Ground water contamination at natural gas dehydration sites

Processing of natural gas at well sites, gathering sites and pipeline/compressor sites has been a growing activity in the energy industry. A common activity in this handling of natural gas is the dehydration process where water vapor and entrained liquids are separated from the gas and removed. Glycol units are commonly used for this process and the glycol is recycled by means of a reboiler. In the process of recycling the glycol, water absorbed from the gas is boiled off and is vented from the system. It would appear that the vented water vapor contains petroleum hydrocarbons, including benzene, toluene, ethylbenzene and xylene (BTEX). In addition, it has been observed that liquid product, normally classed as condensate, is also discharged from the system. In some areas it has been a commonly found industry practice to discharge this liquid product, the dehy drip, into or onto the ground. In several instances this material has reached a ground water aquifer and has created dissolved phase contaminant plumes, occasionally reaching 1,000 feet or more in horizontal extent, and with vertical thicknesses of up to 50 feet. Intensive state regulatory programs implemented in Michigan have prompted in-depth investigations and expensive remediation of existing or former dehydrator sites. This paper discusses the dehydrator contaminant issue in detail and provides a case description of an on-site screening technique for soil and ground water sampling analysis to delineate the ground water contaminant plume and subsurface soil in a cost-effective, time-efficient manner