An Experimental Method for Measuring the Three-Phase Relative Permeability of Oil, Gas and Water By Nuclear Magnetic Resonance

Abstract

The three-phase relative permeability of oil, gas, and water place a significant practical emphasis in the study and evolution of compact sandstone condensate gas traps. However, most investigations on itare relied on forecast patterns that make an effort to appraise it from the relative permeability of two phases. We have measured it of artificial dense sandstone core by online NMR tests. Firstly, the extracting of tight sandstone condensate gas reservoirs was mimicked using a steady-state flow toward, and crude oil, nitrogen and formation water were injected into tight sandstone simultaneously at room temperature according to the variation mechanism of reducing gas injection, and increasing water and oil injection. Secondly, the three-phase saturations were obtained by the different partition of oil-water phases in the 2D T1-T2 spectrum and the volume balance method. Finally, the relative permeability of three phases under various saturations was determined based on Darcy's formula. The findings indicated that in the 2D T1-T2 spectrum, the aqueous phase was mainly concentrated at the position where the T1/T2 ratio was 1, and the oil phase was mainly concentrated at the position where the T1/T2 ratio was greater than 1. Compared with the T2 spectrum, the T1 spectrum could effectively distinguish the oil and water phase, and their boundary was about 10 ms at the T1 relaxation time. The relative permeability of each phase exhibited a trend toward decreasing over time as gas injection decreased and water and oil injection increased. The relative permeability of the water phase dropped, albeit not as much as that of the oil-gas phases. The relative permeability curve of three phases was convex to the point where the oil saturation was equal to 1. As a result, the relative permeability of the gas-oil phases will be significantly impacted within the mining period of tight sandstone condensate gas accumulations when a little amount of condensate water arrives in the reservoir. Therefore, it is necessary to take measures to reasonably control the precipitation of water in condensate gas reservoir. In order to better understand the three-phase relative permeability, an innovative study has been conducted. And its results can more accurately predict and guide the production of condensate gas reservoirs.