Characteristics and Effects on Gas Accumulation of the Sinian-Lower Cambrian Temperature-pressure Field in the Central Paleo-Uplift, Sichuan Basin
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摘要: 根据热史研究成果,结合川中古隆起沉积埋藏史,恢复了震旦系—下寒武统烃源岩成熟度演化历史,确定了原油裂解的时期。利用盆地模拟方法,恢复了一维单井和二维剖面的压力演化历史,分析了川中古隆起震旦系—下寒武统异常压力的成因机制。烃源岩成熟度演化历史表明,震旦系—下寒武统烃源岩经历了早期生油、二次生油、干酪根裂解生气及晚期原油裂解四个演化阶段;原油裂解的开始时间大致是中、晚三叠世。川中古隆起震旦系—下寒武统主要经历了常压—增压—卸压的压力演化过程,白垩纪中期寒武系达到最大压力系数约1.7;威远—资阳地区压力系数较低,高石梯—磨溪构造带压力系数相对较高。研究发现快速埋藏、生烃作用及原油裂解是该地区超压形成的主要因素;燕山—喜山期的构造抬升使剩余压力降低,现今寒武系在局部地区仍保持超压。温压演化对天然气生成、运移、成藏及后期保存具有重要影响。Abstract: The evolution of maturity of the Sinian-Lower Cambrian source rocks was reconstructed, and the starting time for oil cracking was also determined on the basis of the tectono-thermal history of Central Paleo-uplift, Sichuan Basin. The pressure evolution of some typical wells and 2D profile was simulated and the genetic mechanism of abnormal pressure in the Sinian-Low Cambrian was analyzed. The evolution of maturity indicated that the Sinian-Lower Cambrian source rocks experienced four stages, including first oil generation, second oil generation, kerogen cracking and late oil cracking. Oil cracking started at Middle-Late Triassic. The paleo-pressure evolution of the Sinian-Lower Cambrian consists of normal pressure, overpressure and pressure relief. The pressure coefficient of Cambrian maximized about 1.7 in Middle Cretaceous, and it was higher in Weiyuan-Ziyang area than Gaoshiti-Moxi structural belt. Rapid burial, hydrocarbon generation and late oil cracking are the primary factors for the overpressure. The excess pressure was relieved due to the tectonic uplift in Yanshan-Himalaya Periods, which resulted in the normal pressure in Sinian of the whole area and in Cambrian of Weiyuan-Ziyang area. However, the pressure coefficient of Cambrian maintains a high value about 1.5 in Gaoshiti-Moxi structural belt. The evolutions of temperature and pressure impacted gas generation, migration, accumulation and preservation significantly.
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Key words:
- temperature /
- pressure /
- basin modeling /
- gas accumulation /
- the central paleo-uplift
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