Microgravity Characterization of An Existing Well Field in the Karst Region of the Yucatan Peninsula, Mexico

The central area of the Yucatan Peninsula is a predominantly karstic region noted for the occurrence of cenotes (surface-expressed dissolution cavities) and interconnected channels which are intersected by an aquifer system consisting of an upper freshwater layer overlying brackish and increasingly saline groundwater at depth.  To support a new industrial facility in the area, a shallow extraction and deep reinjection well network was designed and installed to provide a peak load of approximately 4000 gpm of fresh water make-up and a brine reinjection capacity of just under 1100 gpm.  Due to the pronounced heterogeneity of the karst geomorphology, the well field proved to be inadequate both in terms overall capacity and extracted water quality.

In an attempt to enhace the reliability of the extraction well system, additional investigations were conducted using microgravity survey techniques.  Microgravity and elevation profiles were assembled in order to identify anomalous differential lows that could be indicative of enhaced voiding and potentially enhanced water production opportunities.  A large portion of the existing site access roads and clearings were surveyed and several areas of interest were identified.  These target areas represent promising locations to conduct subsequent exploratory drilling to quantify potential production well capacities and associated water quality.

A brief summary of the previous hydrologic investigations and site hydrogeology are provided as well as the results of the recent geophysical investigations.  Unique characteristics of the system are discussed and lessons learned shared.  Substantial variability has been observed between extractions wells, in both specific capacity and produced water quality, even between wells within very close proximity (< 10 m).  Results of the directed exploratory drilling program, and the corresponding measure of success of the geophysical characterization, are discussed to the extent possible based on the progress of the on-going investigations.