Non-Darcy Flow in Dissolved Cas-Drive Reservoirs

ABSTRACT Gas reservoirs have been simulated for turbulent (more appropriately visco-inertial) flow in the past. A study is extended to single-phase oil, and to two-phase non-Darcy flow in a solution-gas drive reservoir. The effects of normal sequence (increasing rate) and reverse sequence (decreasing rate) schedules, and the effects of liberation of gas on the Absolute Open Flow Potential (AOFP) and skin are considered. Analysis of the results obtained from the two-phase, one-dimensional radial model reveals that the oil non-Darcy pressure drawdown behaves like pressure drawdown in gas wells with turbulent flow. Formation flow capacity calculated from the constant rate drawdown test indicates that non-Darcy flow induces a skin which is rate dependent. The performance of a depletion-drive reservoir obeying a non-Darcy type motion is compared to the performance of the same reservoir producing in a Darcy fashion. The pressure profile and the GOR curve are lower, and the gas saturation profile is higher for a given flowrate in the non-Darcy case in the range investigated. The non-Darcy AOFP is lower than the corresponding Darcy AOFP for a flow-after flow performance. Above the bubble point pressure, an increasing skin decreases the visco-inertial effects. When gas is present or is flowing, an increasing skin stabilizes the visco-inertial effects.