Analysis On Production Performance And Research On Influencing Factors Of Sweep Efficiency Of Steam Flooding In Block Qi40

Block Qi40 of Liaohe oilfield is the first international pilot test reservoir of mid-deep heavy oil steam flooding,but compared with other heavy oil reservoirs at home and abroad,reservoir is buried deeply,about-622 to-1050m,so there is no mature experience of steam flooding to learn.Steam sweep efficiency is a key factor affecting steam flooding recovery for steam flooding reservoir,how to improve steam sweep efficiency becomes the key to improve steam flooding recovery.In this paper,production performance and influencing factors of sweep efficiency of steam flooding in block Qi40 are researched,the development effect of steam flooding in the block is tracked in real-time,main influencing factors of steam swept volume are analyzed,the potential to improve steam swept volume is predicted,how to improve steam swept volume is studied.to improve development effect of steam flooding,reliable theoretical basis for steam flooding of block Qi40 and similar reservoir is provided,so the subject has important practical significance and scientific value.The main research works are as follows:Production performance changes of steam flooding of the overall and regional well groups in block Qi40 were analyzed in detail by investigating a large number of production data.Results showed that 138 steam injection wells and 650 oil wells are opened,daily steam injection is 14325t,daily oil output is 1820t,instantaneous production injection ratio is 0.9,oil-steam ratio is 0.13 by the end of 2011.Among them,production effect of steam flooding of 65 well groups in main area is relatively good,the average number of active wells is 264,the average composite water cut is 84%,the average oil-steam ratio is 0.2,but 65 well groups has entered production decline stage.the output of 74 well groups in the edge stabilize at 870t/d basically,the average number of active wells of steam flooding is 310,the composite water cut has fallen steadily from 90%to 84%,the integrated oil-steam ratio increase from 0.1 to 0.15,the effect of steam flooding is improved gradually,74 well groups are in stable stage of steam flooding.Proceeding from development practice of heavy oil steam flooding in block Qi40 of Liaohe oilfield,production characteristics in different stages and the impacts of various factors on development law of heavy oil steam flooding in block Qi40 were analyzed.According to production performance and tracking result of numerical simulation,stage division standard of steam flooding process in block Qi40 is established.Steam flooding effect of different sedimentary microfacies is obtained:underwater distributary channel>interdistributary>frontal thin sand layer.strong heterogeneity of block Qi40 cause that the difference of steam extension speed of different direction in displacement process is bigger,oil layers don't absorb vapor bisically when longitudinal permeability contrast is greater than 4,vapor absorption difference is larger.the development effect of structural updip direction is better than that of structural downdip direction,the development effect of well groups is best when structural dip is less than 10°.the higher the steam stimulation recovery percent is,the less the interwell remaining oil is,the less the output in steam flooding stage is,the poorer the development effect is.steam flooding law is obvious for well groups which are qualified to layered steam injection,oil-steam ratio is more than 0.5,good steam flooding effect can be obtained.The impacts of various factors on steam swept volume and development effect were studied by the base model of steam flooding in block Qi40.Results showed that steam swept volume,recovery percent and oil-steam ratio increase gradually as permeability variation coefficient of positive rhythm reservoir incerases,when permeability variation coefficient is more than 0.7,swept volume,recovery percent and oil-steam ratio decrease.as permeability variation coefficient of reverse rhythm reservoir increases,steam swept volume,recovery percent and oil-steam ratio decrease gradually.As reservoir dip angle increases,steam swept volume of updip direction increases,steam swept volume of downdip direction and total swept volume decrease,steam breakthrough speeds up.As dip angle increases,recovery percent decreases and production time is shortened gradually until steam breakthrough occurs.As interlayer thickness increases,steam swept volume,recovery degree and oil-steam ratio decrease gradually,steam breakthrough is later,breakthrough speeds up when interlayer thickness is more than 8 meters,the development effect without interlayer is worse than which with it.Regardless of reservoir interlayer,steam swept volume is the largest,the corresponding recovery percent and oil-steam ratio are the hightest when lower 1/3 position is perforated.The stronger the plane permeability anisotropy is,the smaller the steam swept volume is,the lower the recovery percent and oil-steam ratio are,the poorer the development effect is.The more the layered steam injection series is,the larger the steam swept volume is,the better the development effect is.According to production performance of steam injection test area,the methods like detailed geologic modeling and history matching of numerical simulation were used to simulate steam flooding of typical well groups in the west,north and south of test area.Results showed that due to well pattern,well spacing,structural dip angle and physical properties,plane steam sweep efficiency of western,northern and southern well groups are 48.7%,32.6%and 39.33%respectively.Due to effective reservoir thickness,structural dip angle,perforating thickness and vertical physical properties,vertical steam sweep efficiency of western,northern and southern well groups are 31.2%,19.8%and 25.7%respectively.Steam volume sweep efficiency of western,northern and southern well groups are 15.19%,6.46%and 10.11%respectively at present.Poor producing reserves are mainly distributed in parts of low structure,poor vertical physical properties and below perforated interval.By predicting,final steam volume sweep efficiency of western,northern and southern well groups can reach 43.9%,52.54%and 59.66%respectively.Due to vertical steam absorption effect,the thicker the reservoir is,the smaller the steam swept volume is.Moreover,the thinner the reservoir is,the larger the steam swept volume is at the end of steam flooding.