The study on tight sandstone gas reservoir stress sensitivity is conductive to set a certain production of gas well and to manage gas field with high efficiency. Traditionally, it is recognized that the stress sensitivity level of tight sandstone is very high based on the experiment report. However, it is not reflected by the production data. In this paper, it is discussed a number of issues which center around the stress sensitivity experiment of tight sandstone, to improve the experiment and develop a new model to evaluate the stress sensitivity level of tight sandstone.
During analyzing the stress sensitivity experiment test, it is found that there exist small interspaces on the core surface which can lead to experiment problems. Based on the study in loose sandstone and analysis on core deformation behavior, two improvements are made, including the pressure drop standard uniform and core ageing treatment. In addition, the capillary bundle model has been developed during the evaluation process, which makes it reasonably possible to deduce the theoretical relationship between the permeability and reservoir pressure drop by the Kozeny-Carman equation to unify and transform the flow in porous media and pipe.
According to the model and improved experiment, it is demonstrated that there exists a linear relation between the permeability and the reciprocal of reservoir pressure drop, which agrees well with experiment observation. Meantime, it can be concluded that and stress sensitivity level of tight sandstone is weak, not as strong as it is reported before.