1961 Middle East Regional Meeting; Dhahran, March 27–29, 1961


The slope of the oil/water interface in edge water drive reservoirs is investigated. Equations of motion of the interface and their boundary conditions are presented, with possible computational techniques to solve these equations numerically. These equations are solved in some detail, especial emphasis being placed on the change of the angle of tilt with time, in two special cases: the first assuming no cross flow perpendicular to the bedding plane, the second assuming that there is maximum cross flow in that direction.


Theoretical analysis, laboratory investigation, and field observation all show that the advance of edge water in a water drive reservoir tends to distort the oil water interface. Pressure gradients caused by oil production and subsequent pressure drop in the producing area vary along the oil/water interface, thus causing the water to move with varying speeds in the different parts of the reservoir. This results in the distortion of the oil water interface.

Distortion of the interface as a result of oil production can be divided broadly into two categories local and field wide. These correspond to the pressure drawdowns in the reservoir, which can also be divided into bottom hole pressure differentials limited to the vicinity of the producing well, and to an overall pressure decline in the reservoir. We can picture the overall pressure decline at any time as a smooth curve varying from point to point in the reservoir. The bottom hole pressure differentials can be thought of as localized 'sinks' superimposed on this curve.

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