Simulation of Supercritical Carbon Dioxide Fracturing in Shale Gas Reservoir
Simulation of Supercritical Carbon Dioxide Fracturing in Shale Gas Reservoir
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DOI：
10.1007/s11630-021-1477-5
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发表时间：
2021-07
影响因子：
2.5
通讯作者：
Weiqiang Song;H. Ni;P. Tang;Shichuan Zhang;Jichao Gao;Junming Zhang;B. Shen
中科院分区：
文献类型：
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作者：
Weiqiang Song;H. Ni;P. Tang;Shichuan Zhang;Jichao Gao;Junming Zhang;B. Shen
为了以二氧化碳为工质压裂页岩气藏，首先进行了室内实验，测量了二氧化碳浸泡对页岩岩性质的影响，然后基于黏性带模型模拟了水力压裂过程中应力与渗流的耦合机制。对比了相同工况下二氧化碳和水的压裂能力，并结合现场应用进行了敏感性分析（包括页岩弹性模量、过滤系数、泵排量和二氧化碳粘度）。结果表明：与二氧化碳在30 MPa、335.15 K条件下地热作用2 h后，页岩弹性模量提高32.2%，泊松比降低40.3%，抗压强度降低22.9%；与水压裂相比，二氧化碳压裂的裂缝长度增加了25.3%，裂缝宽度减小了40.8%。随着页岩弹性模量的增大，裂缝有变长变窄的趋势。随着过滤系数的增大，裂缝最大宽度显著减小，裂缝最大长度变化不大。裂缝长度和最大宽度随泵流量的增加而增加，但长度变化率呈减小趋势。二氧化碳黏度对裂缝宽度和裂缝长度的影响可以忽略不计，验证了二氧化碳压裂在不同地层条件下的稳定可行性。
In order to fracture shale gas reservoir with carbon dioxide as the working fluid, laboratory experiments were firstly conducted to measure the influence of carbon dioxide immersion on shale rock’s properties, and then the coupling mechanism between stress and seepage during hydraulic fracturing was simulated based on cohesive zone model. The fracturing ability of carbon dioxide and water was also compared under the same working conditions, and finally sensitivity analysis (including elastic modulus of shale, filtration coefficient, pump rate and viscosity of carbon dioxide) were conducted based on field application. The results show that, the elastic modulus of shale increased by 32.2%, the Poisson's ratio decreased by 40.3% and the compressive strength decreases by 22.9% after geothermal reaction with carbon dioxide under 30 MPa and 335.15 K for 2 hours. Compared with water fracturing, carbon dioxide fracturing induces longer fracture (increased by 25.3%) and narrower fracture (decreased to 40.8%). The fracture tends to get longer and narrower with increasing elastic modulus of shale. As filtration coefficient increases, the maximum width of fracture decreases significantly, whereas the length changes little. Both the length and maximum width of fracture increase with increasing pump rate, however the changing rate of length tends to decrease. The influence of viscosity of carbon dioxide on both fracture width and length is negligible, which validates the stable feasibility of carbon dioxide fracturing in different formation conditions.