In order to monitor and prevent the channeling outside the casing

we established a well-testing interpretive mathematical model of the vertical wells in dual layer reservoir considering the semi-permeability of the interlaminar and the bore hole storage effect. Then we solved and drew the typical well test curves by the Laplace transformation. According to the test curves

there are four flow sections: intermediate flow period

transition section

interporosity flow section and systematic radial flow period. By the analysis of the influence factors of the type curve

we conclude that:（1）Well testing curves are influenced by many parameters

for example

the well storage coefficient affects the early curves

while the skin factors

permeability

fluid viscosity

oil layer thickness

and cross flow coefficient affect its transition stage and interporosity flow stage.（2）The parameters of the test layer and neighbor layer have an opposite effect on the well test curves.（3）The main controlling factors of the strength of the interporosity flow outside the casing include the interporosity flow coefficient

the permeability of neighbor layer and the skin factors of test layer.（4）The reason of the interporosity flow outside the casing is the damage degree of the cement sheath outside the casing

and the corresponding monitoring method is put forward.