A Comparison of Dissolved Gas Sampling Techniques

Tapping the natural gas reservoirs throughout the United States has long been a viable solution for energy independence; however until recently getting to these gas reservoirs was very difficult. Now, through the development of horizontal drilling in conjunction with hydraulic fracturing or “fracking”, these reservoirs have become much easier to tap for natural gas. However, there are some environmental concerns with the fracking process that have come to light as fracking has gained popularity. One major concern is the potential for natural gas to migrate into drinking water sources. In order to test for dissolved gases, the RSK-175 Standard Operating Procedure (SOP) was developed. Since RSK-175 is an SOP and not an EPA or ASTM method; laboratories have employed different approaches in order to calibrate for the dissolved gases. This study will evaluate a standard calibration using serial dilutions of saturated gas samples. The LGX50 autosampler will do the rest of the work by creating headspace in the sample vial while maintaining sample integrity and transferring the headspace to a GC/FID for analysis. This automation provides the capability to treat calibration samples in the same manner as field samples thus reporting field sample results requires no back calculation using the Henry’s Constant.