For Operators - Underground Injection Control

An operator requesting approval for an underground injection project must provide detailed data that, in CalGEM’s judgment, are pertinent and necessary for the evaluation of a proposed project. (14 CCR § 1724.6.) The application must include a detailed engineering study that includes a statement of the primary purpose of the project; the reservoir and fluid characteristics of each injection zone; and the planned well drilling and plugging and abandonment program to complete the project, including a flood-pattern map showing all injection, production, and plugged and abandoned wells, and unit boundaries. The engineering study must also include casing diagrams for all idle, plugged and abandoned, and deeper-zone producing wells within the area affected by the project. The casing diagrams in the engineering study must evidence that plugged and abandoned wells in the area will not have an adverse effect on the project or cause damage to life, health, property, or natural resources. (14 CCR § 1724.7(a).)

Along with the engineering study, a geologic study and injection plan must also be submitted. At a minimum, the geologic study must include a structural and isopach map, a cross section, and a representative electric log that identifies all geologic units, formations, freshwater aquifers, and oil or gas zones. (14 CCR § 1724.7(b).) The injection plan must include a map showing all injection facilities; maximum anticipated injection pressure and volumes; monitoring system or method used to ensure that injection fluid is confined to the intended zone or zones of injection; method of injection; corrosion protective measures; the source, analysis, and treatment of the injection fluid; and the location and depth of water-source wells to be used in conjunction with the project. (14 CCR § 1724.7(c).)

Additional information can be requested for projects that may be hazardous, large, unusual, or particularly complex. (14 CCR § 1724.7(e).) In instances where an operator desires to change or modify any of the originally approved operating methods or conditions of a project, such as an increase in size, a change of the injection interval, or an increase of the injection pressure, the operator must first obtain approval from DOGGR. (14 CCR § 1724.10 (a).)

In order to expedite the application process, operators should evaluate the data being submitted to determine if the program requirements discussed below will be met. It is the operator’s responsibility to demonstrate to DOGGR’s satisfaction that the program requirements are met.

As explained above, every injection project must be supported by an engineering study that includes casing diagrams for all idle, plugged and abandoned, and deeper-zone producing wells within the area affected by the project. The casing diagrams in the engineering study must evidence that plugged and abandoned wells in the area will not have an adverse effect on the project or cause damage to life, health, property, or natural resources. (14 CCR § 1724.7(a)(4).) Additionally, CalGEM must evaluate casing diagrams for all wells within the area affected by the project.

In determining the “area affected by the project”, DOGGR references the Area of Review (AOR) requirements found in the federal SDWA regulations. Under the federal regulations, the AOR is a minimum fixed radius of 1/4 mile from the well bore, unless an approved mathematical model is used to determine the “zone of endangering influence.” (40 CFR § 146.6.) The federal regulation provides a modified “Theis equation” as an example of such a mathematical model. (40 CFR § 146.6(a)(2).) For an AOR using a 1/4 mile fixed radius, the following factors are to be taken into consideration: chemistry of the injected and formation fluids; hydrogeology; population; ground water use and dependence; and historical injection practices in the area. (40 CFR § 146.6(b).) For further discussion of the federal AOR requirements see this clarification from the U.S. EPA:

Clarification of UIC Permit Application Requirements for Class II Wells

The Division of Oil, Gas, and Geothermal Resources nominally defines an AOR boundary for a proposed injection well as a ¼ mile perimeter around the portion of the well’s path that lies within the approved zone of injection as projected on a horizontal plane at ground level. However, this definition is a starting point in determining an AOR boundary. The AOR boundary may be reduced or expanded based on pertinent information regarding the well’s completion, the local geology, and the injection parameters, including approved mathematical modeling.

The UIC Program is predicated on confinement of injection fluid to the intended zone or zones of injection. Every injection project must include an injection plan that ensures that the injection fluid will be confined to the intended zone or zones of injection. (14 CCR § 1724.7(c)(3).) To confirm that injection fluid is confined to the approved zone or zones, mechanical integrity testing must be performed on each injection well upon commencement of injection and periodically thereafter. (14 CCR § 1724.10(j).)

In order to determine whether abandoned wells within the AOR could act as a conduit for injection fluid, well data must be examined to ascertain the condition of the wells. Consistent with the requirements discussed below, it is safe to assume that a well does not threaten to act as a conduit if it has a verified 100 linear feet of cement above the approved zone of injection, or a calculated 150 linear feet of cement above the approved zone of injection. (When the top of cement is determined by calculation a substantial margin of safety is needed to allow for variations in hole size, cementing procedures, pre-flush conditions and displacement of fluids.)  For abandoned wells, consideration must be given to the cement both inside and outside all casing strings, but for active and idle wells, only the cement outside of all casing strings is relevant.

The specific requirements to be considered when examining the data for wells within the AOR include the following:

• Plugged and abandoned wells are required to have oil-bearing or gas-bearing strata isolated. Operators are required to use every effort and endeavor to protect any underground or surface water suitable for irrigation or domestic purposes from the infiltration of detrimental substances. (Public Resources Code § 3228.) State Water Resources Control Board Resolution No. 88-63 (Appendix A) states that water with total dissolved solids (TDS) of 3,000 mg/L or less is suitable, or potentially suitable, for municipal or domestic use. A minor aquifer exemption may be required for water with TDS between 3,000 and 10,000 mg/L. (40 CFR 146.4.)
• Current regulation requires operators to fill the annular space to at least 500 feet above oil and gas zones and anomalous pressure intervals. However, prior to 1978, operators were only required to have 100 feet of cement in the annular space above oil and gas zones and anomalous pressure intervals. DOGGR may provide a variance to this requirement if supported by known geological conditions.  (14 CCR § 1722.4.)
• Plugged and abandoned wells are required to have cement across all perforations and the plug shall extend at least 100 feet above the top of a landed liner, the uppermost perforations, the casing cementing point, the water shutoff holes, or the oil and gas zone, whichever is highest. (14 CCR § 1723.1(b).)
• In an open hole, a minimum 200-foot plug is required across all fresh-saltwater interfaces. An interface plug may be placed wholly within a thick shale if the shale separates the freshwater from the brackish or saltwater sands.  If there is cement behind the casing across the fresh-saltwater interface, then a 100-foot plug is required inside the casing across the interface.  Squeeze-cementing, a cavity shot, or other special plugging procedures may be required in certain circumstances. (14 CCR § 1723.2.)

