Study On Phase Behavior Change And Flow Law Of Tight Sandstone Condensate Gas Reservoir

Tight sandstone condensate gas reservoir is an important part of unconventional gas reservoir,which is widely distributed in the world and has high exploitation potential.Compared with conventional condensate gas reservoir,the flow process of tight sandstone condensate gas reservoir is more complex.Its main migration channel is nano-pore-throat.The effects of adsorption,capillary force and non-Darcy effect cannot be ignored.When the local formation pressure drops below the dew point pressure,condensate precipitates and blocks some flow channels,further improving the difficulty of development.Therefore,it is urgent to study the fluid phase change and seepage characteristics,so as to provide theoretical guidance for the design of targeted development scheme.The original phase parameters of condensate gas are tested through PVT experiment,the changes of retained components in different pressure stages of reservoir are simulated by using core component monitoring experiment and material balance calculation method,the characterization method of variable components in the depletion development process of tight sandstone condensate gas reservoir is established,the dynamic phase diagrams of condensate gas development process with high,medium and low oil content are drawn,and the predicted dew point pressure is constructed Three mathematical models of dew point pressure,maximum reverse condensate pressure and maximum reverse condensate volume.Then,through numerical simulation combined with core depletion experiment,the anti-condensation distribution characteristics of tight sandstone condensate gas reservoir are clarified,the traditional condensate gas reservoir seepage theory is modified,and the depletion development process of tight sandstone condensate gas reservoir is divided into pure gas area,foggy flow area,movable gas immovable oil area and movable gas movable oil area.The existence of foggy flow is confirmed,and a new flow mechanism model of tight sandstone condensate gas reservoir is established.The experimental results show that the permeability damage of low,medium and high oil-bearing condensate gas is 56%,62 and 66% respectively.The fractured reservoir is 8%～10% higher than the porous reservoir,and the near well end is 2%～8% higher than the far well end.It is considered that the phase change caused by the change of reservoir composition should be considered in the actual production,and the scheme should be adjusted accordingly.Considering the expansion of foggy flow in the development process can effectively improve the recovery of condensate.The above understanding can provide reference and guidance for practical development...