After the 26-in. hole has been drilled, it is time to run the 20-in. casing. All tools, etc., required for this operation have been prepared in accordance with the checklist for "Running 20-in. casing." The casing will have been measured ahead of time and the operator's drilling supervisor or engineer will make out a running list. The list defines the correct order in which to run the casing.
The first joint to be picked up is the shoe joint. The bottom 10-15 ft is painted white to aid visibility when entering the 30-in. housing. A rotating ring is attached to this joint, about 10-12 ft from the bottom, for guide ropes.
When the shoe joint is picked up, water is pumped into it to test the integrity of the shoe. The shoe is basically a nonreturn valve. After the shoe joint is confirmed to be in good working order and is lowered through the rotary table, the guide ropes can be secured from the rotating ring to the guide lines. These guide ropes act as a guide for entering the 30-in. housing.
Now all of the remaining intermediate joints can be run. After these joints have been run, it is time to pick up the 183/4-in. wellhead housing. Depending on the operator, the housing may already be made up and standing in the derrick, or the running tool will have been installed on deck.
Before picking up the wellhead housing, it is good practice to count the joints of casing remaining on deck to confirm the total number of joints reflected in the running list.
With the wellhead resting on the rotary table, a third-party engineer will check operation of the running tool. After the running tool is checked and reinstalled, the complete casing string is run on drill pipe (landing string).
Before the 30-in. housing is stabbed, the compensator should be unlocked and put in mid stroke. The ROV should be present on the seabed to aid in stabbing. The last stand of the landing string will have a crossover from the pipe connection to a 2A in. WECO union fitted on top.
The landing string will have been "spaced" out so that the wellhead, when landed in the 30-in. housing, will have approximately 10-20 ft of pipe sticking above the rotary. Once the wellhead is landed, the driller will overpull 20,000 lb to ensure engagement of the latch ring that connects the wellhead to the 30-in. housing.
When the driller is satisfied that the latch has connected, a circulating line from the mud pumps or cement line can be rigged up. All of the equipment required for the cement job will have been checked according to the "Cement 20-in. casing" checklist.
Once the circulating line has been hooked up, it is customary to pump at least the volume of the casing using either the rig mud pump or the cement pump. When pumping is complete, the cement unit will be lined up to the circulating line.
