川中地区须家河组气藏勘探成果及潜力分析

上三叠统须家河组气藏是四川盆地川中地区天然气勘探最具潜力的重要目标层系之一，目前仅在1022km²范围内就已获得须家河组天然气探明储量3 049.78×10⁸ m3，初步形成了广安须六段、合川须二段、八角场须四段等规模效益气田。总结该区域勘探开发成果，优选有利勘探区块，将为该区域勘探的可持续发展提供支撑。研究认为：烃源条件、古今构造条件、储层和裂缝是须家河组气藏最终成藏的关键。须家河组气藏主要以构造-岩性复合油气藏为主，烃源岩是控制油气区域分布与天然气聚集规模的关键；有利的沉积微相与成岩相控制了储层的发育分布；古今构造的规模、隆起幅度对油气的聚集及气水分异程度有一定的控制作用；有利的储层或裂缝的发育程度控制气藏的分布范围。平缓构造背景、储层广泛发育分布、大面积含气以及典型岩性气藏等特征，证明该区域具备形成大中型气田的地质条件。根据有利勘探区带划分原则，评价优选出了该区须家河组气藏须二、四、六段具有较大勘探潜力的有利区块或有利区带目标。

Exploration achievements and potential analysis of gas reservoirs in the Xujiahe formation, central Sichuan basin

Gas reservoir in Upper Triassic Xujiahe formation is the most potential target gas layer for gas exploration in the middle Sichuan basin. At present, the explored natural gas reserves of 304.978 mcm have been achieved within the area of 1022 km2 in the Xujiahe formation, so the industrial gas fields have come into being including Guang’an (Xu 6), Hechuan (Xu 2), and Bajiaochang (Xu 4), etc.The favorable exploration blocks were selected from the previous exploration and development results, which provide robust support for the sustainable development of exploration in this region. It is concluded from study that hydrocarbon source, ancient and modern structure, reservoir, and fracture are essential factors for gas accumulation in the end. Most of gas reservoirs in the Xujiahe formation are lithostructural composite hydrocarbon reservoirs. Hydrocarbon source rock is the main factor controlling hydrocarbon accumulation scale and areal distribution; deposit microfacies and diagenetic facies dominate the growth and distribution of reservoirs; ancient and modern structure scale and uplift amplitude play important role in hydrocarbon aggregation and gas/water differential degree; favorable reservoirs and how the fractures develop regulate the distribution range of gas reservoirs. All the features like gentle structures, widely developed reservoirs, gas bearing in a large area, typical lithological gas reservoirs, etc. demonstrate that this region is equipped with good geological conditions of medium and large scale gas field. According to the principle on defining the favorable exploration zones or blocks, the Xu 2, 4, and 6 of Xujiahe formation are evaluated as great potential targets for further gas exploration in this region.