| 摘要: |
| 采用水平层状各向异性介质中的并矢Green函数计算随钻电磁波测量仪器在地层中的响应。根据发射天线与接收天线的交叉排列方式和顺序排列方式提出将来自钻头前方地层的信号与来自仪器周围地层的信号进行最大程度解耦的方法。针对各向异性地层,还提出在这两种信号中将地层垂直电导率信息与水平电导率信息进行最大程度解耦的方法。结果表明:接收天线中来自仪器周围地层的感应电动势只受最低位置与最高位置天线之间地层电导率的影响,对钻头前方地层的存在并不敏感,可以利用该电动势精确获得地层的电导率参数;接收天线中来自钻头前方地层的感应电动势只受层界面的影响,利用该信号可以进行钻头前向探测从而指示出地层交界面的存在;来自钻头前方地层的信号与来自仪器周围地层的信号解耦程度与地层相对于仪器轴向的倾角有关,倾角越大,两种信号的解耦程度越低。 |
| 关键词: 钻头前向探测 并矢Green函数 随钻测量 解耦 |
| DOI：10.3969/j.issn.1673-5005.2019.01.004 |
| 分类号::P 631.9 |
| 文献标识码:A |
| 基金项目:国家科技重大专项(2017ZX05019-006)；中央高校基本科研业务费专项 (15CX05047A) |
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| Decoupling of electromagnetic MWD tool 's signals and its application for ahead-of-bit detection |
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WEI Baojun1, WU Kangkang1, LIN Nan2, DANG Feng3, REN Chen1
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(1.College of Science in China University of Petroleum(East China), Qingdao 266580, China;2.Drilling Technology Research Institute of Shengli Oilfield, SINOPEC, Dongying 257017, China;3.China Petroleum Logging Company Limited, Xi 'an 710077, China)
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| Abstract: |
| The response of the electromagnetic MWD tool was computed via the dyadic Green 's functions in horizontally stratified anisotropic media. A method of decoupling anomalous formation signals ahead of the bit from formation signals around the tool to a maximum extent has been obtained for both alternating arrangement and serial arrangement of transmitter and receiver antennas. A method to maximiaze decoupling of horizontal conductivity from vertical conductivity in the two sets of signals above has also been obtained for anisotropic formations. The results show that the induced electromotive force from around-the-tool formations is only affected by the formation resistivity in between the lowest and highest antennas, and is not sensitive to the presence of layers ahead of the bit, therefore the formation conductivity can be accurately obtained. The induced electromotive force from ahead-of-bit formations is only affected by the layers suggesting that it can be used for ahead-of-bit detection to accurately detect the presence of the layer. The decoupling extent of the ahead-of-bit signal from the around-the-tool signal is related to the dip angle of the formation with respect to the tool 's axis, and large dipping angle leads to significant degradation in the decouping effect. |
| Key words: ahead-of-bit detection dyadic Green 's functions measurements-while-drilling (MWD) decouple |
