Abstract: The shale caprock at different diagenetic stages in the petroliferous basin has different sealing abilities. At early period the sealing ability of caprock gradually formed with the compaction and consolidation of the sediments, while at late period the sealing ability becomes worse due to the reduced ductility resulting in the microfracture. We considered the sealing ability of Silurian caprock in Tarim basin by using the advanced reservoir-caprock assemblage logging interpretation method. It is suggested that the caprock evolved too much to favor the hydrocarbon preservation. Thus its sealing ability is the key to hydrocarbon accumulation.

Key words: Tarim basin, Silurian, Caprock, Hydrocarbon accumulation, Log interprelation