Cal. Code Regs. tit. 14 § 1935.2

Current through Register 2024 Notice Reg. No. 45, November 8, 2024

Section 1935.2 - Surface Casing

Surface casing shall provide for control of formation fluids, for protection of shallow usable groundwater, and for adequate anchorage for blowout prevention equipment. All surface casing shall be cemented with sufficient cement to fill the annular space from the shoe to the surface. The following requirements may be modified or waived by the Division for low-temperature geothermal wells.

(a) Length of Surface Casing.

(1) In areas where subsurface geological conditions are variable or unknown, surface casing in general shall be set at a depth equaling or exceeding 10 percent of the proposed total depths of wells drilled in such areas. A minimum of 60 meters (about 200 feet) and a maximum of 400 meters (about 1,300 feet) of surface casing shall be set.

(2) In areas of known high formation pressure, surface casing shall be set at a depth determined by the Division after a careful study of geological conditions.

(3) Within the confines of designated geothermal fields, the depth at which surface casing shall be set shall be determined by the Division on the basis of known field conditions.

(b) Cementing Point for Surface Casing.

Surface casing shall be cemented through a sufficient series of low permeability, competent lithologic units (such as claystone or siltstone) to ensure a solid anchor for blowout prevention equipment and to protect usable groundwater and surface water from contamination. A second string of surface casing may be required if the first string has not been cemented through a sufficient series of low permeability, competent lithologic units, and either a rapidly increasing thermal gradient or rapidly increasing formation pressures are encountered.

(c) Drilling Fluid Return Temperatures. The temperature of the return drilling fluid shall be monitored continuously during the drilling of the surface casing hole. Either a continuous temperature monitoring device shall be installed and maintained in working condition, or the temperature shall be read manually. In either case, return drilling fluid temperatures shall be entered into the log book after each joint of pipe has been drilled down (every 10 meters, about 30 feet).

Cal. Code Regs. Tit. 14, § 1935.2

1. Amendment filed 8-16-79; effective thirtieth day thereafter (Register 79, No. 33).
2. Change without regulatory effect amending first paragraph and subsections (a)(2)-(3) filed 12-26-2006 pursuant to section 100, title 1, California Code of Regulations (Register 2006, No. 52).

Note: Authority cited: Section 3714, Public Resources Code. Reference: Sections 3739 and 3740, Public Resources Code.