Part 9. Solution mining

This Part covers the design, construction, operation and abandonment aspects for salt solution mining in Ontario.

Where other publications are referenced within this Part, the reference shall be read as a reference to the most current edition of the publication in effect, including all published amendments.

9.1 Design and construction

Salt solution mining operations shall be designed, operated and constructed to:

  1. protect potable water and other fluid bearing zones;
  2. ensure the structural stability of the salt bed and overlying geological formations is maintained;
  3. protect the surface and subsurface for other potential uses;
  4. ensure that salt solution mining is occurring in suitable formations; and
  5. optimize the salt resource extraction without adversely impacting public safety or the environment.

9.2 New project development

Proposals for new salt solution mining projects shall be submitted to the Ministry with the following information:

  1. a map showing the type and surveyed location, and depth of all wells within a 1 kilometre radius of the proposed mining property;
  2. a table of the wells identified in (a), showing the date the well was drilled, its depth, and current status;
  3. a geological cross-section interpreted from gamma ray and neutron density well logs and any applicable well records identifying the geologic formations between the surface and the top of the salt formation and the depths at which they occur;
  4. the depth and formation of fresh water bearing and other formation water bearing strata likely to be encountered;
  5. the proposed location of salt solution mining well(s);
  6. a geological analysis of the salt formation proposed for mining, including its depth and thickness;
  7. a subsurface schematic drawing (wellbore diagram) of each proposed well;
  8. a schematic drawing of the proposed surface facilities including the wellheads and pipelines;
  9. the structural stability model to be used in the development of the mining plan; and
  10. a mining plan.

9.3. Mining plan

The mining plan submitted in section 9.2 shall include the following:

  1. the physical properties of the salt formation including assessment of creep and closure potential under the proposed mining plan;
  2. the structural top and base of the salt formation including any fluid interfaces;
  3. the mechanical behaviour of the formations above the salt formation;
  4. the impact of impurities and other anomalies on the strength of salt formation and formations above the salt formation including an assessment of regional, local and internal faulting and their implications on the mining plan;
  5. the potential for fluids to migrate to or from the salt solution mining zone or to or from other formations;
  6. an assessment of the regional stresses;
  7. the designed shape of the cavern or gallery including maximum diameter;
  8. the proposed salt extraction rates and anticipated subsidence rates;
  9. the designed distance between caverns and/or galleries;
  10. the designed injection and extraction rates including flow rates, pressures, roof and shape control;
  11. depth of extraction and the circulation method;
  12. the maximum extraction ratios;
  13. an assessment of the magnitude of the ground subsidence as a function of time during and after active solution mining.
  14. subsidence monitoring program, monuments and measurement;
  15. sonar monitoring program with specified sonar frequency;
  16. the planned total extraction of salt from each well;
  17. the final designed shape of the cavern around each well; and
  18. contingency plans in case of spills and cavern collapse.

9.4 Injection pressure

The maximum injection pressure shall not exceed 75% of the local fracture gradient.

9.5 Mining restrictions

Salt solution mining operations shall be limited to:

  1. property that is owned or under mineral lease to the operator;
  2. wells located at least 150 metres from the operator’s property or lease boundaries;
  3. salt extraction that is not closer than 50 metres from the operator’s property or lease boundary lines.

9.5.1 Hydraulic control

All caverns and galleries shall have tight hydraulic control during the salt solution mining operations.

9.6 Roof control

The operator shall employ a blanketing material continuously throughout the solution mining process for roof control.

9.7 Drilling

All solution mining wells shall be drilled and completed in accordance with Part 3 with the following exceptions:

  1. surface, intermediate and production casings shall be cemented to surface as shown on Figure 4;
  2. the production casing shall be set at least 3 metres into the producing salt formation;
  3. the mechanical integrity testing procedure shall be conducted prior to commencing solution mining operations and shall include:
    1. a cement bond log (or equivalent) and a casing evaluation log on the production casing,
    2. a pressure test on the production casing and seat, and
    3. a pressure test of the formation immediately below the production casing seat; and
  4. the hanging tubing string(s) shall be in accordance with API Spec 5CT, Specification for Casing and Tubing.

9.8 Mining operations

Salt solution mining and salt production shall be carried out in accordance with the written mining plan.

9.8.1 Operation and monitoring

The operator shall:

  1. have a written procedures that include:
    1. operating and maintenance procedures,
    2. emergency response procedures, and
    3. procedures that specify the necessary system isolation required to perform maintenance functions, including venting and blowdown;
  2. operate the facility in conformance with the procedures in (a);
  3. keep records necessary to administer such procedures;
  4. ensure that operations and maintenance personnel are trained and familiar with all procedures;
  5. update procedures from time to time as experience dictates and as changes in operating conditions require;
  6. limit the maximum injection and withdrawal rates to less than a velocity of 4.5 metres/second (15 ft/sec);
  7. maintain records and documents for the:
    1. maintenance and operation activities on wells, pipelines and associated equipment, and
    2. down hole activities including copies of all logs; and
  8. keep daily records of:
    1. the volume of water injected and/or brine recovered, and
    2. the volume and pressure of the blanketing material and the volume of any blanketing material added or removed.

9.8.2 Mechanical integrity testing

The operator shall:

  1. conduct mechanical integrity testing of the production casing once every five years by:
    1. a casing evaluation log;
    2. a pressure test of the casing or a water brine interface test; or
    3. other equivalent methods acceptable to the Ministry; and
  2. provide for an Examiner to certify the mechanical integrity of each well.

9.8.3 Hydraulic control monitoring

The operator shall monitor hydraulic closure by continuous direct flow or pressure measurements and provide for an Examiner to certify hydraulic closure to the Ministry annually.

9.8.4 Sonar surveys

The operator shall:

  1. conduct a sonar survey through each well at every 360,000 net tonnes interval of salt production from the well;
  2. plot the results of the sonar survey on a maximum radii plot along with other well sonar surveys on a mining property layout plan; and
  3. use these surveys to ensure that solution mining is occurring in accordance with the mining plan.

9.8.5 Subsidence monitoring

The operator shall:

  1. conduct subsidence monitoring annually using a qualified surveyor; and
  2. plot on a continuous graph the subsidence survey data and provide such data to the Ministry in a tabular format.

9.8.6 Servicing blowout prevention

Operators of solution mining wells shall comply with sections 8.1, 8.6 and 8.7 when conducting well service operations.

9.9 Abandonment

Solution mining well abandonment shall include:

  1. a sonar survey on the cavern;
  2. a mechanical test on the casing; and
  3. plugging the well in accordance with Part 11 of this Standard with the exception that cement shall be placed over the full length of the well bore.