Abstract:

There are mainly two types of pores(primary and secondary) in the space of volcanic rock reservoirs in northern Mingqiao region of Jinhu depression in Subei basin. The primary pores consisting of intergranular pores,intercrystalline pores, gas pores and primary joints were formed during the accumulation of volcanic rocks and diagenesis. The distribution of the primary pores are mostly isolated and filled. The secondary pores including intraparticle dissolution pores, dissolution pores, seams and caves etc. were formed after the diagenesis of volcanic rocks caused by the effects of weathering, leaching, dissolution and structural stress. The secondary pores can improve reservoir quality greatly especially for structural joints and play very good rule in communicating isolated primary pores. The ratios of porosity and permeability of a rock flow unit in the profile are observed to have a trend of being enlarged gradually from downwards to upwards by analyzing volcanic rock porosity and well log of permeability. Variations of porosity and permeability in a rock flow group correspond to these in a rock flow unit or reveal several repetitions of the same regularity above. The ratio variations of porosity and permeability of east-west in the study area are quite big while ratio variations of south-north are relatively stable. Reservoir qualities of Ⅶ-Ⅺ rock flow group in 1st member of Funing formation and Ⅲ rock flow group in 2nd member of Funing Formation are quite good.

Key words: volcanic rock, primary porosity, secondary porosity, rock flow unit, rock flow group