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Informational Letter IL 94-2

16 March 1994

To: All Oil, Gas, and Oil Sands Operators

INJECTION AND DISPOSAL WELLS
WELL CLASSIFICATIONS COMPLETION, LOGGING AND TESTING REQUIREMENTS

The Energy Resources Conservation Board (ERCB) issued Informational Letter IL 84-12 (IL 84-12) in November 1984 which specified surface casing and logging requirements for approval of injection or disposal wells. In administering these requirements it has become apparent that clarification is required in a number of areas. In addition, a system of classification of injection and disposal wells has been developed. This classification system, similar in nature to that used by the United States Environmental Protection Agency, was developed by the ERCB in conjunction with Alberta Environmental Protection (AEP), disposal well operators and users, and certain special interest groups.

This informational letter supersedes Informational Letter IL 84-12 and introduces ERCB Guide G-51 which clarifies completion, logging, testing, monitoring and application requirements for injection and disposal wells. The intent of the guide is to specify procedures and practices designed to protect the subsurface environment, including all useable groundwaters and hydrocarbon-bearing zones, from the potential impacts of casing failure and zonal communication.

Wells used for injection or disposal service will be classified, based on the fluid injected or disposed as follows:

Wells used for solids disposal, into a rock matrix or to a salt cavern, are not included in the classification system or construction, operating and monitoring requirements outlined in this IL. Deepwell injection of solids is an emerging technology with the regulatory requirements currently under development.

Specific details particularly related to Class Ia, Class Ib and Class II wells, including specific waste lists and criteria, are also included in Guide G-51.

With respect to casing and cementing requirements, Class Ia disposal wells will be required to have surface casing set and cemented to surface from a minimum of 25 metres (m) below the lowest usable groundwater zone. Wells that do not meet this criteria would not typically be approved for Class Ia service.

With respect to determination or verification of hydraulic isolation, the requirements presented in the guide represent a significant revision from IL 84-12 as it moves away from inferential techniques such as cement bond and cement evaluation logs towards direct measurements of flow behind casing. Evaluation of hydraulic isolation of the injection zone will therefore require a temperature survey plus a radioactive tracer survey, oxygen activation log, or cement bond/evaluation log. The ERCB believes that this combination of logs can provide a cost-effective alternative to standard cement logs while at the same time provide a more definitive evaluation of hydraulic isolation. The aforementioned logging requirements are based on evaluation of current economical and readily available logging options. The ERCB recognizes, however, that advances in technology may well yield new acceptable and economic alternatives which may include improved cement logging capabilities. It is not the intent to exclude such future logging options as they become available.

With respect to casing integrity, casing inspection logs are required for all wells converted to injection/disposal services. The ERCB expects these logs to be capable of supplying certain minimum information. Casing inspection logs (or a combination of logs) are expected to be fully interpreted, on a joint-by-joint basis, to determine the extent of both external and internal corrosion, remaining wall thickness, and to detect holes, pits, perforations or any other anomalies.

Industry is reminded that all injection and disposal wells shall comply with sections 6.101 and 6.120 of the Oil and Gas Conservation Regulations. In summary, all injection into a well, except those fluids identified herein as Class IV, shall be through tubing. A packer shall be set as closely above the injection interval as practical. The tubing/casing annulus shall be filled with a corrosion inhibiting fluid and annual packer isolation tests shall be performed. Exemption from these requirements for a well or project may be granted by the ERCB where it is not feasible to use a packer in the wellbore completion.

Operators of approved injection and disposal wells will be notified by the ERCB within the next three months as to the classification assigned to each of their wells. Operators of waste disposal wells (Class Ia and Ib) will be required to provide an assessment of each well to verify the proposed classification. This assessment must be submitted within three months of notification of the proposed well classification assignment and will be reviewed over the following twelve months. During this period the existing approval will remain in effect. Assessment of each waste disposal well should be based on the waste streams that are injected and the monitoring and testing that is currently conducted. The initial logging and testing requirements listed in the guide need not be conducted at this time.

Effective immediately, the minimum requirements for newly drilled or converted injection or disposal wells shall be as described in Guide G-51. The guide should be referenced for complete details and discussion of well classifications and related requirements.

Copies of Guide G-51 are available at the ERCB's Information Services Section for a fee of $10.

Questions or concerns regarding Guide G-51 should be directed to the ERCB Drilling and Production Department at 297-8474.

[Original signed by]

R. J. Cox, P. Eng.
Assistant Manager, Drilling
Drilling and Production Department