Geochemical Characteristics and Main Controlling Factors of Middle-Upper Cambrian Carbonate Reservoir

Abstract

The Cambrian system in the Ordos Basin has good exploration potential, and the Zhangxia Formation and the Sanshanzi Formation of the Middle and Upper Cambrian are important targets for the exploration of the Cambrian system. In this paper, the characteristics, genesis and main controlling factors of the Zhangxia Formation and the Sanshanzi Formation reservoir are studied through field section observation, thin section observation, drilling and geophysical logging data combined with experimental analysis data. The reservoir space types of the Cambrian carbonate rocks in the Ordos Basin mainly include intercrystalline pores, intercrystalline dissolution pores, dissolution pores, dissolution sutures and dissolution fractures, among which intercrystalline dissolution pores, dissolution pores and dissolution fractures constitute the most important reservoir space type. There are three reservoir types: pore type, fracture - dissolution cavity type and fracture type. The development of Cambrian strata in Ordos Basin is mainly controlled by three factors: high-energy sedimentary facies zone, epigenetic diagenesis and tectonic movement. Granular beach facies and dolomite tidal flat facies are favorable zones for reservoir development in Zhangxia Formation and Sanshanzi Formation. The fault zone in the basin provides a migration channel for late hydrothermal fluid, which can significantly improve reservoir performance. Tectonic fracture itself is an effective pore system, which becomes the migration channel of geological fluid, and also plays a role in communicating pores, which plays a positive role in reservoir.