# Oil reserves

Last updated

Oil reserves denote the amount of crude oil that can be technically recovered at a cost that is financially feasible at the present price of oil. [1] Hence reserves will change with the price, unlike oil resources, which include all oil that can be technically recovered at any price. Reserves may be for a well, a reservoir, a field, a nation, or the world. Different classifications of reserves are related to their degree of certainty.

Petroleum is a naturally occurring, yellowish-black liquid found in geological formations beneath the Earth's surface. It is commonly refined into various types of fuels. Components of petroleum are separated using a technique called fractional distillation, i.e. separation of a liquid mixture into fractions differing in boiling point by means of distillation, typically using a fractionating column.

## Contents

The total estimated amount of oil in an oil reservoir, including both producible and non-producible oil, is called oil in place . However, because of reservoir characteristics and limitations in petroleum extraction technologies, only a fraction of this oil can be brought to the surface, and it is only this producible fraction that is considered to be reserves. The ratio of reserves to the total amount of oil in a particular reservoir is called the recovery factor. Determining a recovery factor for a given field depends on several features of the operation, including method of oil recovery used and technological developments. [2]

Oil in place (OIP) is a specialist term in petroleum geology that refers to the total oil content of an oil reservoir. As this quantity cannot be measured directly, it has to be estimated from other parameters measured prior to drilling or after production has begun.

Reservoir engineering is a branch of petroleum engineering that applies scientific principles to the fluid flow through porous medium during the development and production of oil and gas reservoirs so as to obtain a high economic recovery. The working tools of the reservoir engineer are subsurface geology, applied mathematics, and the basic laws of physics and chemistry governing the behavior of liquid and vapor phases of crude oil, natural gas, and water in reservoir rock. Of particular interest to reservoir engineers is generating accurate reserves estimates for use in financial reporting to the SEC and other regulatory bodies. Other job responsibilities include numerical reservoir modeling, production forecasting, well testing, well drilling and workover planning, economic modeling, and PVT analysis of reservoir fluids. Reservoir engineers also play a central role in field development planning, recommending appropriate and cost effective reservoir depletion schemes such as waterflooding or gas injection to maximize hydrocarbon recovery. Due to legislative changes in many hydrocarbon producing countries, they are also involved in the design and implementation of carbon sequestration projects in order to minimise the emission of greenhouse gases.

The extraction of petroleum is the process by which usable petroleum is drawn out from beneath the earth's surface location

Based on data from OPEC at the beginning of 2013 the highest proved oil reserves including non-conventional oil deposits are in Venezuela (20% of global reserves), Saudi Arabia (18% of global reserves), Canada (13% of global reserves), and Iran (9%). [3]

The Organization of the Petroleum Exporting Countries is an intergovernmental organization of 14 nations, founded in 1960 in Baghdad by the first five members, and headquartered since 1965 in Vienna, Austria. As of September 2018, the then 14 member countries accounted for an estimated 44 percent of global oil production and 81.5 percent of the world's "proven" oil reserves, giving OPEC a major influence on global oil prices that were previously determined by the so called "Seven Sisters” grouping of multinational oil companies.

Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and a large number of small islands and islets in the Caribbean Sea. The capital and largest urban agglomeration is the city of Caracas. It has a territorial extension of 916,445 km2. The continental territory is bordered on the north by the Caribbean Sea and the Atlantic Ocean, on the west by Colombia, Brazil on the south, Trinidad and Tobago to the north-east and on the east by Guyana. With this last country, the Venezuelan government maintains a claim for Guayana Esequiba over an area of 159,542 km2. For its maritime areas, it exercises sovereignty over 71,295 km2 of territorial waters, 22,224 km2 in its contiguous zone, 471,507 km2 of the Caribbean Sea and the Atlantic Ocean under the concept of exclusive economic zone, and 99,889 km2 of continental shelf. This marine area borders those of 13 states. The country has extremely high biodiversity and is ranked seventh in the world's list of nations with the most number of species. There are habitats ranging from the Andes Mountains in the west to the Amazon basin rain-forest in the south via extensive llanos plains, the Caribbean coast and the Orinoco River Delta in the east.

