Gas extraction and earthquakes: Shaky future?
Earth tremors are becoming a scary reality for some mature hydrocarbon producing areas. Are they controllable with changes to operating practices, or can they be guarded against with local building preparation? Jeremy Bowden, columnist for Flame, explores the impending options that the industry faces.
The ring of fire around the Pacific, including California, has always been associated with earthquakes, but over recent years, Oklahoma, situated near the centre of the USA - and the centre of the country’s oil and gas industry - has become its second most seismically active state. It’s not the only part of the world experiencing growing seismicity resulting from gas and oil extraction. Some in Kuwait are now calling for improved building standards as a precaution, following a trend of rising seismicity. Better known examples include the earth tremor that halted fracking in the UK, and the rising tremors in Holland, which have led to a sharp reduction in permitted output from the old Groningen gas-field, Europe’s largest.
The U.S. Geological Survey, in a recent report on "induced earthquakes," – or earthquakes caused by drilling or related activities - said as many as 7.9 million people in parts of Kansas, Colorado, New Mexico, Texas, Oklahoma and Arkansas now face the same earthquake risks as those in California. The report found that oil and gas drilling activity, particularly practices like fracking, or related waste water disposal, were the main cause.
While there always were tremors around the Ozarks range in Oklahoma, recent earthquakes in November and September 2016 reached 5.6 on the Richter scale, and tremors (over 2.7 magnitude) reached 4000 per year 2014-2015, up from just two per year from 1980 to 2000. In response, 37 disposal wells have been closed, which together with other reduced activity, has cut the level of wastewater being injected deep underground. This appears to have also reduced the seismic activity over recent months.
While the ideal situation would be no earth tremors at all, most of the additional seismicity is relatively minor - comparable with the impact of coal mining or filling a reservoir, which can have more effect on the tensions that build up in the earth’s crust than fracking or even deep disposal of fracking waste water. However, injecting the wastewater underground is not thought to trigger earthquakes everywhere it is practiced — in North Dakota, for example, it is fine.
Rolling dunes
There is some concern in the greatest hydrocarbon producing basin of them all. Last February, the General Supervisor of the National Seismic Network at the Kuwait Institute for Scientific Research, Dr Abdullah Al-Enezi, told the national press that Kuwait was “not far from the dangers of a huge earthquake that could leave serious impacts on buildings, especially skyscrapers”.
He said the hydrocarbon extraction processes and the injection of land with liquids were among the factors increasing the chance of a “huge” earthquake. Al-Enezi stressed the need for a special earthquake code for Kuwait, rather than an international one, which he said had insufficient safeguards considering the risks from hydrocarbon extraction activity.
Al-Enezi said that earthquakes occurred in Kuwait “on a weekly basis,” but that their magnitude was “less than 3 on the Richter Scale”, which meant most people did not feel them. But he said these repeated small earthquakes were an indication of a rising risk of a bigger earthquake in future.
Tremors keep European gas in the ground
Meanwhile in Europe, a tremor in northern England halted fracking for many years. And, more significantly, at Holland’s Groningen field - which is Europe’s largest and has been producing since 1952 - the Dutch government has cut output in response to a spate of earthquakes that have caused extensive property damage in the country’s northernmost province.
Output at the field was capped at 26 billion cubic metres (bcm) in 2016 (a halving of output since 2013), and is at 24 bcm from this year onwards, unless it is revised down further as a result of coalition negotiations in the wake of the country’s general election in March. The earthquakes are still there, and the reduced production is being accompanied by work reinforcing houses in the affected areas.
Nevertheless, Groningen is the exception, both in terms of scale, and age, as well as its’ proximity to large population centres. On the whole tremors from hydrocarbon extraction are a manageable and relatively insignificant risk, and owe as much to the underlying stresses and tensions in the bedrock, as to the drilling activity itself.