Study On Seepage Mechanism Of Underground Gas Storage

Underground gas storage is the inevitable demand of the rapidly development of natural gas, which is found all around the world since a century ago. As main type of building into gas storage, the depleted gas reservoir shows varying degrees of water flooding in most of the reservoirs when they are abandoned. The flooded gas storage reservoir contains its own unique percolation mechanism, which is very different from the driving mechanism of general gas reservoir. The in-depth discussions about these are very little both at home and abroad. The necessary experience and theoretical basis are very rare. In this thesis, researches are funded by Sinopec Group with the project "the injection-production percolation mechanism study of wen96underground gas storage". It plays an important role in guiding this kind of gas storage to running and enriching the theory of building into a gas storage.This paper improved the design of experimental program to be more appropriate on the basis of domestic and foreign researches. Aiming at wen96underground gas storage, the research methods of "physical simulation-based, supplemented by numerical simulation" are done. Firstly,under the conditions of both high and general temperatures, with constant confining pressure, these researches carried out six groups tests of rock stress sensitivity during multiple injection-production cycles. Secondly,based on the conventional relative permeability, this thesis studied on twophase flow characteristics of multiple times water-gas mutual flooding under different conditions (high temperature and high pressure) and different combination methods (single and parallel connections) by six groups tests. After then, for the percolation process of the gas only zone specially, it researched the changes of storage capacity and flow capacity after sevral times injection-production under different combinations through six groups tests. Finally, it found the relative permeability impact to injection-production ability of gas storage through numerical simulation on the basis of sevral times water-gas mutual flooding.The major results made by these researches are as follows:(1) The stress sensitivity of wen96gas storage belongs from no sensitive to weak sensitive. We can ignore the impact of stress sensitivity during actual production process.(2) During gas-water transition zone, with the mutual flooding time rising, the injection-production ability of gas storage will decline and the injected gas will have a certain loss.(3) The fingering phenomenon becomes very obvious because of either the interlayer heterogeneity or the vertical heterogeneity of the reservoir. This phenomenon will have significant influence on the expansion storage capacity of gas storage.(4) Because of their greater storage capacity and flow capacity, the reservoirs with high permeability are more suitable for gas storage operation.(5) The storage capacity and flow capacity in gas only zone increase with the operating time rising. After reaching a certain extent, the growth rates slow down.