Energy in Saudi Arabia involves petroleum and natural gas production, consumption, and exports, and electricity production. Saudi Arabia is the world's leading oil producer and exporter. Saudi Arabia's economy is petroleum-based; oil accounts for 90% of the country's exports and nearly 75% of government revenue. The oil industry produces about 45% of Saudi Arabia's gross domestic product, against 40% from the private sector. Saudi Arabia has per capita GDP of \$20,700. The economy is still very dependent on oil despite diversification, in particular in the petrochemical sector.

Because the geology of the subsurface cannot be examined directly, indirect techniques must be used to estimate the size and recoverability of the resource. While new technologies have increased the accuracy of these techniques, significant uncertainties still remain. In general, most early estimates of the reserves of an oil field are conservative and tend to grow with time. This phenomenon is called reserves growth . [4]

Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated earth system science and planetary science.

Exploration geophysics is an applied branch of geophysics and economic geology, which uses physical methods, such as seismic, gravitational, magnetic, electrical and electromagnetic at the surface of the Earth to measure the physical properties of the subsurface, along with the anomalies in those properties. It is most often used to detect or infer the presence and position of economically useful geological deposits, such as ore minerals; fossil fuels and other hydrocarbons; geothermal reservoirs; and groundwater reservoirs.

Reflection seismology is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite or Tovex blast, a specialized air gun or a seismic vibrator, commonly known by the trademark name Vibroseis. Reflection seismology is similar to sonar and echolocation. This article is about surface seismic surveys; for vertical seismic profiles, see VSP.

Many oil-producing nations do not reveal their reservoir engineering field data and instead provide unaudited claims for their oil reserves. The numbers disclosed by some national governments are suspected of being manipulated for political reasons. [5] [6]

## Classifications

All reserve estimates involve uncertainty, depending on the amount of reliable geologic and engineering data available and the interpretation of that data. The relative degree of uncertainty can be expressed by dividing reserves into two principal classifications—"proven" (or "proved") and "unproven" (or "unproved"). [7] Unproven reserves can further be divided into two subcategories—"probable" and "possible"—to indicate the relative degree of uncertainty about their existence. [7] The most commonly accepted definitions of these are based on those approved by the Society of Petroleum Engineers (SPE) and the World Petroleum Council (WPC) in 1997. [8]

The Society of Petroleum Engineers (SPE) is a 501(c)(3) not-for-profit professional organization whose mission is to collect, disseminate, and exchange technical knowledge concerning the exploration, development and production of oil and gas resources and related technologies for the public benefit and to provide opportunities for professionals to enhance their technical and professional competence.

The World Petroleum Council (WPC) is an oil and gas industry forum and international organization representing the petroleum sector worldwide

### Proven reserves

Proven reserves are those reserves claimed to have a reasonable certainty (normally at least 90% confidence) of being recoverable under existing economic and political conditions, with existing technology. Industry specialists refer to this as "P90" (that is, having a 90% certainty of being produced). Proven reserves are also known in the industry as "1P". [9] [10]

Proven reserves are further subdivided into "proven developed" (PD) and "proven undeveloped" (PUD). [10] [11] PD reserves are reserves that can be produced with existing wells and perforations, or from additional reservoirs where minimal additional investment (operating expense) is required. [11] PUD reserves require additional capital investment (e.g., drilling new wells) to bring the oil to the surface. [9] [11]

Until December 2009 "1P" proven reserves were the only type the U.S. Securities and Exchange Commission allowed oil companies to report to investors. Companies listed on U.S. stock exchanges must substantiate their claims, but many governments and national oil companies do not disclose verifying data to support their claims. Since January 2010 the SEC now allows companies to also provide additional optional information declaring 2P (both proven and probable) and 3P (proven plus probable plus possible) provided the evaluation is verified by qualified third party consultants, though many companies choose to use 2P and 3P estimates only for internal purposes.

