Abnormal pressure is of great significance for hydrocarbon generation, migration and accumulation. The tight gas reservoirs in the Middle Jurassic Shaximiao Formation of the Sichuan Basin are characterized by considerable underpressure, which origin and evolution are still unclear. In this study, the pressure distribution was characterized by repeat formation test and Bowers’ method using sonic and density well log data. The origins of underpressure were analysed by geological analysis and quantitative calculation. Basin modelling method was also applied for pressure evolutionary process reconstruction. The results showed that underpressure developed at depths of 1900–2300 m with pressure value of 9.24–17.19 MPa and the pressure coefficients of 0.45–0.89. Laterally, the pressure coefficient showed a decreasing tendency from the western to the eastern portion of the study area, which was characterized by considerable underpressure. The results of the underpressure origin analysis indicated that the elastic rebound and temperature reduction led to pressure reductions of approximately 12–15 and 3–4 MPa, respectively. However, the source rocks of Lower Jurassic Ziliujing Formation and Upper Triassic Xujiahe Formation provided pressure increasing by hydrocarbon generation as two of the main sources in the Sichuan Basin. The gas generating process in the source rocks of the Xujiahe Formation increased the pressure by more than 20 MPa which compensated for the pressure decrease in the western part of the Central Sichuan Basin. However, the gas generation of the Ziliujing Formation only provided less than 10 MPa of pressure compensation for the eastern part, which was then characterized by widely distributed underpressure. Consequently, the western and eastern portions of the Central Sichuan Basin underwent different pressure evolution processes, which lead to different pressure distributions at present. This study provided a basis for underpressure analysis of gas reservoirs in quality and quantity in the Central Sichuan Basin and may be helpful for similar gas fields worldwide.

异常压力对油气生成、运移和聚集具有重要意义。四川盆地中侏罗统沙溪庙组致密气藏具有显着负压特征，其成因和演化尚不清楚。在这项研究中，压力分布通过重复地层测试和 Bowers 方法使用声波和密度测井数据进行表征。通过地质分析和定量计算分析了负压成因。盆地建模方法也被应用于压力演化过程重建。结果表明，在1 900～2 300 m深处出现负压，压力值为9.24～17.19 MPa，压力系数为0.45～0.89。横向，研究区压力系数自西向东呈递减趋势，表现为相当大的负压。负压起源分析的结果表明，弹性回弹和温度降低分别导致约 12-15 MPa 和 3-4 MPa 的压力降低。而下侏罗统自流井组和上三叠统须家河组烃源岩作为四川盆地的两个主要烃源，生烃压力增加。须家河组烃源岩成气过程使压力增加20 MPa以上，弥补了川中西部地区的压力下降。然而，自流井组产气仅对东部提供不足 10 MPa 的压力补偿，呈负压分布广的特点。因此，川中西部和东部地区经历了不同的压力演化过程，导致目前不同的压力分布。该研究为川中地区气藏的质、量欠压分析提供了依据，对世界范围内的类似气田具有一定的借鉴意义。