Greenhouse gas (GHG) emissions related to shale gas extraction are much lower than previously cited estimates and assumptions, according to a new report from Massachusetts Institute of Technology (MIT). The study, released on November 26, 2012, shows that companies are using green completion technologies to capture most of the emissions rather than vent or flare them. It emphasizes the economic sense capture technologies, as drillers generate revenues to cover their installation costs. The finding is important as it comes at a time when U.S. shale is emerging as a game changer in the global energy market.
- GHG emissions related to hydraulic fracturing have not led to marked increases in the industry’s total emissions.
- Previous studies claiming that shale gas is GHG-intensive were based on limited data and assumptions.
- Drillers are opting to use emissions-capturing technologies during well completion as fugitive methane has commercial value.
According to a new MIT study, shale gas extraction produces far lower GHG emissions than previously estimated. Unlike previous research, the MIT report is based on a comprehensive dataset from wells across the five major shale fields drilled in 2010, and considers the current field practices used to handle fugitive emissions.
In 2012, U.S. carbon emissions dropped to a 20-year low, largely driven by higher natural gas use over coal. Electricity generated from natural gas-fueled power plants emits 50% less carbon dioxide than coal-fired power. However, the growth in natural gas production from shale sources, had raised concerns about other GHG emissions, mainly from fugitive methane emissions vented during the hydraulic fracturing process.
The process involves injecting a proppant and carrier fluid under high pressure to create fractures in the shale rock and allow gas flow. In the subsequent flowback-stage, the well releases gas, which can be captured to prevent environmental pollution. In the past, the shale drilling process required venting of the initial output from gas wells to filter debris before connecting to a pipeline. In current practices however, an increasing number of drillers are installing reduced-emission completion equipment to separate the gas by filtering out the sand, debris and hydraulic fracturing fluids.
The MIT study reveals that previous reports on fugitive methane emissions have been based on incomplete data, and thus misleading. Assumptions that large quantities of gas are vented during flowback have led to debates about the GHG intensity of shale gas. The new study, intended to analyze this debate, considers a 9-day flowback period to assess GHG emissions from 3,948 shale gas wells. It observes that current gas handling practices vent 15% of fugitive emissions, flare another 15% and capture 70% of the emissions for treatment and sale. The results show that the potential fugitive emissions level in 2010 was 900 Gg CH4 (228 Mg CH4 per well). It further shows that flaring and green completions reduced the emission levels to about 216 Gg CH4 (50 Mg CH4 per well).
Looking at current practices across the major U.S. shale plays makes clear the impracticability of assuming that all emissions are vented. A 2011 study out of Cornell University claimed that shale gas emissions were higher than conventional gas, oil and coal, assuming that all fugitive emissions are vented. However, that study was based on limited datasets and unfounded assumptions, whereas current field technologies and regulatory standards require some extent of emissions capturing. Current field technologies and green completions have reduced actual emissions from fracturing wells.
The introduction of green completions demonstrates the quick advancements in shale gas extraction technology. Green completion has also undergone significant advancements towards becoming a standard practice for drilling wells. In fact, capturing fugitive emissions is economic – drillers add to their bottom line by capturing and selling fugitive methane, instead of flaring or venting it. Additional revenue earned by selling emissions captured during flowback covers the cost of installing reduced-emission completion equipment. The cost comparison has led most drilling companies to capture emissions; as per the study, more than 90% of well completions involve emission capturing equipment.
While additional measures can further drive down emissions, shale gas production has not led to marked increases in the industry’s total emissions. The EPA’s hydraulic fracturing rules requiring the implementation of green completion technology will take effect in 2015. These oncoming regulatory standards will further boost emissions reduction practices in the natural gas sector.
The MIT study was a welcome addition, revealing basic misconceptions around shale-related emissions, and reducing uncertainties associated with the environmental footprint of the shale gas drilling industry.