关键词: 原位条件, 渗透率, 应力敏感, 微观结构

Abstract:

In order to study the effect of confining press and pore press on permeability, the new method of evaluation on stress sensibility is proposed. Three pieces of low permeable reservoir rock samples in Songliao Basin are selected. A servo-controlled triaxial rock mechanics test system is employed to investigate the permeability of sandstone samples under conventional conditions and in situ conditions. The results show that: 1) The permeability of three pieces of samples reduce with confining press increasing and pore press reducing. 2) The denser the rock is, the stronger stress sensitivity is, in situ conditions, which explains the mechanism of low permeability reservoir sensitivity differences by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), constant speed mercury injection experiment. What’s more, throat size and shape, plastic mineral content and type contribute to the differences of permeability sensitivity. 3) Mineral content and type of plastic are the major factor of the sensitivity of permeability differences. The stress sensitivity of tight reservoir permeability rock becomes strong with the increasement of mica, clay and other plastic mineral content. In the practical work, evaluation on stress sensitivity of permeability, the effect of confining pressure single factor is mostly considered, butthe effect pore presss would be ignored, which is bound to bring larger human error. So evaluation on stress sensibility in situ conditions is essential, which is significant for further understanding of stress sensitivity of low permeability reservoir characteristics and development.

Key words: in situ conditions, permeability, stress sensitivity, microscopic structure