Loose core and sanding make it very difficult to carry out core experiments for acquisition of the flow parameters including capillary pressure and relative permeability. Studies on pore network models available in literature are not generally considering the influence of stress sensitivity and clay swelling which are studied as the main factors affecting the flow parameters. Firstly, a three-dimensional pore network model from the digital core is used to calculate the flow parameters. Secondly, on the basis of pore network theory, combined with the study of stress sensitivity and clay swelling, a series of dynamic models are established, which are used to describe the variations of pore microscopic parameters. At last, the flow parameters under different conditions were simulated through programming in MATLAB.

From this study, some results and conclusions can be obtained as following:

  1. Because of stress sensitivity and clay swelling, the pore microscopic structure is changed. The pore shrinks, the shape factor reduces and the pore-throat ratio along with coordination number also decrease. These variations cause capillary pressure to increase and the relative permeability curve shifts to the right.

  2. At the early period of the exploitation, stress sensitivity and clay swelling all make contributions to the changes of the flow parameters, but at the later stage, the effect of clay swelling could be faded to vanish because the clay has been saturated with water.

  3. With the increase of effective stress and the effect of clay swelling, the wetting phase's relative permeability increases but the nonwetting phase's relative permeability declines. This is mainly because of the pore's shrinkage that makes the whole flow ability of the fluid decreasing. But the non-wetting phase occupies the middle of pore throat and the pore wall makes little influence on it, inversely, its capacity of relative movement could increase.

You can access this article if you purchase or spend a download.