What Is Fracking or hydraulic fracturing?

A controversial process for extracting natural gas from shale, is drawing criticism as opponents question what effects pumping thousands of gallons of water and chemicals underground will have.

The Christian Science Monitor reported that public hearings being held in Binghamton, N.Y., drew hundreds of protesters on Monday. The hearings are part of the Environmental Protection Agency's investigation into how fracking affects people and the environment.

The EPA explained that hydraulic fracturing is a process used to extract underground resources such as oil, natural gas and geothermal energy. It involves the pressurized injection of water and chemical additives into a geologic formation in hopes that the pressure is enough to exceed the strength of the rock and enlarge fractu

res in it.

"Propping agents" s

uch as sand or ceramic beads are pumped into the fractures to keep them open and pumping pressure is released as the fracturing fluids return to the surface. Natural gas will then flow from pores and fractures in the rock into a well that will extract more.

The EPA is attempting to determine whether, among other concerns, there could be any effects on drinking water supplies.

Philly.com reported that the hearings have drawn strong views on both sides. Those against it hope that the

EPA study will prove that fracking is an environmental danger that needs to be regulated or banned by the federal government.

Rep. Maurice Hinchey (D-N.Y.), said fracking has been linked to "numerous reports of water contamination" nationwide.

The gas industry fears new restrictions could impair the industry which it said is one of the few current economic bright spots in and around Pennsylvania.

"Now is especially not the time to furthe

r limit energy-job opportunities for those in need," John Harmon of the African American Chamber of Commerce testified at a hearing.

PERFORATING

Since the pay zone is sealed off by the production string and cement, perforations must be made in order for the oil or gas to flow into the wellbore. Perforations are simply holes that are made through the casing and cement and extend some distance into the formation. The most common method of perforating incorporates shaped-charge explosives (similar to those used in armor-piercing

shells). Shaped charges accomplish penetration by creating a jet of high-pressure, high-velocity gas. The charges are arranged in a tool called a gun that is lowered into the well opposite the producing zone. Usually the gun is lowered in on wireline (1). When the gun is in position, the charges are fired by electronic means from the surface (2). After the perforations are made, the tool is retrieved (3). Perforating is usually performed by a service company that specializes in this technique.

ACIDIZING

Sometimes, however, petroleum exists in a formation but is unable to flow readily into the well because the formation has very low permeability. If the formation is composed of rocks that dissolve upon being contacted by acid, such as limestone or dolomite, then a technique known as acidizing may be required. Acidizing is usually performed by an acidizing service company and may be done before the rig is moved off the well; or it can also be done after the rig is moved away. In any case, the acidizing operation basically consists of pumping anywhere from fifty to thousands of gallons of acid down the well. The acid travels down the tubing, enters the perforations, and contacts the formation. Continued pumping forces the acid into the formation where it etches channels – channels that provide a way for the formation’s oil or gas to enter the well through the perforations.

FRACTURING

When sandstone rocks contain oil or gas in commercial quantities but the permeability is too low to permit good recovery, a process called fracturing may be used to increase permeability to a practical level. Basically, to fracture a formation, a fracturing service company pumps a specially blended fluid down the well and into the formation under great pressure. Pumping continues until the formation literally cracks open. Meanwhile, sand, walnut hulls, or aluminum pellets are mixed into the fracturing fluid. These materials are called proppants. The proppant enters the fractures in the formation, and, when pumping is stopped and the pressure allowed to dissipate, the proppant remains in the fractures. Since the fractures try to close back together after the pressure on the well is released, the proppant is needed to hold or prop the fractures open. These propped-open fractures provide passages for oil or gas to flow into the well. See figure to the right.