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How Relief Wells Work


Parts of a Back-up System: Relief Wells in Detail

The parts of a relief well -- steel piping, steel or diamond drill bits and bent pipe joints used to angle the drill's direction -- do all the behind-the-scenes work during boring. Above ground, there's another set of tools at work.

A sensor attached to the drill bit steers the bit and is managed by an on-site computer controlled by workers [source: Tasker]. While a temporary derrick houses the workers' tools of the trade, it also offers a way to pump liquid into the relief well so it can block the blowing well. By pumping seawater into the relief well, workers can test whether the seawater is transferring into the blowing well. If it is, it will displace some of the escaping oil. Next, mud will be poured into the relief well, followed by concrete. Because both materials are denser and heavier than oil, they should block any pressurized oil moving up the relief well as well as the blowing well [source: James].

When the relief well is complete, it could be used to continue producing oil from the site [source: Hargreaves]. If this is the case, a pump jack will be installed at ground level. The pump jack moves oil or gas out of the ground through the drilled hole by using a series of weights, valves and a sucker rod [source: National Science Foundation]. You can read more about it in How Oil Drilling Works. Similar pumping equipment, although on a smaller scale, can be used to operate water relief wells. More often, however, water wells are driven by a modern version of the pump jack: a jet pump.

Most water relief well jet pumps contain a few standard features, including a well casing and filter; the well casing lines the pump hole and the filter prevents anything other than water from entering the pump. The water is pumped according to signals from a pressure switch mounted near a motor above ground. If the pressure hits a designated level, the pump will cycle water from the well up through the pipes and into a storage tank or into a series of drainage pipes.

Whether relief wells are controlling water or oil, they all have one thing in common after a pump is put into place: Routine maintenance and natural disaster aside, most don't require that much attention. In fact, many producing wells are operated by remote. Instruments take on-site output measurements and transmit the data to a central off-site location where it is processed and monitored [source: DeFlow]. Of course, if the relief well's only job is to deliver heavy materials, such as mud or concrete, and "kill" an out-of-control catastrophe, its role will be short-lived and it, too, will be closed.

Read on to the next page to learn more about oil drilling and wells.


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