### Unproven reserves

Unproven reserves are based on geological and/or engineering data similar to that used in estimates of proven reserves, but technical, contractual, or regulatory uncertainties preclude such reserves being classified as proven. [12] Unproven reserves may be used internally by oil companies and government agencies for future planning purposes but are not routinely compiled. They are sub-classified as probable and possible. [12]

Probable reserves are attributed to known accumulations and claim a 50% confidence level of recovery. Industry specialists refer to them as "P50" (i.e., having a 50% certainty of being produced). The sum of proven plus probable reserves is also referred to in the industry as "2P" (proven plus probable). [9]

Possible reserves are attributed to known accumulations that have a less likely chance of being recovered than probable reserves. This term is often used for reserves which are claimed to have at least a 10% certainty of being produced ("P10"). Reasons for classifying reserves as possible include varying interpretations of geology, reserves not producible at commercial rates, uncertainty due to reserve infill (seepage from adjacent areas) and projected reserves based on future recovery methods. The cumulative amount of proven, probable and possible resources are referred to in the industry as "3P" (proven plus probable plus possible). [9]

### Russian reserve categories

In Russia, reserves categories A, B, and C1 correspond roughly to proved developed producing, proved developed nonproducing, and proved undeveloped, respectively; the designation ABC1 corresponds to proved reserves. The Russian category C2 includes probable and possible reserves. [13]

### Strategic petroleum reserves

Many countries maintain government-controlled oil reserves for both economic and national security reasons. According to the United States Energy Information Administration, approximately 4.1 billion barrels (650,000,000 m3) of oil are held in strategic reserves, of which 1.4 billion is government-controlled. These reserves are generally not counted when computing a nation's oil reserves.

### Resources

A more sophisticated system of evaluating petroleum accumulations was adopted in 2007 by the Society of Petroleum Engineers (SPE), World Petroleum Council (WPC), American Association of Petroleum Geologists (AAPG), and Society of Petroleum Evaluation Engineers (SPEE). It incorporates the 1997 definitions for reserves, but adds categories for contingent resources and prospective resources. [7]

Contingent resources are those quantities of petroleum estimated, as of a given date, to be potentially recoverable from known accumulations, but the applied project(s) are not yet considered mature enough for commercial development due to one or more contingencies. Contingent resources may include, for example, projects for which there are no viable markets, or where commercial recovery is dependent on technology under development, or where evaluation of the accumulation is insufficient to clearly assess commerciality.

Prospective resources are those quantities of petroleum estimated, as of a given date, to be potentially recoverable from undiscovered accumulations by application of future development projects. Prospective resources have both an associated chance of discovery and a chance of development.

The United States Geological Survey uses the terms technically and economically recoverable resources when making its petroleum resource assessments. Technically recoverable resources represent that proportion of assessed in-place petroleum that may be recoverable using current recovery technology, without regard to cost. Economically recoverable resources are technically recoverable petroleum for which the costs of discovery, development, production, and transport, including a return to capital, can be recovered at a given market price.

"Unconventional resources" exist in petroleum accumulations that are pervasive throughout a large area. Examples include extra heavy oil, oil sand, and oil shale deposits. Unlike "conventional resources", in which the petroleum is recovered through wellbores and typically requires minimal processing prior to sale, unconventional resources require specialized extraction technology to produce. For example, steam and/or solvents are used to mobilize bitumen for in-situ recovery. Moreover, the extracted petroleum may require significant processing prior to sale (e.g., bitumen upgraders). [7] The total amount of unconventional oil resources in the world considerably exceeds the amount of conventional oil reserves, but are much more difficult and expensive to develop.

## Estimation techniques

The amount of oil in a subsurface reservoir is called oil in place (OIP). [11] Only a fraction of this oil can be recovered from a reservoir. This fraction is called the recovery factor . [11] The portion that can be recovered is considered to be a reserve. The portion that is not recoverable is not included unless and until methods are implemented to produce it. [12]

### Volumetric method

Volumetric methods attempt to determine the amount of oil in place by using the size of the reservoir as well as the physical properties of its rocks and fluids. Then a recovery factor is assumed, using assumptions from fields with similar characteristics. OIP is multiplied by the recovery factor to arrive at a reserve number. Current recovery factors for oil fields around the world typically range between 10 and 60 percent; some are over 80 percent. The wide variance is due largely to the diversity of fluid and reservoir characteristics for different deposits. [15] [16] [17] The method is most useful early in the life of the reservoir, before significant production has occurred.

