How Hydraulic Fracturing Helps Extract Shale Gas

Hydraulic fracturing causes fractures in the rock formation, which stimulates the flow of natural gas or oil, thereby increasing the amount recovered.

FREMONT, CA: Hydraulic fracturing is a method of producing "unconventional" gas. Using a special stimulation technique, such as hydraulic fracturing or another special recovery process and technology, can "unconventional" reservoirs produce gas at a low cost. This is frequently due to the gas being widely dispersed throughout the rock rather than in a concentrated underground location.

Unconventional gas extraction is still in its early stages. For example, coalbed methane extraction began in the 1980s, while shale gas extraction is even more recent. However, the main enabling technologies, hydraulic fracturing and horizontal drilling have opened up new oil and gas development areas, emphasizing natural gas reservoirs like shale, coalbed, and tight sands.

Extraction of Shale Gas. In the United States, shale rock formations have emerged as a significant source of natural gas. Shale gas can be found in many parts of the contiguous United States, including areas where no oil or gas production has ever occurred.

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Coalbed Methane Production Coalbed methane (CBM) was first extracted from coal mines as a safety precaution to mitigate the explosion risk posed by methane gas in the mines. Methane is now captured and used as a source of energy. Deeper coal formations may necessitate hydraulic fracturing to liberate natural gas.

Tight Sands. Tight sands are low-permeability, gas-bearing, fine-grained sandstones or carbonates. Unless there are natural fractures, almost all tight sand reservoirs require hydraulic fracturing to release gas.

Wells can be drilled hundreds to thousands of feet below the land surface and can include thousands of feet of horizontal or directional sections.

Fractures are formed by pumping large amounts of high-pressure fluids down a wellbore and into the target rock formation. Hydraulic fracturing fluid is typically made up of water, proppant, and chemical additives that open and enlarge fractures in the rock formation. These fractures can extend hundreds of feet from the wellbore. The proppants, sand, ceramic pellets, or other small incompressible particles, keep the newly formed fractures open.

When the injection process is finished, the internal pressure of the rock formation causes fluid to flow back to the surface via the wellbore. This fluid referred to as "flowback" or "produced water," may contain the injected chemicals and naturally occurring materials such as brines, metals, radionuclides, and hydrocarbons. Flowback and produced water are typically stored on-site in tanks or pits before being treated, disposed of, or recycled. As a result, it is frequently injected underground for disposal. However, if this is not an option, it may be treated and reused or processed by a wastewater treatment facility before being discharged to surface water.