ABSTRACT

Analysis of approximately 600 stabilized formation-fluid pressures in northern Alberta indicates a correlation of pore pressures not only with depth of measurement but also with elevation of the well-head. Deviations of observed formation pressures from nominal hydrostatic values were plotted against depth and elevation and were found to be arranged according to patterns expected theoretically for gravity-induced and regionally unconfined flow systems of various boundary conditions. These pressure differences are therefore considered to represent the difference between static and dynamic conditions and are termed the dynamic pressure increment. Effects of geologic heterogeneities and the topographic relief on the subsurface pressure-distribution are reflected by changes in the vertical and lateral spacing of the iso-p contours as well as by their configuration. The method does not give site-specific information on pressure and flow conditions; rather it indicates the type, nature and dimensions of the flow systems.

On the basis of comparisons between observed and theoretically generated patterns of p (d, z) three major hydrodynamic zones were recognized in the area of study. Both the general conclusions and, to some extent, the details of the analysis based on the dynamic pressure increment were corroborated by and complementary to analyses of formation-fluid dynamics by other energy-related parameters. Consequently, the dynamic pressure increment is considered to be a valid parameter in the study of formation-fluid flow in large drainage basins.