McMullen County, TX includes some of the best development areas for the Eagle Ford Shale, but wells in the county have been found to yield higher concentrations of H2S gas compared to other areas. According to experts, early Eagle Ford well results indicated the reservoir was a relatively sweet, yielding low concentrations of H2S gas, at less than one percent. Well results from some McMullen County wells, however, have yielded H2S gas concentrations greater than four percent.

In October of 2014, Patricia DuBois, a Staff Geologist at Murphy Exploration & Production Co., and Dr. Huzeifa Ismail, a Consultant at Maxoil Process Solutions, conducted an SPE Study Group to further discuss the reasons why McMullen County wells have higher H2S concentrations. It was found deep faults intersect the wellbores of wells with higher H2S gas concentrations. Mapping of these features ultimately allowed for the prediction of areas with high H2S. An economic model was then developed based on the expected H2S concentration and production forecast to direct long term drilling and completions strategy and selection of H2S treatment options.

For more on SPE Study Groups visit spegcs.org