Trap
Sarir C is contained in a structural-stratigraphic trap, represented by dips to the east, south, and west and the major northeast-southwest-trending fault on its northwest flank. In much of the central and northwest, the reservoir subcrops and is sealed by shales that unconformably overlie it. Minor sand accumulations in the transgressive series above the basal sands occur in updip, pinchout traps.
Sarir C's main trap is not full to the spill point, which is downplunge on the ridge west of the structure. The oil column has a maximum height of 91 m, with a 122 m vertical closure. Crude distribution in the trap is affected by lithological variation. Oil-water levels are common in the main reservoir members, but the transgressive series is 43 m higher.
Sarir North is a separate trap with its own oil-water contact, 30 m deeper than Sarir C. L-65 also has an independent oil-water contact. The field has no gas cap; petroleum has a low gas-oil ratio between 60-225 standard ft3/bbl. Some crude differentiation occurs, probably due to gravity separation. Overall, it consists of a fairly light, waxy crude having a mean gravity of 37° API, wax content of 19%, and a sulfur content under 0.25%. The pour point ranges from 12° to 24°C.
Gravity segregation of crude in the trap produced a peripheral tar mat in permeable intervals of the reservoir intersecting the oil-water level. The tar mat varies in thickness, reaching a 21 m maximum in the east. Viscous oil from the top of the tar mat has a mean gravity of 24°-25° API, a pour point of about 71°C, wax content of 15%, and an asphaltene content of 14-22%.
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Famous quotes containing the word trap:
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—Ralph Waldo Emerson (1803–1882)
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Whimper-whine; whose unridiculous
Lost softness softly makes a trap for us.
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—Gwendolyn Brooks (b. 1917)
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—Robinson Jeffers (1887–1962)