Chapter 1 - Tight sandstones: overview, distribution, and global significance

Abstract

Conventional oil and gas resources are gradually running out and with the current rates of global production, most of which are in the second half of their life. Unconventional resources such as shale gas, tight gas, coalbed methane (CBM), and gas hydrate resources will address the world’s future energy demand. The current chapter reviews the main tight gas sandstone resources of the world classified by their countries, formations, geologic time, and sedimentary basins. Tight gas sandstones are normally compacted and deep formations with matrix permeability less than 0.1mD and porosity less than 10%. From the lithological and depositional point of view, tight gas sandstones are similar to conventional reservoirs. What makes them different from the conventional sandstones is the deep burial and severity of the destructive diagenetic overprints making their macropores and mesopores reduce to micropores and nanopores. Most of the tightest gas sandstone accumulations are found in the abnormally pressured basin-centered or deep basin settings. They can also occur in fluvial systems, alluvial fans, delta fans, submarine fans, barrier bars, and tidal bars. Tight gas sandstones can form in different tectonic settings ranging from compressional and extensional basins such as foreland, craton, rift, passive continental margin, and back-arc basins.