Gamma Ray Log Analysis in Determining the Depositional Environment of Reservoir Sands: A Case Study of Shaka Field, Onshore Niger Delta
- September 16, 2020
- Posted by: RSIS Team
- Categories: Environmental Science, IJRIAS
International Journal of Research and Innovation in Applied Science (IJRIAS) | Volume V, Issue III, February 2020 | ISSN 2454–6186
Joshua O.Mene1*, Kingsley O. Okengwu1
1Department of Geology, University of Port Harcourt, Choba Rivers State, P.M.B. 5323, Nigeria
*Corresponding Author
Abstract– This research covers the use of gamma ray log as a basic tool in determining the depositional environments of reservoirs. Analysis was carried out on reservoir sands in four wells SHA-001, SHA-002, SHA-003 and SHA-004 across the field. The Sand/Shale cutoff was set at Vsh<0.6 for Sands, 0.6>Vsh<0.85 for Silts and Vsh>0.85 for Shale to determine the Reservoir-Non-Reservoir zones (RNR) and to generate lithofacies logs for lithologic log description. Three reservoirs were delineated A, B and C with variable gamma ray log motif shapes. Reservoir A was interpreted as fining upward, fine to medium grain fluvial channel deposited sands, Reservoir B was interpreted as consistent deposited coarse to fine grain tidal sands lobes and reservoir C was interpreted as variable deposited coarse to fine grain tidal sands lobes with shaley bands sediments from the tidal flats. The grain sizes of these reservoirs trended East-West from coarsest in SHA-004 to finest in SHA-001 and possibly shales out. It was therefore concluded that reservoir sands within the fields was deposited in a prograding coastal depositional environment that was influenced by both fluvial and tidal settings.
Keywords-Gamma Ray Logs, Reservoir, Lithologic Description, Depositional Environments
