A hydrodynamic study of several stratigraphic units in the Permian Basin shows a regional west-to-east dip of the potentiometric surface. The potentiometric surfaces of the Ellenburger and Devonian have both closed lows and closed highs against faults on the Central Basin platform, and that of the Ellenburger is low around the Fort Stockton uplift. Data for the Devonian show a steeper dip of the potentiometric surface in New Mexico than in Texas. The Mississippian data are too sparse to show significant features other than dip to the north, east, and south from Terry County, Texas. The Strawn potentiometric surface has steeper east dip on the east flank of the Midland basin, and approaches hydrostatic conditions around the Central Basin platform. The dip of the potentiome ric surface of the Wolfcamp is to the east and north in New Mexico, and east and northeast in Texas. The San Andres shows east dip. The Delaware Mountain group has general east dip, but anomalous conditions are suggested in central Reeves County.

The potentiometric surfaces of all units mapped have some common regional characteristics in spite of the wide differences in elevation and location of the outcrops and subcrops. However, locally, there are many variations. Tilting of the hydrocarbon accumulations is a significant factor in a few fields, but much apparent tilting is caused by discontinuous porous lenses and by low permeability. Vertical and horizontal pressure relationships around faults and subcrops, vertical and horizontal continuity of oil, relative permeability to oil, and other hydrodynamic conditions can be critical factors to be considered in exploration in the Permian Basin.

Salinity maps of the Basin waters show a northwest-southeast trend of high salinity through the southeast corner of New Mexico. It is separated from a parallel high trend to the north, by a low trend with less than 50,000 ppm total solids.

The quality of drillstem-test instrumentation and programming in the Permian Basin needs to be improved to furnish the pressure data that should be available to the industry.