Main flow channel index in porous sand gas reservoirs and its application

Based on well test interpretation, production performance analysis, overburden permeability and porosity test, gas-water core flooding test and high-pressure mercury injection, a quantitative correlation has been built of in-situ effective permeability with routine permeability and water saturation, and the ranges of Main Flow Channel Index (MFCI) are determined for different permeability levels in porous sand gas reservoirs. A new method to evaluate the in-situ effective permeability of porous sand reservoir and a correlation chart of reserves producing degree and main flow channel index are established. The results reveal that the main flow channel index of porous sand gas reservoirs has close correlation with routine matrix permeability and water saturation. The lower the routine matrix permeability and the higher the water saturation, the lower the MFCI is. If the routine matrix permeability is greater than 5.0x 10(-3), the MFCI is generally greater than 0.5. When the routine matrix permeability is from 1.0x10(-3) to 5.0x 10(-3), the MFCI is mainly between 0.2 and 0.5. When the routine matrix permeability is less than 1.0x10(-3), the MFCI is less than 0.2. The evaluation method of in-situ effective permeability can be used to evaluate newly discovered or not tested porous sand gas reservoirs quickly and identify whether there is tight sand gas. The correlation chart of reserves producing degree and main flow channel index can provide basis for recoverable reserves evaluation and well infilling, and provide technical support for formulation of reasonable technical policy of gas reservoir.