The benefits of using hydraulic fracturing (HF) to stimulate gas and oil flow from both new and existing wells are obvious. However, the downside is that this technique consumes huge quantities (along the lines of millions of gallons per well) of often regionally scarce water. Opponents to HF also claim this process can contaminate drinking water supplies. The US Environmental Protection Agency recently initiated a new, science-based study to determine if the (HF) practice does indeed pose a risk to human health or the environment.
Meeting the challenge.
To help address some of the water-related issues, several leading water-technologies companies have introduced mobile water treatment solutions. These mobile units are designed to treat and to recycle both HF flowback and brine water produced during drilling, HF and other industrial operations. Such efforts reduce the strain on freshwater supplies. Onsite water treatment also lowers the need to transport HF flowback and produced water offsite for safe disposal. Water technology companies are also building permanent treatment facilities designed to lower the percentage of total dissolved solids from the HF flowback produced water before processing at municipal wastewater treatment facilities that often are not equipped to handle this effluent type.
In addition, several universities, including Texas A&M, Carnegie Mellon University and West Virginia University have initiated research projects (often involving substantial funding from the US Department of Energy) intended to develop new, more effective technologies for treating effluents from oil and gas drilling and HF operations.
HF consume huge quantities of water.
With HF, water under high pressure forms fractures in the rock, which are propped open by sand or other materials thus providing pathways for gas (and oil) to move to the well. Petroleum engineers refer to this fracturing process as stimulation. A variety of different chemicals, typically representing less than 0.5% of the total volume, are also used to facilitate this process. The tremendous volumes of water required (typically two to five million gallons per well), of which 25% to 100% may be returned to the surface as flowback water, must be recovered and disposed of responsibly (or recycled for further industrial usage) before gas production can commence.
For western US states, in particular, freshwater supplies are already extremely scarce; thus, HF can further strain existing water resources. Water used for drilling and fracking active wells in the Barnett Shale area can equal the typical water usage for 185,000 households (or more).
According to a US Geological Survey (USGS) fact sheet, Texas state and county agencies now closely monitor volumes of water used during drilling, and a consortium of Barnett Shale drilling companies have developed best-management practices for water conservation. The goal is to keep the pace of drilling and production activities within the bounds of sustainable water usage. Producers in Marcellus Shale gas production areas have had similar discussions.
Reduce, reuse and recycle.
Water treatment solutions enable water reuse to reduce freshwater and transportation requirements. Produced water from HF operations is typically disposed of in three ways:
1. Transported offsite for disposal in permitted underground wells
2. Transported offsite for treatment before disposal to surface waters
3. Treated onsite for reuse in HF or drilling operations
The unique nature of the flowback water produced from HF operations located in different geographic regions (and different chemicals used) requires different water-treatment solutions. For example, water treatment operations in the Marcellus Shale region in the eastern US must be able to deal with the extremely high-brine content of the HF flowback water.
Several companies, including both Siemens Water Technologies and GE Power & Water, have introduced mobile treatment units that can treat produced water onsite for reuse via a variety of different technologies. The onsite approach both reduces the strain on local water resources and minimizes the cost, wear on roads and greenhouse-gas emissions associated with hauling large quantities of flowback and produced water to distant disposal wells or offsite treatment facilities in tank trucks. The Siemens solution utilizes flotation/filtration technology, while the GE solution utilizes evaporation methodology. As with most technology approaches, each has its pros and cons.
Clearly, the limited availability of water appropriate for HF operations constrains the oil and gas industrys ability to produce shale gas and other unconventional energy sources. Furthermore, the present high cost of treating and/or transporting and disposing of both produced water and HF flowback water represents a considerable cost. The current concerted effort by leading water indus-try suppliers, government and academia to develop, commercialize and deploy new mobile and fixed technologies for cost-effectively treating produced water and HF flowback water will provide significant benefit to the oil and gas industry and the general public.
ARC Advisory Group is preparing a series of reports on industrial water management for its Advisory Service clients. These reports will include approaches and success stories. HP
|The author |
Paul Miller is a senior editor/analyst at ARC Advisory Group and has 25 years of experience in industrial automation industry. He has published numerous articles in industry trade publications. Mr. Miller follows both the terminal automation and water/wastewater sectors for ARC. For more information, readers can contact the author at firstname.lastname@example.org.