The Characteristics Research And Applications For Gas Flow Through Porous Mediumon Gas Condensate Reservoir

Phase behavior makes gas condensate reservoir's percolation mechanisms complex.In case bottom hole flowing pressure decrease below dew point,condensate forms and gathers gradually around the wellbore and begins to flow when the saturation reaches critical flow value.Gas and liquid phases flowing together cause percolation mechanisms hard to study,particularly near wellbore area.The area shows obvious effect of high velocity flow,namely capillary number effect and Non-Darcy effect.In addition,the condensate in porous media is hard to produce,which leads to a waste of resources.Therefore,it is important to master the percolation law which would provide theoretical guidance and reasonable capacity evaluation for gas condensate reservoir.In base of theoretical research of gas condensate reservoir percolation about previous references,this paper made further study on percolation mechanisms of deferent pressure stages,combining the complex geological and seepage characteristics.The main research results are as follows:1.The paper analyzed the characteristics of phase behavior and the equation of state for gas condensate reservoir.Considering the blocking effect of condensate,gas condensate reservoir can be treated as single-phase seepage model,two zones,three zones and four zones model.The last model was emphatically studied.2.Single-phase and two phases stable(pseudo-steady)seepage mathematical model were established for gas condensate reservoir on the basis of state equation and phase equilibrium theory,considering capillary number effect and non-Darcy effect,and pseudo-pressure was used in two phase model in order to get more reliable results.3.Single-phase,three zones,four zones unstable(pseudo-steady)seepage mathematical model were constructed and solved according to different pressure stages.Finally,pseudo-pressure and its derivative curve were calculated to analyze gas condensate reservoir characteristics.4.High velocity flow's influence on the seepage flow of gas condensate reservoir was studied using multicomponent numerical simulation technology,including bottom hole flowing pressure,pressure profile,condensate saturation change and gas phase relative permeability.The results show that high velocity flow effect can improve condensate blockage's influence.5.According to above theoretical research,the gas condensate well productivity was calculated for YaHa gas condensate reservoir.Traditional productivity equation sometimes leads to negative slope.Blocking skin factor method,changing-skin factors method and the new method of considering capillary number effect were respectively adopted to correct the productivity equation.The result shows that the mew method is more accurate.Then the absolute open flow potential was obtained and guide the reasonable allocation of gas reservoir production.