Many people probably recall seeing an old movie showing an oil gusher. When the drill bit breaches the high pressure zone containing hydrocarbons, the oil travels up the well at a very high rate, forcing out the drill string and creating a gusher that shoots 200 feet or higher into the air. The oilmen, happy upon discovering their new-found wealth, are joyfully splashing about in the oil. Of course, the Hollywood reality is quite far removed from the reality as this gusher, more properly known as a blowout, typically was fatal to the workers involved in the drilling as flying wreckage crushed or severed oilmen in two. Those that weren’t killed or injured close to the drilling rig often lost their hearing due to the loudness of the explosive concussion from the well. The environmental damage due to blowouts typically was quite profound; thousands of barrels of oil would end up wasted on the landscape. As a metal structure shredded or electrical equipment of the drilling rig was compromised, sparks that occur during the blowout easily led to explosions and fires that were usually very difficult to extinguish.
Such was a common hazard in the oil and gas industry in the late 1800s to early 1900s, till the roll-out of the first commercial blowout preventer in 1926. A blowout preventer (BOP) is a mechanical device placed at the top of the well just under the floor of the drilling rig. The BOP consists of mechanical rams which constrict flow and increase pressure back into the well to constrain a potential blowout. In modern oil and gas drilling, catastrophic blowouts have become rare although they do still happen.
The most famous blowout in recent history is the BP/Deepwater Horizon oil spill that occurred in the Gulf of Mexico in April of 2010. In that case, high pressure methane gas expanded into the drilling riser and then rose into the drilling rig where it ignited and exploded, engulfing the entire offshore platform in flames and killing 11 workers. A report from the U.S. Chemical Safety Board released June 5, 2014, detailed what many already suspected shortly after the disaster occurred: a faulty blowout preventer and bad management led to the disaster.
Blowout preventers are actually the last-ditch prevention device. The very first line of defense against a blowout is what’s known as the drilling fluid, also called drilling mud. As the well is drilled, the drilling mud is pumped down the drill string to the drill bit at the bottom and returns up the well-bore in the space, or annulus, between the outside of the drill pipe and the casing, or the larger-diameter pipes, that line and protect the well. The column of drilling fluid being pumped down, which would be a mile or more, has considerable weight and exerts a tremendous downward hydrostatic pressure in the well. At the bottom, where there is no casing, the circular tubing through which the well drilled, the hydrostatic pressure provides an “overbalance” of pressure that exceeds the natural pressure of the reservoir into which the well is drilled. The overbalance of pressure prevents oil and gas fluids from entering and coming up the well bore. The most common weighting material in the drilling mud is barite.
Drilling mud also provides other important properties for the drilling operation, such as the lubrication, support and cooling of the drill bit and drilling assembly, and suspension, release and removal of cuttings from the well.
Roughly 85% of the global barite market is employed for drilling mud in the oil and gas industry and this trend is expected to continue and grow as the recent fracking boom continues.
Mabwe Minerals, which owns the mineral and metals rights to the Dodge Mine in Zimbabwe, is emerging as a new commercial source of barite. With the closest competitors from Chennai, India, Mabwe Minerals is strategically located to serve the oil & gas demands of Africa and the Middle-East.
For more information visit www.mabweminerals.com
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