摘要
伊拉克米桑油田位于扎格罗斯山前构造挤压带,油田地面地雷密布。为了解决井场建设难题及提高单井产量,设计采用直井段钻穿盐膏层后,采用水平井钻盐下易漏、易塌裂缝性石灰岩及白云岩地层开发Mishrif层位,形成了一套针对米桑油田裂缝性地层的非标井眼水平井钻井技术。结果表明:①米桑油田在最小地应力方位坍塌压力最低,定向钻进方位选择最小水平主应力方位最利于井壁稳定;②"AQUA-MAX钻井液体系"具有高效封堵能力,使用后有效提高了地层承压能力,拓宽了安全钻井的密度窗口,极大延伸了水平段安全作业长度,可有效抑制盐下裂缝性地层井段的井漏和井塌;③优选钻进排量、转速等钻井参数,优选钻井工具,合理控制钻井液密度,准确控制井底当量密度在安全当量密度窗口范围之内,可有效防范井漏和卡钻的风险。结论认为:该非标井眼水平井钻井技术克服了地层压力窗口窄、裂缝性地层岩性复杂、非标小井眼窄间隙环空作业等技术难题,降低了井下复杂情况和事故的发生,大幅提高了钻井效率。
Located at a piedmont structural compression zone of Zagros Mountains,Missan oilfield in Iraq is scattered with mines.In order to solve difficulties to construct well sites and improve production of single well,a set of horizontal-well drilling technologies with non-standard borehole was developed for fractured formations in this field,such as running horizontal hole in presalt leaky and collapsible fractured limestones and dolomites to develop Mishrif Formation after drilling through salt and gypsum layers by vertical hole.Results show that(1)in this field,its collapse pressure along the direction of the minimum in-situ stress is the lowest,so selecting the direction of the minimum horizontal principal stress as directional drilling one is the most favorable for borehole stability;(2)a drilling-fluid system called AQUA-MAX is capable of high-efficient plugging.After its application,the tolerable formation pressure is increased effectively,the safety density window of drilling mud is broadened,and the limit length of horizontal section for safe operation is extended extremely,so that both circulation loss and borehole collapse can be prohibited effectively;and(3)some risks of circulation loss and pipe sticking may be prevented effectively by optimizing two parameters of drilling displacement and rotation speed,selecting drilling tool,reasonable controlling drilling-fluid specific gravity,and keeping bottomhole equivalent density within safety window.In conclusion,the application of horizontal-well drilling with non-standard borehole may tackle several technical challenges of narrow window of formation pressure,complex lithology in fractured formations,and narrow annulus operation in non-standard slimhole,reduce occurrence of downhole complexities and accidents,and improve drilling efficiency a lot.
作者
陈国军
Chen Guojun(Drilling and Completion Engineering Technology Department of Drilling Division,China Oilfield Services Limited,Tianjin 300450,China)
出处
《天然气勘探与开发》
2020年第2期45-52,共8页
Natural Gas Exploration and Development
关键词
伊拉克米桑油田
裂缝性地层
非标井眼
水平井
井漏
卡钻
Missan oilfield in Iraq
Fractured strata
Non-standard borehole
Horizontal well
Circulation loss
Pipe sticking
