Experimental Study On The Nonlinear Flow In Ultra-low Permeability Reserviors

To seek the relation between low-permeability microscopic pore structure and non-linear fluid flow through porous medium and discover the influencing factors of non-linear filtering flow, it's needed to research microscopic pore structure and determination tests of non-linear filtering flow curves. This demands a higher precision of non-linear fluid flow experiments. This paper made an advancement of experimental procedure of non-linear fluid flow to improve precision of experiments and accuracy of testing curves. Also it started with microscopic pore structure to study mechanism of non-linear fluid flow low-permeability through low-permeability porous medium by studying cores from eight typical low-permeability blocks of JiLin Oilfield, in addition to tests of conventional Hg injection and rate-controlled Hg penetration.This paper analyzed parameters of pore structure and non-linear filtering flow curves of eight blocks of JiLin Oilfield. It turns out the percentage of large-radius throat determines the effective filtering flow ability. It increases as the percentage of large-radius throat increases. Seepage in the sandstone core exhibits a non-linear behavior and start press gradient exists. Physical characteristics and character of fluid are the main factors that affect the non-linear behavior and the start pressure gradient. The more the heterogeneity is, the extent of non-linear filtering flow curves is larger and the start pressure gradient is bigger as the permeability is lower and viscosity of the fluid is bigger.The experimental test results verifies the non-linear filtering flow model. The parameters of describing non-linear filtering flow curves is determined by analysis and comparison, and the connection between them and parameters of pore structure, which builds the foundation of the application of pore-structure parameters in calculation.