﻿ 超高阻盐膏层随钻电磁中继传输特性研究

Research on Downhole Electromagnetic Repeater Transmission Characteristics in Ultra High Resistivity Gypsum-Salt Layers
CHEN Xiaohui, GAO Bingtang, SONG Zhaohui
Sinopec Research Institute of Petroleum Engineering, Beijing, 100101, China
Abstract: In order to solve the problem that electromagnetic telemetry signal easily interrupts transmission in ultra high resistivity gypsum-salt layer due to fast attenuation, an adaptive HP finite element method (FEM), which could automatically select space or order thinning, was used to simulate the electromagnetic relay in ultra high resistivity gypsum-salt layers.The falling velocity and transmission distance of electromagnetic signals in ultra-high resistivity gypsum-salt layer under different carrier frequencies were obtained.A prediction method of relay installation position was formed, and compared with conventional finite element calculation.It had advantages in convergence rate and calculation accuracy.The the algorithm was verified correct in Well AJ214 of AGHA JARI Block, Iran.The calculation result of signal attenuation rate tallied well with the practical application, and the prediction accuracy of repeaters' installation position was over 90%.The research showed that the transmission model could accurately predict the installation position of repeaters, and ensure the continuous transmission of electromagnetic signals across the ultra high resistivity gypsum-salt layer.The model can serve as a theoretical reference and foundation for EM-MWD applications.
Key words: logging while drilling     electromagnetic repeat transmission     ultra high resistivity     gypsum-salt layer     adaptive     finite element method

1 中继传输模型的建立及求解 1.1 有限元模型的建立

 图 1 井下电磁中继转发初始几何模型 Fig.1 Downhole initial mesh model of electromagnetic relay while drilling

 (1)

 (2)

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1.2 模型求解

1) 设求解的最大误差容许范围Δer>0, 将初始求解域ΩH, P中所有网格进行H细化和多项式阶次P加1, 此时求解域Ωref变为：

 (8)

2) 初始网格中选择网格K细化成4个子单元Ki(1≤i≤4), 此时子单元计算误差eri为：

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 (10)

3) 如er≤Δer, 则计算完成；否则, 将所有细化单元按误差递减顺序加入序列L中。

4) 在序列L中选择误差最大的单元作为下一次计算的初始网格, 继续从步骤2)开始计算, 直至er≤Δer, 此时各子单元求解得到的电场强度即为子单元所在地层位置处电场强度的最终解。

2 超高阻盐膏层中继衰减特性分析

 图 2 AJ214井地层电阻率分层情况 Fig.2 Formation resistivity of Well AJ214

 图 3 地面接收到的电磁MWD信号强度与井深的关系 Fig.3 Relationship curves between surface EM-MWD signal intensity and well depth
 图 4 地面接收到的电磁中继器信号强度与井深的关系 Fig.4 Relationship curves between surface Repeater signal intensity and well depth

 图 5 2种有限元算法的计算效率对比 Fig.5 Correlation curve for two finite element algorithms' computational efficiency
3 现场试验

AJ214井实际施工前期，地面接收到的电磁MWD信号一直处于一个正常衰减的过程, 0~1 700.00 m低电阻率井段的地面信号幅度从-2~0 dBV缓慢衰减至约-10~-8 dBV；进入井深1 700.00 m以深盐膏层后, 地面信号幅度锐减至约-70~-60 dBV, 但地面接收机仍能正常接收信号；由于电磁信号衰减严重, 钻至井深2 123.00 m时, 在距离电磁MWD 2 107.00 m处加装电磁中继器, 此时地面可同时接收到电磁中继器和电磁MWD信号；钻至井深2 700.00 m时, 接收不到电磁MWD信号；钻至井深2 856.00 m完钻时, 地面接收到的电磁中继器信号强度约为-53 dBV, 整个施工过程中数据传输连续, 仪器工作稳定, 满足现场定向施工要求。仪器实际应用效果和仿真结果基本一致, 电磁MWD传输距离预测准确率超过90%。

