Study On Displacement Characteristics In Extra High Water Cut Stage Of Sazhong Development Zone

After years of development,Sazhong development zone of Daqing oilfield has entered the period of extra high water cut and the output is decreasing year by year.For now,some development problems were very serious such as low water utilization efficiency,great difficulty in finding residual oil,production declining rapidly.So water injection adjustment,remaining oil identification,production index prediction and development effect evaluation have become the focus of oil field workThis paper starts with the relative factors of permeability,taking into account the characteristics of high water cut stage,large water injection and low water injection utilization rate,and the relative permeability changes of oil and water in high water cut stage under long term erosion are studied emphatically.Also the effects of long-term erosion,pressure gradient,petrological characteristics and clay minerals on relative permeability curves are analyzed.By the time,the influencing factors of water content change in extra high water cut stage are analyzed from two aspects of Geology and development and the study shows that high permeability zone and heterogeneity are the main factors affecting the moisture content in the extra high water cut stage.Finally,the influencing factors of displacement characteristics are studied.It is found that displacement velocity,net overburden pressure and two-phase start-up pressure gradient are the main influencing factors of displacement characteristicsBased on a large number of field data,this paper studies on water flooding law of Sazhong development zone in different region.By analyzing the production well history data,it is found that after three times well network adjustment,the oil field enters the extra high water cut stage,and the water flooding law enters a new pattern at this time.This paper takes the extra high water cut stage as the starting point,studying water drive curve in different areas of Sazhong development zone respectively from four aspects.By data fitting and data difference comparison,the water drive curve types in 12 areas of Sazhong development area are selected respectively.By the way of data fitting and data difference comparison,the law of production decline is analyzed in each region of Sazhong development zone.The initial production time in this study was when production began to decrease after the three times well network adjustment.Production measures and influence of the production system were ensured not affect the final data fitting.In this study,production data are fitted from three aspects: exponential decrease,hyperbolic decrement and harmonic decrease.And the data analysis shows that in the extra high water cut stage,the production of each block of the Sazhong development zone decreases exponentially,the law is obvious,and the data fitting is good.In order to get the model of water content and yield change with time,the water drive law curve and production decline curve are combined.According to the types of water drive curves and the types of production decline in each block of Sazhong development zone,the theoretical models of corresponding curves are obtained,and the available water content and yield prediction models are obtained.By comparing the precision of the fitting,it is found that the prediction model obtained by the joint solution has higher prediction accuracy and better adaptability.