摘要
碳酸盐岩地层钻井中,重力置换气侵时常发生,会对井底压力产生影响,若控制不当,重力置换气侵则会引起井喷事故。根据气-液两相流理论,建立了井筒气侵计算模型及气侵边界条件和初始条件;通过对井底不同进气量模拟,得到了重力置换气侵井底压力、泥浆池增量及井筒不同深度含气率的变化,得到了井口回压对重力置换的影响;通过改变边界条件,得到了重力置换气侵转变为欠平衡气侵时井筒流动参数的变化。研究认为,当井底压力控制不当时,重力置换气侵会转变为欠平衡气侵,井底压力、泥浆池增量和井底含气率会发生突变,造成井筒压力失控,对过平衡钻井重力置换气侵认识及控制具有指导意义。
During the drilling process of carbonate formation, gravity replacement often causes gas kicks which affect the bottomhole pressure. Improper control of gravity-replacement gas kick may lead to blowout accident. In this study, the theory of gas-liquid two- phase flow was followed to establish a wellbore gas kick model and set up boundary and initial conditions of gas kick. Bottomhole gas kick was simulated at different rates to obtain bottomhole pressure, mud pit increment, gas void changes at varying depths, and the influence of wellhead backpressure on gravity replacement gas kick. The boundary condition of gas kick was adjusted to examine the changes in wellbore flow parameters when gravity-displacement gas kick transforms to underbalanced gas kick. The results suggest that when bottomhole pressure is controlled improperly, gravity-displacement gas kick will transform to underbalanced gas kick with sudden changes in bot tomhole pressure, mud pit increment, and bottomhole gas fraction, leading to the out of control over wellbore pressure. This research provides reference data for understanding and controlling of gravity-displacement gas kick during overbalanced operations in carbonate formation.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2014年第5期958-962,共5页
Acta Petrolei Sinica
基金
国家重大科技专项子课题"窄密度窗口安全钻井技术与配套装备"(2011ZX05021-003)
国家自然科学基金项目"深层碳酸盐岩地层与井筒耦合作用机理与压力自动控制方法"(No.51274221)资助
关键词
重力置换气侵
欠平衡气侵
井底压力
泥浆池增量
气液两相流
gravity replacement
underbalanced gas kick
bottomhole pressure
mud pit increment
gas-liquid two-phase flow
