Porosity evolution characteristics of sandstones in sedimentary basins: A case study from Ordos Basin

摘要

It is a direction to study for the porosity evolution characteristics of clastic formation from qualitative analysis to quantitative research. To master the porosity evolution rule of sandstones during geologic processes could help to deepen knowledging about the hydrocarbon accumulation mechanism. This paper takes the Member-8 sandstones, Yanchang Formation in Zhenjing Area of Ordos Basin as the research object, and has analysised the current porosity evolution charactersitcs.The sandstone porosity evolution can be divided to a continuous decreased-porosity model mainly due to the mechanical compaction and cementation and a regional enhanced-porosity model mainly due to the dissolution. The superposition of those two types of processes constitutes the entire porosity evolution. Meanwhile, porosity-reduced effects is persist during the whole evolution stage, and porosity-enhanced effects is selective while the organic acids massively dissolves the minerals at the right temperature and depth.