| Abstract |
This report is the final of a series of reports resulting from a BGS-EA collaboration to characterise the risks to groundwater from new developments in onshore oil and gas (OOG) exploration in England. The previous three reports (Mallin Martin and Smedley, 2020, Mallin Martin and Smedley, 2021a, Mallin Martin and Smedley, 2021b) were focused on establishing groundwater baseline chemical compositions, particularly of those analytes that are and could be associated with OOG activities, in order to facilitate distinction between current compositions and any new industrial contamination from such activities. This synthesis report uses the experience gained from these earlier reports to develop an assessment methodology for identifying the influence of both the baseline environment and anthropogenic impact on groundwater quality prior to any new OOG activity. The methodology also has relevance for other subsurface activities._x000D_
The previous three reports in this series concluded that key influencing factors on baseline groundwater quality when considering OOG-type compounds were not the location of hydrocarbon extraction sites, but instead aquifer lithology and overlying superficial deposits._x000D_
The methodology detailed in this report has been designed to provide a rapid assessment for the potential presence of OOG-type contaminants and other deep subsurface compounds in groundwater. The assessment has been designed to consider the magnitude of influence that each factor is likely to have on groundwater quality. The compounds may be either organic or inorganic: each are essential to understanding sources of contamination, but also for understanding the hydrogeological system. The findings from the case study area reports have been used to justify the weighting that each factor has on groundwater quality. The key factors to be considered are geological (e.g. aquifer lithology, proximity to organic rich sediments), hydrogeological (confined, unconfined) and anthropogenic activities (e.g. hydrocarbon extraction, surface activities). Conducting this assessment for a specific aquifer requires a baseline conceptual understanding of both the hydrogeology and hydrogeochemistry which is a key step in the process. The aim is that this can then be used to understand the potential impact a specific aquifer setting may have on groundwater quality, in relation to OOG and other deep subsurface compounds, prior to any development. |
