Associated and nonassociated gas
There are two primary sources of gas: associated gas reserves and nonassociated gas reserves. The economic drivers for monetizing gas from these two basic sources are quite different and are likely to lead to different gas utilization routes. Hence, it is useful to understand the difference in economic characteristics of these two broad categories of gas sources.
Nonassociated gas reserves are developed primarily to produce natural gas. There may or may not be condensate production together with the gas. Under these conditions, it is essential that there be a profitable market to which to deliver the gas.
Associated gas is gas produced as a byproduct of the production of crude oil. Associated gas reserves are typically developed for the production of crude oil, which pays for the field development costs. The reserves typically produce at peak levels for a few years and then decline.
Associated gas is generally regarded as an undesirable byproduct, which is either reinjected, flared, or vented. According to 2010 statistics from the US Energy Information Administration, worldwide approximately 4.3 Tcf/yr of gas was flared or vented, and an additional 17.1 Tcf/yr of gas was reinjected. The need to produce oil and dispose of natural gas (as is the case with associated gas) requires unique approaches in the field-development plans.
With increasing focus on sustainable development, flaring may cease to be an option. Some countries have already legislated against gas flaring. For example, current Nigerian policy required all flaring to be eliminated by 2008. This policy is expected to eliminate the waste of a valuable resource for Nigeria and attendant negative impacts on the environment. Consequently, several key gas utilization projects have either been recently completed or are at various stages of implementation in Nigeria. Examples of such projects include:
- Obite Gas Plant
- ChevronTexaco Escravos GTL project
- West African gas pipeline project
- Nigeria liquefied natural gas (LNG) project.
- US Energy Information Administration. 2010. International Energy Statistics. http://www.eia.gov/cfapps/ipdbproject/iedindex3.cfm?tid=3&pid=48&aid=1&cid=regions&syid=2007&eyid=2011&unit=BCF (accessed 11 April 2013).
- Erinne, N.J. 2001. Africa in Perspective: Natural Gas Offers Nigeria Huge Potential, Challenge. Oil & Gas J. (2 July): 17.
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