Study on Fluids Flow Characteristics of Water-Gas Mutual Flooding in Sandstone Underground Gas Storage with Edge Water
Authors: Li Chun , Wang Jieming , Xu Hongcheng , Tang Ligen , Sun Chunliu 
Published: May 2016

Abstract
It is distinguished from that of a routine gas field that the physics simulation study on multiphase flow characteristics of water-gas mutual flooding in sandstone Underground Gas Storage with edge water. The former mainly solves multiphase flow characteristics of water-gas mutual flooding by the alternating displacement of fluids and much higher flow rates. So it has its particularity and complexity in the design of the experimental system and the process. By independent designing physical simulation experiment system and process on water-gas mutual flooding, the paper mainly solved evaluation technique of multiphase flow characteristics on multi-cycle water-gas mutual Flooding, and established evaluation methods of pore volume utilization on multi-cycle water-gas mutual flooding. All of these provide a better idea to evaluate fluids flow mechanism of water-gas mutual flooding in Underground Gas Storage with Edge Water. Gas-water relative permeability through cores with three different permeability levels was investigated by physical simulation experiments of multiple water-gas mutual flooding. The results of the study show that, with the increase in the number of water-gas mutual flooding, gas relative permeability reduced in the same water saturation. Meanwhile gas-water two phase flowing regions became narrow, and both of the gas flowing capacity and pore volume utilization were reduced. After three times water-gas mutual flooding, pore volume utilization was about 45.9~70.0%.

Introduction
Now Underground Storage of Natural Gas is a mature industry developed as a subdiscipline of the Gas Technology field in the world. Underground Gas Storage rebuilded by gas reservoirs is one of the most economical and effective underground storage. The multiphase Flow Characteristics in the Underground Gas Storage with Edge Water is distinguished from that of a routine gas field. The most essential characteristics of former is that Water-Gas front is always kept in the cyclic variation state between expanding and shrinking, and gas-water transition zone has the feature of multiphase flow characteristics of water-gas mutual flooding. The indoor experiments and field operations show that water-gas mutual flooding not only affects gas injection and withdrawal, but also influences pore volume utilization degree in the gas-water transition zone. Foreign scholars studied the Percolation characteristics of water-gas mutual flooding early, but related literatures and reports searched in the network are less [Ref.1–6]. And the domestic research is at the beginning [Ref.7–8]. So it is very lack of experience and theoretical basis. With theoretical study of Underground Gas Storage deeply, Researcher must make more detailed study on multiphase Flow Characteristics of water-gas mutual flooding in Sandstone Underground Gas Storage with Edge.
According to the particularity and complexity in the process of water-gas mutual flooding, the paper designed physical simulation experiment system and experimental processes of water-gas mutual flooding. Gas-water relative permeability through cores with three different permeability levels was investigated by physical simulation experiments of multiple water-gas mutual flooding. The variation laws of fluid flow Characteristics in the water-gas mutual flooding were evaluated qualitatively. Meanwhile, concepts and mathematical models of the pore space utilization were put forward for quantifying pore volume utilization in gas-water transition zone. All of these provided a Better idea to evaluate Fluids Flow mechanism of water-gas mutual flooding in Sandstone Underground Gas Storage with Edge Water.