Abstract:

By use of drilling, logging and analysis data, combined with gas reservoir profile, it is concluded that there are two types of cap-rocks in Xujiaweizi fault depression, that is, mudstone and volcanic rock. By analyzing the identification mark, distribution and seal ability of cap-rock of deep gas in Xujiaweizi fault depression and its controlling action to gas accumulation and distribution, it is considered that there are two sets of regional cap-rocks (K₁q¹⁺² and K₁d²), local cap-rock (K₁yc¹) on top, and interlayers in K₁yc¹ and K₁yc³ of deep gas in Xujiaweizi fault depression. Regional and local cap-rocks are widely distributed with large thickness, higher displacement pressure and strong seal ability, which control regional accumulation and distribution of deep gas in Xujiaweizi fault depression； Interlayers are limited distributed with thin thickness, low displacement pressure and weak seal ability, which only control local accumulation and distribution of gas in reservoir.

Key words: Xujiaweizi fault depression, cap-rock, gas reservoir, sealing ability, control action