缝洞型碳酸盐岩气藏高温高压气水两相渗流特征

Gas-water flowing characteristics under high temperature and high pressure in fracturedcavity carbonate gas reservoir

与孔隙型储层比较,缝洞型气藏存在孔隙、裂缝、孔洞多尺度渗流空间,其渗流特征复杂。取得川中震旦系缝洞型气藏储层岩心,采用人工造缝、造洞方式模拟缝洞发育储层岩心,分别开展常温常压、高温高压(160℃、56 MPa)条件下气驱水相渗曲线测试。研究表明,高温高压条件下气水黏度比、流度比及界面张力低,岩心的残余水饱和度低,相渗曲线整体上移,气相、水相的流动能力强。受重力的影响,缝洞型气藏不同连通方式(水平连通、垂直连通)气水两相渗流特征不同。缝洞垂直连通时,残余水饱和度低、两相共渗区变大、气驱水效率高。因此,产水气藏应采用实际储层条件下相渗曲线,气水两相的渗流能力更强。钻开缝洞型底水气藏顶部储层有利于气藏带水生产。

Compared with pore reservoirs, the seepage characteristic of fractured-cavity gas reservoir is complex because of the multiple seepage space of pores, fractures and cavities. The developed core is created by artificial fracture and hole formation after getting undeveloped Siehuan Sinian fractured-cavity gas reservoir core. Then the gas-water relative permeability curve is tested un- der room temperature with normal pressure and high temperature and high pressure （160 ~C, 56 MPa）. The difference between the relative permeability curves obtained by the several methods shows that, under high temperature and high pressure, there exist low- er gas-water viscosity ratio, mobility ratio, interracial tension and irreducible water saturation. Meanwhile, the integral relative per- meability curve moves upward. These phenomena result in the stronger flowing ability of gas and water. There is a big difference of gas-water two phase flow characteristic between horizontal connection and vertical connection due to the influence of gravity differ- entiation. When the fractured-cavity is horizontally connected, there exist lower irreducible water saturation, larger two-phase seepage zone and higher displacement efficiency. Due to the stronger gas water two phase percolations, the relative permeability curve of actual formation conditions is used in the water-yielding gas reservoir. Drilling on the top of the reservoir is beneficial to the production of gas reservoir with water in the gas reservoirs with bottom water.