Diagenesis of the deep-seated fine-grained clastic reservoirs: An example from the 3rd member of the Funing Formation in the Zhangjiaduo Oil Field,Subei Basin

Currently much attention is given to the fine-grained clastic reservoirs with the exploration and development of dense oil and shale gas. The diagenesis of the deep-seated fine-grained clastic reservoirs from the 3rd member of the Funing Formation in the Zhangjiaduo Oil Field is dealt with in this paper on the basis of cast section examination,X-ray diffraction analysis and SEM. The results of research are outlined as follows. (1)The intergranular pores can be well preserved when the disequilibrium compaction took place,and the fine-grained clastic reservoirs with relatively higher compositional maturity and textural maturity are commonly sealed by mudstones;(2)Abundant micropores are caused by higher contents of matrix due to weakly hydrodynamic conditions during the deposition of the fine-grained clastic reservoirs;(3)The occurrence of abundant clay minerals leads to the increase of specific surface of the pores and the decrease of the precipitation of siliceous and carbonate cements;(4)The increase of specific surface of the pores slows down the convective velocity and diffusive velocity of pore fluids,and may be unfavourable for the formation of the secondary pores. The study of the diagenesis of the fine-grained clastic reservoirs in this paper is of both theoretical and practical values.