A New Method to Calculate the Gas Saturation of the Sand and Shale Formations Based on Logging Rock Mechanics Parameters

To improve the precision of interpretation of gas reservoir to correlate with the rate of logging, a study using logging rock mechanics parameters to calculate gas saturation of sand and shale rock formations was carried out(hereinafter referred to as the new method).Based on the physical volume in the rock model and the bulk modulus, the formulas of volume compressibility, the fluid compressibility and gas compressibility factors were deduced, and a gas saturation calculation model was established.Based on the logging data in S gas field, the gas saturation results were calculated by the new method, the Archie formula, the Physical Analysis were contrasted, and a controlled evaluation with gas testing conclusion was conducted.The study revealed that the average error of the gas saturation calculated by the new method with the gas saturation from the Archie formula, and the gas saturation from the Physical Analysis in the gas zone was 3.5%, and the poor gas reservoir was 4.0%, the values of the saturation were quite the same.The values of the saturation calculated by new method were quite different with another two methods in dry layer and poor reservoir, but the same with the gas testing result.This proved the advantages of the new method.Studies suggested that this method of calculating the gas saturation could be used as an effective complement to Archie formula.