CalGEM recommends that operators provide the information and data detailed below when submitting AOR data in support of active or proposed injection operations. This information and data will generally facilitate CalGEM’s review and expedite a determination of whether it has been satisfactorily demonstrated that wells within the AOR will not have an adverse impact on the injection project or cause damage to life, heath, property or natural resources.

It is CalGEM​’s preference to receive all data in both hard copy and electronic format.  If spreadsheets are provided electronically, only Microsoft Excel format can be accessed by CalGEM.

• Supporting data used in determining the AOR boundary (i.e. a directional survey or a well bore plat map of the subject well). (Examples provided in Appendix B.)
• Well bore plat map with AOR boundary and well bore paths of all wells within and near the AOR boundary. See example .
• Vertical sub-sea structure map of the top of the approved zone of injection over the entire AOR, superimposed over the well bore plat map. It is helpful if a mark is placed on all well bore paths where the well bore path penetrates the top of the zone of injection. It is also helpful if indication is provided next to the mark of the true vertical depth (sub-sea level) in feet of the top of the zone of injection for that particular well bore path.
• List of all wells within the AOR boundary.
• Since CalGEM staff must review casing diagrams for all wells within the area affected by the project, submitting all diagrams will expedite the project application review. (Discussion and example provided in Appendix C .)
• To speed up CalGEM’s internal evaluation, the results of the operator’s own consideration of its AOR, identifying the following:
  • Wells that clearly would not act as a conduit for injection fluid.
  • Wells that do not have ample cement above the zone of injection that, in the operator’s opinion, will not act as a conduit for injection fluid. CalGEM encourages operators to provide explanation of why such a well will not have an adverse impact on the injection project or cause damage to life, heath, property or natural resources.
  • Wells in need of remediation. CalGEM​ encourages operators to lay out the plan for remediating problem wells within the AOR.

Operators are required to maintain data establishing the performance and safety of an injection project and make that data available for periodic review by CalGEM. (14 CCR § 1724.10(h).) It is CalGEM​’s policy to review the data for each project on an annual basis. The purposes the annual injection project review include:

• Determining if the injection project is still consistent with the permit conditions and is meeting its purpose.
• Ensuring that all required testing has been performed.
• Determining if there have been any changes to the project, including if any wells within the AOR have been drilled, reworked, or abandoned, and determining that well work was completed appropriately.
• Confirming that the injection fluid is confined to the permitted zone of injection.
• Confirming that no damage is occurring as a result of the injection project.

It is the responsibility of both the operator and CalGEM to ensure the injection project is operating as permitted and to ensure that no damage is occurring as a result of the injection.

The maximum allowable surface injection pressure (MASP) for an injection project must be below the fracture pressure, and prior to sustained injection, a step-rate test must be conducted to determine the MASP. (14 CCR § 1724.10(i).) CalGEM must be notified in advance of the step-rate test so that it may be witnessed. Test pressure must be from hydrostatic to the pressure required to fracture the injection zone or the proposed injection pressure, whichever occurs first. Friction loss is not used in determining the MASP, but rather provides for an additional margin of error for safety.

Operators must monitor all injection wells to confirm that injection is at or below the approved MASP. If the injection pressure is above the approved MASP, the operator must immediately reduce the injection pressure.

A Standard Annular Pressure Tests (SAPT) must be performed for each injection well prior to commencement of injection and at least once every five years thereafter. (14 CCR § 1724.10(j)(1).) In addition, all injection piping, valves, and facilities must meet or exceed design standards for the maximum anticipated injection pressure, and shall be maintained in a safe and leak-free condition. (14 CCR § 1724.10(f).)  Where there is only a single string of casing across water protected by the SDWA (10,000 mg/l TDS or less), the SAPT must be tested at the approved MASP for the well. All tests shall be evaluated to ensure casing integrity, i.e. that there are no leaks in the casing and that the fluid is confined to the permitted zone.

CalGEM​’s well construction standards, consisting of the use of casing, mud, and cement, serve to prevent fluid migration and the comingling of lesser quality fluids. Injection wells must have, in addition to cement above the oil and gas zones, cement across the base of freshwater interface (BFW) with at least 100 feet above the BFW interface (CCR §1723.2). The hole and casing annulus space, between the top of the cement isolating the oil and gas zones and the base of the cement covering the BFW interface should have heavy mud to prevent the movement of fluids. (14 CCR §§ 1722.6 and 1723(b).)

For water disposal wells with proposed injection into a non-hydrocarbon zone, well construction should be consistent with disposal well completed into depleted oil and gas zones. In order to ensure that injected fluids are confined to the intended zone, there must be 100 feet of cement across and above the top of the intended injection zone.

Appendix A: State Water Resources Control Board Resolution No. 88-63 Adoption of Policy Entitled "Sources of Drinking Water"

Appendix B: Examples of Well Bore Paths

Appendix C: Casing Diagram Information

Coastal

Inland

Northern

Southern​