Paleo-pressure Reconstruction Of The Deep Carbonate Formation And Its Coupling With The Temperature In The Central Paleouplift,Sichuan Basin

The deep Sinian and Cambrian carbonate formation in the Central Paleo-Uplift of the Sichuan Basin(Southwest China),is the major targets of exploration,where Weiyuan and Moxi large gas fields have been found.However,the pressure evolution and its relationship with the temperature,which have an important effect for the hydrocarbon generation and accumulation,are still ambiguous.According to the analysis on the collected present-day pressure and temperature data,this study found that the present-day pressure coefficient of the Neo-Proterozoic Sinian Dengying Formation and Cambrian Longwangmiao Formation showed a significant positive correlation with the formation temperature.Based on the measured fluid inclusion data includes homogenization temperature,freezing temperature,and salinity,PVT and basin modeling,we reconstructed the paleo-pressure evolution histories of some typical wells,which indicated that the Neo-Proterozoic Sinian Dengying Formation and Cambrian Longwangmiao Formation experienced four periods since the Jurassic: normal pressure(before200Ma)-weak overpressure(200Ma?170Ma)-strong overpressure(170Ma?90Ma)-pressure relief(90Ma up to now).The profile evolution of four paleopressures simulated and recovered by the basin indicates that the residual pressures of the two strata,Cambrian Longwangmiao Formation and Sinian Dengying Formation,have gradually decreased since the late Cretaceous in the Gaoshiti-Moxi area of Central Sichuan Basin,and that the Sinian Dengying Formation reached normal pressure in the Neogene,while the Cambrian Longwangmiao Formation still maintains overpressure.The pressure evolution shows that the paleopressure in the critical period of hydrocarbon accumulation is also affected by the temperature evolution.The decrease of formation temperature is an important reason for the decrease of pressure.The distribution of natural gas reservoir is closely related to the temperature and pressure.This study provides new insights for the paleo-pressure evolution of the Central Paleo-Uplift in the Sichuan Basin and its coupling with the temperature,which are very important for the further hydrocarbon exploration.