Deep Well Casing
As operators push exploration into deeper, hotter and higher-pressure reservoirs, the casing string — not the drill bit — becomes the limiting factor on how deep a well can safely go. Deep well casing is the high-strength tubular lining specified for wells whose total vertical depth typically exceeds about 15,000 ft (4,500 m), where the string must support its own weight over kilometers of length, resist collapse and burst from deep formations, and retain integrity under elevated temperatures. It is supplied as Oil Country Tubular Goods (OCTG) to API Spec 5CT (harmonized with ISO 11960), most often in the highest-strength grades such as P110 and Q125.
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