Southeastern New Mexico Water Quality Trend Maps

Groundwater (GW) and produced water (PW) databases were used to create maps of the groundwater chemistry of geologic formations. Although trends are present, water quality in both databases is highly variable within formations and short sampling distances.

The groundwater database contains samples from formations at or near the surface, and most of the samples are relatively fresh (less than 3000 TDS.) The produced water database samples are from the deep basin, and have higher salinity, with TDS up to 400,000 mg/L.

The purpose of this mapping is to find the geochemical distributions and trends of solutes, and to discover where, and in which formations, groundwater flushing (in which relatively fresh water moves through a formation, eventually replacing the original saline brine) is taking place in the Permian Basin of southeastern New Mexico.

Expected Trends

The work of previous investigators, together with hydrogeological data gathered in the course of this project, have indicated that several patterns of water movement should be expected. These include:

1) eastward regional flow;

2) relatively high flow through highly fractured carbonates such as the reef zones in the Capitan and Abo, and regionally extensive carbonates such as the Mississippian through Ordovician;

3) more intermediate flow rates through carbonates with interbedded shales such as the Pennslyvanian and Wolfcamp;

4) low flow rates through formations with variable lithology including carbonates, evaporites, redbeds, and shales, including the Artesia Group and Upper Leonardian Formations;

5)The Delaware Mountain Group and Ochoan formations, composed of low permeability fine-grained sandstone, and evaporites respectively, are expected to have very low flow rates and briney waters.

Although there is a large amount of variability between samples, these trends are born out in general. A major exception is the presence of brines within the Ordovician despite its carbonate composition; this is because the Ordovician is cut off from the recharge zone by a major fault zone (the Central Basin Platform) and is not vertically connected with the upper formations.

The Permian Basin in southeast New Mexico is complex both geologically and hydrologically. The basin lithology and history, combined with the interaction of groundwater as it moved through the deep basin aquifer through geologic time, has greatly influenced the chemical characteristics of waters within the basin in a reasonably consistent and predictable fashion. The uplift and eastward tilting of the area in the late Tertiary and Quaternary is likely the cause of much of the chemical distribution of the waters that we see today, although it is impossible to tell the timing of groundwater flushing without more detailed chemical analyses and modelling.