Experimental Study On Characteristics Of Gas-Water Two-Phase Flow In Tight Sand Gas Reservoir

Tight sandstone gas reservoir is characterized by low porosity,low permeability and high water saturation.At present,the gas water phase permeability curve is mainly determined in the conventional experimental conditions,having large differences with the actual conditions of the formation.Therefore,in order to study the characteristics of gas water two-phase flow in tight gas reservoir accurately,gas water two-phase seepage experiments are done with simulating formation condition.It provides an important theoretical support for the accurate understanding of gas and water two-phase flow in tight gas reservoirs and the enhancement of gas field development.In this paper,firstly,the microscopic characteristics of tight reservoir are studied.On the basis of the study,the irreducible water saturation of tight reservoir is studied by means of displacement experiments and NMR experiments.The irreducible water saturation under different temperature and pressure conditions is calculated by the mathematical model established with the fractal theory.On the basis of the experimental determination of the irreducible water saturation,gas water two-phase seepage experiments are done with simulating formation conditions.Based on experimental research and theoretical analysis,following conclusions are achieved.The irreducible water saturation of tight sandstones and gas-water relative permeability are not only affected by core properties but also temperature,confining pressure,differential pressure measuring conditions.With the increase of temperature,the irreducible water saturation decreases the seepage zone becomes wider and gas phase permeability decreases.With the confining pressure increasing,the irreducible water saturation increases,infiltration zone is narrowed,gas phase permeability increases and water permeability decreases.With the displacement pressure increasing,the irreducible water saturation decreases,infiltration area becomes wider,gas phase permeability decreases,water permeability increases.Generally speaking,the better the physical properties,the smaller the irreducible water saturation is,the wider seepage zone.Therefore,in order to obtain an accurate gas phase permeability curve,the actual flow conditions should be simulated as far as possible.