Geophysical Surveys For Mapping Migration Of Brines From Evaporation Pits And Ponds

Practices of disposal of liquid oil field wastes are now<br>regulated to prevent contamination of soils and ground water.<br>Current disposal often is by means of deep injection wells.<br>However, a legacy of poorly designed disposal sites of the past<br>require evaluation of the extent and pathways of contaminant<br>migration, so that remediation efforts to contain further<br>migration can be designed, and the effectiveness of removal of<br>contamination from soil and ground water can be monitored.<br>Surface geophysical surveys were undertaken on three oil<br>field brine disposal sites on lands in southwest Texas. The<br>objectives of the surveys were to determine the extent of brine<br>migration emanating from pits used for disposal of oil field<br>brines. These pits were devised to evaporate water leaving a<br>solid (salt) residue. This process, however, also resulted in<br>seepage of liquid brine into the subsurface.<br>The technical approach utilized is a combination of<br>frequency domain electromagnetic profiling with the Geonics EM-<br>34 to quickly determine lateral extent of brine migration, and<br>time domain EM soundings with the Geonics EM-47 to determine the<br>vertical distribution of brine.