Research On Dynamic Reserves And Water Invasion Characteristics Of S Edge Water Gas Reservoir

Water drive gas reservoirs are widely distributed in China.At present,the water drive gas reservoir accounts for about 40%-50%of the gas reservoirs that have been developed in China.Due to the good connection between the water drive gas reservoir and the surrounding waters,the formation pressure decreases with the exploitation of gas reservoir.When the pressure wave propagates into the waters,the formation water begins to invade the gas reservoir,which leads to the emergence of gas water two-phase flow and the reduction of gas recovery rate,and the serious water invasion may lead to the water-flooding in the gas well,resulting in the abandonment of the gas well and the reduction of development benefit in the whole gas reservoir.Therefore,research on the dynamic reserves and water invasion characteristics of water drive gas reservoirs is of great significance for the development of this kind of gas reservoirs.On the basis of a large number of literature investigation,the main theoretical work completed in this paper is as follows:(1)Starting with the water invasion mechanism of the water drive gas reservoir,the macroscopic and microscopic mechanisms of water invasion are studied,and the mechanism of the water drive gas reservoir is preliminarily recognized.(2)On the basis of the theory of material balance method,the application of traditional reserves methods to early identification of water drive gas reservoir is studied,and the identification process of water source identification method for single well is analyzed.(3)The water drive curve method widely used in reservoirs is applied to reserve calculation in water drive gas reservoirs.(4)Based on the two-phase seepage theory,combined with the relative permeability equation,the material balance equation of the water drive gas reservoir and the calculation model of flow pressure,an automatic fitting algorithm for dynamic reserves of water and gas reservoirs is established.The optimum fitting of the fitting values and actual values is achieved by the least square method,and the water invasion strength and the dynamic reserve value of the single well are finally obtained.(5)The 4 calculation models of water influx are analyzed,including steady state flow model,non steady state model,pseudo-steady state model and automatic fitting method,and the advantages and disadvantages and applicability of various methods are analyzed.(6)The calculation method of water invasion strength and water drive index are analyzed,and the criteria for determining the active degree of water are introduced.(7)By means of two-phase motion equation and relative permeability equation,the calculation method of gas saturation of single well is established for water invasion analysis.Based on the above theoretical research,a case study is carried out on the 2-5-11 layer of S edge water gas reservoir.On the basis of the deep understanding of the production law and geological survey of the layer,the water invasion of the layer is identified by the traditional reserve method,and the water source of the 27 production wells in the layer is identified by the water source discrimination method.Material balance method,water drive curve method and automatic fitting method are used to calculate the reserves of the layer and each single well,and the reservoirs producing amount of the layer is evaluated.The size of the surrounding waters of the layer is determined by the dynamic method.The activity of water of the layer is evaluated by the parameter of water drive index.By establishing the plane distribution map of the water invasion strength of the layer,the water activity of the layer in different regions is evaluated.The water influx of the layer is calculated by using the unsteady model and pseudo-steady state model.The water influx of each well is calculated by the automatic fitting algorithm.By establishing the plane distribution map of gas saturation at four stages,the water invasion rule of different stages of the layer is analyzed.Based on the above work,a set of method for dynamic reserves and water invasion characteristics of water drive gas reservoirs is formed,which helps to develop water drive gas reservoirs reasonably and efficiently.