Abstract
Building upon the foundation of the prior investigations, a three-fold classification of tight gas reservoirs is proposed in this paper which is based primarily on dynamic relationship between gas charging history and reservoir tightening process, coupled with tectonic evolution, source-reservoir relationship, migration and charging pattern. The three categories of tight gas are: (1) “pre-existing” basin-centered gas reservoir, in which the reservoir sands experienced earlystage tightening processes, occurring before peak gas generation, expulsion from source rock, and charging of reservoir; (2) “pre-existing subsequent-improved” tight gas reservoir, in which the reservoir sands were also tightened before gas charging and then underwent reservoirs improvement mainly caused by the tectonic activities; and (3) “subsequentconventional” tight gas reservoir where reserved sands were tightened after the peak of gas generation, expulsion from source rock, and charging of reservoir. This type of tight gas initially formed conventional gas accumulation during gas charging of reservoir, and subsequently modified to tight gas reservoir. All the three categories of tight gas have different geological conditions of gas accumulation and gas accumulation patterns, which can be used as characteristics to classify these tight gas systems, and thus have distinctive control on regional gas distribution. The results of applying this tight gas classification for an actual basin show that correctly distinguishing these three kinds of tight gas reservoirs from each other could contribute greatly to the exploration and development of tight gas reservoirs.
Highlights
The increasing demand for energy in the world has made it imperative to explore for and exploit unconventional oil and gas resources
In the United States, a large-scale commercial production has been achieved from tight gas systems, and contributed as much as 26% of the total annual gas production in 2010; the tight gas resources in China have got rapid progress in exploration and development recently, with a series of significant breakthroughs in the Erdos basin and Sichuan basin and subsequent discoveries in the Tarim basin, Tuha basin, Songliao basin and several other basins, and has become the most realistic, economically important unconventional gas resources for a long time in the future [2, 3]
We provide an example, by applying this tight gas classification to Denglouku formation, through two sides of the Central Faulted-uplift Zone of northern Songliao basin in China, to show how useful it is in exploration and development of tight gas reservoirs
Summary
The increasing demand for energy in the world has made it imperative to explore for and exploit unconventional oil and gas resources. Of which tight gas accumulations are products, are potentially one of the more economically important, unconventional gas resources in the world [1], and have attracted considerable industry attention and become a focus area of global unconventional gas exploration. We provide an example, by applying this tight gas classification to Denglouku formation, through two sides of the Central Faulted-uplift Zone of northern Songliao basin in China, to show how useful it is in exploration and development of tight gas reservoirs
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