Code of Colorado Regulations
400 - Department of Natural Resources
402 - Division of Water Resources
2 CCR 402-10 - RULES AND REGULATIONS FOR PERMITTING THE DEVELOPMENT AND THE APPROPRIATION OF GEOTHERMAL RESOURCES THROUGH THE USE OF WELLS
9 - Minimum Standards For Type B Geothermal Wells

Universal Citation: 2 CO Code Regs 402-10 ยง 9

Current through Register Vol. 47, No. 17, September 10, 2024

9.1 Well Construction- The construction standards of the Water Well Construction Rules, 2 CCR 4022, shall apply to the construction of a Type B geothermal well, with the additions and modifications stated in this Rule. However, a Type B geothermal well need not be constructed by or under the supervision of a contractor licensed by the State Board of Examiners of Water Well Construction and Pump Installation Contractors.

9.2 Surface Casing- Steel surface casing must be set at least twenty-five (25) feet into impervious and competent bedrock to insure a solid anchor for blowout prevention equipment. Sufficient cement shall be used to seal the entire length of the surface casing.

9.2.1 In areas where subsurface formations and pressures are not known, surface casing shall not be set less than ten (10) percent of the proposed total depth of the well or a minimum of fifty (50) feet, whichever is greater.

9.2.2 In areas where subsurface conditions have been established by prior well construction, the surface casing shall be set at a depth to protect all known and potential aquifers and to prevent blowouts or uncontrolled flows, but in no instance shall the depth of steel surface casing be less than fifty (50) feet.

9.3 Protection or Production Casing- The setting depths and cementing intervals for each proposed well shall be designed and selected to prevent fluids from migrating through the annulus between the casing and the borehole. All well casings shall be selected and designed to protect against failure due to internal pressures, collapse due to external pressures, or corrosion.

9.4 Approved Grout and Placement- Only cement shall be used to grout a Type B geothermal well, unless other grouts have been specifically approved by variance from the State Engineer (see Rule 14). Cements and additives shall be selected to withstand anticipated temperatures and corrosive fluids. A cement slurry shall be placed by positive displacement in one continuous operation from the bottom of each interval or stage.

9.4.1 Cement shall be placed immediately above the top of any potential producing geothermal reservoir for a minimum interval of two hundred (200) feet or to the surface if the depth of the reservoir is less than two hundred (200) feet.

9.4.2 A minimum of fifty (50) vertical feet of cement shall be placed opposite each confining layer penetrated by the borehole (see Rule 4.2.7).

9.4.3 All cemented casing strings shall stand under pressure until the cement reaches a compressive strength of five hundred (500) psi. The condition "under pressure" will be complied with if a "float" or back pressure valve is used or if pressure is otherwise held on the casing and no back flow is observed.

9.4.4 All casing and cements shall be tested prior to resuming well construction operations. The test shall consist of applying a minimum pressure of five hundred (500) psi to the casing and holding that pressure for thirty (30) minutes. Test details shall be recorded and reported to the State Engineer.

9.5 Blowout Preventers- As soon as surface casing is set, a Type-B geothermal well shall have blowout preventers or control heads installed. This equipment shall be selected and designed to contain reasonably anticipated pressure and maintain control of the well at all times, and shall be maintained in good working order. This requirement for blowout preventers may be waived by variance from the State Engineer (see Rule 14) if the owner or operator can show from prior experience in the area that this equipment is not necessary.

Disclaimer: These regulations may not be the most recent version. Colorado may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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