Identification and tracing of near-source petroleum transport system based on reservoir bitumen index (RBI) method: A case study of the lower cambrian in the Tazhong-Bachu area, Tarim Basin, China

Abstract

The exploration of deep layers has become increasingly important in the global oil and gas industry. The Tazhong-Bachu area of the Tarim Basin is a pioneering target for deep petroleum exploration in China, but only Wells Zhongshen1 and Zhongshen5 have found industrial oil flow in the Cambrian. Noteworthily, the occurrence of reservoir bitumen in the Lower Cambrian coring interval in many wells indicates that large-scale hydrocarbon migration had occurred here in geological history. Effective identification of reservoir bitumen in the Cambrian dolomite reservoirs is crucial to understanding hydrocarbons' distribution and migration. In this study, we adopt the Reservoir Bitumen Index (RBI) method to deduce a quantitative calculation formula for reservoir bitumen, and classify the transport system into four types based on differences in hydrocarbon transport behavior and characteristics. The results show that the deep carbonate low permeability-tight reservoirs of the Lower Cambrian in the Tazhong-Bachu area generally develop reservoir bitumen, most likely derived from underlying Precambrian source rocks. Therefore, the Lower Cambrian carbonate reservoir is considered a near-source discrete petroleum transport system, providing great potential for further oil and gas exploration in the Lower Paleozoic in the Tazhong-Bachu area.