川西坳陷三叠系须家河组油气富集与地层压力关系

Correlation between formation pressure and hydrocarbon enrichment in Triassic Xujiahe Formation, Western Sichuan Depression

川西坳陷新场构造带的上三叠统须家河组是四川盆地重要的致密砂岩油气勘探开发目的层。为提升勘探开发成效,提出以流体动力学为切入点,从动态角度研究油气运动特征,并结合静态研究成果确定油气分布特征的方法,开展油气富集与地层压力关系研究。该区域发育超压,须三段超压发育程度最高,主要产气层须二段地层压力普遍在60~80 MPa之间;剩余压力最高可达40 MPa,大部分区域的剩余压力梯度在0~3 MPa/km之间,最高可达10 MPa/km。通过动态法油气富集理论和对剩余压力、剩余压力梯度等的相关研究,认为其与断层、流体、油气分布具有重要的关系:剩余压力梯度较高(1~2 MPa/km)的区域能兼顾断层改善流体运移能力和较好储层的优势,有利于长期高产稳产。

The Upper Triassic Xujiahe Formation in the Xinchang structural belt of the Western Sichuan Depression is an important exploration target for tight sandstone hydrocarbon in the Sichuan Basin. Several studies are carried out in this paper to improve the effectiveness of exploration and development including the characteristics of oil and gas movement with a view of dynamic point combining with fluid dynamics, determine the distribution characteristics of oil and gas in combination with static research results, and study the relationship between hydrocarbon enrichment and formation pressure. Overpressure is developed in the study area, and the degree of overpressure in the third member of Xujiahe Formation is the highest. Whilst the formation pressure of the main gas producing layer, the second member of Xujiahe Formation, is generally between 60-80 MPa with the maximum residual pressure reaches 40 MPa. The residual pressure gradients in most areas distribute between 0-3 MPa/km and up to 10 MPa/km as the highest. According to dynamic hydrocarbon enrichment theory and the relevant research on residual pressure and residual pressure gradient, it is considered that it has an important relationship with faults, fluids, hydrocarbon distribution and production performance. The area with higher residual pressure gradient(1-2 MPa/km) both improves fluid migration capacity and provides favorable reservoir, which is conducive to long-term high-yield and stable production.