Abstract:

Previous evaluations on stress-sensitivity of volcanic rocks are limited to qualitative analysis, and the influence factors of the stress-sensitivity are not comprehensive. Basing on the results of stress-sensitivity experiment on volcanic rocks and the theory of stress-deformation, this paper has established a relatively comprehensive quantitative evaluation method. This paper has analyzed the factors that affect the stress-sensitivity of volcanic rocks, finding that fracture development situation and pore structure are the key factors. The result of stress-sensitivity experiments is highly consistent with the result of quantitative comprehensive evaluation on stresssensitivity of volcanic rocks with the 0.94 of linear fitting R², verifying the high reliability of this evaluation method. All the influence factors of stress-sensitivity are fracture type, fracture filling situation, permeability, the ratio of porosity to permeability, fracture number, fracture width, porosity, clay mineral content and depth in descending order. In addition, the volcanic gas well productivity equation with stress-sensitivity is established, which can forecast gas well productivity with stresssensitivity under different reservoir pressure. And the analysis result of the effect of stress-sensitivity on gas well productivity shows that the stronger the stresssensitivity is, the more the gas well productivity losses under the same condition.

Key words: volcanic rock, permeability, stress-sensitivity, quantitative analysis, comprehensive evaluation, productivity loss