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.

在过去的几十年中，页岩气藏具有典型的超低渗透率，一直是油气生产的主要焦点。在本文中，我们使用 Wolfcamp 页岩和 Niobrara 页岩地层研究了近井特性的生物地质力学改变如何可能影响低渗透储层的油气采收率。除了对页岩气样品的矿物学、微观结构以及孔隙度和渗透率测量之外，我们首先使用划痕测试方法获得了地质力学特性。随后，我们在不同条件下用培养的微生物溶液处理岩心样品。此外，除了受该过程影响的样品的新矿物学、微观结构和孔隙度测量值之外，我们还获得了相应的新地质力学特性。最后，我们展示了近井特性改变对页岩气储层油气回收的影响。我们的结果表明，在页岩气藏中，微生物引起的近井特性改变可能会暂时降低其机械完整性（Wolfcamp 页岩 = -21% 无侧限抗压强度，-42% 划痕韧性；Niobrara 页岩 = -24% 无侧限抗压强度强度，-14% 的划痕韧性），增加孔隙率 (+43%) 和渗透率 (+6430%)，并影响微观结构和矿物学特性。近井眼生物地质力学改造可能通过增强以下方面来提高油气采收率： (1.) 在储层增产过程中诱导裂缝成核和扩展的敏感性；(2.) 提高油气采收率的流动路径。