塔河油田缝洞型油藏深井注气提高采收率配套工艺

塔河油田储层深(5500~7000m)、地层压力高(50~60MPa)、非均质性强、流体性质差异大;溶洞是最主要的储集空间,裂缝主要起连通通道作用,缝洞单元是基本开发单元。储集体类型复杂,导致剩余油分布认识不清,主要依靠弹性和水驱开发,采收率较低。对于单井缝洞单元而言,目前采取的主要手段是注水替油,前期取得良好效果。但随着注水替油轮次的增加,部分井组注采比逐步上升,替油效果逐渐变差,失效井数增加,导致大量剩余油无法采出。特别是钻遇缝洞储集体边部或相对低位置的油井,其剩余油主要分布在缝洞体的高部位,注水替油效果不明显。考虑到气体注入地层后,在重力作用下向高部位上升,会形成"气顶",排驱原油下移,可有效启动单纯注水无法驱动的"阁楼油"。所以,油田开发后期,采取注气提高采收率技术。在实施注气提高采收率过程中,完善了深井注气的配套工艺,形成了注气-采油一体化井口、注气-掺稀生产一体化管柱、掺稀气举阀、高压气密性封隔器、气水混注工艺设计方法、腐蚀结垢处理方法等一系列配套工艺。2013年1~8月,塔河油田累计实施注气69井次,累计产油5.49×104t。

Matching Technologies of EOR by Gas Injection in Deep Wells of the Fractured Vuggy Reservoir in Tahe Oilfield

Tahe oilfield has the characteristics of deep buried depth （5500-7000m）,high formation （50-60MPa）,serious heterogeneity and great difference among fluid features.Its dominant gathering space is cavern connected with the creaks.Fracture vug unit is the basic development one.Complex reservoir types result in unclear knowledge of the remaining oil distribution.Elastic recovery and water flooding is the main way with low recovery efficiency.Oil displace by water injection is the main way in fracture-vug unit of the single well,and good results achieved at early stage.But along with the times increase of water injection to displace oil,injection-production ratio gradually increased in part of the well groups,and oil displacement ef- fect gradually became poor.The number of failure wells is increasing and a large number of remaining oil cannot be produced.The effect of water injection to displace oil is not obvious especially in the oil wells drilled at the edge of fracture-vug reservoirs or relatively low position for their remaining oil mainly dis- tributes at the high position of the fracture-vug reservoirs.When the gas is injected into the formations,gas cap may be formed under the action of gravity at the high place and drive crude oil down ,which can effectively start the ＂attic oil＂ that water injection can＇t drive.So gas injection may improve the recovery efficiency in late oilfield development.During the process of gas injection,matching technologies of gas injection in the deep wells is improved and a series of technologies is formed：integrated gas injection-oil production well head,integrated string of gas injection-mixed with light oil production,gas lift valve of light oil mixed with, high pressure air tight packer,design method of gas-water mixed injection technology and treatment for colrosion and scaling.From January to August in 2013,the gas injection was implemented for 69 well-times totally and cumulative oil production was 5.49×10 4t in Tahe oilfield.