Low Permeability Gas Tibet Ultra Overbalanced Put Into Theoretical Research

The novel technique of extreme overbalance perforating(EOP) was evolved in 1990's,field application has been broadened greatly abroad because of its dramatic and cost-effective improvement in initial well productivity, but less applications in China because of lacking of theoretical foundations. Although underbalance perforating is widely used and accepted as an industrial standard, it applicability decreases, however, with a decline in reservoir pressure, permeability or rock strength, where exetreme overbalance perforating can sidestep these problems as a complemental technique. In order to put this new technique (EOP job) into practice more effectively in China and benefit from it, It is very necessary to launch a program to study the characteristics, influencing factors and mechanism of extreme overbalance perforating, accordingly, get the way of designing of EOP job. Incorporating with productivity analysis and economic evaluation, the EOP field operations will be guided reasonably and effectively and the maximum benefit could be expected.Based on its suitability analysis for low permeable gas formations and fracture initiation study, the characteristics and mechanism of extreme overbalance perforating have been addressed in this paper. The design method for operational parameters of EOP has also been proposed after numerical modeling of wellbore flowing and fracture propagation during EOP process. The oilfield application shows good results according to well test interpretation and it is very helpful in oil productivity enhancement.