摘要: |
为探究机械比能理论指导下PDC钻头破岩效率的影响因素,通过简化钻头与地层相互作用模型并推导滑动摩擦系数,结合室内试验分析各因素对钻头滑动摩擦系数的影响。结果表明:钻压通过切削齿的吃入深度影响摩擦系数,当切削齿完全吃入地层所产生的摩擦系数最大;钻速过快导致的岩屑过多且无法有效移除时摩擦系数会减小;转速增加会使摩擦系数减小;不同类型的岩样其最终稳定的摩擦系数不同,但一般在0.4~0.6;钻头直径不会影响摩擦系数最终稳定值;钻进软至中硬地层时,应选取尽量大的钻压和转速,即使较大钻压和转速对于提升破岩效率并无裨益,但却会明显提升机械钻速,此时机械比能增加并不明显,说明钻头能量利用率保持在一个稳定的阶段;钻进较硬地层时,提升钻压、转速水平会明显提高机械钻速,增大机械比能,降低破岩效率,钻头机械能量利用率下降,此时钻进参数的选取就需要综合钻速、机械比能、破岩效率等因素判定。 |
关键词: PDC钻头 破岩效率 滑动摩擦系数 参数优选 机械钻速 机械比能 |
DOI:10.3969/j.issn.1673-5005.2019.05.010 |
分类号::TE 242 |
文献标识码:A |
基金项目:国家科技重大专项(2016ZX05022-002);国家留学基金项目(201806450093);长江学者和创新团队发展计划(IRT_14R58) |
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Experimental study on rock-breaking efficiency of PDC bit based on mechanical specific energy and sliding frictional coefficient |
GUAN Zhichuan1, HU Huaigang1, WANG Bin1, SUN Meiwei2, LIU Yongwang1, XU Yuqiang1
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(1.School of Petroleum Engineering in China University of Petroleum (East China), Qingdao 266580, China;2.Qingdao Shidahuatong Technology Company Limited, Qingdao 266580, China)
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Abstract: |
In order to investigate the influencing factors of the rock-breaking efficiency of PDC bits based on the mechanical specific energy(MSE) theory, a simplified bit-formation interaction model was established and the sliding frictional coefficient was derived, along with the analysis of the effect of various factors on the sliding frictional coefficient based on the relevant experimental results. The results show that the weight on bit (WOB) can exert an effect on the sliding frictional coefficient(μ) value through the depth of cutting, and the μ value becomes the largest when the cutting teeth completely penetrates into the formation. The μ value will decrease when drlling debris cannot be removed effectively due to high rate of penetration (ROP) and when the revolutions per minute (RPM) increases. The μ value will change in different types of rocks, but it is generally in the range of 0.4-0.6. The diameter of the drill bit has little effect on the stable μ value. When drilling in soft to medium hard strata, maximum WOB and RPM should be applied, even if it is not beneficial to enhance the rock-breaking efficiency. Large WOB and RPM will significantly improve the ROP, meanwhile the MSE value will not increase obviously, indicating that the energy utilization rate of the drill bit remains in a stable stage. When drilling in harder strata, reducing WOB and RPM will obviously improve the ROP. It can also increase the MSE, reduce the rock-breaking efficiency and decrease the mechanical energy utilization rate of the bit. The selection of optimal drilling parameters needs take ROP, MSE, rock-breaking efficiency and other factors into consideration. |
Key words: PDC bit rock-breaking efficiency sliding frictional coefficient parameters optimization rate of penetration mechanical specific energy |