黔中隆起及其周缘地区海相下组合与油气勘探前景

黔中隆起及其周缘地区,主要包括黔西北地区及其东部相邻的麻江古油藏地区,均属扬子台地的一部分,具有相似的构造及盆地演化历史。海相下组合主要是指震旦系、寒武系、奥陶系和志留系。黔中隆起褶皱平缓,断裂活动弱,利于印支期及以前所形成的原生油气藏的保存。黔中隆起的下寒武统烃源岩特别是牛蹄塘组烃源岩比麻江地区古油藏烃源岩发育程度高,震旦系和寒武系白云岩为良好储层,下寒武统泥岩及中上寒武统的膏盐岩可作为直接盖层及区域盖层;再加上该区相对稳定的构造保存条件,只要现今地表淡水下渗的深度不足以沟通深层原生油气藏并使之遭受完全破坏,该区就可能成为中国南方海相下组合石油和天然气勘探的重要地区之一。

Marine Lower Assemblage and exploration prospect of Central Guizhou Uplift and its adjacent areas

The Central Guizhou Uplift and its adjacent areas mainly include northwestern Guizhou Province and the adjacent Majiang Palaeo-oil Reservoir area to the east,which are all parts of the Yangtze Region(Yangtze Platform).They have similar structure and basin evolution history,but the folds in the Central Guizhou Uplift are relatively slight,the movements of the faults are not strong,and the strata occurrences are smooth,these features are favorable for the preservation of primary oil and gas pool formed in the Indosinian episode or before this period.The basic sedimentary assemblages of the source rocks,reservoir rocks,and cap rocks are systematically summarized in the study area.It is considered that the Lower Cambrian source rocks,especially the Niutitang Formation source rocks in Central Guizhou Uplift are better than that in the Majiang area of eastern Guizhou Province.Dolomites developed in the Sinian and the Cambrian could be better reservoir rocks,and the sealing strata are mainly the Lower Cambrian mudstones and the gypsum and salt rocks developed in the Middle-Upper Cambrian.Considering the relatively non-active structure preserving condition,the meteoric water seepage depth is not deep enough to connect the deep-buried oil reservoir and make it being damaged,the Central Guizhou Uplift may be one of the important areas for oil and gas exploration of Marine Lower Assemblages.