Proof of sinian reservoir bitumen in Sichuan Basin as oil cracking cause

In order to reveal the cause of the largely distributing bitumen in Sinian reservoirs of Sichuan Basin, geochemical characteristics of the bitumen have been studied. From its microscopic optical characteristics, large proportion of the solid bitumen was found as cavity-filling. What's more, the steroid and terpenoid biomarkers of the bitumen in the reservoir distribute normally, and 25-norhopane standing for degradation and washing function hasn't been detected. Last but not least, condition of crude oil cracking was also possessed, as from the thermal evolution history of Sinian stratum of Sichuan. All of the above suggested that the bitumen was caused by oil cracking in the reservoir.