Gas storage capacity estimates of shales are routinely assessed using laboratory data from unconfined methane sorption and porosity measurements. In this study, the stress dependence of the methane excess sorption capacity and specific pore volume are investigated simultaneously. Experiments were performed on dry core plugs (Cambrian–Ordovician Alum, Jurassic Bossier, Late Cretaceous Eagle Ford, and Jurassic Kimmeridge shales) at 30°C under controlled confining stress up to 40 MPa and gas pressures up to 20 MPa.Increasing overburden stress results in a significant decrease of both specific pore volume and excess sorption capacity. The stress sensitivity of the specific pore volume was most prominent for the total organic carbon (TOC)–rich Kimmeridge sample (45% TOC) and further decreased in the order of Bossier, Eagle Ford, and Alum. Stress dependence of the methane excess sorption capacity, expressed as percentage reduction at 40-MPa overburden as compared to unconfined conditions, decreases in the order Eagle Ford (∼56%), Bossier (∼30%), Kimmeridge (∼14%), and Alum (∼5%). Although the decrease of specific pore volume is definitely caused by poroelastic compression, the mechanism(s) leading to the reduction of excess sorption capacity with stress require further investigation.Gas storage calculations show that routine methods based on unconfined data may grossly overestimate the total storage capacity. In this scenario, at 2500-m depth, the total gas storage capacity will be overestimated by 5% for the Alum, 28% for the Bossier, 18% for the Eagle Ford, and 28% for the Kimmeridge if the stress dependent reduction of volume and sorptive storage capacity is not considered.

中文翻译：

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实验确定富含有机物的页岩的孔隙度和甲烷吸附能力与有效应力的关系：对储气能力的影响

页岩储气能力的估算通​​常使用来自无限制甲烷吸附和孔隙度测量的实验室数据进行评估。在这项研究中，同时研究了甲烷过量吸附能力和比孔体积的应力依赖性。在30°C的干围岩心（寒武纪-奥陶纪明矾，侏罗纪博西尔，晚白垩纪伊格尔福特和侏罗纪金梅里奇页岩）上进行了试验，控制围岩应力最大为40 MPa，气压最大为20 MPa。增加了上覆应力明显降低了比孔体积和多余的吸附能力。对于总有机碳（TOC）丰富的Kimmeridge样品（45％TOC），比孔体积的应力敏感性最为突出，并且按Bossier，Eagle Ford和Alum的顺序进一步降低。甲烷过剩吸附能力的应力依赖性，表示为在40 MPa过载下与无限制条件相比降低的百分比，按Eagle Ford（〜56％），Bossier（〜30％），Kimmeridge（〜14％），和明矾（〜5％）。尽管比孔体积的减少肯定是由孔隙弹性压缩引起的，但导致应力降低过量吸附能力的机理仍需进一步研究。储气量计算表明，基于无约束数据的常规方法可能会严重高估总储量容量。在这种情况下，在2500-m深度处，如果因压力而降低了压力，明矾的总储气量将被高估5％，博西尔为28％，鹰福特为18％，金梅利奇为28％。不考虑体积和吸附存储容量。