The middle and upper reservoir sandstones in the Penglaizhen Formation, Luodai gas field, western Sichuan

The reservoirs of the gas pools in middle and upper parts of the Penglaizhen Formation, Luodai gas field, western Sichuan consist dominantly of four microfacies distinguished on the basis of petrography, physical parameters and pore throat structures: subaqueous distributary channel, channel-mouth bar, subaqueous crevasse channel and distal bar. The sedimentary microfacies have apparently exerted an influence on the types and distribution of reservoir sandstones. The reservoir spaces are represented by intergranular openings and intragranular solution openings. The porosity of the reservoir sandstones generally ranges between 8% and 16% and the mean values of permeability is 1.970×10^-3μm, indicating a low to moderate porosity and low permeability of the reservoir sandstones. The reservoir quality and permeability depend upon the contents of calcite, anhydrite, feldspar and clay minerals.