Abstract
The Western Sichuan Basin, which is located at the front of Longmen Mountain in the western Sichuan Province, China, is a foreland basin formed in the Late Triassic. The Upper Triassic Xujiahe formation in the Basin includes several tight gas sandstone reservoirs, whose porosity is less than 6.0 % and permeability less than 0.1 md. According to data of cores, thin sections, FMI, SEM and experiments, we summarize the reservoir characteristics, analyze the origin of these tight gas sandstones, and discuss the factors controlling the formation of relatively high-quality reservoirs. Xujiahe Formation is a set of terrestrial clastic rocks with low compositional maturity, low cement content, and medium textural maturity. Secondary dissolution pores are abundant, but pore spaces are small with narrow pore throats and high capillary pressures. Due to the existence of abundant fractures and intense diagenesis, these tight gas reservoirs are characterized by high reservoir heterogeneity, complex seepage system, and strong stress sensitivity. The original sedimentary facies belt and later tectonism co-control the distribution of favorable reservoirs. The intense compaction and cementation are the main factors making the Xujiahe formation to be tight.
Highlights
Tight gas reservoirs are referred to gas-bearing rocks with in situ permeability to gas of less than 0.1 md (Zhu et al 2008; Zou 2011; Ameen et al 2012)
According to data of cores, thin sections, FMI, SEM and experiments, we summarize the reservoir characteristics, analyze the origin of these tight gas sandstones, and discuss the factors controlling the formation of relatively high-quality reservoirs
The Upper Triassic Xujiahe Formation in the Western Sichuan Foreland Basin is tight gas sandstones deposited in a terrestrial setting
Summary
Tight gas reservoirs are referred to gas-bearing rocks with in situ permeability to gas of less than 0.1 md (Zhu et al 2008; Zou 2011; Ameen et al 2012). With demand for oil and gas resources increasing, attention is sharply focused on unconventional resources Much of this attention is directed at tight gas sandstones (Shanley et al 2004; Zhu et al 2008; Zou 2011). The Upper Triassic Xujiahe Formation in the Western Sichuan Foreland Basin develops abundant gas sources with thick reservoirs, large traps, and good sealing conditions. It is equipped with the gas accumulation conditions for forming large gas field, and has huge exploration potential (Wei et al 2005; Zhu et al 2009). Most of the reservoirs are tight gas sandstones with low porosity, ultralow permeability, well-developed fractures, and great reservoir heterogeneity. According to data of cores, thin sections, and experiments, this paper discusses the geological characteristics and origin of tight gas sandstone reservoirs and the factors controlling the formation of relatively high-quality reservoirs
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