The Purpose Of A Frac Job In Horizontal Drilling For Natural Gas
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The Purpose Of A Frac Job In Horizontal Drilling For Natural Gas

Frac jobs or horizontal fracturing is used to recover more natural gas.

What is a Frac Job In Oil and Gas Drilling?

Currently a number of new natural gas reserves around the United States are being developed. Most of these new discoveries are in a kind of rock known as shale. Shale gas, as some call it, was not seen as a productive source of natural gas until a technology called horizontal drilling was developed. This new way of drilling, at ninety degrees across the underground rock bed, can allow more valuable hydrocarbons to escape. Often several wells will be drilled outward from a single well location, which reduces the environmental footprint of natural gas drilling.  In this manner, with a group of horizontal wells all branching out in different directions, the shale can be drained of natural gas over the years.

The Purpose of a Frac Job

Shale such as the Barnett Shale do not release much natural gas into a vertical oil well. Horizontal drilling allows much more gas to flow out of the well but even so, much remains behind due to the very hard nature of shale rock. Most oil and gas reservoirs are composed of porous rock, such as sandstone. Think of shale like the material that makes up a bowling ball. All of the natural gas that has built up in the shale over millions of years, through the action of microbes or heat, is still trapped in the tight rock.

Oil companies that drill horizontal wells in shale almost always do a "frac job". Hydraulic fracturing refers to using high pressure fluid, which is pumped down the newly drilled horizontal well at extreme pressure. Thousands of pounds per square inch of pressure actually breaks apart the hard shale rock and creates fractures, from which trapped natural gas can escape. After the rock has been fractured, tiny glass beads are often pumped down the well to keep the fissures propped open.

Potential Problems With Frac Jobs In Shale Gas Formations

Already in some areas where shale gas drilling is being done, such as the Barnett shale near Cleburne, Texas, there have been reports of small earthquakes. These earthquakes, most less than 3.0 on the Richter Scale, don't do any damage but can cause land to shift or slide where it is vulnerable. So far no reports of major damage from frac job induced earthquakes has been reported however long term effects, such as on water wells and underground water quality may be possible.

Another potential problem with pumping extremely high pressure fluid underground is the possibility of ruining the well. In some cases a frac job that has been done has resulted in breaking down the barrier that lies between a water filled formation and thus ruining the gas well. An influx of water from a water bearing rock formation above or below the gas shale will destroy the economic value of the gas well, which may have cost millions to drill.

Technologies like horizontal drilling and hydraulic fracturing are being used with great success to bring new sources of clean burning gas to the market and reduce our dependence on imported oil.

For a map of the shale gas reserves being developed by horizontal drilling and hydraulic fracturing see. Map Of Shale Gas Reserves In The U.S.

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