High Pressure Mercury Intrusion Porosimetry Analysis of the Influence of Fractal Dimensions on the Permeability of Tight Sandstone Oil Reservoirs

Abstract

In this paper, fractal characteristics of sandstone in the Chang 7 section of the Triassic Yanchang Formation of the Dingbian oilfield, Ordos Basin, China were analyzed by high pressure mercury intrusion porosimetry and the fractal model. The influence offractal parameters on rock permeability is discussed. Results show that fractal dimensions (D_f) of sandstone samples range within 2.759-2.987, with an average of 2.890, and the mean capillary tortuosity fractal dimension (D_T) ranges within 1.194-1.553, with an average of 1.391; D_f is larger than D_r There is a strong negative correlation between rock permeability and D_f or D_r Both D_f and D_T decrease with decreasing porosity of sandstone samples, indicating that connectivity between rock sample pores becomes poor and capillary tortuosity increases. The seepage path in low-permeability (tight) sandstone is much longer than in moderate-permeability sandstone, which is an important reason for the low permeability of the tight sandstone oil reservoir Meanwhile, the fractal model is an effective predictor of the permeability of tight sandstone oil reservoirs.