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| 随钻方位电磁波测井仪器偏心响应模拟及分析 |
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巫振观1,2,范宜仁1,2,王磊1,2,刘家雄1,2,邢涛1,2
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(1.中国石油大学地球科学与技术学院,山东青岛 266580;2.中国石油大学CNPC测井重点实验室,山东青岛 266580)
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| 摘要: |
| 为研究随钻方位电磁波测井仪器偏心响应特征,基于交错网格时域有限差分方法,进行复杂偏心条件下测井响应模拟分析。采用共形网格技术实现复杂边界电导率等效,并通过与半解析解对比,验证算法正确性;进而对比分析仪器居中和偏心条件下电磁场分布特征;讨论不同仪器参数及井眼环境下单发单收结构的测量信号变化规律;最后探讨复杂偏心条件下随钻方位电磁波测井响应特征及方位信号变化。结果表明:油基钻井液和电阻率大于0.5 Ω·m的水基钻井液中随钻方位电磁波响应基本不受仪器偏心的影响;电阻率小于0.1 Ω·m的水基钻井液中,低频长源距测量模式可忽略偏心影响,能够较好地用于地质导向;而高频短源距测量模式受井眼环境影响严重,应当考虑适当的校正。 |
| 关键词: 随钻方位电磁波测井 仪器偏心 三维时域有限差分 共形网格 |
| DOI：10.3969/j.issn.1673-5005.2017.05.008 |
| 分类号::P 631.8 |
| 文献标识码:A |
| 基金项目:国家自然科学基金项目(41474100,8, 41674131)；山东省自然科学基金项目(ZR2013DM015)；中央高校基本科研业务费专项资金(17CX06041);中国石油大学(华东)研究生创新工程(YCX2017004,YCX2015003) |
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| Numerical modeling and analysis of eccentricity effect on borehole response of azimuthal electromagnetic logging while drilling tool |
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WU Zhenguan1,2, FAN Yiren1,2, WANG Lei1,2, LIU Jiaxiong1,2, XING Tao1,2
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(1.School of Geosciences in China University of Petroleum, Qingdao 266580, China;2.CNPC Key Laboratory for Well Logging in China University of Petroleum, Qingdao 266580, China)
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| Abstract: |
| In order to investigate the eccentricity effects of azimuthal resistivity LWD tools,the eccentric response is analyzed based on a staggered-grid finite-difference time-domain(FDTD) method. A conformal grid technology is implemented to obtain the effective conductivity of the complex boundary, and the algorithmis validated by comparing the results obtained by 3D-FDTD with the semi-analytic results. The electromagnetic field distribution is described under the centered and eccentric borehole conditions, and the signal law of dual coils configuration with different tool parameters and borehole environments is analyzed. Finally, the characteristics in the response and azimuthal signals of the LWD tool in eccentric borehole are investigated. The modeling results show that the eccentricity effects can be ignored in oil-based mud drilling, or water-based mud of which the resistivity is larger than 0.5 Ω·m. However, in water-based mud where the resistivity is less than 0.1 Ω·m, the eccentricity effects seem to correlate with the tool parameters. It is concluded that the long spacing and low frequency azimuthal signals can be used in geosteering directly, while the short spacing and high frequency azimuthal signals should be corrected to eliminate the borehole effects. |
| Key words: azimuthal resistivity LWD eccentricity effect 3D-finite-difference time-domain(FDTD) conformal grid |
