威东-安岳地区上三叠统须家河组四段沉积相及岩相古地理特征研究

STUDY OF SEDIMENTARY FACIES,LITHOFACIES PALAEOGEOGRAPHIC OF FOUR MEMBER OF XUJIAHE FORMATION OF UPPER TRIASSIC IN THE WEIDONG-ANYUE AREA

四川盆地须家河组具有巨大的勘探开发潜力,但对研究区沉积相研究成果却相对较少,成为蜀南地区唯一的一块面积大而勘探程度低,烃源和保存条件好、具备多套储产层的勘探潜力区域,本文根据岩石类型、沉积构造、剖面结构特征将研究区须家河组四段划分为三角洲和湖泊2种沉积相类型,三角洲相可进一步划分为三角洲平原和三角洲前缘亚相,而湖泊沉积相在研究区中只发育浅湖亚相,并对各沉相的沉积微相构成特征进行了详细的研究。在上述沉积相研究基础上,以须四段各亚相为编图单元,编制了各亚段的岩相古地理图,并对其时间演化特征进行了详细研究。表明须四段各亚段由南至北均具有三角洲平原—三角洲前缘—浅湖的古地理展布特征。研究成果的取得,为进一步的储层预测提供了基础地质资料。

The Xujiahe Formation of the Sichuan Basin has huge potential for exploration and development, but its sedimentary facies research results are relatively insufficient, so this is the unique broad area in south of Sichuan Province that has been less explored, has good conditions for hydrocarbon source reservation and shows potential for exploration of more than one storage and productive layer. Based on rock types, sedimentary structures and section structure features, this paper divided the Xujiahe Formation into delta and lake facies, and the former is further divided into delta plain and delta front sub-facies, while the latter only shows the development of shallow-lake sub-facies in the area studied, and then made a study in detail of the compositional features of micro facies of each sedimentary facies. On the basis of the above-mentioned study, with each subfacies of the Xusi member as map formation units, the authors prepared lithofacies palaeogeographic map for each sub-facies and researched into their time framework of evolution. The results indicated that the sub-facies of the Xusi member are expressed from south to north as delta plain, delta front and shallow lake. The results serve as basic geological data for further prognosis of reservoir..