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" Reservoir characterization of the Bekasap "A" Sandstones of Kotabatak Field, Riau, Sumatra, Indonesia "
B. P. Kantaatmadja
R. R. Berg
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Latin Dissertation
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English
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| Record Number
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1112436
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TLpq304065426
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| Main Entry
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B. P. Kantaatmadja
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R. R. Berg
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| Title & Author
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Reservoir characterization of the Bekasap "A" Sandstones of Kotabatak Field, Riau, Sumatra, Indonesia\ B. P. KantaatmadjaR. R. Berg
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| College
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Texas A&M University
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| Date
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1991
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| student score
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1991
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| Degree
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Ph.D.
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| Page No
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296
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| Abstract
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The Early Miocene Bekasap "A" Formation of the Sihapas Group occurs at a depth of 4400 to 4900 feet (1333.3 to 1484.8 meter) and ranges from 60 to 160 feet (18.2 to 48.5 meter) in thickness. There are commonly four sandstones, the Bekasap A-1, A-2, A-3, and A-4 members, separated by shale. Sedimentary structures and petrographic analyses indicate that the sandstones were deposited in a fan-delta environment during periodic falls of sea level and/or tectonic activity. The two principal facies are the fluvial facies and prodelta facies. The fluvial facies is the major oil reservoir in the field, with average porosity and permeability values of 17.2% and 383 md, respectively. The current porosity and permeability are primarily the diagenetic in origin. Fractures and dissolution of carbonate cements, labile grains, and shell fragments contribute significantly to the reservoir quality. The most likely source rock for oil in the Central Sumatra basin is the Upper Pematang Formation, which has a geothermal gradient of 4F/100 feet, it is estimated that this source rock entered the oil-generation stage approximately 14 m.y. before present. Oil expulsion started after the structural traps formed in Pliocene-Pleistocene time, about 5 m.y. before present. Primary migration is interpreted to be related to clay dehydration and microfracturing in the source rock. Two types of hydrocarbons were produced by the source rocks: naphthenic and paraffinic oil types. In Kotabatak Field, the hydrocarbon comprises 74% paraffinic oil and 26% naphthenic oil. Production from 27 of 68 producing wells has yielded 96 million barrels of oil and 4.5 million cubic feet of gas. Production is not uniform across the field and follows the trend of the inhomogeneities of Bekasap "A" sandstone bodies. The life of the field is predicted to extend until the year 2023, with cumulative production of 110 million barrels of oil and 5.5 million cubic feet of gas.
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Earth sciences
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Geology
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sandstone
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