Abstract:

Because of the particularity of neutral and basic volcanic reservoir, it is difficult to compute its gas saturation by the traditional electric conduction model. Through the study on the type and feature of pore and on the litho-electric experimental data of neutral and basic volcanic reservoir, the paper finds that the main pore types are blowhole, corrasion hole and micro-crack, which is of extremely high pore throat radius ratio; there is non-electric conduction pore in the  conductive background. Because of this, through the analysis of Maxwell conductivity model, the total porosity can be divided into conductive porosity and non-conductive porosity. By introducing communicating pore factor, the paper gets the conductive porosity. With the principle of conductivity superposition, the model of the reservoir gas saturation based on the conductive pore is obtained. Comparing with the saturation from the analysis of capillary pressure data, the gas saturation by this model is of less than 3% mean absolute error, and agrees with the well testing data.

Key words: saturation, electric conductivity, neutral and basic volcanic reservoir, the conductive pore, Maxwell conductivity model