Saller and Henderson (1998) presented an article concerning porosity and permeability variations in two west Texas oil fields (North Riley and South Cowden fields). These fields occur within dolomitized Permian platform carbonates near the basinward shelf edge of the Central Basin platform, a paleogeographic element that influenced Permian deposition in west Texas. Their carefully documented study outlines several anomalous aspects concerning porosity distribution. They noted, in particular, that porosity distribution is not strictly facies dependent but that porosity tends to increase in a basinward direction. They suggested that porosity developed largely during dolomitization by the action of hypersaline evaporative fluids that flowed downdip in a basinward direction during the Permian. These brines were generated in restricted shelf interior lagoons and moved downdip parallel with bedding in a shallow reflux type of hydrologic system driven by subsurface fluid density differences in the Permian Clear Fork and Grayburg formations, as shown here in Figure 1 (see figure 18 in Saller and Henderson [1998]). Figure 1 Part A shows the scenario proposed by Saller and Henderson (1998) for porosity creation, dolomitization, and dolomite cementation of the Permian Clear Fork and Grayburg formations of west Texas. They suggested that macrodissolution of calcium carbonate occurred contemporaneously with dolomitization and dolomite cementation. This process of brine backreaction, however, would cause a net increase of porosity in the shelf interior, the opposite of what is observed. Part B shows a two-stage scenario proposed here to circumvent the problem of limestone macrodissolution by shelf interior brines that must have been initially in approximate bulk equilibrium with calcium carbonate. The first stage records dolomitization by replacement of limestone with little macrodissolution. In stage two, evaporative shelf interior brines may have evolved in equilibrium with dolomite only and became undersaturated with calcite and aragonite. Reflux migration of these brines downdip may …