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The Upper Permian Changhsing Formation is one of the most important gas-bearing formations in the Eastern Sichuan Basin. Nonetheless, the primary factors controlling the reef-shoal gas reservoirs of different regions are diverse. Clarifying the controlling factors for the formation of intra-platform reef-shoal reservoirs will promote the exploration and development process of the Changhsing Formation. By using outcrop data, core observation, thin section identification, scanning electron microscope analysis, physical property study, and logging interpretation, this paper analyse the characteristics and factors controlling the reef-shoal reservoir in Dianjiang area of the Eastern Sichuan Basin. The results show that the reef cap and reef base microfacies fine-to-medium crystalline dolomite reservoir have the best physical properties, and the reservoir spaces are primarily composed of intercrystalline pores, intercrystalline solution pores, karst caves, and fractures. The main lithology of reservoir formation is reef-shoal facies. The results for the carbon and oxygen isotopes show that dolomites of different particle sizes are formed in three environments. Affected by regression in the late Changhsingian Age, the reef-shoal of the Changhsing Formation were subaerially exposed to meteoric water diagenesis environments, resulting in the highly dispersed particles in rocks that formed a honeycomb karst system, which greatly improved the physical properties of the reservoirs. After reflux dolomitization, the honeycomb karst system was well preserved due to strong resistance to pressure and dissolution of dolomite. Therefore, dolomitization in the Changhsing formation contributed to reservoir porosity. Later, tectonic fracturing has adjusted and modified the reef-shoal reservoir. In summary, penecontemporaneous karstification was the key to the formation of the reef-shoal reservoir. [ABSTRACT FROM AUTHOR]

A large number of studies have analyzed the annual growth rings and environmental drivers in subtropical China. However, how environmental and physiological effects define the isotopic composition of the wood in this region is poorly understood. Here, we explored the potential of applying three components (whole wood, holocellulose, and α-cellulose) of stable carbon isotopes from Masson pine (Pinus massoniana Lamb.) to dendroclimatology. Sampling sites were covered at the northern, eastern, southern, and western margins of the Masson pine distribution in subtropical China. The results showed that the mean δ13C of holocellulose and α-cellulose both had more enriched values than whole wood, with differences of 1.261 ± 0.233‰ and 1.311 ± 0.189‰, respectively, within individual trees. The three components displayed uniform year-to-year variations and common significant climatic signals, indicating that the δ13C of whole wood from Masson pine was enough to reconstruct interannual paleoclimate information without cellulose isolation due to its high climate sensitivity and low time requirements. The mean δ13C record was significantly and negatively correlated with autumn hydroclimatic parameters (e.g., relative humidity and precipitation) in each study area. This study provides evidence of the influence of hydroclimatic variation on Masson pine forests at a large spatial scale and further enhances the interpretation of climate variations. [ABSTRACT FROM AUTHOR]