The Basics - Operations
A comprehensive report outlining several R&D examples of the technologies and methods that can be used to reduce the environmental footprint in shale gas development was published by the American Oil and Gas Reporter in July 2010: Technologies, Methods Reflect Industry Quest To Reduce Drilling Footprint.
A comprehensive overview of measures to minimize the environmental impact of discrete steps and processes related to shale gas development is provided by the website on Reducing the Environmental Impact of Natural Gas Development. This review focuses on the U.S. Fayetteville shale play in Arkansas.
Latest developments in hydraulic fracturing technology research and development to reduce the environmental footprint and enhance effectivity are described in R&D Areas Key To Improving Fracturing (American Oil and Gas Reporter, December 2011).
Drilling wells a few thousand meters deep into rock formations involves heavy equipment, such as drill rigs, that emit noise and often show little mercy to the surrounding landscape. The adverse impacts of drilling can be mitigated with low footprint rigs that take up less land space, transport more easily and use less energy. These rigs are becoming increasingly automated and require smaller crews. Read about low footprint rigs in a recent RIGZONE article: First Movers in 'Green' Drilling: Low-Footprint Rigs.
Overall operational procedures can be improved using the Low Impact Drilling Scorecard developed by the Environmentally Friendly Drilling Systems Program (EFD). This scorecard is an environmental management tool that can assist operating companies in planning and implementing practices to manage operational risks. You can read about the Low Impact Drilling scorecard here: Technologies, Methods Reflect Industry Quest To Reduce Drilling Footprint.
Well pads, access roads, and utility corridors are necessary constructions for the development of a shale gas play. According to industry estimates, the average size of a multi-well pad for the drilling and fracturing phase of operations is 3.5 acres (=0.014 km²); 1.5 acres (=0.006 km²) is the estimated average after the required partial reclamation (SGEIS 2011, chapter 5). To use a visual comparison: A standard soccer field covers 1.76 acres or 0.007 km².
Large numbers of wells are required to exploit a shale gas play. In the U.S. Barnett shale play, for example, almost 15,000 wells were drilled by the end of 2010 over an area of 13,000 km². An average well density of 1.15 wells per km² was calculated for the overall Barnett Shale play but regionally there may be up to ~6 wells per km² (Lechtenböhmer et al., 2011).
Estimates on future well spacing in U.S. shale plays, e.g. the Marcellus, indicate that spacing will be significantly less dense due to the introduction of multiple horizontal wells that will be drilled from a single well pad. With this technology, the total number of drill pads in a field can be significantly reduced. This is important, especially in densely populated areas such as Europe. Additionally, the number of trips by heavy vehicles will be reduced and drilling rigs will not need to be moved as many times. The reduction in surface impact caused by multiple well pads has been described in more detail in an article featured in the American Oil and Gas Reporter (August 2010): Technologies Reduce Pad Size, Waste.
Natural gas production related activities result in emissions of methane, smog-forming volatile organic compounds and NOx, as well as air toxics including BTEX group, formaldehyde, and hydrogen sulfide. Emissions come from normal operations, routine maintenance, system upsets and fugitive leaks. Incremental air emissions from shale gas development, as opposed to conventional gas development, occur during the completion process, in which new and re-stimulated hydraulically fractured gas wells are prepared for production.
Proven cost-effective technologies now exist, which can capture natural gas that would otherwise escape to the atmosphere and sell it, resulting in significant environmental and economic benefits. These technologies are summarized on the U.S. Natural Gas STAR program website. One of the most effective measures is the use of Reduced Emission Completions (REC) whereby natural gas and associated air pollutants are captured from the flowback fluids from the well after hydraulic fracturing.
The U.S. EPA has released Final Air Rules for the Oil and Natural Gas Industry in April 2012. One of the main requirements is the compulsory use of "reduced emissions completion (REC)" for wells drilled from 2015 onwards. Earlier recommendations on air quality improvement were made in the U.S. SEAB Shale Gas Production Subcommittee´s final report (2011).
Noise is mainly produced by drilling operations. Drill pad and access road construction, as well as fresh and waste water transportation by trucks, are additional noise sources. The overall duration of activities for all operations of a six well multi-well pad prior to production was estimated to be 500 - 1,500 days (Wood et al., 2011), with high noise levels occurring intermittently.
While truck traffic can be reduced significantly through on-site water recycling practices and the use of multi-well drill pads, drilling rig noise can be effectively reduced with available mitigation systems, such as temporary perimeter sound walls, rig floor and substructure blanket panels, as well as generator pac sound control systems.