Abstract:

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: ①Well 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. ②The parameters of the test layer and neighbor layer have an opposite effect on the well test curves. ③The 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. ④The 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.

Key words: dual layer reservoir, vertical well, cross flow behind casing, well-testing interpretive model