The Natural Gas Pools Characteristics in Sulige Gas Field, Ordos Basin, China

Abstract

There are abundant natural gas resources in Sulige gas field, Ordos Basin. The ascertained resources are relatively low, because of complex geologic setting and reservoir heterogeneity. The characteristics of natural gas pools were analyzed from gas composition, gas saturation, permeability, pressure, and gas-water distribution in this paper. Methane is the main composition of natural gas in Sulige gas field, but C2+ hydrocarbon content is relatively high, gas dryness is less than 0.95. The gas density is generally 0.6kg/m3. The carbon isotope of methane is heavier. The original of gas is coal. The reservoir permeability and porosity is low. The gas reservoirs are defined as low porosity, low permeability or very low permeability reservoirs. The low or very low permeability reservoirs are controlled by the radius of pore throat that is thin, generally 0.25-1.5 um according to mercury inject data. The reservoirs are mainly of subnormal pressure reservoirs, and formation pressures are affected by gas-water characteristics. The gas saturations are low, and generally less than 70%. There are some relations between gas saturation and the porosity, permeability. The gas-water distributions are complex. Vertically, multi-gas layer are mutual doublications; laterally, there are some complex characteristics, e.g., the entire layer has gas, there are not unified gas-water contact, the distributions of gas and water are normal, and the distribution are inverted.