Enrichment patterns and resource prospects of tight oil and shale oil: A case study of the second member of Kongdian formation in the Cangdong sag, Huanghua depression

WANG Wenguang; LIN Chengyan; ZHENG Min; LU Shuangfang; WANG Min; ZHANG Tao

Abstract：The paper aims to explicit the enrichment conditions and resource prospects of the second member of Kongdian formation in the Cangdong sag,Huanghua depression.Based on the data analysis of casting thin section,scanning electron microscopy,geochemical and other material,and the analytic procedure of sedimentology,structural geology and petroleum geology,the enrichment conditions,controlling factors and enrichment patterns of tight oil and shale oil in the second member of Kongdian formation were elaborated and established.Then,the inferred resource of the two types of oil were evaluated by facet method and volumetric method.The results show that:1) The Cangdong sag of Huanghua depression experienced depressed-rifted basin superimposition in Paleogene,which leads to the different tectonic evolution of northern section inversion type and southern section succession type.2) The tight oil and shale oil in the second member of Kongdian formation distributed near the mature organic shale in the secondary depression and the slope belts of the structural inversion type and succession type,with obvious characteristics of "source control","reservoir control" and "belt control".Namely,the mature shale rich in Type Ⅰ and Ⅱ kerogen provides the source for oil and gas;tight sandstone and shale reservoirs provide the reservoir space for oil and gas;the mature organic shale controls the spatial distribution of shale oil in the two types of slope belts and secondary depression,while the distribution of tight oil is controlled by mature organic shale and tectonic activity.3) The enrichment patterns taking tight oil and shale oil as the core,with constraints of "source control","reservoir control" and "belt control",were established.4) Taking the enrichment patterns of the second member of Kongdian formation as the guidance,according to the facet method and the volumetric method,the tight oil and shale oil resource in the second member of Kongdian formation are 4.2 × 108 t and 18.2 × 108 t respectively.