Method and apparatus for closing a wellhead casing

#The present invention relates to devices for extinguishing oil well fires and, in particular, to a steerable assembly including means for collapsing the casing.

#The inherent risk in owning and operating a producing oil well is the danger of a fire starting at the wellhead. Such fires are extremely difficult to extinguish due to the presence of high pressure flammable liquids and vapors which are emitted from the well. Even if temporarily extinguished, the high pressures can re-supply flammables to sustain the fire. That is, the presence of heated metal and other debris in the vicinity can exceed the flashpoint of the flammables and can restart a fire. The pressures also present difficulties in containing the flames, if attempting to cap the fire.

#Further difficulties can arise depending upon the location of the rupture and type of rupture. The rupture may occur either above or below the ground and affect the ability to gain access. The rupture may also consist of a split verses a clean break. Debris or other devices, such as explosive mines, in the case of fires started in the aftermath of the Persian Gulf War, may also limit access. The manner of extinguishing a fire may therefore have to be adjusted to the prevailing circumstances.

#FIG. 1 is a generalized perspective drawing of a drag cable directed, skid mounted construction of the invention.

#FIG. 2 is a generalized perspective drawing of a track vehicle which has been adapted to include the invention.

#FIG. 3 shows a top plan view of an articulating compression assembly with the clamp arms shown in an open condition.

#Referring to FIGS. 1 and 2, generalized perspective drawings are shown of assemblies 2 and 4 which find application for extinguishing fires at an oil wellhead casing. Either the assembly 2 of FIG. 1 or the assembly 4 of FIG. 2 can be directed under remote control into alignment with the casing 6 at a point beneath a casing rupture. Once aligned, each assembly 2 and 4 includes a compression means 8, which supports a pair of compression dies 10 and 12, to deform and compress the casing 6 to sealoff the casing bore 14. Once sealed, the bore 14 can be welded to assure a sustained closure.

#The compression assembly 8 is operational, upon encircling the casing 6, to compress the casing 6 to prevent additional rupture or splitting of the casing as the sidewalls are collapsed. This end is achieved through the shaping of the dies. Under some circumstances, the casing 6 may be sequentially grasped and partially collapsed at a number of points along the casing, prior to effecting complete closure at an intermediate point.

#FIG. 1 particularly depicts an assembly 2 which can be dragged into engagement with the casing 6, whereas FIG. 2 depicts an assembly 4 which can be remotely steered into engagement. The principal distinction is that a skid framework 16 and drag cables 18 are provided with the assembly of FIG. 1. The drag cables 18 mount to winch means (not shown). A remote operator independently controls each of the drag cables 18 via powered winch drums to direct the skid 16 and compression assembly 8 into abutment with the casing 6.