4 结论

1) 超高阻盐膏层会导致电磁MWD和电磁中继器的发射信号产生-50 dBV以上的断崖式衰减。在合适位置加装电磁中继器是确保井下电磁信号连续传输、解决超高阻盐膏层地区电磁MWD传输问题的必要手段。

2) 利用基于局部求解域的有限元迭代网格模型和自适应HP有限元计算方法, 分析随钻电磁中继衰减特性, 从而预测井下电磁中继器的安装位置, 预测结果与实际工况相符, 能够满足现场施工前对电磁随钻测量可行性应用评价和电磁中继器安装位置预判的需求。

3) 与经典有限元算法相比, 自适应HP有限元算法在收敛速度和求解精度两方面都具有较大的优势。

 [1] 闫宏亮, 石文龙, 李琳. 随钻测量信息传输方式的发展现状综述研究[J]. 重庆科技学院学报(自然科学版), 2015, 17(6): 69–72, 83. YAN Hongliang, SHI Wenlong, LI Lin. Research on the status and future of the MWD data transmission[J]. Journal of Chongqing University of Science and Technology (Natural Sciences Edition), 2015, 17(6): 69–72, 83. [2] 袁鹏斌, 余荣华, 欧阳志英. 无线随钻测量信息传输的现状与问题[J]. 焊管, 2010, 33(10): 65–69. YUAN Pengbin, YU Ronghua, OUYANG Zhiying, et al. The current status and problems of wireless signal transmission in measurement while drilling[J]. Welded Pipe and Tube, 2010, 33(10): 65–69. DOI:10.3969/j.issn.1001-3938.2010.10.012 [3] 马哲, 杨锦舟, 赵金海. 无线随钻测量技术的应用现状与发展趋势[J]. 石油钻探技术, 2007, 35(6): 112–115. MA Zhe, YANG Jinzhou, ZHAO Jinhai, et al. Status quo and development trend of MWD technique[J]. Petroleum Drilling Techniques, 2007, 35(6): 112–115. [4] 汤明, 何世明, 邢景宝, 等. 大牛地气田DP14水平井氮气泡沫钻井实践与认识[J]. 天然气工业, 2010, 30(3): 74–76. TANG Ming, HE Shiming, XING Jingbao, et al. Practices and knowledge from nitrogen foam drilling at the Well DP-14 in the Daniudi Gas Field[J]. Natural Gas Industry, 2010, 30(3): 74–76. [5] 呼石磊, 鄢泰宁, 李晓. 地层对电磁随钻测量信号的影响研究[J]. 煤炭科学技术, 2011, 39(9): 114–117. HU Shilei, YAN Taining, LI Xiao. Study on strata affected to electromagnetic with drilling measuring signal[J]. Coal Science and Technology, 2011, 39(9): 114–117. [6] 刘修善, 侯绪田, 涂玉林, 等. 电磁随钻测量技术现状及发展趋势[J]. 石油钻探技术, 2006, 34(5): 4–9. LIU Xiushan, HOU Xutian, TU Yulin, et al. Developments of electromagnetic measurement while drilling[J]. Petroleum Drilling Techniques, 2006, 34(5): 4–9. [7] 李林, 弓志谦, 王磊, 等. 扩展EM-MWD传输深度及提高可靠性的方法与对策[J]. 钻采工艺, 2010, 33(4): 25–27, 38. LI Lin, GONG Zhiqian, WANG Lei, et al. Methods of improving EM-MWD transmissive depth and reliability[J]. Drilling & Production Technology, 2010, 33(4): 25–27, 38. [8] 邵养涛, 姚爱国, 张明光. 电磁波随钻遥测技术在钻井中的应用与发展[J]. 煤田地质与勘探, 2007, 35(3): 77–80. SHAO Yangtao, YAO Aiguo, ZHANG Mingguang. Application and development of electro-magnetic telemetry in drilling operation[J]. Coal Geology & Exploration, 2007, 35(3): 77–80. [9] 胡长翠, 张明友, 张琴, 等. 井下测试数据无线传输技术探讨[J]. 钻采工艺, 2011, 34(1): 48–51. HU Changcui, ZHANG Mingyou, ZHANG Qin, et al. Research on wireless telemetry technology of downhole test data[J]. Drilling & Production Technology, 2011, 34(1): 48–51. [10] 胡越发, 杨春国, 高炳堂. 井下电磁中继传输技术研究及应用[J]. 