One or more strings of casing run between the surface casing and the production casing or the production liner and is cemented in place. intermediate casing is generally run in deeper wells to isolate abnormal pressured formations, lost circulation zones, salt sections, and unstable shale sections so deeper drilling can proceed with normal mud weights. A large number of wells are drilled without running intermediate casing.
Source: API BULLETIN E3, Environmental Guidance Document: Well Abandonment and Inactive Well Practices for U.S. Exploration and Production Operations, First Edition, January 1993 (Reaffirmed June 2000). Global Standards
Casing that is set when geological characteristics or wellbore conditions require isolation. These conditions include, but are not limited to, prevention of lost circulation, formation fluid influx or hole instability. Multiple intermediate casing strings can be run in a single well.
Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global Standards
Long casing string (12 1/4 in. drift, sizes range 13 3/8 in. to 14 in.) with casing hanger in the subsea wellhead housing. Normal clearance casing OD in.: 13 3/8. Tight clearance casing OD in.: 13 5/8. NOTE These are examples only. Each well can have variations in number of casing strings and sizes. Naming conventions can vary. The heavy-wall surface casing designs may allow 13 5/8 in. to be run as a liner and not tied back.
Source: API RP 96, Deepwater Well Design and Construction, First Edition, March 2013. Global Standards
“Intermediate casing” means a casing string run between the surface casing and the production casing or production liner and cemented in place to isolate abnormally geo-pressured strata, lost circulation zones, salt sections, or unstable shale sections.
Source: Alaska Oil and Gas Conservation Commission, Definitions, Alaska Admin. Code tit. 20, § 25.990, December 7, 2012. Regulations
“Intermediate casing” means the casing string or strings run after setting the surface casing and prior to setting the production string or liner.
Source: Corporation Commission, Oil and Gas Conservation, Oklahoma Administrative Code 165:10, February 2013. Regulations
“Intermediate casing” means one or more strings of casing set after surface casing has been cemented through the base of the deepest underground source of drinking water, but before drilling into the permitted hydrocarbon reservoir(s) to isolate hydrocarbon or brine bearing flow zones, stabilize the wellbore, to isolate protected groundwater if encountered after drilling below surface casing, isolate lost circulation zones or other potential geologic hazards, or serve as a base for well control equipment.
Source: Division of Mineral Resources Management – Oil and Gas, Ohio Administrative Code, Chapter 1501:9, January 2012. Regulations
Intermediate casing—A string of casing set after the surface casing and before production casing, not to include coal protection casing, that is used in the wellbore to isolate, stabilize or provide well control.
Source: Oil and Gas Wells, Pennsylvania Code, Title 25, Chapter 78, December 2012. Regulations