Fracking – Shale Oil & Gas
Recent massive discoveries of shale oil and shale gas have been made around the world. Various methods of extraction are being considered, but the most popular is ‘Fracking’ the process of initiating and subsequently propagating a fracture in a rock layer, by means of a pressurized fluid, in order to release petroleum, natural gas, coal seam gas, has come under attack from many quarters and may halt the growth of this expanding sector.

Recent major discoveries include;
- An estimated 1.5 trillion barrels of oil in the USA.
· Israel, in the Elah valley, where 2.5 billion barrels of shale oil is thought to have been discovered, 30 miles from Jerusalem, and also a massive under sea gas field called Leviatian, between Israel and Cyprus.
· The UK, where a find of 2 trillion cubic feet of shale gas has been made in Lancashire and drilling has been blocked at Bridgend in Wales.
Fracking is the process of drilling down and creating tiny explosions to shatter and crack hard shale rocks to release the gas inside. Water, sand and chemicals are injected into the rock at high pressure which allows the gas to flow out to the head of the well. The process is carried out vertically or, more commonly, by drilling horizontally to the rock layer. The process can create new pathways to release gas or can be used to extend existing channels.
The expression ‘fracking’ is shorthand for hydraulic fracturing and refers to how the rock is fractured apart by the high pressure mixture. There are concerns that potentially carcinogenic chemicals can sometimes escape and find their way into drinking water sources by disruption to acquifers. Some American householders also claim that shale gas leaking into their drinking supply causes tap water to ignite.
A hydraulic fracture is formed by pumping the fracturing fluid into the wellbore at a rate sufficient to increase pressure downhole to exceed that of the fracture gradient of the rock. The rock cracks and the fracture fluid continues farther into the rock, extending the crack still farther, and so on. To keep this fracture open after the injection stops, a solid proppant, commonly a sieved round sand, is added to the fluid. The propped fracture is permeable enough to allow the flow of formation fluids to the well. Formation fluids include gas, oil, salt water, fresh water and fluids introduced to the formation during completion of the well during fracturing.
Environmental concerns with hydraulic fracturing include the potential contamination of ground water, risks to air quality, the potential migration of gases and hydraulic fracturing chemicals to the surface, the potential mishandling of waste, and the health effects of these.
Wikiepedia reports a number of incidents: In 2006 drilling fluids and methane were detected leaking from the ground near a gas well in Clark, Wyoming; 8 million cubic feet of methane were eventually released, and shallow groundwater was found to be contaminated. In the town of Dimock, Pennsylvania, 13 water wells were contaminated with methane (one of them blew up), and the gas company, Cabot Oil & Gas, had to financially compensate residents and construct a pipeline to bring in clean water; the company continued to deny, however, that any “of the issues in Dimock have anything to do with hydraulic fracturing”.
On 21.9.11 the BBC reported that an energy firm had found vast gas resources off the Flyde coast in March, by using ‘Fracking’ to map the reserves. In Lancashire tests were stopped in June when two earthquakes of 1.5 and 2.2 magnitude occurred in the Blackpool area.
However, Tim Yeo MP – chairman of the energy select committee – told the BBC: “We can’t see any evidence that UK water supplies might be at risk from shale gas – if it is done properly.” The committee has also said that environmental problems suffered in the US could be overcome by tight regulation and good industry practice.
The industry itself also vigorously denies that shale gas is unsafe and blames pollution incidents as examples of bad practice, rather than an inherently risky technique.
Shale oil extraction
Shale oil extraction began in the late 1970s under Presidents Gerald Ford and Jimmy Carter, who were also keen to develop the use of solar power as the main form or renewable energy. A shale – boom emerged with new ‘boom towns’ growing up in Rifle, Parachute, Rangely and Meeker in Colorado. But after Black Monday on May 2nd 1982, Exxon shut down it’s Colony Oil Shale project leaving the vast deposits in Colorado unrefined.
Recent discoveries such as that in the Shfela Basin in Israel where it is believed that 250 billion barrels of oil are held, comparable to Saudi Arabia’s entire reserves, have brought about a renewed interest in shale oil extraction. Led by Harold Vinegar, a veteran who had been Shell Oil’s chief scientist with 240 patents to his name in shale extraction, IDT corp headed by Lord Jacob Rothschild, uses heated rods to produce high value jet fuel and diesel.
Numerous other fields are now being worked in the USA and Canada, Other major finds have been reported in Brazil, Australia and China which has proven reserves of 331.5 billion tonnes, centred on the towns of Fushun and Maoming the north east of the country.
Industry analysts have created several classifications of the technologies used to extract shale oil from oil shale.
By process principles: Based on the treatment of raw oil shale by heat and solvents the methods are classified as pyrolysis, hydrogenation, or thermal dissolution.
By location: A frequently used distinction considers whether processing is done above or below ground, and classifies the technologies broadly as ex situ (displaced) or in situ (in place). In ex situ processing, also known as above-ground retorting, the oil shale is mined either underground or at the surface and then transported to a processing facility. In contrast, in situ processing converts the kerogen while it is still in the form of an oil shale deposit, following which it is then extracted via oil wells, where it rises in the same way as conventional crude oil.
By heating method: The method of transferring heat from combustion products to the oil shale may be classified as direct or indirect.
By heat carrier: Based on the material used to deliver heat energy to the oil shale, processing technologies have been classified into gas heat carrier, solid heat carrier, wall conduction, reactive fluid, and volumetric heating methods. Heat carrier methods can be sub-classified as direct or indirect.
By raw oil shale particle size: The various ex situ processing technologies may be differentiated by the size of the oil shale particles that are fed into the retorts. As a rule, gas heat carrier technologies process oil shale lumps varying in diameter from 10 to 100 millimeters (0.4 to 3.9 in), while solid heat carrier and wall conduction technologies process fines which are particles less than 10 millimeters (0.4 in) in diameter.[14]
By retort orientation: “Ex-situ” technologies are sometimes classified as vertical or horizontal. Vertical retorts are usually shaft kilns where a bed of shale moves from top to bottom by gravity. Horizontal retorts are usually horizontal rotating drums or screws where shale moves from one end to the other. As a general rule, vertical retorts process lumps using a gas heat carrier, while horizontal retorts process fines using solid heat carrier.
By complexity of technology: In situ technologies are usually classified either as true in situ processes or modified in situ processes. True in situ processes do not involve mining or crushing the oil shale. Modified in situ processes involve drilling and fracturing the target oil shale deposit to create voids in the deposit. The voids enable a better flow of gases and fluids through the deposit, thereby increasing the volume and quality of the shale oil produced.
Originally posted 2011-10-26 00:00:00.
