The occurrence of caverns, vugs, fractures, or fractures plus vugs is typically characteristic of a carbonate or volcanic reservoir, such as an Ordovician carbonate reservoir in Tarim or a Carboniferous volcanic reservoir in Karamay. Because the two reservoir types are highly heterogeneous and they are distributed in blocks, it is difficult to determine the productivity of a well therein. For this reason, the reservoir within the area controlled by the well is divided into two accumulation systems, i.e. fracture accumulation system & cavern accumulation system, so that a dual-seepage model is established to calculate its productivity. Calculation results of five real-life wells are consistent with the actual production data. And the scope of the fracture accumulation system along with the fracture parameters is determined by means of log interpretation or some other procedure.