The Study On Law Of Water Cut And Remaining Oil Distribution Of Horizontal Wells In Jiaowei Formation Of WZ11-1 Oilfield

The reservoirs of Jiaowei Formation in WZ 11-1 oilfield are divided into east and middle blocks by the faults,and the east block is driven by edge water and the middle block is driven by bottom water,and the two have independent oil-water interface,which belongs to two reservoirs.In the east block,two sets of high resistivity and low resistivity layers are developed vertically,while only one of low resistivity layer is developed in the middle block.The main problem is that the horizontal wells in the low resistivity layers produced water in the beginning stage of production,the law of water-cut is very complicated and have obvious differences in different wells.Aiming at the above problems,this paper detailedly analyzes the types of water cut by reservoir engineering,describes the controlling factors that affect the water cut of horizontal wells and explains the causes of different types of water cut by numerical simulation.On this basis,the main controling factors and distribution law of remaining oil are analyzed and the effective adjustment recommendations are proposed.The paper points that there are three kinds of water cut rising types of horizontal wells at the effect of edge water,bottom water and movable water,which are slow-rapid rising type,rise-down-rising type,rapid rising type.The factors that affect the law of water cut in horizontal wells include the reservoir heterogeneity,interlayer and the distribution characteristics of the inital fluid.The heterogeneity of horizontal wells is the main factor to affect the water cut law,there are significant differences in the shale content,irreducible water saturation,seepage capacity between different reservoir types;The interlayers are divided into calcareous,muddy and physical.The distribution of calcareous interlayer at the oil-water interface is large and consecutive,which has important influence on the law of water cut.Through the analysis of reservoir forming force,the distribution characteristics of initial fluid are defined.The initial water saturation of the low resistivity layer is far greater than the irreducible water saturation,and it is proved that the movable water exist in the low resistivity layer,which is effectively explaining the initial water cut problem of the reservoir.The paper points that according to the partition of the relative permeability curves and the establishment of the initial water saturation distribution by using J function,the accuracy of historical fitting is improved.Based on numerical reservoir simulation,three kinds of rising pattern of water cut of horizontal wells are determined: edge water propulsion pattern,movable water production pattern,bottom water coning pattern.Based on numerical reservoir simulation,the distribution of remaining oil is predicted.The control of the remaining oil is clarified by the factors such as heterogeneity,micro structure,reservoir type,interlayer and well pattern.The remaining oil is mainly enriched in the favorable facies of the main body of the foreshore sand dam.Finally,the adjustment measures such as raising liquid in the east block and arranging new horizontal wells in the middle block are put forward to improve the development effect.