Subsurface temperature logs in the vicinity of Taos, New Mexico
— M. Reiter and J. Sandoval

Temperature logs (T logs) measure temperature as a function of depth in wells. Temperature logging technique, equipment, and interpretation methodology are described in Reiter et al. (1980) and Reiter (2001). The variation of rock thermal conductivity can affect the T log profile, but because we do not know the thermal conductivity of the rocks along the bore hole wall, we consider only the most pronounced T log characteristics which suggest the influence of ground water flow. In a subsurface environment of constant thermal conductivity, characterized by only conduction heat transfer, the temperature profile with depth (T log) is a straight line. Both surface temperature change and ground water flow can perturb the temperature depth profile. The movement of ground water along faults, fractures, thin layers, and within the borehole is usually observed as abrupt changes in the T log. Vertically downward flow and cooling sub-horizontal flow, over tens of meters depth, will produce a concave upward curvature in the T logs; whereas, vertically upward flow and warming subhorizontal flow over tens of meters depth will produce a convex upward T log. Surface temperature change can also produce curvature in the T log which is most profound near the surface; these effects are not obvious at the Taos sites. Quantitative analysis of T logs to estimate ground water flow characteristics typically assumes steady state conditions below the water table, a reasonable approximation in many areas (Reiter, 2001).

Subsurface temperatures (T logs) were measured in wells at eight sites in the vicinity of Taos, New Mexico, in 2001 and 2002 (Figure 1). From these T logs (Figures 2 and 3) several characteristics regarding the hydrogeology of the area may be suggested.