A subsea well of the type concerned herein will have a wellhead supported on the subsea floor. One or more strings of casing will be lowered into the wellhead from the surface, each supported on a casing hanger. The casing hanger is a tubular member that is secured to the threaded upper end of the string of casing. The casing hanger lands on a landing shoulder in the wellhead, or on a previously installed casing hanger having larger diameter casing. Cement is pumped down the string of casing to flow back up the annulus around the string of casing. Afterward, a packoff is positioned between the wellhead bore and an upper portion of the casing hanger. This seals the casing hanger annulus.
Casing hanger running tools perform many functions such as running and landing casing strings, cementing strings into place, and installing and testing packoffs. Testing the packoff is traditionally performed by pressuring under the blow out preventer (BOP) stack, but more recent casing hanger running tool designs incorporate an “internal” or “down the drill pipe” test which isolates the test pressure to a small volume just above the hanger. An internal test has several benefits including reducing the annular pressure end load reacted against the hanger and making leak detection more direct, which is especially beneficial for sub-mudline casing strings which can be located several thousand feet from the BOP stack. The cost of the added functionality is complexity in the form of additional ports and seals.
Virtually all casing hanger running tools to date incorporate a cam that acts as a mechanical program for the tool. Rotational inputs to the cam drive it axially, causing it to drive engaging elements such as dogs radially, allows seal-setting pistons to communicate with the stem, and opens up additional ports for internal testing. Typically, cams occupy the radial space between the stem and the body of the running tool and must be thick enough to withstand radial loads generated by the dogs and pressure loads from setting and testing packoffs. If the cam could be eliminated, the radial space it normally occupied could be used to thicken up the body and the stem, thus increasing the hanging capacity of the tool. A need exists for a technique that addresses increased hanging capacity of a running tool, coupled with the ability to internally test a packoff. The following technique may solve one or more of these problems.
USPTO Backgrounds
USPTO Backgrounds