Dual-Porosity Modeling of Tight Unconventionals

Abstract

Enhancing oil recovery in tight unconventional has been a great interest over the last decade. Huff-n-puff gas EOR becomes the most popular method among many alternatives, particularly after EOG Resources, Inc. claimed that they had succeeded implementing such method in the Eagle Ford shale.

Little information was released by EOG regarding the employed method as they affirmed such details are their proprietary. Instead, they provided that miscible displacement plays an important role to its success along with the utilization of existing wells. Approximately the incremental range of 30% to 70% is expected according to their simulation model if such method is exerted relative to not having it at all.

Simple model was carried to understand the behavior of DPM in tight unconventionals during two periods, namely depletion and gas injection. Subsequently, the results were compared to SPM along with the necessity to modify the model to preserve the reliability of the results. It is found that DPM can represent SPM results during depletion phase, although some modifications on matrix-fracture exchange transmissibilities (TEX) may be needed. In contrast, DPM yields overoptimistic performances during gas injection phase even with modifying TEX. In other words, DPM provides a misleading result from SPM when injection is acquainted.