Study On Technical Policy Of Horizontal Well Adjustment Measures Of Positive-rhythm Secondary Bottom-water Reservoir L2

L2 reservoir is exploited by water flooding.After 40 years of water flooding,it has entered a period of high water cut.The main problems are low reserves utilization in upper rhythm section,dispersed residual oil between wells,rapid water cut rise after water breakthrough in horizontal wells,high water cut in single wells and low oil recovery rate.Therefore,through the study of water invasion law and horizontal well adjustment technology policy,it provides the basis for later horizontal well adjustment and has certain guiding significance for oil field production.This paper calculates and evaluates reservoir development indices by reservoir engineering theory and method from the aspects of water cut change law,production decline,energy condition evaluation,applicability of injection-production well pattern and oil recovery prediction.Based on the geological conditions of the reservoir,a numerical simulation model reflecting the basic characteristics of the reservoir is established to study the water invasion characteristics.Several theoretical methods are used to calculate the critical production and water breakthrough time of horizontal wells.Through the establishment of horizontal well model,the influence of horizontal well pattern,horizontal position,well trajectory,interlayer permeability,horizontal section length,liquid production rate,injection horizon and injection-production ratio on the water cut rise law of horizontal wells is studied.According to the development characteristics of positive rhythm secondary bottom water reservoir,the adjustment technology of horizontal wells in later stage of reservoir development is studied.The study of water invasion law shows that water injection and natural edge water in L2 reservoir advance along the bottom high permeability section preferentially in the development process,which makes L2 reservoir evolve into secondary bottom water reservoir.In the same rhythm layer,horizontal wells should be completed in the upper part of the structure,and the trajectory of the wellbore is parallel to the structure line.When there is an effective interlayer,it can block the rise of bottom water.The choice of the length of horizontal section is mainly based on economic considerations,which has little influence on the law of water invasion of edge and bottom water.Lower liquid production rate can be used in the early stage,and better results can be obtained in the high water cut stage.In the initial stage of branch well adjustment,higher fluid production rate can be used to maintain higher single well oil production rate,while in the middle and later stages,lower fluid production rate can be used to control water cut and reduce development costs.Horizontal well dual-pipe co-production has a good restraint effect on bottom water ridge entry.The well should be located in the high part of the structure as far as possible during well placement.In the initial stage of adjustment,higher liquid production rate should be adopted to obtain larger oil production.In the middle and later stages,lower liquid production rate should be adopted to control development cost.At the same time,the maximum drainage-production ratio should be controlled at 2:1,and the drainage layer should be close to the oil-water interface.