Facies and Reservoir Characteristics of the Ngrayong Sandstone in the Rembang Area, Northeast Java (Indonesia)
- 1 Department of Earth Resource Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan
- 2 Geological Engineering Department, Faculty of Engineering, Gadjah Mada University, Yogyakarta, Indonesia
- 3 Geological Engineering Department, Faculty of Engineering, Gadjah Mada University, Yogyakarta, Indonesia
- 4 Department of Earth Resource Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan
Abstract
The Rembang area is a well-known prospective region for oil and gas exploration in Northeast Java, Indonesia. In this study, the reservoir characteristics of the Ngrayong Sandstone were investigated based on outcrops in the Rembang area. Petrological, mineralogical, petrophysical and sedimentological facies analyses were conducted. These sandstones are grain- and matrix-supported, and composed of very fine to medium, sub-angular to poorly-rounded, moderately- to very well-sorted sand grains. These sandstones are mainly composed of quartz, orthoclase, plagioclase, and micas with minor amounts of clay minerals, and therefore are predominantly classified as sub-lithic arenite and sub-felds pathicarenite. Petrographic observations and grain size data indicate that these sandstones are texturally quite mature, based on their good-sorting and the occurrence of minor amounts of matrix clays. Common clays in the samples include illite, smectite, kaolinite, and gibbsite. The porosity of the Ngrayong sandstones ranges from 25.97% to 40.21%, and the permeability ranges from 94.6 to 3385 millidarcies. Thus, these sandstones exhibit well to excellent reservoir qualities. Eight lithofacies were identified from five measured stratigraphic sections, and are dominated by foreshore and tide-dominated shoreface facies. The Ngrayong sequence shows a single transgressive-regressive cycle. Cross-bedded sandstone and massive sandstone are identified as the most promising potential reservoir facies based on their characteristics in outcrops, their lateral and vertical distributions, their sedimentological characteristics and their petrophysical properties.
- Mohaghegh, S., Arefi, R., Ameri, S., Aminiand, K., and Nutter, R. (1996) Petroleum Reservoir Characterization with the Aid of Artificial Neural Networks. Journal of Petroleum Science and Engineering, 16, 263-274. https://doi.org/10.1016/S0920-4105(96)00028-9
- Ardhana, W. (1993) A Depositional Model for the Early Middle Miocene Ngrayong Formation and Implications for Exploration in the East Java Basin. Proceedings, Indonesian Petroleum Association, Twenty Second Annual Convention, Jakarta, 12-14 October 1993, 395-441.
- Pettijohn, F.J., Potter, P.E., and Siever, R. (1987) Sand and Sandstone. 2nd Edition, Springer-Verlag, New York, 553 p. https://doi.org/10.1007/978-1-4612-1066-5
- Pettijohn, F.J. (1975) Sedimentary Rock. Halper and R Brother, New York.
- Koesoemadinata, R.P. (1980) Geologi minyak dan gas bumi. ITB, Bandung, 296 p.
- Nichols, G.J. (2009) Sedimentology and Stratigraphy. 2nd Edition, Blackwell Scientific Publications, Oxford, 419 p.
- Kadar, D., and Sudijono. (1993) Systematic Geological Map, Indonesia, Quadrangle Rembang 1509-1 and 6 Scale 1:100.000: Geological Research and Development Centre: 1 Sheet.
- Allen, J.R.L. (1982) Sedimentary Structures: Their Character and Physical Basis. Vol. 1. Developments in Sedimentology. Elsevier, Amsterdam.
- Pringgoprawiro, H. and Baharuddin. (1979) Biostratigrafi Foraminifera Planktonic dan Bidang-Bidang Pengenal Kaenozoikum-Akhirdari Sumur-Sumur Tobo, Cepu, Jawa Timur. Proceedings PIT VIII Ikatan Ahli Geologi Indonesia, Jakarta, 11-12 December 1979, 21-31.