### Materials balance method

The materials balance method for an oil field uses an equation that relates the volume of oil, water and gas that has been produced from a reservoir and the change in reservoir pressure to calculate the remaining oil. It assumes that, as fluids from the reservoir are produced, there will be a change in the reservoir pressure that depends on the remaining volume of oil and gas. The method requires extensive pressure-volume-temperature analysis and an accurate pressure history of the field. It requires some production to occur (typically 5% to 10% of ultimate recovery), unless reliable pressure history can be used from a field with similar rock and fluid characteristics. [12]

### Production decline curve method

The decline curve method uses production data to fit a decline curve and estimate future oil production. The three most common forms of decline curves are exponential, hyperbolic, and harmonic. It is assumed that the production will decline on a reasonably smooth curve, and so allowances must be made for wells shut in and production restrictions. The curve can be expressed mathematically or plotted on a graph to estimate future production. It has the advantage of (implicitly) including all reservoir characteristics. It requires a sufficient history to establish a statistically significant trend, ideally when production is not curtailed by regulatory or other artificial conditions. [12]

## Reserves growth

Experience shows that initial estimates of the size of newly discovered oil fields are usually too low. As years pass, successive estimates of the ultimate recovery of fields tend to increase. The term reserve growth refers to the typical increases in estimated ultimate recovery that occur as oil fields are developed and produced. [4]

## Estimated reserves by country

The unit bbl = barrel of oil. A sample calculation for the reserve/production ratio is ${\displaystyle (296.5\times 1000)/(2.1\times 365)=386.8}$for Venezuela.

Summary of Proven Reserve Data as of 2012 [3]
CountryReserves [19]
109 bbl
Reserves
109 m3
Production [20]
106 bbl/d
Production
103 m3/d
Reserve/ Production Ratio1
years
1 Venezuela 296.5047.1402.1330387
2 Saudi Arabia 265.4042.1958.91,41082
4 Iran 151.2024.0394.1650101
5 Iraq 143.1022.7513.4540115
6 Kuwait 101.5016.1372.337027
7 United Arab Emirates 97.8015.5492.438018
8 Russia 80.0012.71910.01,59015
9 Libya 47.007.4721.727076
10 Nigeria 37.005.8832.540041
11 Kazakhstan 30.004.7701.524055
12 Qatar 25.414.0401.11705
13 China 25.404.0384.165017
14 United States 25.003.9757.01,11010
15 Angola 13.502.1461.930019
16 Algeria 13.422.1341.727015
17 Brazil 13.202.0992.133017
Total of top seventeen reserves1,540.43244.90959.59,46071
Notes:
1 Reserve to Production ratio (in years), calculated as reserves / annual production. (from above)

It is estimated that between 100 and 135 billion tonnes (which equals between 133 and 180 billions m3 of oil) of the world's oil reserves have been used between 1850 and the present. [21]

## OPEC countries

Since OPEC started to set production quotas on the basis of reserves levels in the 1980s, many of its members have reported significant increases in their official reserves. [22] [23] There are doubts about the reliability of these estimates, which are not provided with any form of verification that meet external reporting standards. [22]

The sudden revisions in OPEC reserves, totaling nearly 300 bn barrels, have been much debated. [24] Some of it is defended partly by the shift in ownership of reserves away from international oil companies, some of whom were obliged to report reserves under conservative US Securities and Exchange Commission rules. [22] [25] The most prominent explanation of the revisions is prompted by a change in OPEC rules which set production quotas (partly) on reserves. In any event, the revisions in official data had little to do with the actual discovery of new reserves. [22]

Total reserves in many OPEC countries hardly changed in the 1990s. [22] Official reserves in Kuwait, for example, were unchanged at 96.5 Gbbl (15.34×109 m3) (including its share of the Neutral Zone) from 1991 to 2002, even though the country produced more than 8 Gbbl (1.3×109 m3) and did not make any important new discoveries during that period. [22] The case of Saudi Arabia is also striking, with proven reserves estimated at between 260 and 264 billion barrels (4.20×1010 m3) in the past 18 years, a variation of less than 2%, [22] while extracting approximately 60 billion barrels (9.5×109 m3) during this period.

