The classification assessment of tight sandstone reservoirs is one of the most important research focus of tight oil resource evaluation.Criteria of classification assessment for tight reservoirs can be effectively and accurately established by calculating the limits of various physical properties of tight oil reservoir

providing a theoretical basis for the classification of tight reservoirs.The tight sandstone reservoir in the 1st member of Funing Formation in the Gaoyou Sag

is taken as an example in the study.Its lower limit of oil-bearing property is calculated by methods of oil-bearing occurrence and nuclear magnetic resonance (NMR);its lower limits of physical properties for oil flowing are worked out by methods of NMR

minimum flowing pore throat radius and formation testing;and its upper limits of physical properties are figured out by balancing the buoyance and capillary resistance of oil in pores.Then following the characterization of tight reservoir permeability and verification of pore structure classification

we established the criteria for classification assessment of tight sandstone reservoirs.The tight reservoirs in the 1st member of Funing Formation

Gaoyou Sag

were accordingly classified into four classes

namely ineffective tight reservoir

oil-bearing tight reservoir

oil-movable tight reservoir and highly oil-movable tight reservoir

with the permeability boundaries of 0.07×10

-3

μm

2

0.12×10

-3

μm

2

0.50×10

-3

μm

2

1.13×10

-3

μm

2

respectively.The consistency of the classification results and production tests serves to prove the accuracy and applicability of the method proposed in the study.