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Cavern MIT

Cavern Storage

A hydrocarbon storage well shall be tested for integrity by the nitrogen-brine interface method or an alternative approved by the Commission, or its designee. Each hydrocarbon storage well shall be tested for integrity prior to being placed into service, at least once every five years, and after each workover that involves physical changes to any cemented casing string. 

  • The operator shall submit a written test procedure to the commission in Austin for approval at least 10 days before the test. Submit via email to cavern_reports@rrc.texas.gov
  • The operator will propose the layout and the details of the test procedure. The operator is responsible for conducting the test in a practicable and prudent manner and in accordance with current, acceptable industry standards. Commission staff will review the test for satisfaction of the burden of proof required by rule. 
  • The operator shall notify the district office orally at least 48 hours before the test.

Nitrogen-Brine Interface Test

  • Storage well pressures shall be allowed to stabilize to a rate of change of less than 10 psi in 24 hours before the testing period begins. 
  • A half-hour or one-hour casing test is expected. 
  • The test duration must be at least 24 hours. 
  • A minimum detectable leak rate must be established. 
  • A calculated leak rate must be established. 
  • An initial interface log and final interface log are required. 
  • The test pressure should be approximately equal to, but not to exceed, the maximum allowable operating pressure.  For liquid storage caverns, the maximum operating pressure at the shoe of the lowermost cemented casing shall not exceed 0.8 pounds per square inch per foot of depth.  For gas storage caverns, the maximum operating pressure at the casing seat shall not exceed 0.85 pounds per square inch per foot of depth. 

Product-Brine Interface Test

  • Appropriate technical justification is expected as to why this testing method is used instead of the nitrogen-brine interface method.
  • Storage well pressures shall be allowed to stabilize to a rate of change of less than 10 psi in 24 hours before the testing period begins.
  • The test duration must be at least 24 hours. 
  • A minimum detectable leak rate must be established. 
  • A calculated leak rate must be established. 
  • The test pressure should be approximately equal to, but not to exceed, the maximum allowable operating pressure.  For liquid storage caverns, the maximum operating pressure at the shoe of the lowermost cemented casing shall not exceed 0.8 pounds per square inch per foot of depth.  For gas storage caverns, the maximum operating pressure at the casing seat shall not exceed 0.85 pounds per square inch per foot of depth. 

System Compressibility Test

  • Appropriate technical justification is expected as to why this testing method is used instead of the nitrogen-brine interface method. 
  • Storage well pressures shall be allowed to stabilize to a rate of change of less than 10 psi in 24 hours before the testing period begins.
  • The test duration must be at least 24 hours.
  • The system compressibility must be established.
  • An acceptable margin of error for the inventory variance must be established.  The operator may be required to justify the value on request.
  • The test pressure should be approximately equal to, but not to exceed, the maximum allowable operating pressure.  For liquid storage caverns, the maximum operating pressure at the shoe of the lowermost cemented casing shall not exceed 0.8 pounds per square inch per foot of depth.  For gas storage caverns, the maximum operating pressure at the casing seat shall not exceed 0.85 pounds per square inch per foot of depth. 

Gas Mass Balance Test

  • If the test is the initial test for a gas storage cavern, appropriate technical justification is expected as to why this testing method is used instead of the nitrogen-brine interface method.  For gas storage caverns, this testing method is authorized by rule to be used for tests following the initial test.
  • Storage well pressures shall be allowed to stabilize to a rate of change of less than 10 psi in 24 hours before the testing period begins. 
  • The test duration must be at least 72 hours. 
  • An initial temperature log and final temperature log are required. 
  • A minimum calculated inventory variance must be established.
  • A calculated inventory variance must be established.
  • The test pressure should be approximately equal to, but not to exceed, the maximum allowable operating pressure.  For liquid storage caverns, the maximum operating pressure at the shoe of the lowermost cemented casing shall not exceed 0.8 pounds per square inch per foot of depth.  For gas storage caverns, the maximum operating pressure at the casing seat shall not exceed 0.85 pounds per square inch per foot of depth. 

Casing Inspection

Storage wellhead components and casing shall be inspected for corrosion, cracks, deformations or other conditions that may compromise integrity and that may not be detected by the five-year test at least once every:

  • 5 years for liquid storage cavern wells in salt domes with a single casing string cemented to surface; 
  • 10 years for liquid storage cavern wells; 
  • or 15 years for gas storage cavern wells.

The operator may request an extension of up to five years from the Commission for good cause. Factors the Commission may consider in determining good cause pursuant to this paragraph include by are not limited to the age, location, and configuration of the well; well and facility history; operator compliance record; operator efforts to comply with this subsection; and accuracy of inventory control.

Brine Mining

  • The operator shall submit a written test procedure to the commission in Austin for approval at least 15 days before the test. Submit via email to cavern_reports@rrc.texas.gov.
  • The operator shall notify the district office orally at least 48 hours before the test.

Brine Mining MIT Standard

Brine mining injection wells (or “brine mining wells”) must demonstrate mechanical integrity annually. See 16 Tex. Admin. Code § 3.81(f)(16)(B). An operator must demonstrate that a well has mechanical integrity as follows:

  1. The operator must demonstrate that there is not a significant leak in the casing as follows (see 16 Tex. Admin. Code § 3.81(f)(16)(A)(i)):
    1. Conduct a fluid pressure test in accordance with 16 Texas Administrative Code § 3.81(f)(16)(C)(i)-(iv).
    2. In lieu of an annual fluid pressure test, the operator may monitor the pressure of a hydrocarbon pad or blanket contained in the annulus space of the well, provided the operator has obtained written approval prior to using this method. See 16 Tex. Admin. Code § 3.81(f)(16)(D).
  2. The operator must also demonstrate that there is no significant fluid movement into freshwater strata through vertical channels adjacent to the wellbore. See 16 Tex. Admin. Code § 3.81(f)(16)(A)(ii). One of the following methods must be used to demonstrate the absence of significant fluid movement into freshwater strata through vertical channels adjacent to the wellbore:
    1. The results of a temperature or noise log; or
    2. Where the nature of the casing precludes the use of a temperature or noise log, Staff can review cementing records demonstrating the presence of adequate cement to prevent significant fluid movement. See 16 Tex. Admin. Code § 3.81(f)(16)(E).

If the operator is unable to submit evidence to demonstrate either of the above-specified requirements (i.e., no significant leak, no significant fluid movement), Staff will fail the MIT.

Brine hydrostatic

Applies to brine mining wells only.  The well is shut-in and allowed to stabilize.  After the well is stabilized, test pressure will be held on the casing. 

    1. The proposal must state that the district office will be notified at least 48 hours in advance. 
    2. The proposal must state that the cavern will be shut in and allowed to stabilize before the test. 
    3. The proposal must state that the test duration is >= 4 hours. 
    4. The proposal must NOT state that there is a definite numerical pass/fail criteria. 
    5. The proposal must state a test pressure.  The test pressure must be approximately equal to regular operating pressure and not greater than max permitted pressure. Unless the MIT proposal states otherwise, RRC staff will determine the regular operating pressure from the average pressure reported on Form H-10H.

Conventional H-5

Applies to brine mining wells that have tubing and packer. Follows regular Form H-5 instructions.

  • The well must have an injection packer.
  • The proposal must satisfy all of the requirements of the Form H-5 instructions.


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