Sadad al-Huseini, former head of exploration and production at Saudi Aramco, estimates 300 Gbbl (48×109 m3) of the world's 1,200 Gbbl (190×109 m3) of proven reserves should be recategorized as speculative resources, though he did not specify which countries had inflated their reserves. [26] Dr. Ali Samsam Bakhtiari, a former senior expert of the National Iranian Oil Company, has estimated that Iran, Iraq, Kuwait, Saudi Arabia and the United Arab Emirates have overstated reserves by a combined 320–390bn barrels and has said, "As for Iran, the usually accepted official 132 billion barrels (2.10×1010 m3) is almost one hundred billion over any realistic assay." [27] Petroleum Intelligence Weekly reported that official confidential Kuwaiti documents estimate reserves of Kuwait were only 48 billion barrels (7.6×109 m3), of which half were proven and half were possible. The combined value of proven and possible is half of the official public estimate of proven reserves. [23]

In July 2011, OPEC's Annual Statistical Review showed Venezuela's reserves to be larger than Saudi Arabia's. [28] [29]

## Prospective resources

### Arctic prospective resources

A 2008 United States Geological Survey estimates that areas north of the Arctic Circle have 90 billion barrels (1.4×1010 m3) of undiscovered, technically recoverable oil and 44 billion barrels (7.0×109 m3) of natural gas liquids in 25 geologically defined areas thought to have potential for petroleum. This represented 13% of the expected undiscovered oil in the world. Of the estimated totals, more than half of the undiscovered oil resources were estimated to occur in just three geologic provinces—Arctic Alaska, the Amerasia Basin, and the East Greenland Rift Basins. More than 70% of the mean undiscovered oil resources was estimated to occur in five provinces: Arctic Alaska, Amerasia Basin, East Greenland Rift Basins, East Barents Basins, and West Greenland–East Canada. It was further estimated that approximately 84% of the oil and gas would occur offshore. The USGS did not consider economic factors such as the effects of permanent sea ice or oceanic water depth in its assessment of undiscovered oil and gas resources. This assessment was lower than a 2000 survey, which had included lands south of the Arctic Circle. [30] [31] [32]

## Unconventional prospective resources

In October 2009, the USGS updated the quantity of the Orinoco tar sands, in Venezuela, to 513 billion barrels (8.16×1010 m3). [33]

In June 2013 the U.S. Energy Information Administration published a global inventory of estimated recoverable tight oil and tight gas resources in shale formations, "Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside the United States." The inventory is incomplete due to exclusion of tight oil and gas from sources other than shale such as sandstone or carbonates, formations underlying the large oil fields located in the Middle East and the Caspian region, off shore formations, or about which there is little information. Estimated technically recoverable shale oil resources total 335 to 345 billion barrels. [34]

Energy and resources:

## Related Research Articles

Hydrocarbon exploration is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas, in the Earth using petroleum geology.

Peak oil is the theorized point in time when the maximum rate of extraction of petroleum is reached, after which it is expected to enter terminal decline. Peak oil theory is based on the observed rise, peak, fall, and depletion of aggregate production rate in oil fields over time. It is often confused with oil depletion; however, whereas depletion refers to a period of falling reserves and supply, peak oil refers to the point of maximum production. The concept of peak oil is often credited to geologist M. King Hubbert whose 1956 paper first presented a formal theory.

The question of whether to drill for oil in the Arctic National Wildlife Refuge (ANWR) has been an ongoing political controversy in the United States since 1977. As of 2017, Republicans have attempted to allow drilling in ANWR almost fifty times, finally being successful with the passage of the Tax Cuts and Jobs Act of 2017.

