Abstract: At present，the research on theory and application of transient well test of horizontal well in composite reservoirs
can hardly be found in publications. Aiming to slove this problem，the transient well test model of horizontal well in 2-zoned
composite reservoir is established. A new method to solve the model is studied by using modern mathematic methods，including
Laplace integral transformation，separation of variables，eigenvalue and eigenfunction etc.，and the solutions to the model in
Laplace space are obtained. Type curves of well test are drawn up by using numerical inversion，and the characteristics of well
bore pressure dynamic response are analyzed. There are different typical responses for different external boundaries for top
constant pressure boundary or bottom constant pressure boundary，the pressure derivative curves go down early and swiftly，
so it cannot reflect the traits of 2-zoned composite reservoir. For both top and bottom closed boundaries the type curves can
reflect the traits of 2-zoned composite reservoir. The example analysis shows that this model can be applied to transient well
test analysis of horizontal well in 2-zoned composite reservoir.

Key words: orizontal well, transient well test, composite reservoir, type curves, boundary conditions