关键词: 四川盆地东南缘, 吼滩剖面, 志留系, 古油藏, 沥青, 油气充注, 裂变径迹

Abstract:

The forming characteristics of the Silurian destroyed reservoir in the Houtan section in the southeastern margin of Sichuan Basin were studied according to the basic geologic conditions of source rocks, reservoir rocks and cap rocks,as well as the geochemistry characteristics of bitumen and the thermochronology of detritus minerals. The main reservoir rock of the destroyed oil reservoir is sparite with bioclastic. The bitumen distributed in the inter-grain pores of biological detritus and their solution inner-grain pores. The content and distribution of isoprenoid, steranes and terpanes from bitumen in Silurian illustrated that the source rocks were deposited in the reduced environment, and the organic source mainly came from the low-grade hydrobiosm. The stable carbon isotope showed that the bitumen came from source rock of the Silurian. The mean homogenization temperature of saline inclusions coexisting with hydrocarbon inclusions is 97.2℃. Combined with the burial history of the studied area, the hydrocarbon infilling time was determined to be about 200 Ma before present. The fission track age of apatite in the Ordovician Meitan Formation near the destroyed oil reservoir showed that the formation uplifted in anneal zone at about 29 Ma before present and accelerated uplifted at 4.5 Ma before present. The denudation thickness was about 2100—2450 m in the studied area, which finally destroyed oil reservoir.

Key words: southeastern margin of Sichuan Basin, Houtan section, Silurian, destroyed oil reservoir, bitumen, oil and gas charging, fission track