The Western Canadian Sedimentary Basin (WCSB) is a vast sedimentary basin underlying 1,400,000 square kilometres (540,000 sq mi) of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. It consists of a massive wedge of sedimentary rock extending from the Rocky Mountains in the west to the Canadian Shield in the east. This wedge is about 6 kilometres (3.7 mi) thick under the Rocky Mountains, but thins to zero at its eastern margins. The WCSB contains one of the world's largest reserves of petroleum and natural gas and supplies much of the North American market, producing more than 16,000,000,000 cubic feet (450,000,000 m3) per day of gas in 2000. It also has huge reserves of coal. Of the provinces and territories within the WCSB, Alberta has most of the oil and gas reserves and almost all of the oil sands.

World energy resources are the estimated maximum capacity for energy production given all available resources on Earth. They can be divided by type into fossil fuel, nuclear fuel and renewable resources.

The petroleum industry in Russia is one of the largest in the world. Russia has the largest reserves and is the largest exporter of natural gas. It has the second largest coal reserves, the eighth largest oil reserves, and is one of the largest producers of oil. It is the third largest energy user.

Proven reserves, also called measured reserves, 1P, and reserves, are industry specific terms regarding fossil fuel energy sources. They are defined as a "Quantity of energy sources estimated with reasonable certainty, from the analysis of geologic and engineering data, to be recoverable from well established or known reservoirs with the existing equipment and under the existing operating conditions." A reserve is considered a proven reserve if it is probable that 90% or more of the resource is recoverable while being economically profitable. These terms relate to common fossil fuel reserves such as oil reserves, natural gas reserves, or coal reserves.

The Bakken Formation is a rock unit from the Late Devonian to Early Mississippian age occupying about 200,000 square miles (520,000 km2) of the subsurface of the Williston Basin, underlying parts of Montana, North Dakota, Saskatchewan and Manitoba. The formation was initially described by geologist J.W. Nordquist in 1953. The formation is entirely in the subsurface, and has no surface outcrop. It is named after Henry Bakken, a farmer in Tioga, North Dakota, who owned the land where the formation was initially discovered, during drilling for oil.

The Lost Hills Oil Field is a large oil field in the Lost Hills Range, north of the town of Lost Hills in western Kern County, California, in the United States.

Proved oil reserves in Iran, according to its government, rank fourth largest in the world at approximately as of 2013, although it ranks third if Canadian reserves of unconventional oil are excluded. This is roughly 10% of the world's total proven petroleum reserves. At 2006 rates of production, Iran's oil reserves would last 98 years if no new oil was found.

The Monterey Formation is an extensive Miocene oil-rich geological sedimentary formation in California, with outcrops of the formation in parts of the California Coast Ranges, Peninsular Ranges, and on some of California's off-shore islands. The type locality is near the city of Monterey, California. The Monterey Formation is the major source-rock for 37 to 38 billion barrels of oil in conventional traps such as sandstones. This is most of California's known oil resources. The Monterey has been extensively investigated and mapped for petroleum potential, and is of major importance for understanding the complex geological history of California. Its rocks are mostly highly siliceous strata that vary greatly in composition, stratigraphy, and tectono-stratigraphic history.

As of 2005, Azerbaijan produced a range of metals and industrial minerals, including aluminum, lead, iron, and zinc.

The proven oil reserves in Saudi Arabia are the 2nd largest in the world, estimated to be 268 billion barrels, including 2.5 Gbbl in the Saudi–Kuwaiti neutral zone. They are predominantly found in the Eastern Province. These reserves were the largest in the world until Venezuela announced they had increased their proven reserves to 297 Gbbl in January 2011. The Saudi reserves are about one-fifth of the world's total conventional oil reserves, a large fraction of these reserves comes from a small number of very large oil fields, and past production amounts to 40% of the stated reserves.

Oil reserves in Iraq are considered the world’s fifth-largest proven oil reserves, with 140 billion barrels. The sources for this oil is primarily located in the Shiite Muslims-majority and Arab Sunni Muslims-dominated areas on the other hand are comparatively lacking.

There have been widely varying estimates of proven oil reserves in Russia. Most estimates included only Western Siberian reserves, which have been exploited since the 1970s and supply two-thirds of Russian oil. However, there are potentially huge reserves elsewhere. In 2005, the Russian Ministry of Natural Resources estimated that another 4.7 billion barrels of oil exist in Eastern Siberia. In July 2013, the Russian Natural Resources Ministry made official estimates of reserves available for the first time. According to Russian Natural Resources Minister Sergey Donskoy, as of 1 January 2012, recoverable reserves of oil in Russia under category ABC1 were 17.8 billion tons and category C2 reserves were 10.9 billion tons.

