Dual casing hanger

Abstract

A lower casing hanger including a cylindrical block with two holes is landed on a shoulder in the bore of a wellhead housing. The first hole has shoulders that are inclined relative to the axis of the housing. The second hole is smooth and has a constant diameter. A first string of casing is run through the first hole and a C-shaped annular slips is placed around the casing. The outer surface of the slips has shoulders for engaging the shoulders on the lower casing hanger. The casing is lowered until the shoulders engage, thereby preventing further downward movement of the casing. An upper casing hanger then is placed on top of the lower casing hanger. The upper casing hanger has two holes that align with the holes in the lower casing hanger. The second hole has shoulders that mate with exterior shoulders on a second slips. A second string of casing is run through the second hole and the second slips is placed around the second casing. The assembly is lowered through the second hole until the shoulders engage to prevent further downward movement of the second casing. A gasket is placed on top of the upper casing hanger and a top plate is placed on top of the gasket for deforming the gasket against the casings.