Disposal From In Situ Bitumen Recovery Induced the ML 5.6 Peace River Earthquake. Issue 6 (23rd March 2023) - Schultz, Ryan
Abstract: Earthquakes induced by human activities can impede the development of underground resources. Significant induced events (M5) have caused both economic and human losses. The recent M L 5.6 ( M W 5.1) event near Peace River, Alberta occurs in a region of in situ bitumen recovery. We find that 3.4 cm of ground deformation was caused by reverse fault slip (∼29 cm), possibly related to Peace River Arch faulting. Events are located within the shallow basement, nearby to significant wastewater injection into Paleozoic strata. We find a statistical relationship between earthquakes and injection operations. These events were likely related to the in situ bitumen development: dominantly from wastewater disposal induced pore pressure increases, with smaller poroelastic contributions from bitumen recovery. The assessment of this earthquake as induced will likely have implications for future energy development, management, and regulation—including carbon capture and blue hydrogen. Plain Language Summary: Earthquakes can be caused by underground fluid injection; cases of M5 induced events have caused damage and harm. One of the largest recorded earthquakes in Alberta ( M L 5.6) occurred in a region of underground oil sand development. Here, ground shaking and deformation information are combined into an interpreted result: that ancient faults were reactivated with reverse slip. The fault slip is largely within the crystalline basement, with a small portion extending into basal sediments. Nearby injection operations dispose of petroleum‐related wastewater in these basal sediments. This earthquake was likely triggered by the injection process: injection increases pore pressure, which diffuses laterally along permeable sediments, until encountering fractured rock, which channelizes flow into the crystalline basement—the increase of pore pressure within the fault continues until reaching a critical point for slip initiation. This event likely being induced will have important implications for future operations. Key Points: On 30 November 2022 one of Alberta's largest recorded events ( M L 5.6, M W 5.1) occurred in a region of in situ bitumen recovery A well oriented fault was reactivated with reverse slip (29 cm), causing up to 3.4 cm of ground deformation The event was likely induced by pore pressure from disposal, with smaller poroelastic stress changes from bitumen production