DIFFUSION-LIMITED FRACTURE-MATRIX INTERACTION AND GAS RECOVERY IN BARNETT SHALE
Gas recovery in the tight shale formation is probably diffusion-limited by tortuous pathways in shale matrix characterized by nano-sized pore spaces. This work discusses various approaches to investigating pore structure (both geometry and topology) of the Barnett shale. For example, we directly measured chemical diffusion in the saturated Barnett shale using a suite of tracers, followed by chemical mapping using laser ablation-ICP-MS. Tortuosity obtained from tracer diffusion profiles is consistent with those from mercury intrusion porosimetry. Gas production decline behavior from producing Barnett wells is analyzed from the topological aspects of shale pores, using the perspective of percolation theory; several possible explanations about observed decline behavior are offered.