Abstract:

On the basis of the problems existed in analyzing the concepts of secondary pore zone and secondary pore development zone, this study redefined concepts of secondary pore zone, secondary pore development zone, porosity high-value zone and porosity low-value zone, analyzed the characteristics of secondary pore development zone in nearshore subaqueous fans reservoir in the middle part of Es₃ to Es₄ in Minfeng area, Dongying sag, and discussed the proper way to recognize secondary porosity and its guidance significance in deep oil and gas exploration. Secondary pore refers to the new pore formed during the burying process. Original intergranular pore and the solution pore around it should be distinguished as primary pore and secondary pore when recognizing the types of reservoir pore space. Secondary pore zone is the zone that has secondary pore on porositydepth record section, which corresponds to a depth ranging in vertical, and shows a porosity region horizontally. Secondary pore development zone refers to the high porosity reservoirs that have more than 50% secondary pore. Secondary pore development zone includes three meanings: Secondary pore development zone contains more than 50% secondary pore; The reservoir porosity is higher than the effective reservoir porosity cutoff in the secondary pore development zones; High porosity reservoirs concentrate into belts in a depth range on the porosity-depth record section, with the porosity envelope curve bulges to the porosity high-value zone direction. There are four secondary pore development zones in nearshore subaqueous fans glutenite reservoir in the middle part of Es₃ to Es₄, Minfeng area, Dongying sag. The depth ranges are 2 800-3 500 m,3 750-4 050 m,4 300-4 500 m,4 700-4 900 m. Secondary pore development zone and porosity high-value zones are the vital targets of the middle and deep oil-gas exploration. However, the authors think that the present porosity low-value zone on porosity-depth record section may be a neglected exploration target.

Key words: secondary pore, secondary pore zone, secondary pore development zone, significance of petroleum geology, Dongying sag, petroleum gas