Gas-water Two Phase Seepage Numerical Simulation For Fractured Horizontal Well In Shale Gas Reservoir

In this paper,the influence of fracturing fluid on the water saturation in the matrix and seepage mechanism of shale reservoir is analyzed.First of all,the reason of shale reservoir water saturation change is proposed,specifically discusses the causes,influence and mechanism of shale ultra-low water saturation phenomenon,shale gas production factors.Also,the article analyzes the micro mechanism and the influence of imbibition and put forward the calculation of the volume of imbibition.Secondly,analyzes and evaluates the various calculation methods for the existing infiltration amount such as Handy model,Shembreet method,numerical simulation method,advantages and disadvantages of these methods are presented.And then,a new calculation method of the water saturation is proposed,which has nothing to do with the fracturing time and can reflect the formation characteristics.Thirdly,considering the influence of water saturation on the change of gas production,a model of gas-water two phase flow in dual media is established.By means of differential dispersion and equation group coefficient linearization,we can get a numerical model.Finally,this model is applied to a Wei 201-H1 well to predict water and gas production and to analyze the influence of water saturation,the parameters of the hydraulic fracture network and the multi-mechanism.We reach the conclusions that initial water saturation determines stable production period,the reasonable interval of fracturing fluid flow back rate is 0.4-0.8,the optimum fracture conductivity and half-length of hydraulic fractures is 40?m~2·cm and 200m respectively,the influence of diffusion is weaker than slippage,the influence of stress sensitivity is significantly greater than diffusion and slippage.So,the stress sensitivity is the key factor when considering increasing and stabilizing production.