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首页» 过刊浏览» 2020» Vol.5» Issue(3) 327-336     DOI : 10.3969/j.issn.2096-1693.2020.03.028
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随钻电阻率成像测井在裂缝地层中的响应模拟
蔡亚琳,柯式镇,康正明,李新,李铭宇,马雪瑞
1 中国石油大学(北京)油气资源与探测国家重点实验室,北京 102249 2 中国石油大学(北京)地球物理与信息工程学院,北京 102249 3 中国石化石油工程技术研究院,北京 100101
Logging response simulation of a LWD resistivity imaging tool in fractured formations
CAI Yalin, KE Shizhen, KANG Zhengming, LI Xin, LI Mingyu, MA Xuerui
1 State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum-Beijing, Beijing 102249, China 2 College of Geophysics and Information Engineering, China University of Petroleum-Beijing, Beijing 102249, China 3 Sinopec Research Institute of Petroleum Engineering, Beijing 100101, China

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摘要  随着石油勘探的深入发展,随钻测井技术已成为及时准确获取钻井和地质资料的重要手段。其中,随钻 电阻率成像测井在实时井场数据采集、解释、现场决策以及指导地质导向钻井中起着关键作用。然而,目前关 于随钻电阻率成像测井影响因素的研究较少。针对随钻电阻率成像仪在裂缝地层中的测井响应及其影响因素尚 不明确的问题,本文基于三维有限元法,利用COMSOL MULTIPHYSICS有限元仿真平台,对单一裂缝地层及 网状裂缝地层中的随钻电阻率成像测井响应进行了模拟,分析了井眼尺寸、泥浆电阻率、电阻率对比度、裂缝 张开度、裂缝倾角及延伸距离等因素对测井响应的影响。模拟时,采用有限元局部网格细化技术,以达到求解 精度,提高求解速度。数值模拟结果表明,井眼泥浆的电阻率会影响裂缝分辨率,而由于泥浆的存在,当井眼 尺寸较小且仪器纽扣电极距离井壁较近时,仪器对裂缝的分辨率较高。当井眼尺寸保持在 7 in以内时,视电阻 率曲线效果较好。井眼环境对不同尺寸纽扣电极影响不同。当裂缝的张开度小于纽扣电极的分辨率时,随裂缝 张开度增加,裂缝处的视电阻率逐渐接近真实值。而当裂缝张开度大于纽扣分辨率时,随钻电阻率成像测井受 其张开度的影响较大。裂缝的延伸距离对成像结果的影响有限,当该延伸距离超过 0.3 m时,该影响可以忽略。 应用斯伦贝谢解释模型考察异常电流面积A与裂缝张开度的关系,两者呈较好的线性正相关关系,而A与电阻率 对比度呈负相关关系。裂缝倾角会影响成像时的视张开度,随倾角增大,成像图上裂缝的视张开度增大,且倾 角对低角度裂缝的视张开度大小的影响小于高角度裂缝。研究结果对随钻电阻率成像测井仪在复杂裂缝地层中 的测井解释及模型建立具有一定指导意义。
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关键词 : 随钻电阻率成像;测井响应;有限元法;数值模拟;复杂裂缝
Abstract

  With the development of petroleum exploration, logging-while-drilling (LWD) technology has become an important means to obtain timely and accurate drilling and geological data. Resistivity imaging logging-while-drilling plays a key role in real-time well site data acquisition, interpretation, field decision-making and guidance of geological steering. However, there are few studies into the factors influencing resistivity imaging logging while drilling. The factors influencing the logging response of resistivity imaging while drilling in fractured formations are not well understood at present. This paper uses the finite element simulation platformCOMSOL  MULTIPHYSICS based on a 3D finite element method (3D FEM) to simulate the response of resistivity imaging while drilling in single crack and reticular fractured formations. The influence of borehole size, mud resistivity, resistivity contrast, fracture opening,  fracture dip angle and extension distance on logging response are analyzed. In the simulation, local mesh refinement technology is adopted to improve the solution accuracy and the solution speed. The numerical simulation results show that the resistivity of borehole mud will affect the fracture resolution, and due to the existence of mud, when the borehole size is small and the button electrode of the instrument is close to the borehole wall, the resolution of the instrument to the fracture is higher. When the borehole size is kept within 7 inches, the effect of the apparent resistivity curve is credible. The influence of the borehole environment on button electrodes with different sizes is different. When the fracture opening is less than the resolution of the button electrode, the apparent resistivity at the      fracture gradually approaches the true value with an increase of crack opening. When the fracture opening is greater than the resolution, the resistivity imaging logging while drilling is greatly affected by the opening degree. The influence of fracture extension distance on imaging results is limited, and the influence can be ignored when the extension distance exceeds 0.3 m. The Schlumberger interpretation model is used to investigate the relationship between the abnormal current area A  and the fracture opening degree, which shows a good positive linear correlation and a negative correlation with resistivity contrast. With an increase in the dip angle, the apparent opening of a fracture on the image increases, and the influence of the dip angle on the apparent opening of a low angle fracture is less than that of a high angle fracture. The research results have certain guiding significance for logging interpretation and model establishment of resistivity imaging with drilling tools in complex fracture formations.


Key words: LWD resistivity imaging; logging responses; 3D FEM; numerical simulation; complex fractures
收稿日期: 2020-09-29     
PACS:    
基金资助:国家科技重大专项“低渗透储层高精度随钻成像技术研究”(2016ZX05021-002) 资助
通讯作者: wksz@vip.sina.com
引用本文:   
CAI Yalin, KE Shizhen, KANG Zhengming, LI Xin, LI Mingyu, MA Xuerui. Logging response simulation of a LWD resistivity imaging tool in fractured formations. Petroleum Science Bulletin, 2020, 03: 327-336.
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