Study On The Multi-scale Characterization Of Pore Structure In Continental Shale Reservoir

In recent years,the exploration and development of shale oil and gas plays a more and more pivotal role in China,and is an important strategic direction of China’s oil development.Shale oil reservoir has low porosity,complex pore structure and various crude oil occurrence forms.Microscopic pore structure characteristics and development control factors affect the reservoir physical properties.To characterize the microscopic pore structure and explore the pore abundance control factors is the crux to shale oil reservoir evaluation and further exploration and development.This thesis studies the reservoir development characteristics,the quantitative and qualitative characterization of pore structure and the control factors of pore development in the Junggar Basin.In the aspect of reservoir development characteristics,through the analysis of experimental data,it is found that:(1)the reservoir minerals are mainly quartz and dolomite,and the clay content is low.(2)Organic matter is type ⅱ organic matter,with an average TOC content of 0.54% and at maturity stage;(3)With low porosity and permeability,it is an ultra-low porosity and low permeability reservoir.In terms of pore structure characterization,scanning electron microscopy(FIB-SEM)was firstly used to identify three types of inorganic mineral pores,organic pores and micro-fractures in shale reservoirs in the study area.Using low temperature nitrogen adsorption(LTNA),nuclear magnetic resonance(NMR)and high pressure mercury(MIP)to complete the quantitative characterization of shale pore structure,to realize the study area aperture distribution rules.Namely,in general,the shale reservoirs develops micro-pores,mesopore and macro-pores,In terms of the number of different pores,there are more number of micro-pores and the smallest number of macro-pores.As for pore volume and specific surface area,mesopore contributed about 79% and 88%of specific surface area,macropore contributed only about 20% of pore volume,and micropore contributed 10% of specific surface area.In terms of controlling factors of pore development,a multi-parameter regression model for controlling factors analysis was established to identify the main controlling factors of shale pore development in the study area: organic carbon content,clay,quartz,dolomite and other minerals jointly control the development of reservoir pores.The organic carbon content had a positive effect on mesopore development,but had a weak effect on micropore and macropore.Clay content promotes the development of micropore and mesopore,but has no obvious effect on macropore.When the clay content is greater than 6%,the pore volume improves the reservoir significantly;brittle minerals have positive control over the total pore development,but their content does not form a good correlation with the pore at a certain scale.