Biogeomechanical alteration of near-wellbore properties: Implications for hydrocarbon recovery

Abstract

Shale gas reservoirs, with typically ultra-low permeabilities, have been a major focus of hydrocarbon production over the past few decades. In this paper, we investigated how biogeomechanical alteration of near-wellbore properties could potentially impact hydrocarbon recovery from low-permeability reservoirs, using Wolfcamp shale and Niobrara shale formations. We first obtained the geomechanical properties using the scratch test method, in addition to the mineralogical, microstructural, and porosity and permeability measurements of the shale gas samples. Subsequently, we treated the core samples with a cultured microbial solution at distinct conditions. Further, we obtained the corresponding new geomechanical properties, in addition to the new mineralogical, microstructural, and porosity measurements of the samples impacted by the process. Finally, we showed the implications of the altered near-wellbore properties for hydrocarbon recovery from shale gas reservoirs. Our results suggest that in shale gas reservoirs, microbial-induced alterations of near well-bore properties could temporally reduce its mechanical integrity (Wolfcamp shale = −21% unconfined compressive strength, −42% scratch toughness; Niobrara shale = −24% unconfined compressive strength, −14% scratch toughness), increase porosity (+43%) and permeability (+6430%), and impact the microstructural and mineralogical properties. The near-wellbore biogeomechanical alterations could potentially improve hydrocarbon recovery by enhancing: (1.) the susceptibility for induced fractures to nucleate and propagate during reservoir-stimulation; (2.) flow pathways to improve hydrocarbon recovery.