Abstract:

The Chang 6₃ reservoir in Jiyuan oilfield is an ultra-low permeability reservoir. As an effective displacement pressure system is difficult to form in the existing well pattern and the reservoir tends to be depleted, it is urgent to evaluate the injection-production effect of the existing well pattern and provide technical support for subsequent adjustment on well pattern infilling. Therefore, nine indexes for evaluating injection-production effect were selected, including reserves control degree of water flooding, pressure maintenance level, injection-production static pressure difference, flood response ratio, water breakthrough ratio, single-well productivity over two years, reserves producing degree of water flooding, sweep coefficient of water flooding, and dynamic recovery rate. Comprehensive weights were introduced to establish an injection-production effect evaluation model for well pattern in ultra-low permeability reservoirs based on unascertained measurements, helping to evaluate the injection-production effect of Chang 6₃ reservoir in the study area. The evaluation results show that the injection-production effect of the well pattern in this reservoir is poor, and the well pattern needs to be adjusted immediately. The evaluation results are consistent with the current production status of the reservoir, which proves the accuracy of the evaluation model, and provides a new idea or method for evaluating injection-production effect of existing well pattern in ultra-low permeability reservoirs.

Key words: Jiyuan oilfield, Yanchang formation, ultra-low permeability reservoir, well pattern, injection-production effect evaluation, analytic hierarchy process, similar weight method, comprehensive weight, unascertained measurement