Pore Pressure Behavior And Solid-phase Output Mechanism For A High-pressure Gas Well With A Finite-conductivity Vertical Fracture During Well Tests

There are so many high-pressure gas wells in Kuche foreland fault structure in Tarim oilfield.It is serious trouble of the sand production from the high-pressure gas well,and it reduces production rate and economic benefit.The flow mechanics is complicated for the high-pressure gas well,in particular for the high-pressure gas well with a vertical fracture.It is urgent that how to mimic the flow property.In this paper,the results are as follows:(1)Linear flow models for the high-pressure gasLinear flow is often used as a flow model for the well with a vertical fracture.It models the flow in the fracture toward the wellbore.Based on the continuity equation,the momentum equation,the ideal gas equation and the adiabatic equation,the govern equation is given after nondimensionalising the above equations.The analytical solution of the pressure is given,and the relation between mass flux and bottomhole flowing pressure is given.The importance of gas acceleration is quantified in terms of a dimensionless parameter;and conditions under which gas acceleration effect needs to be considered in the gas pressure profile and mass flux are identified.The result is successfully applied to published experimental data.Forchheimer drag reduces the critical dimensionless outlet pressure,but its effect is small when gas acceleration is either weak(?(27)0.5)or strong(?(29)14).(2)Radial compressible porous media flows for a vertical gas wellConsider the radial porous media flow of a compressible gas into a vertical well.Based on the continuity equation,the momentum equation,the ideal gas equation and the adiabatic equation,the dimensionless govern equation is given.For unchoked flows,the properties of a compressible accelerating gas flow can be modeled by a Darcy-Forchheimer flow with an upward adjusted Forchheimer drag coefficient.For choked flows,the Darcy-Forchheimer equation cannot be used to mimic the accelerating flow no matter how large the Forchheimer drag coefficient is.It is demonstrated that the value of the Forchheimer drag coefficient in some previous studies was inflated due to omission of the gas acceleration in the momentum equation.The plastic zone for Darcy-Forchheimer flows is smaller than that for acceleration flows in the high-pressure gas well.(3)The flow model in a high-pressure gas well with a finite conductivity vertical fractureTwo flow regions are considered: the reservoir and the fracture.Darcy's law is applied in the reservoir flows,and acceleration equation is applied in the fracture.The gas pressure in the finite conductivity vertical fracture is given.The pressure gradient for Darcy-Forchheimer flows is smaller than that for acceleration flows with the same pressure drawdown.The method for computing the gas flow rate from high-pressure gas well with a finite conductivity vertical fracture is proposed.(4)The short-up flow model in a high-pressure gas well with a finite conductivity vertical fractureTwo flow regions are considered: the reservoir and the fracture.Darcy's law is applied in the reservoir flows,and acceleration equation is applied in the fracture.The gas pressure gradient near the wellbore is enlarged as the time increases.(5)Solid-phase output mechanism for a high-pressure gas wellThe radial stress is given for the thick-wall cylinder with a finite outer line by the semi-inverse method.Stress distributions with varying pore pressure are used.The varying pore pressure is obtained from acceleration flows.The tensile stress contains two parts,pull stress and tensile stress caused by poroelasticity.The tensile stress exists in the high-pressure gas well with finite conductivity vertical fractures and without hydraulic fractures.These tensile stresses are responsible for the solid-phase output.