Study On The Methods Of Surpressured Gas Reservoir Deliverability Analysis

Surpressured gas reservoir, being a kind of special gas reservoir, can be found all over the world, whose pressure coefficient is generally greater than 1.0 and over 1.5.After the gasreservoir putting on production, lower along with reservoir pressure, the effective burden stress that rock frame bear will increase, the rock pore structure become deformed, and the ability of rock flow changed,that's stress sensitivity.Because of the prominent stress sensitivity,the surpressured gas reservoir's flow potential will cause a certain deviation,if using conventional deliverability analysis method.Based on the studies of a great number of literatures, this paper start with surpressured gas reservoir' s genesis and basic feature,considered the peculiarity of overpressured gas reservoir,and detailed formulated the calculation method of the petrophysics and fluid physical property parameters. In the foundation of the predecessors' studying,this paper analysed influence about the variety of effective stress to these parameters. And it have a systematic research about the influence of surpressured to these petrophysics(Φ, K, C_f),established the evaluation method of the surpressured gas reservoir's stress sensitivity. In the multidisciplinary analysis about the variety of the parameters with the effective stress, the paper tallied up the mathematics model of being the widespread suitable using.Moreover,base on the conventional deliverability analysis method,the paper modified the deliverability equation of the conventional gas well,and fetched the deliverability equation being applicable to the surpressured gas well.It also had a systematic analysis about the factors that affect the gas well's flow potential. At last, by means of example analysis, it verified the validity and practicability of the deliverability analysis mothods.By means of these researcheses we knows, the calculation of surpressured gas Z-factor can adopt the modified model of LXF.The model calculation process is simple, and easy to usage. At the same time, the calculation of BHFP considered surpressured should give high opinion,because the accuracy of parameters affect the precision of deliverability analysis directly. At the beginning of pressure decreasing, along with output of the reservoir fluid, reservoir rock will take the elastic plastic deformation.The noticeable stress sensitivity make the reservoir's porosity and permeability precipitous decline. In the beginning the descent is violent, after flatten out gradually,and this kind of damage cannot recover completely. Compared with the surpressured reservoir not carrying microfracture, the microfracture reservoir being of high stress sensitivity. And reservoir's porosity, permeability and formation compressibility factor together with effective pressur being of preferable relativity exponential function. The main factors that affect surpressured gas well flow potential includes:formation conductivity, formation water, formation pressure, bottom contamination, stress sensitivity, erosion flow velocity etc.By comparison analyses of various deliverability equation, author think it is workable that the modified pseudopressure deliverability equation can accurately calculate absolute open flow potential of the surpressured gas well. About the gas well running stress sensitivity analysis experiment, it is necessary to consider about the stress sensitivity variation affect,and modify the deliverability equation,and analyze with the modified deliverability equation. At the begining of the surpressured gas reservoir's exploratory development, author think it is workable that analyze the deliverability with pseudopressure deliverability equation or trinomial deliverability equation.