Abstract: This paper presents microscopic studies and systematic analyses of the buried history of deposits, lithology, pore structure, diagenesis and pore abundance of Triassic-Lower Jurassic clastic reservoirs in Hami depression. Results show that the reservoirs are in low maturity of clastic composition and structure; the diagenesis means the early buried and late uplifted type; the pore assemblage is dominated by residual in-tergranular pore-few solution intergranular pore-mass micropore-diagenetic fissure, with poor pore structures. The diagenetic stage is mainly in late diagenetic stage-B. Higher paleotemperature could be one of the key reasons causing the dense reservoirs; whereas the rapid compaction in early stage and the mass cemented rocks as well as universal poor dissolution might be the direct reason for it. Hence, to make a deep explo-ration would take more risks here.

Key words: Hami, Triassic, Lower Jurassic, reservoir, dense clastic rock, diagenesis