科技导报, 2015, 33(15): 66–71. HU Yuefa, YANG Chunguo, GAO Bingtang. Research and application of downhole electromagnetic relay transmission technology[J]. Science & Technology Review, 2015, 33(15): 66–71. DOI:10.3981/j.issn.1000-7857.2015.15.010 [11] 郑俊华, 宗艳波, 钱德儒, 等. 井下环境模拟试验装置研制[J]. 科学技术与工程, 2017, 17(8): 21–25. ZHENG Junhua, ZONG Yanbo, QIAN Deru, et al. Development of downhole environment simulation test equipment[J]. Science Technology and Engineering, 2017, 17(8): 21–25. [12] 李勇华, 杨锦舟, 杨震, 等. 随钻电阻率地层边界响应特征分析及应用[J]. 石油钻探技术, 2016, 44(6): 111–116. LI Yonghua, YANG Jinzhou, YANG Zhen, et al. The analysis and application of formation interface response characteristics of the resistivity LWD tool[J]. Petroleum Drilling Techniques, 2016, 44(6): 111–116. [13] 李翠, 高德利, 刘庆龙, 等. 邻井随钻电磁测距防碰计算方法研究[J]. 石油钻探技术, 2016, 44(5): 52–59. LI Cui, GAO Deli, LIU Qinglong, et al. A method of calculating of avoiding collisions with adjacent wells using electromagnetic ranging surveying while drilling tools[J]. Petroleum Drilling Techniques, 2016, 44(5): 52–59. [14] 解茜草, 赵志峰. 随钻电磁波测井响应时域有限差分数值模拟[J]. 计量与测试技术, 2014, 41(8): 1–3. XIE Xicao, ZHAO Zhifeng. A study on modeling of electromagnetic wave propagation resistivity logging tool based on the FDTD method[J]. Metrology & Measurement Technique, 2014, 41(8): 1–3. [15] 陈晓晖, 刘得军, 刘得芳, 等. 随钻电阻率测量系统响应模拟算法探讨[J]. 电子测量技术, 2009, 32(6): 21–26. CHEN Xiaohui, LIU Dejun, LIU Defang, et al. Discussion on methods of simulation for resistivity logging-while-drilling (LWD) measurements[J]. Electronic Measurement Technology, 2009, 32(6): 21–26. [16] 胡松, 王晓畅, 孔强夫. 水平井随钻电磁波电阻率数值模拟[J]. 科学技术与工程, 2017, 17(14): 59–66. HU Song, WANG Xiaochang, KONG Qiangfu. Numerical simulation of LWD resistivity in horizontal wells[J]. Science Technology and Engineering, 2017, 17(14): 59–66. DOI:10.3969/j.issn.1671-1815.2017.14.009 [17] 杨震, 肖红兵, 李翠. 随钻方位电磁波仪器测量精度对电阻率及界面预测影响分析[J]. 石油钻探技术, 2017, 45(4): 115–120. YANG Zhen, XIAO Hongbing, LI Cui. Impacts of accuracy of azimuthal electromagnetic logging-while-drilling on resistivity and interface prediction[J]. Petroleum Drilling Techniques, 2017, 45(4): 115–120. [18] 倪卫宁, 张晓彬, 万勇, 等. 随钻方位电磁波电阻率测井仪分段组合线圈系设计[J]. 石油钻探技术, 2017, 45(2): 115–120. NI Weining, ZHANG Xiaobin, WAN Yong, et al. The design of the coil system in LWD tools based on azimuthal electromagnetic-wave resistivity combined with sections[J]. Petroleum Drilling Techniques, 2017, 45(2): 115–120.

文章信息

CHEN Xiaohui, GAO Bingtang, SONG Zhaohui

Research on Downhole Electromagnetic Repeater Transmission Characteristics in Ultra High Resistivity Gypsum-Salt Layers

Petroleum Drilling Techniques, 2018, 46(3): 114-119.
http://dx.doi.org/10.11911/syztjs.2018092