250.421—What are the casing and cementing requirements by type of casing string?
The table in this section identifies specific design, setting, and cementing requirements for casing strings and liners. For the purposes of subpart D, the casing strings in order of normal installation are as follows: drive or structural, conductor, surface, intermediate, and production casings (including liners). The District Manager may approve or prescribe other casing and cementing requirements where appropriate.
| Casing type | Casing requirements | Cementing requirements |
|---|---|---|
| (a) Drive or Structural | Set by driving, jetting, or drilling to the minimum depth as approved or prescribed by the District Manager | If you drilled a portion of this hole, you must use enough cement to fill the annular space back to the mudline. |
| (b) Conductor | Design casing and select setting depths based on relevant engineering and geologic factors. These factors include the presence or absence of hydrocarbons, potential hazards, and water depthsSet casing immediately before drilling into formations known to contain oil or gas. If you encounter oil or gas or unexpected formation pressure before the planned casing point, you must set casing immediately | Use enough cement to fill the calculated annular space back to the mudline.Verify annular fill by observing cement returns. If you cannot observe cement returns, use additional cement to ensure fill-back to the mudline. For drilling on an artificial island or when using a glory hole, you must discuss the cement fill level with the District Manager. |
| (c) Surface | Design casing and select setting depths based on relevant engineering and geologic factors. These factors include the presence or absence of hydrocarbons, potential hazards, and water depths | Use enough cement to fill the calculated annular space to at least 200 feet inside the conductor casing.When geologic conditions such as near-surface fractures and faulting exist, you must use enough cement to fill the calculated annular space to the mudline. |
| (d) Intermediate | Design casing and select setting depth based on anticipated or encountered geologic characteristics or wellbore conditions | Use enough cement to cover and isolate all hydrocarbon-bearing zones and isolate abnormal pressure intervals from normal pressure intervals in the well.As a minimum, you must cement the annular space 500 feet above the casing shoe and 500 feet above each zone to be isolated. |
| (e) Production | Design casing and select setting depth based on anticipated or encountered geologic characteristics or wellbore conditions | Use enough cement to cover or isolate all hydrocarbon-bearing zones above the shoe.As a minimum, you must cement the annular space at least 500 feet above the casing shoe and 500 feet above the uppermost hydrocarbon-bearing zone. |
| (f) Liners | If you use a liner as conductor or surface casing, you must set the top of the liner at least 200 feet above the previous casing/liner shoeIf you use a liner as an intermediate string below a surface string or production casing below an intermediate string, you must set the top of the liner at least 100 feet above the previous casing shoe. | Same as cementing requirements for specific casing types. For example, a liner used as intermediate casing must be cemented according to the cementing requirements for intermediate casing. |
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Code of Federal Regulations
139
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