Deep dissolution of Cambrian-Odovician carbonates in the Northern Tain Basin

Cambrian-Odovician carbonate rocks are one of the main reservoirs in the Northern Tarim Basin. Deep dissolution has important role in the formation of effective porosity of the reservoir rocks. The main charac- teristics of deep dissolution in the region are non-fabric selective dissolution, and dissolution developed mainly along stylolites and fractures. The main evidence for deep dissolution are: 1. The dissolution of late stage diagenetic fabrics or the dissolution developed along late stage diagenetic fabrics (such as atylotea and fractures), 2. The dissolution pores filled with hydrocarbon or other late stage diagenetic minerals; 3. Not only the rnvered region, but also the Kepin outcrop region (continuous depression in early stage一from Cambrian to early Permian, uplift in late stage一from late Permian to present) have above charac- teristics. Based on preliminary analysis, this paper considers that the deep dissolution is mainly related to Co₂-bearing acid water produced by organic matter thermal evolution of source rock.