Caprock directly determines the scale of oil-gas accumulation.The lithology of caprock in large-medium oil and gas fields is mainly mudstone

gypsolyte/saline rock and carbonate rock.In recent decades

we have made great progress in the sealing mechanism and evaluation methods for sealing property study.Scholars have proposed the capillary

hydraulic

overpressure

and hydrocarbon concentration sealing mechanisms through the years.For different sealing mechanisms

the sealing property evaluation criteria were set up

which played an important role both in the evaluation of hydrocarbon plays and the selection of exploration targets.Conventional study on the sealing properties of caprock is mainly based on static evaluation

but in fact

its sealing properties may change during multi-stage burial-uplift tectonic evolution.Jin(2013)established a quantitative evaluation method for the dynamic evolution of caprock sealing properties

which was based on the relationship between the porosity and capillary pressure during burial

the permeability and capillary pressure during uplift

and the OCR

a quantitative prediction method for the evolution of capillary sealing properties.And the method provides a reasonable basis for the study of oil and gas accumulation in multi-stage tectonic evolution basin.Thus

based on the study of the above-mentioned mechanisms and methods

it was pointed out that faults

tectonic fractures and hydraulic fractures were the key factors to the integrity of caprock

and the condition for the oil and gas to break through caprock was clarified

which provided a new way to find the secondary reservoir.The formation and evolution process of faults and fractures and their destruction to the caprock integrity depend on the seal's mechanical characteristics

that is

the caprock brittle-deformation prone or ductile-deformation prone.Based on the density and rock mechanics of mudstone

a method for distinguishing brittle and ductile deformation of mudstone was established.According to Byerlee's friction law and Goetes's criterion

a method for distinguishing brittle-ductile deformation of gypsolyte/saline rock is formulated.Therefore

the mechanisms for destruction of faults and fractures on brittle

brittle-ductile or ductile cap-rocks were clarified.Nowadays

there are still many problems necessary to be explored further

including the effects of different caprocks on hydrocarbon preservation

the effects of regional geologic factors on the sealing properties of caprock

the division of diagenesis stages and the dynamic evolution of sealing properties of shale

the brittle-ductile transition of caprocks and quantitative characterization of fracture conditions

the effect of deep faults on oil and gas migration and preservation

quantitative evaluation of caprock integrity

etc.