Study On The Classification And Development Technology Limits Of Low Permeability Reservoirs In The Eastern Part Of Xingliu District

The eastern part of Xingliu District was put into development in 1966,in which the off-balanced reservoirs were not used in large scale,and the reservoirs were poorly developed and difficult to mine.From the core data,they were jointly developed with the in-situ reservoirs and were inter-layer and intra-layer interference.The impact is large,resulting in no water washing or water washing thickness is small.At present,due to the type of sedimentary genesis of the off-surface reservoirs and the mobilization characteristics of different sand body types,effective development techniques are not formed,which restricts the development adjustment and effect evaluation of the off-balanced reservoirs.Therefore,it is necessary to carry out research on off-balance-sheet reservoir classification and development technology boundaries to guide the adjustment of three well patterns based on off-balance sheet reservoir development.In this paper,the core well data is used to analyze the characteristics of the surface reservoir permeability,porosity,thickness and oil content of the test area.Finally,the thickness of the extra-surface reservoir and the contact relationship between the off-surface reservoir and the surface reservoir are selected.These two parameters are used as the classification indicators of the off-balance layer reservoirs,and the off-balance-sheet reservoirs are divided into five types:breachover flooding type,variable intrusion type,extended gradient type,stable sand mat type,and independent scattered type.On the basis of the establishment of geological model and the history of water flooding,the utilization status of different sedimentary units was analyzed.The current mining degree of the whole area was 37.74%,of which the in-process extraction degree was 37.79%,and the off-balance sheet mining degree was 34.48%.The remaining oils in the region are divided into five types,namely,water absorption difference and interlayer interference type.The main types are the imperfect mining and retention type and the remaining area,and the remaining geological reserves are 104.61×10~4t and 102.33×10~4t,respectively.The remaining geological reserves are 41.99%and 41.08%.The numerical simulation method was used to study the technical limits of different types of off-balance reservoirs.It was clarified that the reasonable formation pressure of different types of off-balance reservoirs was between 8.5MPa of reservoir saturation pressure and 9MPa of original formation pressure.The reasonable water injection strength of different types of off-balanced reservoirs under different oil recovery rates is clarified.For example,the optimum sand injection rate is not less than 0.10%,0.15%,and 0.20%.It is 1.0 m~3/m/d,1.5 m~3/m/d,and 2.5 m~3/m/d.The optimum injection-production ratios of different types of off-balance-sheet reservoirs from different stratum pressure levels to reasonable formation pressures are clarified.Taking stable sand mats as examples,recover from 7.0MPa,7.5MPa,8.0MPa to reasonable formation pressure 8.5MPa.The optimal injection-production ratios are 1.03,1.06,and 1.08,respectively.