Shale oil extraction

Oil extraction

Main article: Oil Shale Extraction

At present, the major shale oil producers are Estonia, Brazil and China, while some other countries as Australia, USA, Canada and Jordan have planned to start or restart shale oil production. Although there are several oil shale retorting technologies, only five technologies are currently in commercial use, which are Kiviter, Galoter, Fushun, Petrosix, and Alberta Taciuk.

The two main methods of extracting oil from shale are ex-situ and in-situ.

Classification of oil shale processing according to heating method and location

Heating Method	Above Ground (ex-situ)	Below Ground (in-situ)
Conduction through a wall (various fuels)	Pumpherston, Fischer assay, Oil-Tech	Shell ICP (primary method)
Externally generated hot gas	PetroSIX, Union B, Paraho Indirect, Superior Indirect	-
Internal combustion	Kiviter, Fushun, Union A, Paraho Direct, Superior Direct	Oxy MIS, LLNL RISE, Geokinetics Horizontal, Rio Blanco
Hot recycled solids (inert or burned shale)	Alberta Taciuk, Galoter, Lurgi, TOSCO II, Chevron STB, LLNL HRS, Shell Spher	-
Reactive fluids	IGT Hytort (high-pressure H2), Donor solvent processes	Shell ICP (some embodiments)
Volumetric heating	-	ITTRI and LLNL radiofrequency

Ex-situ

In case of the ex-situ method, the oil shale is/can be mined either by traditional underground mining or surface mining from the ground and then transported to a processing facility. At the facility, the shale is usually heated to 450–500 °C (750-950°F). At this temperature, the kerogen in the shale decomposes to gas, oil vapour and char, a process known as retorting. The gas and oil vapours are separated from the spent shale and cooled causing the oil to condense. The oil may be sold as a fuel oil or upgraded to meet refinery feed specifications by adding hydrogen and removing impurities such as sulphur and nitrogen. The non-condensible retort gas and char on the spent shale may be burned and the heat may be recovered for heating the raw shale or generating electricity. Combustion exhaust gases and water condenced with the oil need to be treated prior to emission to the environment. Usually the spent shale is cooled and moistened with water before disposal back to the mine, settling ponds or tailing piles.

There are hundreds of patents for oil shale retorting technologies. However, only a few dozen have been tested in a pilot plant (1 to 10 t/h) and less than 10 technologies have been tested at a demonstration scale (40 to 400 t/h). One method of classifying the different ex-situ technologies is by the method that is used to heat the shale to retorting temperature. The classes are internal combustion technologies, hot recycled solids technologies, conduction through a wall technologies, externally generated hot gas technologies, and reactive fluids technologies.

Internal combustion technologies

Internal combustion or directly heated technologies uses heat, which is transferred by flowing gases generated by combustion within the retort. Common characteristics of these technolgies are the feed shale consists of lumps (10-100 mm) and the retort vapours are diluted with the combustion exhaust. The main technologies are Kiviter, Union A, Paraho Direct, Superior Direct, and Fushun processes. The Kiviter processing takes place in gravitational shaft retorts and it's possible only using large-particle feed. The process gas combustion products are used as the heat carrier. In the case of kukersite the yield of crude oil accounts 14-17% of shale and the oil consists only small amount of low-boiling fractions. Main problems of Kiviter process are related with environmental concerns like extensive use and pollution of water in the process, as also solid residue continues to leach toxic substances. The Kiviter process is used by Estonian company VKG Oil, a subsidiary of Viru Keemia Grupp. The company operates several retorts, the largest processing 40 t/h of oil shale.

Like the Kiviter, the Fushun-type retort processes oil shale lumps in a vertical shaft kiln. The Fushun Mining Group in Liaoning Province, China operates the largest shale oil plant in the world employing 80 Fushun-type retorts.

The Paraho Direct is an American version of the lump-processing vertical shaft kiln. Shale Technologies LLC owns and operates a pilot plant facility in Rifle Colorado.

