Heavy Oil And Natural Bitumen–Strategic Petroleum Sources
U.S. Geological Survey
Fact Sheet 70-03
August 2003 – On-line Version 1.0
Heavy Oil and Pure Bitumen–
Strategic Petroleum Sources
By Richard F. Meyer and Emil D. Attanasi
As a result of typical gentle oil can usually be produced at a high charge and a low cost, it has been used before other forms of oil. Thus, standard oil accounts for a declining share of the Earth’s remaining oil endowment. In addition to assessing standard oil sources, scientists of the U.S. Geological Survey’s Vitality Resources Program acquire knowledge on the crude oil prices vs gasoline plentiful power resources obtainable as heavy oil (together with additional-heavy oil) and natural bitumen; see definitions in sidebar. The data in this Truth Sheet are compiled from business databases (NRG Associates, I.H.S. Petroconsultants), unpublished government crude oil prices vs gasoline knowledge, and the printed literature.
Pure bitumen (typically known as tar sands or oil sands) and heavy oil differ from mild oils by their high viscosity (resistance to circulation) at reservoir temperatures, high density (low API gravity), and important contents of nitrogen, oxygen, and sulfur compounds and heavy-metal contaminants. They resemble the residuum from the refining of mild oil. Most heavy oil is discovered at the margins of geologic basins and is thought to be the residue of formerly gentle oil that has lost its light-molecular-weight components by means of degradation by micro organism, water-washing, and evaporation.
The estimated quantity of technically recoverable heavy oil (434 billion barrels) and natural bitumen (651 billion barrels) in identified accumulations is about equal to the Earth’s remaining conventional (mild) oil reserves (table 1, fig. 1).
Desk 1. Regional distribution of estimated technically recoverable
heavy oil and natural bitumen in billions of barrels (BBO).
Region Heavy oil
recoverable BBO Recovery
North America zero.19 35.Three zero.32 530.9
South America zero.13 265.7 zero.09 zero.1
W. Hemisphere 0.13 301.Zero zero.32 531.0
Africa 0.18 7.2 0.10 43.0
Europe 0.15 four.9 zero.14 0.2
Center East zero.12 78.2 0.10 0.Zero
Asia zero.14 29.6 zero.Sixteen 42.8
Russia zero.Thirteen 13.Four 0.13 33.7**
E. Hemisphere 0.13 133.3 zero.13 119.7
World 434.Three 650.7
*Restoration elements have been based mostly on printed estimates of technically
recoverable and in-place oil or bitumen by accumulation. The place
unavailable, recovery elements of 10 percent and 5 percent of heavy oil
or bitumen in place had been assumed for sandstone and carbonate
**As well as, 212.4 billion barrels of pure bitumen in place is located in
Russia however is either in small deposits or in distant areas in jap Siberia.
Determine 1. Distribution of the world’s known recoverable oil assets and reserves by kind. Technically recoverable oil in identified heavy oil and natural bitumen accumulations is about equal to reserves of light oil (API gravity higher than 22°) in known typical accumulations. BBO, billion barrels of oil.
Despite an immense useful resource base, heavy oil and pure bitumen accounted for less than about 3 billion barrels of the 25 billion barrels of crude oil produced in 2000. Compared to mild oil, these assets are generally extra costly to provide and transport. Also, extra-heavy oil and natural bitumen should often be upgraded by lowering their carbon content or including hydrogen before they can be utilized as feedstock for a conventional refinery. The additional production, transportation, and upgrading costs clarify why growth and production of extra-heavy oil and bitumen are nonetheless restricted. Their abundance, strategic geographic distribution, high quality, and prices will shape their function sooner or later oil provide.
Mild oil, additionally called conventional oil, has an API gravity of at least 22° and a viscosity lower than a hundred centipoise (cP).
Heavy oil is an asphaltic, dense (low API gravity), and viscous oil that is chemically characterized by its content material of asphaltenes (very large molecules incorporating many of the sulfur and perhaps ninety percent of the metals in the oil). Though variously outlined, the upper limit for heavy oil has been set at 22° API gravity and a viscosity of 100 cP.
Additional-heavy oil is that portion of heavy oil having an API gravity of less than 10°.
Pure bitumen, also referred to as tar sands or oil sands, shares the attributes of heavy oil however is but extra dense and viscous. Natural bitumen is oil having a viscosity higher than 10,000 cP.
Viscosity is a measure of the fluid’s resistance to circulation. It varies vastly with temperature. Viscosity matters to producers because the oil’s viscosity at reservoir temperature determines how easily oil flows to the effectively for extraction.
Density is a measure of mass per unit quantity and interests refiners because it’s an indicator of yield from distillation. Oil density is expressed in degrees of API gravity, a regular of the American Petroleum Institute. API gravity is computed as (141.5/sp g) – 131.5, the place sp g is the specific gravity of the oil at 60°F.
The Western Hemisphere has sixty nine % of the world’s technically recoverable heavy oil and 82 p.c of the technically recoverable natural bitumen. In contrast, the Jap Hemisphere has about eighty five % of the world’s mild oil reserves.
