Abstract
Summary Developing tight oil reservoirs is challenging due to ultra-low permeability and porosity. Oil recovery through spontaneous water imbibition into water-wet tight matrix is an important mechanism of tight oil development. This paper develops a novel semi-analytical model for spontaneous imbibition (SI) in tight oil reservoirs with fractal theory. Firstly, pore structures of tight sandstones were characterized with fractal geometry, and pore space of tight sandstones are assumed to be bundles of tortuous capillary tubes with fractal characteristics. Then, considering the boundary-layers of initial water and residual oil, the SI in a single tortuous capillary tube was studied. With the assumption of pore size distribution following fractal distribution, the model of SI on core scale were developed and the model reliability was verified with experiment data. Finally, the effects of pore structure parameters, contact angle, IFT, oil-water viscosity ratio on SI oil recovery were quantitatively evaluated.
Published Version
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