Abstract:

Physical characteristics of sandstone in Luozigou basin were studied qualitatively and quantitatively with thin sections, mercury intrusion, SEM, X-ray diffractions and some other methods. Results show that the main lithological types of Dalazi Formation are lithic arkose and arkose with low compositional maturity and low textural maturity. The physical  characteristics of sandstone were characterized by high porosity ( 16.2% to 26.4%) and very low permeability(0.13×10^-3μm² to

1.68×10^-3μm²), and the porosity type was mainly secondary pores which accounst for 88% of the whole porosity. Result of organic element analysis，chromatography，maceral microscopy and rock pyrolysis showed that large amounts of organic acids generated during the thermal evolution of mudstone and shale in Luozigou basin and dissolute feldspar in sandstone, which lead to high secondary porosity. While, at the same time, associated products of the dissolution blocked the throat to some extent. These two processes make the sandstones show high porosity and low permeability.

Key words: physical characteristics of sandstone, organic thermal evolution, organic acids, secondary porosity, Luozigou basin