Heavy oil and natural bitumen are present worldwide (desk 1). Every class is dominated by a single extraordinary accumulation. The biggest further-heavy oil accumulation is the Venezuelan Orinoco heavy-oil belt, which accommodates 90 % of the world’s additional-heavy oil when measured on an in-place foundation. Eighty-one percent of the world’s known recoverable bitumen is in the Alberta, Canada, accumulation. Collectively the 2 deposits comprise about 3,600 billion barrels of oil in place.
In addition to additional-heavy Orinoco oil, South America has an estimated 40 billion barrels of technically recoverable heavy oil, so that, in complete, 61 p.c of the recognized technically recoverable heavy oil is in South America.
Of the 35 billion barrels of heavy oil estimated to be technically recoverable in North America, about 7.7 billion barrels are assigned to identified producing accumulations in the decrease forty eight States, and 7 billion barrels are assigned to the North Slope of Alaska.
The U.S. bitumen accumulations are largely in Utah. No U.S. accumulations are being produced commercially, though, in whole, they’re estimated to include 6.1 billion barrels of recoverable bitumen.
Present Manufacturing Technology
Currently, producers target heavy oil accumulations having higher quality oil by way of chemistry and density. About 66 percent of the heavy oil produced yearly is lighter than 15° API gravity, however about 50 p.c of the estimated technically recoverable heavy oil is denser (less than 15° API gravity) (fig. 2).
Figure 2. Cumulative proportion of annual production (blue) and cumulative share of technically recoverable assets (brown) of heavy oil as a perform of oil density (API gravity) in 2000. Lower than 10 % of the heavy oil produced annually is further-heavy oil (API gravity of 10° or less), whereas 33 p.c of the technically recoverable heavy oil has an API gravity of 10° or less.
In standard production, reservoir pressure from fuel and water associated with the oil is generally adequate to trigger mild oil to circulation to a production properly. If pure reservoir pressure becomes depleted, then oil circulation may be enhanced by injecting fuel or water into the reservoir to push the residual oil to the production nicely.
Historically, heavy oil was discovered by the way through the search for mild oil and was produced by standard strategies when economically feasible. However, to maintain commercial nicely production charges, heavy and additional-heavy oil manufacturing almost always requires measures to cut back oil viscosity and to introduce power into the reservoir. When super-heated steam is injected right into a reservoir, oil viscosity is diminished and reservoir strain is increased by displacement and partial distillation of the oil. Steam may be injected constantly to form a flood or it may be injected in cycles so wells are used alternately for injection and production.
Further-heavy oil commonly requires the addition of diluents (gasoline condensate, natural gas liquids, or light crude) to enable the oil to be transported by pipeline. Further-heavy oil must even be chemically upgraded to scale back density and remove contaminants earlier than it can be used as refinery feedstock. In recent tasks within the Venezuelan Orinoco heavy oil belt, 1 barrel of diluents is required for every three or 4 barrels of extra-heavy oil produced.
Natural bitumen is so viscous that it is immobile within the reservoir. For oil sand deposits lower than 225 ft deep, bitumen is recovered by mining the sands, then separating the bitumen from the reservoir rock by processing it with sizzling waters, and finally upgrading the natural bitumen onsite to a artificial crude oil. In deeper oil sand deposits, the place the bitumen is usually much less viscous, steam is injected into the reservoir to mobilize the oil for restoration by production wells. The product may be upgraded onsite or blended with diluent and transported to an upgrading facility.
Within the Orinoco heavy oil belt, horizontal wells and lateral branches which are optimally positioned and geared up with improved electrical submersible or progressing cavity pumps can ship up to 2,000 barrels of oil per day. Such horizontal effectively prices have been decreased in recent years, and thus this additional-heavy crude oil is business. Nevertheless, the prices associated with the diluents for reservoir injection and for facilitating transport to an upgrading facility are still significant. Concession operators plan to increase Orinoco production to 600,000 barrels of further-heavy oil per day by 2005 and to maintain that price for 35 years (Petroleum Review, 2001, v. Fifty five, no. 653, p. 30).
Natural bitumen is extracted from Alberta oil sand deposits that are too deep to surface mine by a course of known as steam-assisted gravity drainage (SAGD); see fig. 3. Production wells could produce in excess of two,000 barrels of bitumen per day. In 2001, about 735,000 barrels per day had been extracted by mining and by in-situ manufacturing from Alberta oil sands, accounting for 36 p.c of Canada’s whole oil manufacturing. Projected 2011 manufacturing is 2.2 million barrels per day (Alberta Vitality and Utility Board, 2002, Alberta’s Reserves 2001 and Provide/Demand Outlook 2002-2011, Statistical Series 2002-98, p. 2-8 to 2-9).
Determine three. Stacked pair of horizontal wells for steam-assisted gravity drainage (SAGD), a pure bitumen recovery course of. Steam injected by means of the upper nicely mobilizes bitumen, and gravity causes the mobilized fluid to move toward the decrease effectively, the place the bitumen is pumped to the floor. From Carl Curtis and others, 2002, Oilfield Evaluation, v. 14, no. Three, p. 50.
For more data, please contact:
Richard F. Meyer
Emil D. Attanasi
U.S. Geological Survey
956 Nationwide Heart
Reston, VA 20192
U.S. Division of the Inside, U.S. Geological Survey
For more info, contact Richard F. Meyer or Emil D.