SEQUENCE STRATIGRAPHIC DIVISION METHOD OF HYDROTHERMAL SHALE: AN EXAMPLE OF THE LOWER CAMBRIAN SHALE OF YANGTZE REGION IN XIUWU BASIN

It is a common method to use sequence stratigraphic theory to identify favorable intervals in hydrocarbon exploration. The Lower Cambrian shale of Well Jiangye-1 in Yangtze Region in Xiuwu Basin is chosen as the research object. The content of excess silicon of siliceous minerals in shale is calculated quantitatively, and by elements Al, Fe, Mn, it revealed that the excess silicon is of hydrothermally origin and the shale deposited in an environment with hydrothermal activity. When aiming at hydrothermally shale, error is inevitable in sequence division only through the traditional method. The formation elements is mainly applied as U/Th, Ca/ (Ca+Fe) and Ti/Al values in the study, combined with lithology and logging data, in order to divide sequences of the Lower Cambrian shale in Yangtze Region in Xiuwu Basin. The result shows that the shale of the Lower Cambrian shale is recognized as a 2^nd sequence with 5 3^rd sequences (SQ1-SQ5) further subdivided into. Based on the comparison of the reservoir parameters, it tells that SQ2 and SQ3 have relatively higher content of TOC, higher content of brittle minerals, larger effective porosity and higher content of gas, which make it as the most favorable intervals of the Lower Cambrian in Xiuwu Basin.