Based on systematic analyses of microscopic characteristics, thermal maturation and biomarker compounds of reservoir bitumen, it was discussed in this paper the bitumen origin as well as the hydrocarbon migration and accumulation in Dabei region of the Kuqa Foreland Basin. A little black resin bitumen was observed in microscopic fractures of sandstone reservoir under salt bed of the Kumugeliemu Group in Dabei region. 2 groups of bitumen were found in well Dabei202, with reflectivity of 1.07％ and 0.47％. 1 group of bitumen was found in well Tubeil, with reflectivity of 0.43％, and its content was very rare. Solid bitumen in reservoir was the result of mixed precipitation of oil and gas of different origin and stage. Therefore, natural gas in Dabei region is not originated from crude oil cracking. At least 3 stages of hydrocarbon charging took place in under-salt traps such as Dabeil and Dabei2. Crude oil in ancient reservoir migrated into shallow sandstone along the Kelasu thrust fault in the north, and then accumulated in the Dawanqi anticline. Reservoir bitumen was found in well Tubeil near the Kelasu thrust fault, indicating that sandstone worked as the pathway for hydrocarbon migration. Hydrocarbon might accumulate in the higher part of the fault block. The research illustrated the origin of natural gas in the Kelasu structural belt, and might guide ancient reservoir exploration in the region.%根据储层沥青的显微特征、热演化程度和生物标志化合物系统分析,对库车前陆盆地大北地区的储层沥青成因及油气运聚过程进行了探讨.大北地区库姆格列木群盐下砂岩储层显微裂缝中观测到少量黑色胶质沥青,其中,大北202井储层沥青发育2组,其反射率值分别为1.07%和0.47%,吐北1井储层中只检测到一组沥青,且含量极少,反射率值为0.43%;储层固体沥青为不同源、不同期的油、气混合沉淀而成.由此推断,大北地区天然气并非原油裂解成因;大北1和大北2等盐下圈闭至少发生了3期油气充注,其古油藏原油大多沿北部克拉苏逆冲断层进入浅部砂层,再汇聚于大宛齐背斜成藏;位于该断层附近的吐北1井,其储层沥青的存在说明其砂岩层是油气运移的通道,不排除该断块高部位有油气威藏的可能性.该结论对认识克拉苏构造带天然气成因和促进古油藏勘探具有重要意义.
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