Analysis of two-phase flow through low permeability tight sand porous media

Single and two phase flow parameter measurements through porous media of tight sand were conducted at different operating conditions. The single phase gas flow experiments on a slot and solution pore sample showed that excess confining stress creates some permanent change in pore size and pore size distribution inside the sample, which resulted in an overall decrease in permeability of the sample.; A simultaneous two phase flow experiment of nitrogen gas and water at 3000 psig overburden pressure showed that two phase flow through the low permeability medium is dominated by either gas or liquid. There also exists a capillary pressure on the surface of the porous medium which is significantly lower than the porous medium capillary pressure.; An imbibition experiment at 3000 psig overburden pressure and a 500 psi pressure drop across a slot and solution pore type sample, was performed. The gas flowed for 20 minutes continuously, and water pushed the remained trapped gas for 500 hours to reach a steady state. This is about 9 times the required time for the single phase water flow. The single phase water flow experiments under various overburden pressures, following to the imbibition test, showed an overall increase in permeability of the core sample. The chemical analyses of the feed and exit water from the core sample proved the dissolution of some minerals in the core sample, in the traveling water. The transient experiments saved a tremendous amount of time and expenses in performing the experiments, and provided reliable experimental data.; A mathematical model for two phase flow of gas and liquid in a fractured low permeability porous medium was developed. The rock matrix is assumed to be a deformable granular phase. Porosity as a function of pore size and pore size distribution was introduced. The gas and liquid are assumed to flow through two distinct networks of pores. The Weibull distribution function as a distribution function of extremes was used to express the pore size distribution.; A computer program was developed for one-dimensional flow of nitrogen and water in non-fractured low permeability sandstones at steady state. Our model predicts well expected two phase flow patterns throughout tight sand porous medium.