According to the development of fissures and karsts

Jiyang depression can be divided into four types of arched-extension fold

fractured-block fault

weathered- remaining hillock and multi-phases structure composite. Reserving space for the first and second type above mentioned are mainly fissures- dissolution cavities

electric resistances in both flanks of reserving intervals are lower

and time difference of the sound wave often jumps; Space for the third type are karst-remaining hillocks; The fourth type represents features of above multi-compositions. In the lower Palaeozoic in Jiyang depression

reservoirs(bodies) in arched-extension fold type are mainly developed on the weathered crusts of the folded- mountain with evidence of dezoning vertically of the karst effect. In the case of reservoirs in fractured-block fault type covered by the upper Palaozoic roof rocks

the karst belts are developed in stratification and progressing in sequence in large area. In the case of those uncovered by the Upper Palaozoic roof rocks

dissolution cavities

holes and fissures are well developed. Reservoirs in weathered- remaining hillock type are commonly developed on the whole remaining hillock-mountain. Outcrop area in reservoirs in multi-phases structure composite type is a favorable area for the development of reservoir and with the vertical development of the karst belt.