A modified embedded discrete fracture model to study the water blockage effect on water huff-n-puff process of tight oil reservoirs

Abstract

This paper constructs a numerical model to study the water blockage effect on water huff-n-puff process of tight oil reservoirs, by borrowing the conception of “fracturing fluid layer” and modifying embedded discrete fracture model (EDFM). Based on the proposed model, the effects of the permeability, initial water saturation and width of the fracturing fluid layer on water huff-n-puff process are detailly studied. It is found that, (i) initial water saturation of FFL makes little effect on water huff-n-puff process, because the water injection can refresh the water saturation distribution near fractures, and this ‘refreshment effect’ significantly reduce the effect of the initial water saturation of FFL. Moreover, the longer water injection time is, the stronger ‘refreshment effect’ will be, then the smaller effect the initial water saturation of FFL will make. (ii) both of width and permeability of FFL make a significant negative effect on the oil production rate of water huff-n-puff process, and permeability is more influencing than width. These results may give theoretical instructions to optimize the water huff-n-puff process while considering the water blockage effect.