湘中坳陷非常规及常规资源勘探潜力分析

Exploration Potential of both Conventional and Unconventional Resources in the Middle Hunan Depression

以前人对湘中坳陷构造、地层、沉积相的研究成果为基础,结合烃源岩及油气显示等成果分析,初步认为,有利烃源岩和储集岩发育的相带与印支期—早燕山期古隆起或斜坡带相叠置,现今仍有下石炭统测水煤系区域盖层连续分布的区域为天然气富集的有利区。煤层气有利层位是下石炭统测水煤系和二叠系龙潭煤系,有利勘探区块为洪山殿矿区和渣渡矿区。涟源凹陷中部和邵阳凹陷东部凹槽台地相区,中上泥盆统和下石炭统黑色泥页岩系和二叠系泥页岩累计厚度可达几百米,同时具有一定的分布规模,如冷水江一带面积分布广泛,埋藏深度在600～3000m,有机碳含量较高,热演化程度高,并且含有较多的硅质成分,加之构造相对简单,可考虑作为有利页岩气的勘探区域。

According to previous research on the structure, strata and sedimentary facies of the Middle Hunan Depression, and combined with some analysis of both source rock and hydrocarbon show,we consider that:(1)some facies belts in which fa vorable source rock and reservoir rock are developed are overlaid by both paleouplift and slope during Indo-Chinese and early Yanshanian epochs;and(2)an area, which currently the lower Cretaceous measuring water coal system is as regional caprock,is a favorable area with rich natural gas. For coalbed gas, the favor ableones include lower Cretaceous measuring water coal system and Permian Longtan Formation; and favorable exploration blocks include Hongshandian and Zhadu mining areas. In the trough platform of both central Lianyuan Depression and east Sha oyang Depression,the middle and upper Devonian and lower Cretaceous black shales and the Permian shale, with some hundred meters of accumulative thickness, are characterized by certain distribution laws. Shales can be more found around Leishuijiang area,with burial depth ranging from 600 to 3000 meters,higher organic carbon content and thermal evolution degree,and more siliceous composition. So,leishuijiang area can be taken as a favorable exploration one for shale gas.