Abstract:

Tight tuff oil reservoirs, as a special lean oil type, have drawn great attention.The quality of source rocks plays a vital role in the formation of tight oil reservoir. In order to study the oil and gas accumulation law of the Carboniferous volcanic rock reservoir in the Malang Sag in the Santanghu basin in Xinjiang autonomous region,the authors described and evaluated the characteristics of source rock with various lithologies in the Kalagang Formation in Madong area throughthe experiments including rock pyrolysis, kerogen carbon isotope, and GC-MS analysis of saturated hydrocarbon. The results showed that both the tuffaceous mudstone and the dolomitic mudstone have certain hydrocarbon generation potential. The tuffaceous mudstone has greater hydrocarbon generation potential, which is characterized by high abundance of organic matter with TOC greater than 2%, mainly type II kerogen. The source rock is shallowly buried, and the vitrinite reflectance is mainly  0.5%-0.8%, which is in the low-mature stage. Longitudinally, source rocks of different lithologies are alternately superimposed, which is conducive to the formation of self-generated and self-stored reservoirs, and it is of great significance to the formation of tight tuff reservoirs in the Kalagang Formation.

Key words: sourcerock evaluation, geochemicalcharacteristics, tightoil, Santanghu basin, KalagangFormation, Xinjiang