Hot recycled solids technologies

Hot recycled solids technologies use heat, which is transferred by mixing hot solid particles with the oil shale. These technologies usually process oil shale fines (less than 10 mm). The heat carrier (usually shale ash) is heated by combustion in a separate chamber or vessel, thus the retort vapours are not diluted with combustion exhaust. The main technologies are Alberta Taciuk Process, Galoter, TOSCO II, Lurgi-Ruhrgas, Chevron STB, LLNL HRS, and Shell Spher processes. In the Galoter process, retorting takes place in a rotary kiln-type retort and it's possible to use also shale fines. The spent shale is burned in a spouted bed and solid shale ash is used as the heat carrier. In the case of kukersite the yield of crude oil accounts roughly 12% of shale and the oil consists 15-20% of low-boiling fractions. The Galoter process is more environmental-friendly than the Kiviter process, as the water use and pollution is smaller. However, the burning residue causes some environmental problems because of organic carbon and calcium sulphide consistent. The Galoter process is used for oil production by Eesti Energia, Estonian energy company. The company has 2 retorts both processing 125 t/h of oil shale and plans to build 2 more. Another Estonian company, VKG Oil AS, is constructing in 2007/08 a new production line using the Galoter process engineered by Atomenergoproject of St Petersburg

File:ATP.PNG

ATP retort

Like the Galoter process, the Alberta Taciuk processes oil shale fines in a rotary kiln-type retort. The unique feature of the Alberta Taciuk is that drying and pyrolysis of the feed shale and combustion, recycling and cooling of the spent shale all occur in a single multi-chamber horizontal, rotating vessel. The produced oil consists up to 30% of low-boiling fractions. The water pollution in the process is quite moderate. Australian oil companies Southern Pacific Petroleum NL and later Queensland Energy Resources operated a 250 t/h industrial-scale pilot plant using the Alberta Taciuk Processor. The plant closed in 2004. UMATAC Industrial Processes is designing the 6000-ton-per-day Alberta Taciuk Processor in China, scheduled for operation in 2008. Estonian VKG Oil is considering construction of new retort using the Alberta Taciuk Processor. Oil Shale Exploration Company LLC has arranged for an exclusive right to license the ATP for research, development and demonstration near Vernal Utah.

Like the Galoter and Alberta Taciuk, the TOSCO II also processes oil shale fines that are heated with hot recycled solids in a rotary kiln. However instead of recycling shale ash, the TOSCO II circulates hot ceramic balls between the retort and a heater. The process was tested in a 40 t/h test facility near Parachute Colorado that closed in 1972.

The LLNL HRS (hot-recycled-solid) retorting process is worked out by the Lawrence Livermore National Laboratory. The technology was used in a 4-tonne/day pilot plant from 1990 to 1993. A delayed-fall combustor, which is used in this process, gives greater control over the combustion process compared with a lift pipe combustor. A fluidized-bed mixer is used instead of the screw mixer. which is used in the Lurgi process. The majority of the pyrolysis occurs in a settling-bed unit.

Conduction through a wall technologies

Conduction through a wall technologies use heat, which is transferred by conduction through the retort wall. These technologies normally process fines and the retort vapours are not diluted by combustion exhaust. Technologies include Pumpherston, Fischer assay, Hom Tov and Oil-Tech processes. Oil-Tech staged electrically heated retort process is developed by Millennium Synfuels, LLC (former Oil Tech Inc.). In this process, the feedstock material is heated to greater degrees as it goes further down the retort. The retort-style prototype was reported to have passed a test.

In the Hom Tov process (US Patent 5372708), fine oil shale is slurried with waste bitumen and pumped through coils in a heater. Israeli promoters claim that the technology enables the shale to be processed at somewhat lower temperatures with the addition of the catalyzing bitumen. The technology has not been tested in a pilot plant yet.

Fischer Assay is a standardized laboratory test that is used to measure the grade of an oil shale sample. A 100-gram sample crushed to 8-mesh (2.38 mm) screen is heated in a small aluminum retort to 500 °C at a rate of 12 °C per minute, and held at that temperature for 40 minutes. The distilled vapors of oil, gas, and water are passed through a condenser and cooled with ice water into a graduated centrifuge tube. The oil yields achieved by other technologies are often reported as a percentage of the Fischer Assay oil yield.

