雪峰山西侧地区陡山沱组层序地层划分及沉积体系展布

SEQUENCE-STRATIGRAPHIC DIVISION AND DEPOSITIONAL SYSTEMS DISTRIBUTIONS OF THE EDIACARAN DOUSHANTUO FORMATION OF WESTERN XUEFENG MOUNTAINS

埃迪卡拉系陡山沱组发育的厚层炭质页岩为寻找页岩气的有利层位。根据岩芯观察、野外剖面实测和室内镜下岩石薄片鉴定分析,并结合各种沉积相标志研究,确定研究区陡山沱组主要发育浅水型碳酸盐岩台地沉积,进一步划分为碳酸盐岩台地相、斜坡相及若干亚相。以Vail的层序地层学理论为指导,通过以岩性—岩相转换界面为主的层序界面识别,确定陡山沱组发育3个Ⅲ级层序,每个层序可划分出TST和HST两个沉积体系域。在沉积相和层序地层学分析的基础上,编制了岩相古地理图并对其演化特征进行了分析。不同沉积背景下的烃源岩其有机质特征存在明显的差异性,说明岩相古地理对烃源岩的发育和分布具有重要的控制作用。结合各相带烃源岩物性特征,认为台内盆地相为陡山陀组最有利页岩气勘探地区。

The thick succession of black shales of the Ediacaran Doushantuo Formation in western Xuefeng Mountains has recently been targeted for shale gas exploration. Based on field investigation, well log and drillcore data, thin section observation, and sedimentary facies analysis, the Doushantuo Formation in western Xuefeng Mountains is interpreted as shallow water carbonate platform deposits. This sedimentary system can be divided into carbonate shelf and slope facies, as well as several subfacies. On the basis of lithostratigraphic-lithofacies transition surfaces, the Doushantuo Formation can be divided into 3 third-order sequences, each with a TST and a HST. a lithofacies-paleogeographic map is compiled and the paleogeographic evolution is analyzed. The sequence stratigraphic and paleogeographic data provide a framework for hydrocarbon exploration. Our analysis shows that the intraplatform trough is the most favorable target for shale gas exploration.