Shale Gas on the Intensity Scale
(Beijing) -- Precariously placed, the bulk of China's shale gas reserves sit on interlaced earthquake fault lines in the country's southern region. In a country with more shale gas reserves than the United States and Canada combined, plans to extract a high volume of shale gas from earthquake prone regions has researchers concerned such activity could have perilous effects.
Worries have arisen from studies conducted on the effects of fracking, the most popular method for shale gas extraction, which have been correlated to an increase in seismic activity. Fracking involves the creation of fissures in rocks through the high-pressure injection of chemicals and water.
China has been working hard to catch up with the United States in the development of shale gas extraction. The government's lofty ambitions were made clear in the "Shale Gas Development Plan 2011-2015." The plan, issued by the National Development and Reform Commission in March 2012, states that China plans to increase its commercial shale gas production from zero to 100 billion cubic meters by 2015. The controversial hydraulic fracturing technique will be used as the primary method of extraction.
The Sichuan Basin and the Yunnan-Guizhou Plateau in southwest China boasts nearly 40 percent of shale gas resources in China. However, over the past few years, frequent earthquakes have cast a deadly shadow over the people's lives in the region.
Some geologists have expressed cautious concerns over the government's shale gas mining plans.
Insiders in the industry disclosed that the shale gas development in China has yet to factor in seismic risks to feasibility assessments.
China's shale gas extraction process remains at the trial stage, but the seismic risks of industrial activity have long been a subject of study among researchers. Since the 1970s, Chinese researchers have conducted observation programs on the Renqiu Oilfield in Hebei Province, Shengli Oilfield in Shandong, Rongchang gas project in Chongqing Municipality and the Changning salt mine water injection project in Sichuan Province. In every program, scientists registered minor earthquakes caused by processes similar to fracking.
According to Zhang Zhiwei, a researcher at the Sichuan Provincial Seismological Bureau and his colleagues, a January 2009 study in Zigong, Sichuan Province found that when industrial water was compressed into an abandoned natural gas shaft, surrounding areas immediately experienced a number of small earthquakes. The two strongest earthquakes were recorded with a magnitude of 4.4 and 4.2. More than 160 episodes of small-scale quakes were captured by professional equipment. Zhang published their findings in the May edition of Geophysical Journal in 2012.
When the amount of water injection activity was reduced, both quake frequency and magnitude declined.
Similar correlations were also observed in Rongchang County, the booming mining and natural gas zone close to Chongqing municipality.
Since the development of natural gas exploration in the late 1980s, miners started to inject industrial water into the mining shafts after exploration. Since then, more earthquakes have been registered in the region.
According to a joint study conducted by the Chongqing Municipal Seismological Bureau, China Seismological Bureau and Geological Survey of Japan, for the past 20 years, more than 30,000 earthquakes were observed in the Rongchang gas project, two of which hit magnitude 5.0 and 20 earthquakes stronger than magnitude 4.0.
Lei Xinglin, a researcher at the Geological Survey of Japan, and participant in the Rongchang seismic studies, told Caixin that hydraulic fracturing had a direct link to a larger number of earthquakes. The question of an earthquake evolving into a stronger magnitude would depend on geological conditions.
"The geological characteristics of the areas rich in oil and gas reserves in the Sichuan Basin, Yunnan, Guizhou and Guangxi regions show that a high risk of large magnitude earthquakes could occur with large scale exploitation of natural resources underground. Injecting water into deep underground in these areas would undoubtedly raise seismic risks," Lei warned.
The U.S. Energy Information Administration estimates that in 2011, China had more than 36 trillion cubic meters of shale gas reserves that can be accessed by current technology.
However, nearly 40 percent of China's shale gas resources are buried deep down under China's southwestern region, covering Sichuan, Yunnan, Guizhou provinces and Guangxi Zhuang Autonomous Region and Chongqing Municipality.
Quality shale gas resources in southwest China sit mainly in land-based shale deposits between 3,000 to 5,000 meters underground. The complex terrain structure, elevation and population density could make large-scale drilling disruptive not only to the local economy of residents, but also trigger landslides and other geological disasters.
Lei told Caixin that it is possible to produce real-time probability readings of man-made seismic activity based on previous test data. In most cases, the ceasing of pressurized activity underground would immediately reduce the earthquake possibility.
However, since energy companies have refused to release related data on oil and gas exploration and water injection operations citing proprietary concerns, it is impossible for researchers to be involved in earthquake monitoring, said Lei.
"If there was cooperation in advance, scientists could closely monitor the seismic activities of fracking areas. When the risk of a major earthquake is presented, companies can take preventative measures by changing the injection pressure and methods," said Lei.
A source from China Petrochemical Corp. (Sinopec), which is developing a pilot shale gas project in Chongqing, said that at present, domestic gas enterprises haven't formally discussed the geographic impacts of shale gas development.
Lei advocated the use of independent third parties in environmental impact assessments of shale gas projects. Regulatory mechanisms should also be established at the national level to effectively monitor the safety of the operation.
An adviser with a foreign shale gas operator told Caixin that the environmental impact brought about by shale gas development is still a sensitive topic and there have been few discussions open to the public.
"But this doesn't mean that there are no problems. Not enough is known given the current scale of activity," he said.
Bao Shujing, a senior engineer at the Sinopec Petroleum Exploration and Development Research Institute told Caixin that at this stage, earthquake risks are not part of standard environmental impact assessment reports by shale gas companies mainly because many in the industry do not consider the seismic risks of fracking to be anywhere close to natural seismic activity.
Bao said shale gas operators must share information when potential earthquake risks are presented and that companies should incorporate seismic risks in environmental impact assessments for projects. "Hydraulic fracturing could be the last straw in triggering an earthquake. The possibility is there."
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