川中地区须家河组低渗透砂岩气藏产水机理

产水问题是制约四川盆地川中地区上三叠统须家河组低渗透砂岩气藏高效开发的关键问题。为给生产现场形成有效防水、治水技术提供理论依据，开展了储层产水机理研究，通过压汞、岩样气驱水实验及微观可视模型开发物理模拟实验，揭示了储层高含水及产水机理。结果表明：须家河组低渗透砂岩气藏储层微细孔喉发育，微细喉道对气相的毛细管阻力大，成藏过程中，当含水饱和度降低到40%~50%后，成藏动力不足以克服毛细管阻力使气相进入更微细的喉道及其控制的孔隙中，决定了储层高原始含水饱和度的特征；低渗透储层气水呈互封状态后，在开发过程中气体弹性膨胀推动较大孔喉处及其控制的孔隙内水相成为可动水，这就是储层产水的主要原因；水封气能量、可动水饱和度及生产压差控制了储层的产水特征。该研究成果对于降低气井产水风险，提高单井产量具有重要的指导作用。

Water production mechanism of Xujiahe low-permeability sandstone gas reservoirs in Middle Sichuan Basin

Water production is the key issue constraining the efficient development of Xujiahe low permeability sandstone gas reservoirs in Middle Sichuan Basin. To find out the theoretical foundation for effective prevention and control over the water production on site, a research is conducted on water production mechanism of the gas reservoir. Particularly, the mercury injection test, gas drive water test for the rock specimen, and the visual model development physical simulation test are performed to reveal the high water cut and water production mechanism of the reservoir. The following results are achieved. (1) Micro pore throats develop in Xujiahe low permeability sandstone gas reservoirs and have a large capillary resistance to the gas; when the water saturation is decreased to 40% ~ 50% in the process of reservoir formation, the reservoir forming dynamics will become too insufficient to overcome the capillary resistance, thereby the gas is driven into smaller pore throats or the controlled pores, which leads to high original water saturation in the reservoir. (2) Gas and water are mutually sealed in low permeability reservoirs, and in the development process, gas elastic expansion turns water in larger throats and pores into movable water, which is the main reason for water production of oil and gas reservoirs. Water sealed gas energy, movable water saturation and production pressure difference define the water production characteristics of the reservoir. In conclusion, this study plays an important guiding role not only in mitigating the risk of water production in a gas well but in increasing the well yield.