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四川盆地川中古隆起安岳震旦系—寒武系特大型气田的发现,揭示了该区下寒武统烃源岩巨大的天然气资源潜力。综合前人相关数据,构建了川中地区下寒武统烃源岩的地质—地球化学模型,应用PetroMod盆地模拟软件,结合Easy%RO模型,对川中古隆起的代表钻孔在关键地质时期的古地温梯度演化进行恢复,并对下寒武统烃源岩的生烃演化进行模拟。研究结果表明,中生代是川中古隆起下寒武统烃源岩油气生成与演化的关键时期,该时期其古地温梯度较高,并呈现逐渐降低的趋势。研究得到的古地温梯度模型为:3.5℃/100m(≥96Ma)—3.2℃/100m(65Ma)—2.7℃/100m(0Ma)。川中古隆起下寒武统烃源岩经历了早期生油、晚期生气的演化过程,烃源灶位置与文献报道的古裂陷槽基本吻合,其油、气累积生成强度分别可达(8~10)×106t/km2与(55~65)×108 m3/km2。古裂陷槽下寒武统烃源岩在主生油期(中—晚三叠世)生成的液态石油,可通过不整合面与断层组成的网状输导体系运移至磨溪—高石梯构造与威远—资阳构造形成古油藏;古油藏内的原油在侏罗纪—早白垩世期间完全裂解,原油裂解气是这2个构造下寒武统龙王庙组与上震旦统灯影组天然气藏的主要来源。
The discovery of the Anyue Sinian-Cambrian super-large gas field in the Sichuan Basin paleo-paleo uplift reveals the great natural gas potential of the Lower Cambrian source rocks in this area. Based on the previous data, a geo-geochemical model of the Lower Cambrian source rocks in the central Sichuan Basin was established. Using the PetroMod basin simulation software, combined with the Easy% RO model, the paleo- Geothermal gradient evolution to recover, and to simulate the hydrocarbon evolution of the Lower Cambrian source rocks. The results show that the Mesozoic is a key period for the formation and evolution of the Lower Cambrian hydrocarbon source rocks during the paleo-uplift of the Central Sichuan Basin. During this period, the paleogeothermal gradient was high and gradually decreased. The paleogeothermal gradient model studied in this paper is: 3.5 ℃ / 100m (≥96Ma) -3.2 ℃ / 100m (65Ma) -2.7 ℃ / 100m (0Ma). The Lower Cambrian source rocks of the Central Sichuan uplift experienced the evolution process of early oil generation and late gas generation. The location of hydrocarbon source furnace coincided with the ancient rift groove reported in the literature, and the cumulative formation intensity of oil and gas reached up to 8 ~ 10) × 106t / km2 and (55 ~ 65) × 108m3 / km2. Liquid petroleum generated in the Lower Cretaceous source rocks of the Paleogene rifting basin in the main oil-producing period (middle-late Triassic) can migrate to Moxi-Gaoshishi via a network of unconformities and faults The ladder structure and the Weiyuan-Ziyang structure formed the ancient oil reservoirs. The crude oil in the ancient reservoirs was completely cracked during the Jurassic-Early Cretaceous period. The cracked gas of the crude oil was found between the Lower Cambrian Longwangmiao Formation and the Upper Sinian The main source of the Dengdengji natural gas reservoir.