What is unconventional oil and gas?
Unconventional oil and gas is the collective term used to describe tight oil or gas, shale oil and gas and coal bed methane (CBM). In order to be developed and produced, most unconventional oil and gas production requires the rock to be hydraulically fractured ('fracked') or stimulated to allow natural gas to escape from the tight rock and flow through the wellbore to the surface.
What makes unconventional oil and gas different from other fossil fuels?
There is no difference between unconventional oil and gas and conventional oil and gas. The difference lies in the reservoirs, where the oil and gas is found, and some aspects of the process in which it is extracted.
What is unconventional oil used for?
Similar to natural gas, unconventional oil is used for the same purposes as conventional oil. The only difference from where and how it is extracted.
What is unconventional gas used for?
Natural gas, whether it is extracted using conventional or unconventional methods, is the cleanest-burning fossil fuel and can be used to meet the energy demands of many sectors. When used for power generation, for example, natural gas emits up to 60 percent less CO2 than coal. Emissions of other waste products such as mercury, sulphur and nitrogen oxide are also significantly reduced, improving air quality.
How does ‘fracking’ work?
'Fracking' is the general term used for the process of hydraulic fracturing, which involves pumping a pressurized mixture of water, sand and chemical additives down the wellbore and into tight rock formations that contain natural gas. The water pressure creates very thin cracks in the rock, which are then held open by the grains of sand, allowing the trapped gas to flow out through the wellbore to the surface.
How does the extraction process impact local communities?
Before any wells are drilled, extensive surveillance, monitoring and seismic analysis are conducted to study the locations of the underground natural gas reservoirs and to minimize the impact of operations on the local community.
To minimize traffic disruptions, trucks used to carry equipment and hydraulic fracturing fluid are brought in during the day, and usually at off-peak times. Though the noise levels from the site are well within the permitted range, noise barriers are sometimes set up around the perimeter of the area to reduce sound levels even further. Once an unconventional gas well is producing, it is extremely compact and quiet.
How long do drilling, hydraulic fracturing and production operations last?
The drilling stage takes a few months while the hydraulic fracturing, including the preparation work, lasts only up to one week, depending on the type of rock. The production life of the well, however, can vary from a few years up to 20-30 years. This depends on how much natural gas the reservoir contains and how much of it can be extracted at an economical rate.
What are the chemicals used in hydraulic fracturing and why are they needed?
Hydraulic fracturing fluid is typically 98-99.5 percent water and sand, with the remaining 0.5-2 percent comprised of chemical additives that are needed to make the process more effective. The additives are used to reduce friction, inhibit bacterial growth, prevent corrosion and enhance the fracture's effectiveness, thereby making the process safer and more efficient.
Many of the chemical additives used in the process are found in household products such as cosmetics, shampoo and cleaning products. Responsible operators employing hydraulic fracturing techniques, like all processes related to the extraction of unconventional gas, adhere to the highest national environmental and safety regulations.
Will chemicals used in fracturing fluid get into groundwater aquifers?
Hydraulic fracturing used for extraction of unconventional gas occurs far below the groundwater aquifer. Responsible operators implement a series of precautionary measures to ensure that none of the chemicals leak into groundwater aquifers.
The key to groundwater protection is proper well design; when a natural gas well is drilled through an aquifer multiple layers of impermeable steel and cement casing are used to ensure wellbore integrity. Verification of well bore integrity during all phases of operations is an important objective for safe and efficient production. These layers are tested for leak-tightness during all phases of operations, ensuring an impermeable barrier between the well and the water source while fluid is pumped to an area that is hundreds of feet away from the groundwater table.
A variety of testing procedures are implemented by industry throughout operations, including laboratory tests of cement behavior, pressure testing of well bore casings to verify their integrity, and a series of well bore casing inspections. There is no difference in this requirement between an unconventional gas well and conventional oil and gas well.
To ensure integrity of well bores a variety of testing procedures are implemented at ExxonMobil. Verification of well bore integrity during all phases of operations is an important objective for safe and efficient production. In order to achieve this goal, multiple tests for cement and casing integrity are conducted on a regular basis. For example involving laboratory tests of cement behavior, well bore pressure testing of all casings shoes to verify their integrity, and various well bore casing inspection logging runs.
The surface site is also designed to isolate the ground from the drilling and production operations to ensure any risk of fluids entering the ground is removed. These measures are heavily regulated and apply to both conventional and unconventional gas wells.
How much water is used to develop unconventional gas?
The amount of freshwater needed for drilling and fracking over the two to three month set-up, drilling and completion process for a typical well is usually equivalent to about three to six Olympic-size swimming pools. The hydraulic fracturing process itself uses a small amount of water compared to other industrial and recreational uses; coal mining, for example, requires two to four times more water per unit of energy produced while certain agricultural-based biofuels, such as corn-based ethanol, require 80 to 12,000 times more water per unit of energy produced.
What is done with wastewater?
Various treatment technologies allow the produced water to be reused for subsequent hydraulic fracturing operations and other industrial uses or to be disposed. Operators of shale gas wells, however, must first obtain permits for the handling and disposal of produced water. After separating the wastewater and natural gas, water can either be stored or recycled at the surface; if no recycling occurs, the solid and liquid waste are stored temporarily in sealed containers and then shipped to licensed water processing facilities for treatment and disposal according to the permit procedures and applicable regulations.
Who regulates unconventional resource development?
In the United States, the industry is regulated by an integrated network of federal, state, and sometimes local controls. These regulations and processes encompass site development, drilling permitting (which would include hydraulic fracturing), water withdrawals, on-site storage, disposal and reuse/recycling, and well plugging and abandonment.