How Fracturing Works

The Rock: Shale

shale-from-Wikipedia

In its abundant supply worldwide, shale is the most common type of rock found to hold fragments of organic material required to produce oil and gas. Since this material is locked in layers of rock, simply drilling through the formation is not enough to retrieve and release the liquid hydrocarbons. Instead, the rocks must be broken (or fractured) using highly-pressurized water.

The Fracturing Fluid

Fracturing fluid is an essential component of the shale gas extraction process. Water makes up 98% to 99.2% of the fluids used for fracture treatments. The remaining 0.8% consists of friction‐reducing additives, which allow the oil and natural gas to flow easily from the reservoir into the well.

The Fracturing Process

A well is first drilled using drill pipe before fracturing begins to increase the flow of gas (view site tour). The well, which is protected by steel casing and cement, is designed to contain water and be strong enough to sustain the force needed to set off a fracture in the reservoir rock. These multiple layers of cement and casing help not only ensure safe well construction but also protect underground water supplies. This process of pumping fracturing fluid through the well is then repeated several times.

The drilling is then angled at about 500 feet above the shale formation, creating a horizontal line, ultimately forming an L-shaped formation. A tool designed to make small holes is then inserted into the pipe, which allows the hydrocarbons to enter the stream. Fracturing fluids are then pumped into the section under high pressure, creating tears to allow oil and gas to move freely from the rock pores into the pipe. Plugs are inserted into the section as the fracturing repeats across the entire length of the horizontal well. Once complete, all of the plugs are removed, allowing the gas to flow out of the well. The fracturing equipment is then removed, the water is cleared and the well is prepared for the completion process.

Following the drilling and completion process, collection equipment is installed at the surface to prepare the well for production.

Additional Resources

Shale Plays: Environmental Issues Related to Surface Facilities