Keywords: 
• horizontal well /
• affecting factors /
• water injection effect feature /
• decline analysis /
• development effect

Abstract: Since the beginning of scale development of horizontal wells in Changqing Oilfield, as the development supporting technologies have become more and more mature, the single well production of horizontal well has greatly improved, and the difficult-to-produce reserves have been effectively employed. However, the problems such as quick decline and large variation in production of some horizontal wells have also occurred. Block L 1 in Jiyuan Oilfield, which is the typical block where the scale horizontal well development of low-permeability reservoir in Changqing Oilfield, has been taken as an example. In light of the analysis on static data and dynamic production data, the affecting factors of productivity, water injection effect feature and effect cycle of horizontal wells in initial stage of production have been summarized. Through the analysis on the change law and decline law of water content of horizontal well and vertical well as well as the water content and decline feature under different effect and water breakthrough of horizontal well, the main factors which affect the development effect of horizontal wells in initial stage and later period have been determined, so as to bring forth the corresponding countermeasures for such problems. The research has the guiding significance for improving the development effect of horizontal well in similar low-permeability reservoir.