Externally generated hot gas technologies

Externally generated hot gas technologies or indirectly heated technologies use heat, which is transferred by gases that are heated outside of the retort vessel. The main technologies are Petrosix, Union B, Paraho Indirect, and Superior Indirect processes. Like the internal combustion technologies, most of the externally-generated hot gas technologies process oil shale lumps in vertical shaft kilns, however the retort vapours are not diluted with combustion exhaust. The world’s largest surface oil shale pyrolysis reactor currently operating is the Petrosix in São Mateus do Sul, Paraná, Brazil. The 11-m diameter vertical shaft kiln is owned by Petrobras and has being operating since 1992 with high availlability. The company operates 2 retort, the largest of which processes 260 t/h of oil shale.

The largest retort ever built used the Union B technology, developed by Unocal. The Union B processed 400 t/h of oil shale lumps heated by externally generated hot gas. However unlike all other vertical shaft kilns, the Union B pumped the oil shale into the bottom of the retort and hot gas entered at the top. Unocal operated the retort from 1986 to 1992 near Parachute, Colorado.

The Paraho Indirect technology is similar to the Petrosix which is considered a highly reliable technology for use with U.S. oil shale.

Reactive fluids technologies

Reactive fluids technologies are IGT Hytort (high-pressure H2), and Donor solvent processes.

Fluid Bed Reactor

Chattanooga Corp have developed an oil crude extraction method for oil shales, tar sands and other unconventional oil by a fluid bed rector and a associated hydrogen fired heater. At relatively low temperatures(1000 F)through thermal cracking and hydrogenation into hydrocarbon vapors and spent solids. The thermal cracking allows for hydrocarbon vapors to be extracted off the oil shale which is then extracted and scrubbed of solids. The vapor is then cooled, during this cooling condensate drops out of the gas, the remaining hydrogen, light hydrocarbon (HC) and acid gases are passed through an amine scrubbing system to remove hydrogen sulfide which is converted to elemental sulfur. The cleaned hydrogen and light hydrocarbon gases are then fed back into the system for compression or into the hydrogen heater which provide the heat for the fluid bed reactor. This almost closed loop allows for a very efficient process where nearly all the energy needs are provided by the source material and the end result is a valuable light condensate crude. The demonstration plant in Canada was able to produce 51 gal/ton of shale oil at an API gravity between 28-30. With hydrotreating ti would be possible to improve this to 38-40 API. Chattanooga Corp are currently looking at designs o produce a 60,000 b/d facility.

In-situ

The in-situ technologies are usually classified as true in-situ processes (TIS) and modified in-situ processes (MIS). While true in-situ processes do not involve mining the shale, the modified in-situ involves prior to heating mining beneath the target oil shale deposit, and drilling and fracturing the target deposit above the mined area to create void space of 20 to 25 percent to improve the flow of gases and liquid fluids through the rock formation, and by that increasing the volumes and quality of the oil produced. The in-situ technologies could be also classified similarly to the ex-situ classification by the method of heating.

First in-situ oil shale experiment was conducted by Occidental Petroleum in 1972 at Logan Wash. In-situ operations could potentially extract more oil from a given area of land than conventional oil shale mining and retorting, as the wells can reach much deeper than surface strip-mines can. With in-situ processing, the shale is fractured and heated underground to release gases and oils. Several companies have patented methods for in-situ retorting. However, most of these methods are still experimental.

Shell's In-Situ Conversion Process (ICP)

File:Shell Freeze Wall Oil Shae.PNG

Shells Freeze Wall for in-situ shale oil production

The Shell Oil Company has been developing a new method since 2000 under the name the Mahogany Research Project in Colorado, some 200 miles (320 km) west of Denver. This is a true in-situ technology which uses conduction through a wall and reactive fluids (some embodiments) methods for the heating. This method is energy intensive though but favours well when compared to other heavy oil projects like the Tar sands. If a full field project was to be undertaken it is estimated that for every unit of energy consumer 3.5 units would be produced over the project life cycle. It also has the benefit that the hydrocarbons produced is much lighter than traditional crude.

