Tens of thousands of oil wells are scattered across the peatlands of western Canada. When these wells eventually run dry, simple techniques could enable the restoration of natural peatland ecosystems there, a new study suggests.
Peatlands are vital to storing water and making it available across the broader landscape. They also sequester carbon and provide habitat for caribou and other wildlife species.
In the past, trees or grasses have generally been planted on decommissioned well sites. The sand and clay used to build well pads is too dry to support the growth of mosses. Researchers have also tried removing the well pads altogether, but this often leads to the establishment of Sphagnum moss communities rather than the true mosses characteristic of boreal fens.
In the new study, researchers investigated a middle way: removing some of the well pad material to lower the surface of the decommissioned site, then transplanting moss from nearby intact peatlands. The study represents the largest-scale implementation of this strategy yet, the first time it has been applied at the scale of an entire well pad.
The researchers monitored the hydrological dynamics of the study site in detail over the course of two growing seasons with the aim of understanding whether widespread re-establishment of mosses and other peatland vegetation is feasible.
In a growing season with roughly average precipitation, almost half the study site was wet enough to support the growth of mosses, the researchers report in the journal Ecological Engineering.
“Our results suggest that it is possible for peatland mosses to establish on decommissioned oil and gas well pads if we lower their surfaces,” says study team member Murdoch McKinnon, a graduate student at the University of Waterloo in Canada.
Mosses can’t regulate their own water balance and are very sensitive to desiccation: they can survive dry conditions, but go dormant and can’t grow. Moss re-establishment goes best when the water table remains within 6 cm of the soil surface, the researchers found.
These conditions often pertain around the edges of the well pad, where moisture can seep in from adjacent intact peatland. The interior areas of the pad tended to dry out late in the growing season. Mulching these areas with straw didn’t help with moss growth: the problem seems to be with water draining out from below, not evaporating away from above.
The researchers had thought that only the margins of the well pad might support moss growth, so “the fact that a large proportion of the lowered pad did support wet conditions is really promising,” McKinnon says.
During the drier growing season, however, only a small fraction of the pad had conditions suitable for moss re-establishment. And future summers are likely to be drier because of climate change.
Water retention in the center of a restored well pad could improve over time, as mosses and other vegetation get established. Refinements to the restoration protocol such as changing the slope of the well pad surface, installing subsurface conduits for moisture, or mixing a little peat in with the mineral soil could also help improve moisture conditions in the center of the pad and make sites more resilient to rainfall variability. The researchers are now testing such approaches at other decommissioned well pads in northern Alberta.
“The fact that the technique only requires lowering well pads (as opposed to the costly process of removing all of the mineral soil used to build them) also means it has huge potential to be a cost-effective approach,” McKinnon says. “This might enable oil and gas producers’ reclamation budgets to go further, potentially resulting in the restoration of a higher number of peatlands disturbed by well pads.”
Source: McKinnon M.E. et al. “Hydrologic assessment of mineral substrate suitability for true moss initiation in a boreal peatland undergoing restoration.” Ecological Engineering 2025.
Oil rig image by Delfino Barboza on Unsplash.
Animation: ©Anthropocene Magazine
