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Natural gas reserves are plentiful around the world, but many are too small or too remote from sizable population centers to be developed economically. Stranded gas is essentially gas that is wasted or unused. Estimates of remote or stranded gas reserves range from 40 to 60% of the world’s proven gas reserves.  These massive global gas reserves are largely untapped, and conventional means of development face logistical and economic barriers. The local market for gas is usually too small, or the gas field is too far from the industrialized markets. Sometimes excess gas reserves can be classified as stranded because they may result in oversupply of the market. Most stranded gas reserves are in gas fields that are totally undeveloped. It is claimed that there are approximately 1,200 such fields, of different sizes, worldwide. A recent study identified approximately 450 Tcf of natural gas stranded in fields greater than 50 Bcf that can be produced and gathered for less than 0.50 U.S. $/million Btu. Most larger stranded gas fields can produce gas even cheaper.
Sources of stranded gas
Associated gas reserves
Associated gas accounts for approximately 25% of the worldwide proven reserves of natural gas. This is down from approximately 35% in the 1970s, mainly because of the stabilization of the level of oil reserves in Middle Eastern countries and exploration in zones more favorable to nonassociated gas. The proportion of gas flared has been reduced significantly during the last twenty years. This trend has been achieved through the efforts of countries in recovering incremental quantities of associated gas.
Deep offshore gas reserves
A growing share of the proven gas reserves is from offshore gas reserves in the Arctic regions and Siberia, where access is difficult. In recent years, the industry has been pushing even further offshore and into increasingly deep waters, successfully making larger discoveries and developing some of them. Development of these resources will be of importance in the future.
Marginal gas fields
In 1999, in western and southern Africa (excluding Nigeria), there were eight gas fields with reserves of between 0.5 to 1 Tcf, another eight between 0.25 and 0.5 Tcf, and more than 85 fields with reserves of less than 0.25 Tcf.  Identifying commercial processes that make marginal gas reservoirs viable is a challenge. Marginal gas fields account for approximately 15% of the world’s proven gas reserves, and approximately 20% of this can be considered as stranded.
Remote gas reserves
Gas reserves that are distant from consuming areas fall into this category. Examples of such fields are in Africa, South America, and northern Siberia. A significant number of the Middle Eastern fields are also considered too remote to be exploited economically at this time. A rough estimate of the amount of remote gas reserves to be considered as stranded is in the range of 15 to 25% of overall gas reserves. Table 1 summarizes the potential for stranded gas.
Bringing gas to market
Fig. 1 shows the key components involved in bringing gas to market. The exploration and production of gas is the starting point for all gas utilization options. Natural gas from gas fields typically is a mixture of hydrocarbons ranging from methane to heavier hydrocarbon molecules. Methane is invariably the dominant component. Ethane and heavier hydrocarbons are categorized as natural gas liquids (NGLs). Liquefied petroleum gases (LPGs) components refer to a mixture of propane and butane. The quantity of NGL in the gas depends on the type of reservoir from which it originates. Gases with low NGL content are referred to as “lean gas.” The gas may also contain other components such as:
- Carbon dioxide
- Sulfur compounds
For most gas utilization options, the feed will have to be treated for removal of impurities. The treatment will vary depending on the gas utilization option. It is assumed here that treated lean gas is available for monetization. The screening criteria discussed for the various gas utilization options should be adjusted to account for gases that are rich (i.e., have a high NGL content) or contain large quantities of nitrogen, carbon dioxide, or sulfur compounds.
|CII||—||integral incorporated cascade process|
|CNG||—||compressed natural gas|
|GTG||—||gas to gas|
|GTL||—||gas to liquids|
|GTM||—||gas transport module|
|GTP||—||gas to power|
|GTS||—||gas to solids|
|GTW||—||gas to wire|
|LNG||—||liquefied natural gas|
|LPG||—||liquefied petroleum gas|
|MMscf/D||—||million standard cubic foot per day|
|mtpa||—||million tons per annum|
|mTPD||—||metric tons per day|
|NGH||—||natural gas hydrates|
|NGL||—||natural gas liquid|
|ORV||—||open rack vaporizer|
|PNG||—||pressurized natural gas|
|SMDS||—||Shell middle-distillate synthesis|
|VOTRANS||—||volume-optimized transport and storage|
- Stranded Gas Utilization—Methane Refineries of the Future. 2002. Report prospectus, ChemSystems, San Francisco (February).
- Chabrelie, M.-F. and Rojey, A. 2000. Prospects for Exploiting Stranded Gas Reserves. Presented at Gastech 2000, Houston, 14–17 November.
- Thackeray, F. and Leckie, G. 2002. Stranded Gas: A Vital Resource. Petroleum Economist (May): 10.
- World LNG/GTL Review. 2001. Houston, Texas: Zeus Development Inc.
- Kojima, M. 1999. Commercialization of Marginal Gas Fields. Energy Issues (January): 1.
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