Geleki fields about twelve sands have been identified within this pack that has reservoir properties. Sands within this Formation are very thin and have discrete occurrences.

To identify these sands and their spatial and temporal extents by the conventional methods are very difficult. In this endeavor, help of the latest technology and methodology have been adopted to demarcate the locales of these sands in the study area.

On the basis of log study the Kopili Formation was divided in to two major sequences, and subsequently were identified as Kopili top, Kopili middle and Kopili bottom. These markers were further used for the calibration and correlation of seismic horizons on eighteen 3-D volumes (including PSDM volumes) and 209 2-D seismic lines. The seismic and well data covers Panidihing, Disangmukh, Rudrasagar, Lakwa, Banamali-Sonari, Charali-Changmaigaon and Geleki areas.

Sands dispersal pattern within the Formation could be brought out using multi-attributes analysis and spectral decomposition slices which were correlated with the producing wells of Geleki and adjoining areas. With the correlated horizons relief, structure and isochronopach maps were generated, which were further integrated with the results of the multi-attributes analysis and spectral decomposition slices to bring out prospective locales for hydrocarbons entrapment in the study area.

This work has been able to bring out spatial and temporal geometry of the reservoir sands of Kopili Formation and will give lead for Kopili exploration in the North Assam shelf, of India.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery