Lateral Facies and Permeability Changes in Upper Shoreface Sandstones, Berakas Syncline, Brunei Darussalam

Ovinda Ovinda, Joseph J Lambiase

Abstract


DOI: 10.17014/ijog.4.1.11-20

Several outcrops were studied to identify sedimentary facies and to analyze permeability distribution, through which an outcrop analogue for upper shoreface reservoirs can be established. Four facies were identified: upper shoreface, lower shoreface, offshore transition, and tidal ones. Stratigraphic correlation of eleven outcrops indicates that the upper shoreface sandstone is generally clean, well sorted, parallel, and planar cross laminated. The sand becomes thinner and pinches out to the northwest where the mud proportion increases within the sand. Muddier sand was deposited in a relatively low energy upper shoreface setting. The thickness of the upper shoreface reservoir sand generally is 5 m. It decreases to zero over approximately 1.3 km as the sand pinches out to the northwest. To the northeast, the thickness also decreases to 4 m over approximately 4 km. Permeability values are more variable laterally than vertically. The permeability distribution has an obvious relationship to the sedimentary facies and is mainly controlled by the proportion of mud and bioturbation. As the sand pinches out in the northwest, permeability decreases from 590 md to 97 md over 1 km. To the northeast, permeability also decreases to 152 md over approximately 4 km where the sand becomes highly bioturbated. These values indicate that the sands are of good to very good reservoir quality. It appears that there are no major barriers to the lateral flow of fluid within the upper shoreface sandstone.


Keywords


outcrops; facies; upper shoreface; permeability

References


Lambiase, J. J., Back, S., and Warren, J. K., 2001. New prospectives on Petroleum Reservoirs in NW Borneo. Unpub. Field Trip Report for YPF Maxus, 22 - 25 February, 82pp.

Liu, K., Boult, P., Painter, S., and Paterson, L., 1996. Outcrop analog for Sandy Braided Stream Reservoirs: Permeability Patterns in the Triassic Hawkesbury Sandstone, Sydney Basin, Australia. American Association of Petroleum Geologist Bulletin, 80 (12), p.1850-1866. DOI: 10.1306%2F64EDA21C-1724-11D7-8645000102C1865D

Morley, C.K., Back, S., Van Rensbergen, P., Crevello, P., and Lambiase, J.J., 2003. Characteristics of repeated, detached, Miocene-Pliocene tectonic inversion events, in a large delta province on an activ margin, Brunei Darussalam, Borneo. Journal of Structural Geology, 25, p.1147-1169. DOI: 10.1016/S0191-8141(02)00130-X

North, F.K., 1985. Petroleum Geology. Unwin Hyman, Boston, 631pp. Sandal, S.T., 1996. The geology and hydrocarbon resources of Negara Brunei Darussalam (1996 revision). Brunei Shell Petroleum Company/Brunei Museum, Syabas Bandar Seri Begawan, Brunei Darussalam, 243pp.


Full Text: PDF

Refbacks

  • There are currently no refbacks.


Creative Commons License
Indonesian Journal on Geoscience by https://ijog.geologi.esdm.go.id/index.php/IJOG/index is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

 

Indexing Site :

 

 

 

Follow us on:


shopify visitor statistics
View My Stats