Proven oil reserves in the United States were 36.4 billion barrels of crude oil as of the end of 2014, excluding the Strategic Petroleum Reserve. The 2014 reserves represent the largest US proven reserves since 1972, and a 90% increase in proved reserves since 2008. The Energy Information Administration estimates US undiscovered, technically recoverable oil resources to be an additional 198 billion barrels.

Tight oil is light crude oil contained in petroleum-bearing formations of low permeability, often shale or tight sandstone. Economic production from tight oil formations requires the same hydraulic fracturing and often uses the same horizontal well technology used in the production of shale gas. While sometimes called "shale oil", tight oil should not be confused with oil shale, which is shale rich in kerogen, or shale oil, which is oil produced from oil shales. Therefore, the International Energy Agency recommends using the term "light tight oil" for oil produced from shales or other very low permeability formations, while the World Energy Resources 2013 report by the World Energy Council uses the terms "tight oil" and "shale-hosted oil".

The Bazhenov Formation or Bazhenov Shale is a stratum in the West Siberian basin. It was formed from sediment deposited in a deep-water sea in Tithonian–early Berriasian time. The sea covered more than one million square kilometers in the central basin area. Highly organic-rich siliceous shales were deposited during this time in anoxic conditions on the sea bottom. The sea was connected to the world's oceans and contains trace minerals derived from dissolved minerals and organic materials similar to sapropel sediments in the Black Sea.

As of 2013 the Cline Shale, also referred to as the "Wolfcamp/Cline Shale", the "Lower Wolfcamp Shale", or the "Spraberry-Wolfcamp shale", or even the "Wolfberry", is a promising Pennsylvanian oil play east of Midland, Texas which underlies ten counties: Fisher, Nolan, Sterling, Coke, Glasscock, Tom Green, Howard, Mitchell, Borden and Scurry counties. Exploitation is projected to rely on hydraulic fracturing.

an organic rich shale, with Total Organic Content (TOC) of 1-8%, with silt and sand beds mixed in. It lies in a broad shelf, with minimal relief and has nice light oil of 38-42 gravity with excellent porosity of 6-12% in thickness varying 200 to 550 feet thick.

