What is fracking does it produce oil or natural gas?

Answer 1

Hydraulic fracturing, or fracking, is described in the simplest manner as a method to increase the output of a well, regardless of it is an oil or natural gas well.

It is necessary, especially with gas wells, as natural gas is most commonly found in shale formations. Shale isn't exactly a porous (conductive) material, and therefore the output of a well without fracturing will be significantly lower - typically to the point of where it would not be economical for the well to be drilled and put into production without it.

There are many ways to "frack" a well, and the method used by companies that do this vary according to where on the planet it is being done. For example, in western Arkansas the geology is largely sandstone and a nitrogen injection method (at low rates of about 30 barrels per minute) is used. In shale formations, slickwater injection (just water at high rates of typically 100 barrels per minute) is used. Since it is the easiest method to describe, I'll provide details on slickwater fracturing.

In a traditional "plug and perf" method of fracking a well (which is typically done multiple times on a single well), a device called a "gun" is placed downhole at a specific zone of the well where the fracking needs to occur. Think of the gun as a long cylinder, about 30 feet long and a few inches in diameter, full of holes on the outside that look like Golf balls cut in half. These "holes" are filled with shaped explosive charges that are detonated in the well that produces channels where proppant will be injected.

During a frack stage, straight water is initially injected into a well, typically with "frack balls." The purpose of a frack ball is simple: fluids, just like electricity, will always take the path of least resistance, and therefore frack balls will act as a temporary plug to divert water away from it so that all areas of the zone that is being fracked will be done so equally. You can tell when a ball is seated into its place in the well by a spike in pressure, as low as a few hundred PSI, and sometimes as high as a few thousand PSI.

After this spike, acid (hydrochloric, typically 15% concentration), is injected into the well. It is used to weaken the formation and lower inital pressure. After acid is injected, water is injected once again.

After this, a mixture of sand and water is injected into the well. Under pressure, of course, the amount of pressure varies according to the geology of the area, and can be just a couple of thousand PSI, to upwards of 20,000 PSI. Regardless of the pressure pumped at, during a successful frack you will see a drop in pressure (slight) as the stage goes on, and an eventaul rise in pressure, indicating that the zone you are fracking into is reaching its maximum amount of sand that can be injected into it.

The sand type used varies again according to the geology of the area, and the client company that owns the well, and multiple sand types can be used in a single stage, but its function is all the same: it is a proppant, to "prop" open a conductive channel in the well for the gas to flow, as it is far more porous than shale, and it is this sand that makes the difference in the well's output.