Characteristics of a Miocene intrabank channel in Batu Raja limestone, Ramba field, south Sumatra, Indonesia
Ramba field in the South Sumatra basin produces oil from lower Miocene coral and foraminifera-rich wackestones with secondary moldic and vuggy porosity. These wackestones form two low-relief carbonate banks separated by a deeper water, intrabank channel at least 10 km long and 1 km wide. Sediments infilling the channel include (1) carbonate mudstone, (2) carbonate conglomerate (calclithite) composed of dolomite and micrite intraclasts, (3) foraminiferal packstone to grainstone, and (4) terrigenous shale rich in planktonic foraminifera. The channel formed during fault-controlled down-warping during (or followed by) growth of the adjacent carbonate banks. Slow rates of carbonate deposition in the clay-rich environment of the channel resulted in deposition of relatively tight carbonates that form a nonproductive barrier between the A and B oil pools in Ramba field. The channel-fill deposits are economically important for two reasons: (1) where tight, they act as a lateral seal to the reservoir, and (2) the carbonate conglomerate has sufficient porosity and permeability to have provided the spillpoint for oil in the A pool. Thus, although not sufficiently permeable to provide commercial production, it is the distribution of this conglomerate in the channel that limits the height of the oil column in the Ramba field's A pool to only 48 m. 12 figures.
- OSTI ID:
- 6916355
- Journal Information:
- AAPG Bull.; (United States), Vol. 71:10
- Country of Publication:
- United States
- Language:
- English
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