2012 iGEM - University of Lethbridge

CAB Extraction vs. Hydraulic Fracturing

The University of Lethbridge 2012 iGEM team has proposed a modified microbial enhanced oil recovery (MEOR) method for the extraction of unconventional carbonate oil deposits. CAB (CO2, acetic acid, and biosurfactant) extraction will utilize the natural carbon fixation machinery in the cyanobacteria Synechococcus elongatus to convert CO2 into sugars needed to fuel acetic acid and biosurfactant production in Escherichia coli. These products will be pumped down into carbonate oil deposits where the acetic acid will react with the rock to increase the pore sizes and help to pressurize the well site, and the biosurfactant will help reduce viscosity to further enhance extraction yields. In order to develop CAB extraction into a sustainable method for unconventional oil recovery, a comprehensive assessment of the environmental impacts and technological feasibility will have to be performed. The University of Lethbridge 2012 team is aware that our proposed method for CAB extraction would use similar methods for accessing unconventional resources as hydraulic fracturing, and we would like to address some of the issues that have been identified with this technology.

With operations starting as far back as 1949, hydraulic fracturing, or fracking, is a well stimulation process used in the oil and gas industry to enhance underground resource extraction.1,2 The process involves high-pressure injection of fluids into buried geological formations to open and enlarge fractures in the rock, creating pathways for trapped hydrocarbons to flow into the wellbore at higher rates.2,3 The hydraulic fracturing fluids are a composition of water, sand, and various chemicals added to protect the integrity of the wellbore, create and maintain the fractures, and enhance the flow of natural gas.2 Today, computer programs are available that can predict fracture geometry and model fluid movement through the fractures to assist in determining fracturing fluid compositions.4 After fracturing is complete, the injected fluids rise to the surface through the wellbore and are stored in tanks, pits, or underground reservoirs before disposal or recycling.3 Hydraulic fracturing has been criticized by a variety of groups for its negative impact on the environment, including contamination of water sources, induced seismicity, and poor government regulation.

Figure 5. Schematic of horizontal drilling and hydraulic fracturing used to extract shale gas. Steel casing lines are drilled deep underground and cemented in place. Fracturing fluid is then injected at high pressures to create fractures in the shale formation to facilitate extraction. Adapted from “Shale Gas: Applying Technology to Solve America’s Energy Challenges”. NETL (2011).

In March 2011, the United States government released the “Blueprint for a Secure Energy Future” that outlined a collaboration between the Department of Energy (DOE), Department of the Interior (DOI) and the Environmental Protection agency (EPA) to monitor the development of unconventional resource extraction. The three agencies would be responsible for mitigating potential risks ensuing from wellbore integrity, developing green technologies for extraction, evaluating the stress conditions of unconventional resource basin, assessing ecological impact of resource production, and monitoring air and water quality as it pertains to environmental and human health.5 The EPA began a study in 2011 to assess current and potential risks for contamination of drinking water by hydraulic fracturing processes. This is an ongoing study that will focus on both retrospective cases and prospective sites for hydraulic fracturing.6 Recently, the Canadian Association of Petroleum Producers (CAPP) established new guiding principles for water and fluid management in hydraulic fracturing. The guidelines call for full disclosure of fracturing fluid chemical additives, development of lower risk fluid additives, and safeguarding the quality and quantity of water resources.7 In the last few years, the U.S. federal government and several states have developed public disclosure rules intended to provide the public with information about the chemicals added to fracturing fluid and what role those additives serve, such as corrosion inhibitors, friction reducers, gelling agents, and surfactants.

In a report issued by the BC Oil and Gas Commission in August 2012, high pressure fluid injection for recovery of hydrocarbon reservoirs, injection of waste fluids into deep rock formations, and withdrawal of hydrocarbons from reservoirs were identified as potential causes of altered stress conditions of natural fault lines. While thousands of micro-seismicity events can occur as fracturing fluid is injected into gas shales, these events are of such low magnitude that they are not felt on the surface. Larger magnitude events that may be felt at the surface can occur if the fluid injection causes movement along pre-existing stressed faults, however only one such event studied within this report was reported as felt by workers at the surface and no damage or harm to structures or workers was reported.2 The Davis and Frohlich induced seismicity criteria is a generally accepted methodology for the identification of induced seismicity and can be used to monitor seismic activity at and around hydraulic fracturing well sites.

In contrast to hydraulic fracturing, CAB extraction will not require high pressure injection of fluids. Since CAB extraction will rely on increased porosity generated by the reaction between acetic acid and carbonate rock, high pressure fluid injection will not be needed to create pathways for oil flow. The pressure generated by the breakdown of carbonate rock will help to pressurize the well and should not induce seismic activity that can be felt at the surface. However, extensive study of the subterranean geology should be performed as part of initial site selection procedures to ensure that pre-existing fault lines are not nearby or that fracture barrier layers can be utilized to prevent unwanted fracturing of geological formations. Continual monitoring of seismic activity and potential fracturing of upper geological levels will be necessary safety measures. If larger seismic events are reported, pumping rates or injection volumes can be reduced depending on the nature of the seismic activity.

Additionally, CAB extraction will require the addition of fewer harmful chemicals for successful extraction. Sand and other materials used in hydraulic fracturing to maintain fractures will not be necessary since increasing the porosity of the carbonate rock will require only acetic acid. The natural biosurfactant, rhamnolipid, will be used in conjunction with acetic acid to enhance flow rates. Using natural materials will result in lower risk of harmful contamination of ground water. The use of less harmful chemical additives to maintain wellbore integrity will have to be examined. Water sources will have to be monitored for chemical contamination due to direct or indirect results of CAB extraction. Waste water will be stored for reclamation or alternative synthetic biology technology can be developed to recycle it to be used again in CAB extraction or other processes.

Due to new and updated regulations on hydraulic fracturing processes, this technology for the extraction of unconventional natural resources will be more strictly monitored to ensure environmental safety. Following similar guidelines and regulations will be necessary for the safe use of CAB extraction for tapping into carbonate oil deposits in Alberta and around the world, while maintaining high quality of water, air, and soil in these regions.


1. Montgomery, C. T. & Smith, M. B. Hydraulic Fracturing - History of an Enduring Technology. Journal of Petroleum Technology 62, 26-32 (2010).

2. BCOGC. Investigation of Observed Seismicity in the Horn River Basin. (2012).

3. EPA. Hydraulic Fracturing Background Information, (2012).

4. Beckwith, R. Hydraulic Fracturing - The Fuss, the Facts, the Future. Journal of Petroleum Technology 62, 34-41 (2010).

5. Majumdar, A., Hayes, D. J. & Perciasepe, B. Memorandum of Agreement among the U.S. Departments of Energy and Interior and U.S. EPA about Collaboration on Unconventional Oil and Gas Research. (2012).

6. EPA, U. S. Draft Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources. (2011). 7. CAPP. CAPP members establish new Guiding Principles for Hydraulic Fracturing, (2011).

8. GWPC & IOGCC. Chemicals & Public Disclosure - FracFocus Chemical Disclosure Registry, (2012).

9. Davis, S. D. & Frohlich, C. Did (or will) fluid injection cause earthquakes? - Criteria for a Rational Assessment. Seismological Research Letters 64, 207-224 (1993).