Oil and natural gas exist in the pore spaces of rock in the subsurface of the earth. How much oil or gas can be recovered from the rock is a function of rock properties, technology, and economics. Even when it is technically feasible to remove oil or gas from a specific reservoir, the costs involved in doing so may exceed the value of the oil or gas recovered at projected prices. In this case, the oil or gas is uneconomic and will not be developed.
The total amount of oil or gas in the reservoir is called original oil- or gas-in-place. For a specific reservoir, engineers estimate this amount with information about the size of the reservoir trap and properties of the rock (which can be sampled and tested). Some of the original oil and gas deposited millions of years ago has been discovered, while some remains undiscovered (the target of future exploration).
Discovered (or known) resources can be divided into proved reserves and prospective or unproved (probable and possible) resources. "Proved reserves" are the quantities of oil or gas from known reservoirs and expected to be recoverable with current technology and at current economic conditions. Prospective resources are those that may be recoverable in the future with advanced technologies or under different economic conditions. More explanation of reserves and resources definitions.
A primary source for worldwide reserves estimates is the Oil & Gas Journal (OGJ).[1] OGJ estimates that at the beginning of 2004, worldwide reserves were 1.27 trillion barrels of oil and 6,100 trillion cubic feet of natural gas. These estimates are 53 billion barrels of oil and 575 trillion cubic feet of natural gas higher than the prior year, reflecting additional discoveries, improving technology, and changing economics.
The countries with the largest amounts of remaining oil reserves are: Saudi Arabia, Canada, Iran, Iraq, Kuwait, United Arab Emirates, Venezuela, Russia, Libya, and Nigeria.[1] The largest reserves of natural gas are found in: Russia, Iran, Qatar, Saudi Arabia, United Arab Emirates, United States, Algeria, Nigeria, Venezuela, and Iraq.[1] The maps illustrate the distribution of remaining reserves around the world.
At 2003 consumption levels [2], the remaining reserves represent 44.6 years of oil and 66.2 years of natural gas. Does this mean that the world will be out of fossil fuels in 50 years or so? That theory has been around since the 1970s. In fact, the figures for years of remaining reserves have remained relative constant over the past few decades as the industry has replaced consumption with newly discovered oil and gas deposits and has developed technologies to increase the amount of oil and gas that can be recovered from existing reservoirs.
As noted above, three factors affect the amount of oil or gas that can be recovered from a known reservoir — rock properties, technology, and economics. While the industry cannot change the properties of the rock, it can develop new techniques to remove more oil from the rock. The industry has made significant advances to enhance recovery from known reservoirs, adding to the reserves base. When prices rise, marginal reservoirs can be developed economically, adding to the reserve base.
Reserves will also grow as more oil and gas deposits are found around the world. Continental North America and much of continental Europe have already been explored heavily, and any new discoveries are likely to be small. But many areas of the globe are largely unexplored and many large new deposits are waiting to be found. Companies have experienced major success in discovering significant new oil and gas reservoirs offshore Brazil, the Gulf of Mexico, Alaska, off the western coast of Africa, Russia, and many areas of Asia and the Pacific. These are just a few of the current areas of growth. Most observers agree that significant deposits of oil and gas remain undiscovered in the Middle East.
No one can know for certain how much oil and gas remains to be discovered. But geologists sometimes make educated guesses. For example, the U.S. Geological Survey (USGS) conducts periodic assessments of U.S. mineral resources. In its most recent assessment (1995), the USGS estimated that the onshore U.S., including Alaska, has undiscovered, technically recoverable resources of 112.3 billion barrels of oil and 1,074 trillion cubic feet of natural gas. In a separate assessment of offshore resources completed in 2000, the U.S. Minerals Management Service (MMS) estimated that 75 billion barrels of oil and 362 trillion cubic feet of natural gas underlie the areas off the coasts of the U.S. The USGS and MMS resource assessments make clear that, despite being a very mature producing area, substantial resources still exist in the U.S.
World oil resources to 2025 may be more than two times current reserves, based on an estimate from the U.S. Energy Information Administration (EIA) using USGS data. Reserve growth of 730 billion barrels accounts for new discoveries and the expansion of what can be recovered from known reservoirs due to advances in technology and improvements in economics. But EIA estimates that in 2025, countries around the globe will still have more than 900 billion barrels of oil remaining to be discovered. EIA estimates total world oil resources at more than 2.9 trillion barrels of oil.
The oil and gas industry uses advanced technology to aid in the search for the resources that will meet growing world energy needs. Technology advances enable more accurate drilling and extraction of a higher percentage of oil and gas from each field, extending the life of each well. Advanced technology also allows development of resources that were not previously economically viable, such as deep-sea fields, unconventional natural gas, and oil and gas in very deep reservoirs. Together, these new sources of oil and gas will replace production from existing wells as they decline, and help to assure adequate oil and gas supplies to meet world energy needs for the foreseeable future.
[1] Oil & Gas Journal, Worldwide Report, December 22, 2003.
[2] U.S. Energy Information Administration, International Energy Annual 2002, March 2004.
[3] U.S. Energy Information Administration, International Energy Outlook 2004, April 2004.
No comments:
Post a Comment