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ABSTRACT: Water coning is the tendency of the water to drive gas downward in an inverse cone due to the downward movement of water into the perforations of a producing well thereby reducing gas production and the overall recovery efficiency of the gas reservoir. This work addresses water coning issues in a naturally fractured sandstone gas reservoir via a numerical simulation approach on a single-well radial cross-section using the ECLIPSE 100 reservoir simulator. A parametric study is conducted to investigate and analyze the effect of the most relevant parameters on water coning phenomenon in a naturally sandstone fractured reservoir, such as gas production rate, matrix and fracture permeability, vertical and horizontal permeability ratio, etc. Results show that reservoir parameters that affect water coning include gas production rate, matrix and fracture permeability, vertical and horizontal permeability ratio, well penetration and aquifer size. And fracture permeability, vertical and horizontal permeability ratio, and aquifer size have considerable significant effect on water coning.
KEYWORDS: Numerical simulation, Water coning, Fractured gas reservoir, Water gas ratio, Recovery
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1 INTRODUCTION
Water coning is a common phenomenon in the fractured gas reservoirs. There are various reasons affecting this phenomenon, such as water fingering, water coning or the normal rise of water gas contact. The production of water from gas producing wells results in the operating costs, and reduces the efficiency of the depletion mechanism and the ultimate gas recovery [1-4]. Among these mechanisms, water coning is a serious problem in many gas fields especially in the naturally fractured sandstone gas reservoirs, where the gas zone has an underlying aquifer [5].
Since Muskat published the first paper related to water coning [6], many studies concerning with water coning have been reported in oil reservoirs. The study focused on the tendency to the development of correlation for breakthrough time, critical rate and water oil ratio following breakthrough [7-11]. And some general trends observed for the water-oil systems were relevant to the study of gas reservoirs. The reasons for water breakthrough were related to the following parameters, such as production rate, reservoir permeability, aquifer size, well penetration and so on [12-14].
By comparison with oil reservoirs, there are relatively few studies reported aspects of water coning in gas reservoirs especially...