2/21/2023 0 Comments Flux meaning![]() ![]() ![]() Chambers can be moved around the surface to help delineate the spatial distribution of gas at a well site ( Forde et al., 2018 Forde et al., 2019). Flux chamber surveys are nonintrusive and determine gas flux rates directly by measuring the rate at which concentration changes inside the chamber headspace ( Riveros-Iregui et al., 2008 Pumpanen et al., 2004 Mora and Raich, 2007 Nickerson and Risk, 2009 Nickerson et al., 2014). Soil surface flux measurements are not the regulatory standard in Canada, but they have been used in various GM studies ( Erno and Schmitz, 1996 Kang et al., 2014 Schout et al., 2019 Fleming et al., 2021). In-soil gas concentration can vary widely due to the immense spatiotemporal variability of soil properties like texture, porosity and temperature, as well as moisture content and microbial activity ( Marrin, 1988 Pumpanen et al., 2003). However, in-soil techniques are intrusive, and probe gas can be contaminated with atmospheric air during installation and sampling, particularly when large volumes are drawn. Soil probes can also be placed at different depths to build vertical gas concentration profiles and give insight on the behavior of soil processes such as oxidation and biological production ( Riveros-Iregui et al., 2008). In-soil measurements can serve to identify the spatial extent of a gas plume in the subsurface. This method is recommended by the Alberta Energy Regulator (AER Figure 1) and mandated by the British Columbia Oil and Gas Commission (BCOGC) for Well Abandonment GM assessments ( Alberta Energy and Utilities Board, 2003 AER, 2021a, 2021b BCOGC, 2021). Based on our model results and supplemental field measurements, we propose that flux chamber measurements present a more reliable tool to assess the incidence and severity of fugitive GM.Ĭurrently, the in-soil concentration technique is the industry standard in Canada. We also evaluated field measurements of carbon dioxide from an enhanced oil recovery site to demonstrate how seasonal conditions can influence concentrations of trace gases in shallow soil. Flux measurements were more useful for determining severity of the CH 4 leak into the soil and allowed us to differentiate between leak and nonleak scenarios in soils with biological CH 4 production which could complicate a GM assessment. We observed that in-soil CH 4 concentration was strongly controlled by soil texture and environmental conditions, whereas surface CH 4 flux rates were far less sensitive to those same parameters. In this numerical modeling study, both methods were compared to determine how soil texture, environmental conditions (water content, temperature), and CH 4 leak rates into the soil profile influenced in-soil CH 4 concentration and surface CH 4 flux rates. Two common measurement techniques include the shallow in-soil gas concentration approach and soil surface flux measurements using flux chambers. Due to the immense spatiotemporal variability of soils and uncertainty in measurement practice, the detection and quantification of GM emissions is a challenge. As oil and gas wells age and the number of wells drilled increases to meet demand, we may see more instances of fugitive soil gas migration (GM) and associated methane (CH 4) emissions. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |