河流相致密砂岩气藏剩余气精细表征及挖潜对策——以苏里格气田中区SSF井区为例

Fine characterization and potential tapping countermeasures of remaining gas in fluvial tight gas reservoirs:A case study of the SSF well block in central Sulige gas field

苏里格河流相致密砂岩气藏自投入开发以来,由于不同层位、不同位置地层压力的不均匀下降造成了储量动用不均衡,井间及层间存在大量剩余气资源。为提高气藏储量动用程度和天然气采收率,开展了精细储层构型表征、高精度三维地质建模和气藏数值模拟一体化研究,剖析了河流相致密砂岩储层剩余气形成机制及控制因素,建立了剩余气赋存模式,提出了针对性的挖潜对策。研究结果表明:(1)在单一辫流带/曲流带识别基础上,利用直井、定向井资料,定量刻画单砂体内部构型特征,研究区心滩平均宽度450 m,平均长度1040 m;点坝平均跨度950 m,平均宽度1100 m;落淤层平均宽度340 m,平均长度620 m,厚度0.2~0.8 m,倾角0.07°~0.37°;侧积层厚度0.2~0.8 m,倾角3°~7°。(2)分析了河流相致密砂岩储层中3类阻流单元及其对天然气渗流的阻流作用,并将研究区剩余气富集模式划分为:阻流型、井网未控制型、射孔未采出型、未射孔型4种。(3)针对阻流型剩余气采用重复压裂、钻加密井挖潜,针对井网未控制型采用老井侧钻、钻加密井挖潜,针对射孔未采出型采用气井精细化管理、排水采气挖潜,针对未射孔型采用查层补孔挖潜。(4)基于剩余气精细综合表征结果优化部署直井2口,水平井8口,完钻2口水平井测试地层压力平均为28.2 MPa,验证了井网未控制型剩余气的存在。结论认为,所提出的河流相致密砂岩气藏剩余气精细表征方法和挖潜对策,有助于提升气田天然气储量动用程度和采收率,为气藏的经济高效开发提供了技术支撑。

Since the fluvial tight sandstone gas reservoir in the Sulige gas field was put into development,uneven drop of formation pressure in different layers and locations has led to uneven reserve recovery,so there is a large amount of residual gas between wells/layers.In order to improve the recovery efficiency and natural gas recovery,this paper presents an integrated research of fine reservoir configuration characterization,high-accuracy 3D geological modeling and gas reservoir numerical simulation.Then,the formation mechanism and control factors of residual gas in fluvial tight sandstone reservoirs are analyzed,and the occurrence model of residual gas is established.Finally,the targeted potential tapping countermeasures are proposed.The following research results are obtained.First,based on the single braided/meandering zone identified,single sand body and internal architecture of single sand body were quantitatively depicted by using the data of vertical and horizontal wells.It is found that,in the study area,the mid-channel bars are 450 m wide and 1040 m long averagely;the point bars are 950 m wide and 1100 m long averagely;the fall-siltseams are 340 m wide and 620 m long averagely,with thickness of 0.2-0.8 m and dip angle of 0.07-0.37°;and the lateral accretion layers exhibit the thickness of 0.2-0.8 m and dip angle of 3-7°.Second,three flow blocking units in the fluvial tight sandstone reservoir and their blocking effects on natural gas flow are analyzed.The remaining gas enrichment in the study area can be divided into four types:flow blocking type,uncontrolled well pattern type,perforated but unproduced type,and non perforated type.Third,it is suggested to apply refracturing and infill well drilling to tap the potential of flow blocking type residual gas,old well sidetracking and infill well drilling to the uncontrolled well pattern type,fine gas well management and drainage gas recovery to the perforated but unproduced type,and layer checking and reperforating to the non perforated type.Fourth,based on the fine comprehensive residual gas characterization results,2 vertical wells and 8 horizontal wells are optimally deployed.The tested formation pressure of 2 completed horizontal wells averages 28.2 MPa,which confirms the existence of the uncontrolled well pattern type residual gas.In conclusion,the proposed fine characterization method and potential tapping co untermeasures of remaining gas in fluvial tight sandstone gas reservoirs are conducive to improving the recovery efficiency and recovery factor of gas fields,and can provide a technical support for the cost ef fective and efficient development of gas reservoirs.