DOI: 10.3724/SP.J.1249.2013.03306

Journal of Shenzhen University Science and Engineering (深圳大学学报理工版) 2013/30:3 PP.306-312

Microstructural characteristics of the Jurassic tight oil reservoirs in Sichuan Basin

The pore structure, porosity, fluid saturation, T2 cut-off values and permeability coefficients for tight formations are studied in this paper in order to discover the microstructural characteristics of the tight reservoirs. A series of experimental methods, including conventional core analysis, nuclear magnetic resonance (NMR), and high-speed centrifugal separation of gas and water, are applied to obtain the T2 spectrum of water-saturated cores and cores under different centrifugal force. It is found that T2 spectrum can indicate the type of pore in cores. The pore type for tight limestone is pore reservoirs and pore-fracture reservoirs. The pore type for tight sandstone is pore reservoirs and the majority of pores are small pores, with some middle or large pores. Only a few cores have micro-fracture which can significantly improve the permeability. The average gas porosity for tight sandstone and tight limestone is 4.88% and 1.93%, respectively. The porosity obtained by NMR is less than gas porosity and water porosity. The average T2 cut-off values for tight sandstone and tight limestone is 4.25 ms and 11.54 ms, respectively. The average permeability coefficient for tight sandstone and tight limestone is 2.35 and 0.22, respectively. The T2 cut-off values and permeability coefficient are both less than the conventional values.

Key words:petrophysics,Sichuan Basin,tight reservoirs,porosity,permeability,saturation,pore structure,nuclear magnetic resonance (NMR)

ReleaseDate:2014-07-21 16:55:28

Funds:Special Major Science and Technology of CNPC (2012E-2601-04)

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