Abstract:

Utilizing the analysis of drilling cores, rock thin section, scanning electron microscope and cathodoluminescence, the deep clastic reservoir petrology, diagenesis and secondary pores’ distribution and genesis in Changling fault depression in the south of Songliao basin are researched. The results show that deep clastic reservoir lithology of Changling depression is mainly lithic-feldspar sandstone, feldspathic litharenite. The compositional maturity is lower. Diagenetic stage is mostly in middle stage, the main diagenesis types are compaction, cementation and multi-period dissolution. Compaction and cementation led to further loss of primary pore, but the dissolution forming secondary porosity plays a significant role to improve the porosity and permeability of the reservoir. There are two abnormal high porosity zones in the vertical section, whose formation is mainly owing to dissolution of organic acids and CO₂ acidic water.

Key words: Changling depression, diagenesis, secondary pore, carbon dioxide, dissolution