Using seismic attributes and petrophysical analysis for reservoir characterization – a case study of the offshore cape three-points (OCTP) block in the Tano basin, Ghana.

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August, 2015
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Seismic amplitudes and petrophysical analysis of well logs for reservoir characterization have been undertaken in this project. The seismic attribute that was considered in this research was the Root Mean Square (RMS) amplitude which is good discriminator of reservoir sands. A total of three wells were considered in the study and three reservoirs were successfully characterized. 3D seismic data and data from three wells were obtained from the Ghana National Petroleum Corporation (GNPC). The study was carried out in two discovery areas; the Gye Nyame and Sankofa discovery area located in the Offshore Cape Three-Points (OCTP) Basin, Ghana. For each well studied, resistivity log, formation density log, compensated neutron-porosity log and gamma ray logs were collected and analysed. The seismic data was subjected to RMS amplitude extraction that helped to delineate the reservoir sands zones. A detailed petrophysical property model was constructed for each well and the following petrophysical parameters were computed; reservoir thickness, net pay, net-to-gross ratio, porosity and water saturation. The reservoir thickness values ranged from 16.5 to 22.1 m, net pay ranged from 1.7 to 15.3 m, net-to-gross ratio ranged from 10 to 75 %, porosity ranged from 10 to 24 % and water saturation values ranged from 24 to 34 %. The depositional environment for each reservoir was determined from the shape of the gamma ray log. The depositional environment for the reservoir in the Leo 1 well was a fan whiles that of the reservoir in the Capitol well was fine grained sandstone at the upper part of a tidal channel grading into laminated tidal flat mudstone at the base and that of the reservoir in the Silicon well was probably a tidal channel.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, in partial fulfillment of the requirement of the Degree of Masters of Philosophy (Geophysics) College of Science, 2015