Hydraulic fracturing has its problems, and one of the most extreme of these is that it can cause earthquakes. A new study has once again found that fracking does indeed cause earthquakes, however what is surprising is that conventional extraction of oil and natural gas causes more.
The study, ‘Induced Seismicity Potential in Energy Technologies’, and compiled by the National Research Council (NRC), looked into all earthquakes that have been linked to the full range of underground energy technologies, from conventional oil and gas wells, and geothermal energy, to carbon sequestration.
The highest earthquake risks do not come from drilling the well, or using pressurised water and chemicals to fracture the rock, but rather when wastewater from the processes is pumped deep into the formation for permanent disposal. There is also a high chance of triggering earthquakes when water or gas is injected into ageing wells in order to force the remaining contents to the top.
The as-yet-unstudied aspect of earthquake induction by hydraulic injection is the question of whether the total energy released by earthquakes is altered.
The total energy released is a function of the *accumulated* strain on the rock, something not yet measurable. It is probable that multiple small releases can prevent a single large release, so induced microquakes can keep The Big One from happening.