Study On The Variation Of Development Index And The Affecting Factors Of Ultra-high Water Cut Stage In Sazhong Zone

Entering the development period of ultra-high water cut and the production decline, Sazhong Development Zone is faced with some serious problems such as the superior difficulty of tapping residual oil, the intensified reserve-production balance contradiction, the large water consumption, the high Hydraulic oil ratio and the Invalid injection-production cycle. Therefore, comprehensive technical adjustment and development effect evaluation is of great significance in oilfield.We study the water cut rising law of Sazhong Development Zone by well pattern. Concerning the theoretical base of water displacement, the upwarping of water flooding curve can be attributed to the difference between the theoretical assumption and the real variation in ultra- high water cut period of oil- water relative permeability ratio. In this paper, the affecting factors of upwarping time is also studied. Furthermore, we optimized the water flooding curve by well pattern and summarized the impact factors of water cut variation. To study the production decline law, we optimized the production decline curve of each set of well pattern and analyzed the influence factors of production decline rate. As for the well pattern without decreasing production, generalized Wengcycle model is suitable for fitting and prediction.In order to overcome the limitation of displacement performance and production decline curve in development index forecast, we adopts a combined method to accomplish the development index prediction more precisely: get the simultaneous equations of different water flooding displacement performance and production decline model through theoretical derivation; then put the optimum water flooding curve and production decline model for each set of well pattern into the combined solution model to accomplish the development index prediction of all sets of well pattern. As for the well pattern without decreasing production, use the simultaneous equations of generalized Wengcycle model and the water driving displacement performance when predicting the development index. Comparisons of the fitting accuracy of various prediction model show that the combined solution model is better than both of the separate models for the better applicability and lower predication error in each set of well network.Due to the complicated injection-production relationship of all sets of well pattern underground, the geological reserves of every set of well pattern is difficult to split. Faced with this special case, we can evaluate the recoverable reserves of different well pattern using the dynamic tracing prediction method to accomplish the development index along with the introduction of apparent increasing rate of water cut and apparent oil production rate. As the oil field development statistics show, after one set of well pattern being put into production, the effectiveness of conventional stimulation treatment is not obvious. So it’s reasonable to consider the recoverable reserves of every set of well pattern as approximately stable. Therefore, it’s feasible to use the various kinds of curves based on the apparent oil production rate when predicting development index.