| Fu Yang Oil Layer of Daqing Placanticline is located in Formation of Lower Cretaceous formation in the lower Cretaceous.Fu Yang Oil Layer is a low porosity and low permeability sandstone reservoir.Its permeability is ranged from 0.5 to 2mD.In this paper,we take Fuyang advanced water injection development experimental zone of Gaotaizi oilfield in M block of Daqing Placanticline in Songliao Basin for research object.We focused on the geological adaptability of this technique.We analyzed the technical policy of advanced water injection in Fu Yang Reservoir,evaluated the development effects of advanced water injection,and proposed the development and adjustment countermeasure.Achievements and knowledge acquired by investigation and application are as follows.(1)Technology limit research of advanced water injection technology in ultra-low permeable sandstone reservoir mainly consider following points:reasonable well pattern well spacing,reasonable bottom-hole pressure and reasonable formation pressure level.Well spacing generally is ranged from 200 to 300m.Bottom-hole pressure of oil well should not lower than 70.0%of original saturation pressure.The bigger of the oil mobility,the lower the reasonable formation pressure level.(2)Attributes of Fu Yang Oil Layer in M block of Gaotaizi oilfield are as follows.Natural fractures are not developed.Porosity and permeability are low.Radius of throat is small.Flow resistance and threshold pressure gradient are big.Pressure conduction velocity is small.Pressure sensitivity is strong.Therefore,it is appropriate to operate the advanced water injection technology in this oil layer.But the water sensitivity of reservoir is more than moderate.Therefore,it is necessary to optimize the advanced water injection technology of the oil layer with strong water sensitivity during water injection.(3)Technical policy of advanced water injection for Fu Yang Oil Layer was investigated by percolation theory,reservoir numerical simulation method and production dynamic evaluation.Results show that,water intake per unit thickness is 150m3,advanced water injection multiples of pore volume is 0.02PV?0.04PV,advance water injection period is 60?80 days,reasonable injection production ratio is 1.6,reasonable liquid production rate is 3.0%,reasonable oil production rate is 1.2%.(4)The optimal values of M block calculated by reservoir engineering method are as follows.Well spacing density is 27 wells per km2,well spacing is lower than 350m,and row spacing is lower than 150m.Actual well spacing is 300m,actual row spacing is 80m,and actual well spacing density is 37.93 wells per km2.The balance between sand body and well pattern is good,but the row spacing is low,well spacing density is too big.These conditions could lead the bad economic effect.Row spacing could be expanded to 100-150m according to the development scale of sand body when developing the remaining reserves.(5)The average wellhead injection pressure of injection well of Fu Yang Oil Layer in M block is 16.72 MPa,there is a certain pressure space.In current period,average oil well flow pressure is 2.74 MPa.It is lower than the reasonable value.At present,formation pressure is 18.17 MPa.It is lower than reasonable formation pressure.Although advanced water injection technology was adopted in M block,the effective drive relationship is still not fully established between oil and injection wells.In order to improve injection-production connecting relations between oil and injection wells,to keep development effect,it is necessary to take some action to M block.Technology limit of advanced water injection technology,which is raised in this paper,could be applied to Daqing Placanticline Fu Yang oil layer and bad natural fracture development,high crude oil viscosity and low mobility,low porosity,ultra-low permeability reservoir. |
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