A dynamic model for correcting sealing core saturation and its influencing factors

In the process of sealing coring, pore, fluid volume and solved gas vary with the decline of pressure, and consequently the error of measured saturation is larger. To solve this problem, a dynamic model for core saturation correction was developed according to reservoir engineering and seepage mechanics, combined with dissolved gas drive theory and multi-phase fractional flow principle. In this model, the variation of pore, fluid volume and solved gas with the pressure is considered comprehensively. Then, the corresponding calculation procedure was put forward and the sensitivity of all influential factors was evaluated. It is indicated that according to the change rate of composite oil/water saturation of cores, the factors affecting the saturation of sealing cores are ranked from the top to the bottom as dissolved gas viscosity, dissolved gas-oil ratio, crude oil volume factor, oil viscosity, oil/water relative permeability, oil compressibility and rock compressibility. To sum up, the dynamic model for sealing core saturation correction can reflect the variation of core saturation in the process of pressure decline, which is in accordance with the change trend in the process of coring. In addition, the average relative error between the correction result and the calibrated saturation is 0. 8%. Therefore, the dynamic model can provide the reliable basis for analyzing the distribution of oil/water saturation of actual oil reservoirs.