First a freeze wall is constructed to seal off groundwater by drilling 2000' wells, eight feet apart, around the perimeter of a 10 acre working zone, and then circulating with a super-chilled liquid to freeze the ground to -60^oF. This freeze wall is present as an environmental measure to prevent contamination of the groundwater. The working zone is then dewatered. Recovery wells are drilled on 40' spacing within the working zone. An electrical heating element is lowered into each well and allowed to heat the kerogen to 650 to 700^oF over a period of approximately four years, slowly converting it into oils and gases, which are then pumped to the surface. The company believes that it will be possible to recover in the region of 65-70% of the hydrocarbons in place. An operation producing 100,000 barrels a day would require a dedicated electrical generating capacity of 1.2 gigawatts. To maximize the functionality of the freeze walls, working zones will be developed, in succession, adjacent to each other. This in-situ method requires 100% surface disturbance, greatly increasing the footprint of extraction operations in comparison to conventional oil and gas drilling.

The current test sites are expected to produce in the region of 600 to 1,500 bopd

EGL Resources

EGL Resources proposed a method which has also been suggested in Coal Bed Methane production where horizontal wells are drilled in parallel and fractured. These wells are then intersected by vertical wells. The vertical wells will allow steam to be injected into the formation to melt the in-situ hydrocarbons which will then be produced by the horizontal wells. They are currently leasing a 160 acre lease in the Piceance Basin from the US Bureau of land management for their tests.

Chevron

Chevrons in-situ Oil Shale production technique

Chevron Corporation and Los Alamos National Laboratory formed a joint research project in 2006 to develop oil shale. They have leased a 160 acre patch from the US Bureau of land management for their tests. They are investigating whether CO² can be injected into the formation at a raised temperature which will decompose the kerogen into conventional hydrocarbons. The CO² would be injected via conventionally drilled wells and then exposed tot he formation via a series of horizontal fractures where it would circulate around. The hydrocarbons would then be produced also via conventional vertical oil wells.

This method is based upon research and trials carried out in the 1950s by Sinclair Oil and Gas company which developed a method using natural and induced fractures between vertical wells to produce the in-situ kerogen. Continental oil and the University of Akron also demonstrated and were issued patents that showed that CO² was a good carrier gas in helping recover the shale oil.

Petro Probe

Petro probe a subsidiary of Earth Science Search have listened a process involving injecting superheated air in to wells drilled into the oil shale. They are currently in negations with the process patent holder which once complete will allow them to begin a three stage test program to verify the process, the economics and the function ability of a complete working plant. The process involves injecting air which is super heated at the surface into wells drilled into the oil shale. The super-heater air then mixes and melts the in-situ shale oil which is transported back to the surface in the gas which is then cooled and the condensate drop out is collected. The produced gas is then in turned used to heat the air and is injected back with other waste products into the formation there by minimizing the environmental impact.

ExxonMobil Electrofrac

ExxonMobil has been involved in Oil Shale development since the 1960’s and is currently focused on in-situ developments for oil shale. They are concentrating on an in-situ method which heats the oil shale via an electrically conductive heating fluid which has been injected into the reservoir and heats the oil shale via a series of hydraulic fractures. The oil shale is produced by separate dedicated production wells.

It is thought that most likely method is to have horizontal wells which have been hydraulically fractured along the vertical axis. These wells are place in a parallel row with a second horizontal well intersecting them at their toe. This will allow the two different charges to be applied at either end. ExxonMobil is pursuing this method as they believe it provides a better method in which is reach into the surround oil shale and heat it up.

The Electrofrac method has been tested in laboratories and test sites are now currently being considered for a field trial.

Volumetric heating by radio waves technologies

The concept of volumetric heating by radio waves (radio frequency processing) of oil shale was developed at IITRI in the late 1970s. The concept was to heat modest volumes of shale over using vertical electrode arrays. Deeper large volumes could be processed at slower heating rates over a period. The technology was developed later by the Lawrence Livermore National Laboratory (LLNL), and by several other inventors. The LLNL concept based on the use of wells spaced at tens of meters to heat cubic kilometers of deep oil shale very slowly. The concept presumed a radio frequency at which the skin depth is many tens of meters, and thereby overcoming the thermal diffusion times needed for conductive heating.