Abstract In order to quantitatively describe the effect of microfractures on the stress sensitivity features of ultra low permeability reservoir,the stress sensitivity features of ultralow permeability fracture media from the mechanism of fracture medium deformation were analyzed by introducing a permeability stress sensitive theoretical model of single fracture. Then the experiment of stress sensitivity was conducted with microfracture cores fabricated by Brazil experiment and the features of permeability stress sensitivity were analyzed. Finally,the experimental data were contrasted with the theoretical curves. Results indicate that:(1) The theoretical curves quantitatively reveal the stress sensitivity features and the relationships with the microfracture content and roughness;the curves have the stress sensitivity features of fracture media reservoir. (2) The fabricated microfractures can proximately simulate the real situations of microfracture media reservoir and be used in the experiment. (3) The evaluation of stress-dependent permeability of cores should begin with the in-situ stress,or it would be overestimated;the permeability hysteresis loss of tensile-stress microfracture core is smaller and the permeability recovery degree is high so the permeability stress sensitivity is not strong;(4) The theoretical curve accords with the experimental data well,which indicates that the theoretical model can reveal the stress sensitivity characteristics of ultralow permeability fracture media accurately.
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Received: 24 November 2012
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