Low-Permeability Tight Reservoir Self-Water Absorption Process Fractal Characteristics And Influencing Factors

Fractal dimension is a parameter for studying and explaining fractal features.For reservoirs that can be described by fractal features,the fractal dimension can be used not only to describe the pore structure characteristics of the reservoir,but also to characterize the spontaneous infiltration of porous media from the microscopic mechanism.mechanism.The permeability of the tight reservoir core in the study area is 0.0047?0.1860×0-3?m2,and the porosity is 0.48%?9.94%.In the development process,there is also the problem of water lock damage and the improvement of water flooding recovery.Due to the small pore throat of the tight reservoir,extremely strong capillary forces,the phenomenon of fluid seepage in these reservoirs and the impact of the results on the development of tight reservoirs cannot be ignored Therefore,the fractal dimension of core pore structure in the study area calculated by mercury intrusion method is used in this paper.The fractal characteristics and influencing factors of spontaneous infiltration of tight reservoir in the study area are studied experimentally,and the following main research results are obtained:(1)From the fracture foundation theory of reservoir core structure and the calculation method,the fractal dimension distribution of core pore structure in the study area is 2,1557?2.8271,and the fluctuation interval is 0.6714,which indicates that the reservoir core pore structure in the study area is complex and strong heterogeneity;(2)The spontaneous infiltration curves of reservoir cores in the study area can be divided into four types according to the fractal dimension of core pore structure,which are consistent with the characteristics of the permeability curve.The final osmotic water content increases with the increase of the fractal dimension of the core pore structure;(3)Reservoir lithology,pore structure and clay minerals have certain influence on the spontaneous infiltration process.The fractal dimension D of core pore structure can be used as an important parameter to describe the pore characteristics and seepage characteristics of low permeability reservoir in the study area.It's a simple method for studying spontaneous infiltration for a low permeability reservoir;(4)For gas reservoirs,the self-priming frontal fractal dimension Dz can reflect the microscopic infiltration characteristics of the core;(5)Using the fractal expression of mass variation with time established by Cai et al.,it is easy to calculate the final water absorption of the reservoir by fitting the spontaneous infiltration curve of the reservoir in the study area.