Effects of diagenesis on quality of dengying formation deep dolomite reservoir, Central Sichuan Basin, China: Insights from petrology, geochemistry and in situ U-Pb dating

The Ediacaran Dengying Formation in Central Sichuan Basin is the deep dolomite gas reservoir with largest natural reserves China, providing an excellent example for understanding effect of diagenesis evolution on quality. By integrating petrology, geochemistry and situ U-Pb dating, this study aims to reveal genesis different rock fabrics their corresponding diagenetic events, discuss temporal relationship events effects quality Formation. Two phases three cement are identified reservoirs as follows: 1) matrix dolomites (MD), 2) fine-medium crystalline (FMD), 3) fibrous (FD), 4) medium-coarse (MCD), 5) saddle (SD). analyzing petrographic relationships between these fabrics, it suggested that has experienced six stages, including syndiagenetic stage, first-time early epidiagenetic second-time middle stage 6) late stage. Microbial dolomitization during produced limited increase porosity, but great significance preservation spaces. Silicification most unfavorable formation, its duration influence range very limited. At physical properties have been greatly improved. Two-time stages both destructive During two-stage hydrothermal alterations occurred, Late Silurian Devonian Permian, respectively. Hydrothermal alteration MD constructive destructive, overall constructive, improvement For karstified MD, were resulting damage caused by cementation SD one-stage MVT minerals.