Experiment-based reserve calculation for carbonate gas reservoirs:Taking X gas reservoir as an example
The X gas reservoir in the Sichuan Basin is a carbonate reservoir with strong heterogeneity between and within layers,which is one of the challenges in gas reserve calculation.This paper adopts experiments to support the reserve calculation.Firstly,the basic physical properties(e.g.porosity and permeability)of cores from each layer are measured experimentally.The measured per-meability is calibrated to the Klinkenberg permeability.The reservoir is classified into porous and porous-vuggy types according to the physical properties.Then,the lower limits of physical properties of effective reservoir corresponding to the industrial productivity are determined through productivity simulation experiment.Next,the liquid membrane thickness of each target layer is measured by liquid membrane thickness experiment,and combined with the pore size distribution curve measured in mercury injection test,the pro-portion of hydrocarbon pore volume(HCPV)of effective reservoir is obtained.Finally,the gas reserves are calculated from the gas in place(GIP)formula.The results are shown as follows:(ⅰ)The lower limits of physical properties and the proportion of HCPV are de-termined by the experiments of basic physical property testing,productivity simulation,and liquid membrane thickness,laying a foun-dation for the gas reserve calculation.The lower limit of porosity in the X gas reservoir is determined to be 1.21%～1.56%.(ⅱ)The proportion of HCPV ranges from 42.62%to 67.73%,and the effective reserves of the reservoir can be calculated by the GIP formula.(ⅲ)The proposed method is theoretically and practically significant for reserve determination of carbonate gas reservoirs with strong heterogeneity.
Carbonate rockStrong heterogeneityProductivity simulation experimentLiquid membrane thickness experimentLow-er limit of porosityLower limit of permeabilityEffective reservoir
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