The microstructure of tight reservoir affects the charging efficiency of crude oil

and restricts the abundance and distribution of tight oil.Based on experiments including the physical simulation of tight oil charging

stable rate mercury injection

Scanning Electron Microscopy (SEM) and nuclear magnetic resonance (NMR)

the charging process of crude oil and structural characteristics of pore throats of the tight reservoir were quantitatively characterized

and the effects of diagenesis

authigenic mineral growth patterns and pore throat structural features on oil charging in tight reservoirs were discussed.The results show that the oil charging process can be divided into three stages:initial stage

rapid-increase stage and slow-increase stage.This is a result of the dynamic balance between displacement pressure and capillary pressure during the charging process and the distribution of main reservoir space.In detail

there are two increasing modes in the rapid-increase stage

namely

the sustained rapid-increase and rapid-increase by pulses.The two modes reveal the differences in the distribution characteristics of mainstream throat radii in these samples.It is found that diagenesis

including compaction

cementation

dissolution

and authigenic mineral growth

has greatly affected the size and distribution of reservoir space and throat radius

and determined the quality of tight reservoir.Therefore

under the condition of abundant oil source

the key to tight oil enrichment lies in the sufficient driving force and high-quality reservoir

and thus the sand bodies near the open faults/micro-fractures are concluded to be the favorable zones for hydrocarbon exploration.