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6. (Regarding well construction) EPA UIC Program Directors should ensure that a combination of casing and cement isolates the lowermost underground source of drinking water (USDW) encountered in the borehole from hydraulic fracturing (HF) target formations when specifying casing and cementing requirements for Class II wells using diesel fuel for HF.
Owners/operators may be required to ensure proper cement emplacement and zonal isolation via appropriate logs and tests, including sonic, temperature, cement bond, or cement evaluation logs (CELs), as well as fracture finder logs during drilling and construction.
To ensure appropriate precautions are taken to address high injection pressures needed for HF, Program Directors may request the following information to assist in specifying casing and cementing requirements:
- Descriptions of geologic formations overlying the production zone and whether they contain potentially mobile contaminants that require isolation from the well;
- Review of well construction plans for potential pathways of fluid migration between any gas-bearing zones and USDWs;
- Physical and chemical characteristics of injection zone formation fluids and proposed well characteristics;
- Location and operating procedures of other HF/injection wells in the AoR or nearby injection zones;
- Data on sizes and grades of the casing string and classes of cement to be used in construction,
- Proposed cementing plan; and
- Information to ensure that long, multi-well pad horizontal wells will be constructed in a protective manner.
Owners/operators should be prepared to provide all of the above as well as any additional testing deemed necessary to demonstrate a well’s mechanical integrity before, during, and after the diesel fuel HF activities.
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7. EPA UIC Program Directors should ensure the owner or operator applies relevant construction-related requirements to already constructed Class II HF wells using diesel fuels to protect USDWs.
Older wells may not provide adequate levels of protection for HF using diesel fuels and owner/operators of such wells may be required to perform well repairs , including but not limited to replacing injection well tubing or cementing across specific well sections intersecting potentially vulnerable formations to decrease risk of fluid movement. Permits will not be issued when corrective measures are not sufficient to protect USDWs.
8. To account for the unique nature of diesel fuel HF injection—including high pressures and volumes of fluids—EPA permit writers should also consider incorporating into permit conditions procedures to ensure there is no significant leak in the casing and when applicable, tubing and packer through the following:
- Casing integrity testing of casing strings,
- Formation pressure tests,
- Production casing integrity testing of the (or Standard Annular Pressure Test for tubing and packer, and
- Equip wellhead with pressure recording devices on all available annuli and injection strings
To ensure no significant fluid movement in channels adjacent to the well bore, the following cement integrity methods may be considered:
- Monitor/record volume, flow rate, density, and treating pressure of cement during construction, and
- Submit a CEL with the notice of completion.
To assess mechanical integrity, EPA permit writers should consider the following:
- Request permittee to report to the EPA within 24 hours with written confirmation including certification/documentation of remedial cementing within 48 hours if a casing integrity test, formation pressure test, cementing records or CEL indicates inadequate cementing or a failure;
- Additional mechanical integrity testing (MIT) if pressure testing or CELs do not confirm no significant leaks or fluid movements through adjacent vertical channels; and
- Adjust MIT requirements to confirm permit compliance.
Owners /operators may be subject to any or all of the above recommendations per the discretion of the permit writer and/or the Program Director.
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9. EPA UIC Program Directors should modify monitoring and reporting protocols so that the permit writer has adequate information to determine that each planned HF operation using diesel fuel will not endanger USDWs including:
- Monitoring pump rate, pressure, volume, and viscosity of the fracturing fluid to evaluate the HF operations and real-time data to monitor and control operations,
- Allowing flexibility in monitoring for intermittent operations, and
- Utilizing alternative or supplemental monitoring data.
Owners/operators may choose to use American Petroleum Institute guidance for real-time mapping of HF in progress.
10. In addition to the above technical aspects, the guidance also provides detailed information about financial responsibility and public notification permit requirements. The entire guidance document can be downloaded at http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/hydraulic-fracturing.cfm.