Cement plug

The cement is encountered when drilling a cement plug or out of new casing. 

Abandonment. State regulations have rules on plugging and abandoning wells. Cement plugs are normally used for that purpose (see Figure 4-404). 

Kick-off plug. Usually an Ottawa sand-cement plug is used to plug off a section of the borehole. This plug uses a hard surface to assist the kick-off procedure (see Figure 4-405). 

Lost circulation. A cement plug can be placed adjacent to a zone of lost circulation in the hope that the cement slurry will penetrate and seal fractures (see Figure 4-406). 

There are three methods for placing cement plugs. 

Two-plug method is a rather new method and requires the use of the telltale catcher sub (Dowell Schlumberger) to set a cement plug in a well at a rather precise location with minimum contamination. The tell-tale catcher sub is made up to the lower end of a drillpipe string. The sub also has an aluminum tail pipe, a bottom wiper plug (which carries a dart) and a top wiper plug. The sub on the drillpipe is lowered to the depth desired for... 

Balance a 100-sack cement plug of Class C neat cement slurry when 15 bbl of water are to be run ahead of the slurry. The plug is to be run through 2-in., 4.716-lb/ft, EUE tubing. The depth of placement is 4,000 ft. 

Fiber-containing cement was initially developed as a high-strength material that could be used to line a borehole [1789]. Several relatively simple and cheap spin-off applications of fiber cement were identified, such as the use of fiber cement in cement plugs for borehole stabilization and as a lost circulation material. Several companies are already applying or offering fiber cement for these purposes in the field, in both organic fibers and metal fibers [372,1077, 1682-1684]. 

Near wellbore conformance control (cement plug/gel treatment for water and gas shutoff)... 

The classification could never be satisfactory because several processes can be combined. For example, chemicals are added to thermal and miscible EOR processes. Conformance control near wellbore zones, such as cement plug/gel treatment for water and gas shutoff, and acidizing and fracturing well stimulation are grouped into lOR because these processes are not in the reservoir scale even though there are some interactions near the wellbore. 

Hazards analysis Management did not carry out a risk analysis. Had they done so, and had they followed up on any findings, the event could have been avoided. For example, management relied on a single barrier (they did not install a second cement plug when mud was removed). 

The first step - the positive pressure test - was completed in the afternoon of April 20. The blowout preventer (BOP) blind shear ram was closed and well pressure was increased to 2500 pounds per square inch (about 167 atmospheres) and held for 30 min without leakage, so it was considered successful. This test only proved the casing was pressure tight. It did not prove the integrity of the cement plug within the casing annulus. 

In short, well integrity was not established, because the cement plug had failed. Oil and gas entered the well and well control was lost. A large kick of gas overwhelmed the mud/gas separator on Deepwater Horizon and then ignited, and the high-integrity blowout preventer (BOP) 5000 feet below on the seabed failed to operate as intended. 

BP onshore (approved by MMS) set the surface cement plug 3000 feet below the mudline in seawater. 

BP onshore displaced the mud from the riser before setting the surface cement plug. BP onshore chose not to install additional physical barriers during the temporary abandonment procedure. 

However, litigation continues (2014) and these amounts are unlikely be final. BP and Halliburton may share responsibility for the failure of the cement plug, while BP, Transocean and Cameron may share responsibility for failure of the BOP to operate. 

Zimmer Bio-Statak (suture anchor), prostatic stent, suture anchor, bone cement plug Dermik Laboratories Sculptra (injectable facial restoration)... 

Surgical Zimmer (Bio-statak suture anchor and implants bone cement plug), Ethicon... 

---