Three dimensional characterization and quantitative connectivity analysis of micro/nano pore space

Evaluation is performed on pore connectivity of unconventional reservoirs using 3-D FIB-SEM imaging characterization and digital rock techniques. 3-D images are first obtained by FIB-SEM device and then transformed into digital pore structure model through shape correction, brightness correction, depth-of-field correction and phase distinguishing. Based on this model, a new connectivity evaluation method for micro/nano pores in unconventional reservoirs is proposed. This method differentiates dead and live pore space, grades live connected domains (1-grade is the worst and 3-grade is the best) and calculates the connectivity rates of all grades. Selected connected domains can be quantitatively characterized through statistical analysis of connected domain distribution, volume and shape. The applications on nano material, shale and carbonate get distinctive connectivity rates (96%, 22% and 82%) and characteristic differences on connected domain distribution, volume and shape. Through these statistical parameters (connectivity rate, connected domain distribution, volume and shape), the three demonstrated materials and reservoirs are quantitatively characterized and differentiated. Thus, validity of the proposed connectivity method in this paper is proved.