## References

1. Society of Petroleum Engineers, Petroleum reserves and resources definitions, accessed 24 Feb. 2017.
2. "Oil reserve definitions". bp.com. BP. Retrieved 4 December 2013.
3. "OPEC Share of World Oil Reserves 2010". OPEC. 2011.
4. David F. Morehouse (1997). "The Intricate Puzzle of Oil and Gas Reserves Growth" (PDF). U.S. Energy Information Administration. Archived from the original (PDF) on August 6, 2010. Retrieved 2014-08-19.
5. "Proven Oil Reserves". moneyterms.co.uk. 2008. Retrieved 2008-04-17.
6. The Asylum, Leah McGrath Goodman, 2011, Harper Collins
7. "Petroleum Resources Management System". Society of Petroleum Engineers. 2007. Retrieved 2008-04-20.
8. "Petroleum Reserves Definitions" (PDF). Petroleum Resources Management System. Society of Petroleum Engineers. 1997. Retrieved 2008-04-20.
9. "Glossary of Terms Used in Petroleum Reserves/Resources" (PDF). Society of Petroleum Engineers. 2005. Retrieved 2008-04-20.
10. Wright, Charlotte J.; Rebecca A Gallun (2008). Fundamentals of Oil & Gas Accounting (5 ed.). PenWell Books. p. 750. ISBN   978-1-59370-137-6.
11. Hyne, Norman J. (2001). Nontechnical Guide to Petroleum Geology, Exploration, Drilling and Production. PennWell Corporation. pp. 431–449. ISBN   9780878148233.
12. Lyons, William C. (2005). Standard Handbook Of Petroleum & Natural Gas Engineering. Gulf Professional Publishing. pp. 5–6. ISBN   9780750677851.
13. Society of Petroleum Engineers, SPE Reserves Committee,
14. Alboudwarej; et al. (Summer 2006). "Highlighting Heavy Oil" (PDF). Oilfield Review. Archived from the original (PDF) on 2008-05-27. Retrieved 2008-05-24.
15. "Defining the Limits of Oil Production". International Energy Outlook 2008. U.S. Department of Energy. June 2008. Archived from the original on 2008-09-24. Retrieved 2008-11-22.
16. E. Tzimas, (2005). "Enhanced Oil Recovery using Carbon Dioxide in the European Energy System" (PDF). European Commission Joint Research Center. Retrieved 2008-08-23.
17. Green, Don W.; Willhite, G. Paul (1998), Enhanced Oil Recovery, Society of Petroleum Engineers, ISBN   978-1555630775
18. "World Proved Reserves of Oil and Natural Gas". US Energy Information Administration. 2007. Retrieved 2008-08-19.
19. PennWell Corporation, Oil & Gas Journal, Vol. 105.48 (December 24, 2007), except United States. Oil includes crude oil and condensate. Data for the United States are from the Energy Information Administration, U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves, 2006 Annual Report, DOE/EIA-0216(2007) (November 2007). Oil & Gas Journal's oil reserve estimate for Canada includes 5.392 billion barrels (857,300,000 m3) of conventional crude oil and condensate reserves and 173.2 billion barrels (2.754×1010 m3) of oil sands reserves. Information collated by EIA
20. U.S. Energy Information Administration (EIA) – U.S. Government – U.S. Dept. of Energy, September, 2011 EIA - International Energy Statistics
21. How Much Oil Have We Used?, Science Daily, 8 May 2009. Retrieved Mar 2014.
22. WORLD ENERGY OUTLOOK 2005:Middle East and North Africa Insights (PDF). INTERNATIONAL ENERGY AGENCY. 2005. pp. 125–126.
23. "Oil Reserves Accounting: The Case Of Kuwait". Petroleum Intelligence Weekly. January 30, 2006. Retrieved 2008-08-23.
24. Adam, Porter (15 July 2005). "How much oil do we really have?". BBC News.
25. Maugeri, Leonardo (January 23, 2006). "The Saudis May Have Enough Oil". Newsweek.
26. "Oil reserves over-inflated by 300bn barrels – al-Huseini". October 30, 2007. Retrieved 2008-08-23.
27. "On Middle Eastern Oil Reserves". ASPO-USA's Peak Oil Review. February 20, 2006. Retrieved 2008-08-20.
28. Faucon, Benoit (18 July 2011). "Venezuela Oil Reserves Surpassed Saudi Arabia In 2010-OPEC". Fox Business. Retrieved 18 July 2011.
29. "OPEC Share of World Crude Oil Reserves". OPEC. 2010. Retrieved June 3, 2012.
30. United States Geological Survey, (USGS) (July 27, 2008). "90 Billion Barrels of Oil and 1,670 Trillion Cubic Feet of Natural Gas Assessed in the Arctic". USGS. Retrieved 2008-08-12.
31. MOUAWAD, JAD (July 24, 2008). "Oil Survey Says Arctic Has Riches". New York Times.
32. Alan Bailey (October 21, 2007). "USGS: 25% Arctic oil, gas estimate a reporter's mistake". Vol. 12, No. 42. Petroleum News. Retrieved 2008-07-24.
33. Christopher J. Schenk; Troy A. Cook; Ronald R. Charpentier; Richard M. Pollastro; Timothy R. Klett; Marilyn E. Tennyson; Mark A. Kirschbaum; Michael E. Brownfield & Janet K. Pitman. (11 January 2010). "An Estimate of Recoverable Heavy Oil Resources of the Orinoco Oil Belt, Venezuela" (PDF). USGS. Retrieved 23 January 2010.
34. "Technically Recoverable Shale Oil and Shale Gas Resources: An Assessment of 137 Shale Formations in 41 Countries Outside the United States" (PDF). U.S. Energy Information Administration (EIA). June 2013. Retrieved June 11, 2013.