四川盆地平昌—阆中地区侏罗系油气成藏主控因素与勘探对策

四川盆地平昌—阆中地区具有十分有利的油气成藏地质条件,但其油气勘探潜力长期被低估。通过对沉积、生油、储集及压力条件等油气成藏主控因素的综合分析,认为该区中下侏罗统具有大面积连续型油气聚集成藏的特征:①早中侏罗世处于湖水广布的繁盛期,烃源岩与储集岩交互叠置;②烃源岩质优、层厚,已大量生烃;③砂岩和介壳灰岩储层致密,且发育泥页岩油气层;④溶蚀孔洞缝的发育使致密储层的储集性能得到有效改善;⑤油气层普遍高压,油气连续型聚集成藏。因此,若在该地区遵循非常规油气资源的勘探思路,针对滩坝砂岩和介壳灰岩致密储层,采用水平井、加砂压裂等工艺技术,则有望实现侏罗系油气勘探新的突破。

The main factors controlling hydrocarbon accumulation in the Jurassic of Pingchang-Langzhong area in the Sichuan Basin and its exploration strategies

The geologic conditions at the Pingchang Langzhong area in the Sichuan Basin are favorable for hydrocarbon accumulation. However, its exploration potentials has have long been underestimated. Based on a comprehensive analysis of geologic sedimentation, hydrocarbon generation, reservoirs and pressure conditions, it is believed that the Middle Lower Jurassic in the study area has the characteristics of large continuous plays. ①The study area is located in the lacustrine depocenter of the Sichuan Basin during the Early and Middle Jurassic when interbedded source rocks and reservoir rocks were deposited; ②The source rocks are high in quality and large in thickness, with a large amount of hydrocarbons being generated; ③The sandstone and shelly limestone reservoirs are tight and contain well developed hydrocarbon bearing mudstone and shale; ④The well developed dissolution pores, caverns and fractures effectively improve the poroperm characteristics of tight reservoirs; ⑤The hydrocarbon bearing layers are generally in abnormally high pressure and form continuous plays. Should the exploration strategies for non conventional plays be deployed in the study area and horizontal well and sand fracturing techniques be applied in the tight pay zones, a breakthrough will be expected in the exploration of the Jurassic hydrocarbon reservoirs in the Sichuan Basin.