Pressure behavior of vertical wells in low permeability reservoirs with threshold pressure gradient

  • Fu Dai

    Student thesis: Master's Thesis

    Abstract

    Due to the extreme small pore throat radius and high pore throat ratio, fluid flow does not obey Darcy's law in low permeability reservoirs, it is non-Darcy flow associated with threshold pressure gradient. Threshold pressure gradient is the level of pressure gradient that has to be attained to enable fluid to overcome the viscous forces and start to flow. When non-Darcy flow happens in low permeable formations, different formation pressure gradients correspond to different seepage flow areas. The boundary between different seepage flow areas can move with time. The mathematical equations for describing the boundary are called moving boundary conditions. Some work on pressure and deliverability equations for the moving boundary problems are done by previous researchers. However, little research has been done on boundary dominated flow problems, which describes the flow after the moving boundary reaches physical boundary. In this thesis, new mathematical model for the boundary dominated flow problem is established. Two kinds of boundary are studied: 1) Constant pressure boundary, and 2) Closed boundary. Analytical solutions are derived using Greens' function with numerical approximation. A numerical simulation is carried out to validate the analytical solution. Eclipse software is used to simulate single-phase non-Darcy flow in reservoir. In addition, the effects of non-Darcy flow parameters on production are discussed, particularly 1) Dimensionless threshold pressure gradient; 2) Reservoir radius; and 3) pay zone thickness, which can provide theoretical foundations for further low permeability reservoir development.
    Date of AwardDec 2016
    Original languageAmerican English
    SupervisorJing Lu (Supervisor)

    Keywords

    • Applied sciences
    • Boundary dominated flow
    • Low permeability reservoir
    • Pressure behavior
    • Threshold pressure gradient
    • Petroleum engineering
    • 0765:Petroleum engineering

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