Millennium EMS Solutions Ltd.
October 2015
Executive Summary
Introduction
Current analytical techniques allow for convenient and simultaneous analysis of a wide range of metals in environmental samples. Groundwater monitoring programs at upstream oil and gas wellsites in Alberta often track a large number of individual metals, many of which have no known connection to oilfield operations. Some of these metals will exceed Tier 1 groundwater guidelines from time to time as a result of natural variations in background concentrations, and potentially distract the focus of the groundwater monitoring program from the metals that could be related to wellsite operations. Potential sources of anthropogenic metals in shallow groundwater at oil and gas wellsites include disposal of drilling fluids and unintended releases of formation water. This project develops, with rationale, a reduced suite of metals relevant to groundwater monitoring at oil and gas wellsites.
Methodology
Available data were compiled on the likely range of concentrations of each to the Tier 1 metals in i) drilling fluids, ii) formation waters, and iii) unimpacted (background) shallow groundwater. Each of the Tier 1 metals was assessed relative to these data to determine whether there was sufficient justification to include it in the analytical suite for monitoring shallow groundwater at oil and gas wellsites.
Results
The recommended suite of metals for groundwater monitoring at oil and gas wellsites is summarized in Table A. Metals with Tier 1 groundwater guidelines for which it is not considered necessary to analyze include aluminum, antimony, cadmium, lead, mercury, silver, and uranium. It should be noted that the range of shallow groundwater background concentrations for all these metals include the Tier 1 groundwater guideline. For this reason, a significant number of false positive guideline exceedances are to be expected. Consulting Figure 2 will give a qualitative sense of the likelihood of a false positive exceedance for each metal.
Table A: Recommended Suite of Metals for Groundwater Monitoring at Oil and Gas Wellsites
| Arsenic | Iron |
| Barium | Manganese |
| Boron | Nickel |
| Chromium | Selenium |
| Copper | Zinc |
13-AU-SGRC-04