Abstract: The II-Class structural units of Carboniferous basement are regionally classified into such framework as one terrace, two uplifts and three depressions, based on data from surface gravity and geomagnetic survey. Between the depression and the uplift is linked by faulted terrace and fracture belt. 275 prospecting wells were drilled here, and 10 medium-sized complete oil-gas fields have been found by 31 wells of them, all of which are concentrated in traps of successive depression-side uplifts (Kz, Mz) on the fault terrace and fracture belt; in traps of non-successive depression-side uplifts (C, P), only 21 oil/gas-yielding isolated points or wells have been discovered, with 160 water wells due to lack of oil-feeding channels linked with hydrocarbon-generating source rocks; 47 dry wells that are drilled in shale between two distributary channels adjacent to the lobate delta and in tuff around the buried hill. It is suggested that 25 locations of 9 IIIClass anticline structural belts are favorable for finding out proved or controlled reserves.

Key words: gravity and geomagnetic anomaly, II-Class structural belt, regional classification, petroleum distribution, regularity, prediction, potential oil-gas field