Stranded gas

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.

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  Table 1—Stranded Gas Potential

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:

• Nitrogen
• Carbon dioxide
• Sulfur compounds

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  Fig. 1—Key components of bringing gas to market.

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.

Nomenclature

CII	—	integral incorporated cascade process
CNG	—	compressed natural gas
CPL	—	coiled pipeline
DME	—	dimethylether
FT	—	Fisher-Tropsch
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

Noteworthy papers in OnePetro

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External links

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See also

Monetizing stranded gas

Gas utilization options

PEH:Monetizing_Stranded_Gas