摘要
针对大港油田歧口凹陷沙三段泥页岩地层钻井过程中井壁失稳频发的问题,综合运用XRF、XRD、地层压力测试及钻井液评价等技术,揭示了井壁失稳的主控因素并提出优化对策。结果表明:(1)低Ca(Ca含量4.2%~5.1%)、高Fe(Fe含量3.5%~4.7%)、低Al(Al含量5.7%~7.0%)的元素组合易诱发井壁失稳;(2)基于元素与矿物特征构建的脆性指数模型表明,掉块段脆性指数显著高于非坍塌段,高脆性是诱发井壁失稳的内在关键因素;(3)当碳酸盐矿物含量较低(18%~23%)、黏土矿物含量中等(23%~40%)、石英含量较高(25%~40%)时,坍塌风险升高,在此基础上,伊利石含量超过50%时,坍塌风险进一步升高;(4)降低井斜角并沿最小水平主应力方向钻井可提升稳定性;(5)钻井液实验显示,水基钻井液体系(BH-KSM、BH-WEI)掉块段较非坍塌段页岩膨胀率高出1.43%~3.84%,滚动回收率降低17.85%~18.30%,而油基钻井液体系(BH-OBM)对两类岩屑均展现出优异的综合性能,其在掉块段引发的最大膨胀率仅1.41%左右,回收率损失平均约2.50%,抑制作用效果较好,现场推荐优先级为BH-OBM>BH-KSM>BH-WEI。研究成果为歧口凹陷页岩油安全高效开发提供了理论依据与技术支撑。
To address the frequent wellbore instability issues during drilling in the mud shale formations of the third Member of Shahejie Formation in Qikou Sag,Dagang Oilfield,this study comprehensively employs techniques such as XRF,XRD,formation pressure test,and drilling fluid evaluation to reveal the main controlling factors of wellbore instability and propose optimized countermeasures.Key findings are obtained in five aspects.First,an elemental combination of low Ca content(4.2%-5.1%),high Fe content(3.5%-4.7%),and low Al content(5.7%-7.0%)is prone to inducing wellbore instability.Second,the brittleness index model constructed based on elemental and mineral characteristics indicates that the brittleness index of the block-falling section is significantly higher than that of the non-collapsing section.High brittleness is an intrinsic key factor inducing wellbore instability.Third,when the content of carbonate minerals is low(18%-23%),that of clay minerals is medium(23%-40%),that of quartz is high(25%-40%),the risk of collapse significantly increases.On this basis,when the illite content exceeds 50%,the risk of collapse increases.Fourth,Reducing the hole deviation angle and drilling along the direction of the minimum horizontal principal stress can enhance stability.Fifth,drilling fluid experiments show that the water-base drilling fluid systems(BH-KSM BH-WEI)has a shale expansion ratio in the block-falling that is 1.43%-3.84%higher than in the non-collapsing section,with a decrease of 17.85%to 18.30% in rolling recovery rate,while the oil-base drilling fluid system(BH-OBM)exhibits excellent overall performance for both types of rock cuttings,the maximum expansion ratio caused by it in the block-falling section is only about 1.41%,and the average recovery ratio loss is about 2.5%,indicating a good inhibitory effect.The recommended on-site priority is BH-OBM>BH-KSM>BH-WEI.The findings provide a theoretical basis and technical support for the safe and efficient development of shale oil in Qikou Sag.
作者
沈文洁
张雨欣
尹磊
于春勇
段善府
邵慧
SHEN Wenjie;ZHANG Yuxin;YIN Lei;YU Chunyong;DUAN Shanfu;SHAO Hui(No.1 Mud Logging Company,BHDC,CNPC,Tianjin 300280,China;Tianjin Gas Storage Company,PetroChina Dagang Oilfield Company,Tianjin 300074,China)
出处
《录井工程》
2025年第4期130-137,共8页
Mud Logging Engineering
关键词
歧口凹陷
泥页岩
井壁失稳
地层压力
钻井液评价
Qikou Sag
mud shale
wellbore instability
formation pressure
drilling fluid evaluation
