适用于油基钻井液的随钻电阻率成像测井方法

The Resistivity Imaging LWD Method Suitable for Oil-Based Drilling Fluid

  • 摘要: 油基钻井液会阻断直流电流通路从而使常规的随钻电阻率测井方法失效,为解决该问题,基于电容耦合非接触电导检测技术,提出了可用于油基钻井液的随钻电阻率成像测井方法。综述了随钻电阻率测量的主要方法,介绍了电容耦合非接触电导检测技术的原理与特点。将电容耦合和电感耦合相结合,建立了油基钻井液条件下的方位测井模拟模型,并利用该模型进行了多种工况下的测井模拟试验,分析了周向位置与电流幅值、电极周向位置与电流相位的关系及钮扣电极成像原理,模拟结果表明,钮扣电极具有方位探测能力,所提出的测井方法具有可行性。设计了地面模拟测井系统,进行了方位测井室内试验,发现该测井系统能够实现地层成像和测量地层倾角,试验结果与实际地层倾角的相对误差仅为4.7%。研究认为,提出的随钻电阻率成像测井方法可以在油基钻井液条件下进行随钻侧向电阻率测量,并且使测得的电阻率成像,从而得到较为可靠的测井结果。

     

    Abstract: The goal of this study was to solve the problem of drilling fluids blocking circuits and losing signal during the logging process. Oil-based drilling fluids are prone to blocking the DC circuit and hence invalidating conventional resistivity when using the LWD method. In order to solve this problem, researchers proposed implementing the capacitive coupling-based non-contact conductance detection technology with a resistivity imaging LWD method suitable for oil-based drilling fluids. This paper summarized the main methods of resistivity measurement while drilling, and introduced the principle and characteristics of capacitive coupled non-contact conductance detection technology. The azimuth logging simulation model for oil-based drilling fluids was established by combining capacitive coupling principle and inductive coupling principle. Then, the logging simulation experiment under various working conditions was carried out with this model, and the relationships between the circumferential position and current amplitude, circumferential position of electrode and the current phase, as well as the imaging principle of button electrode were analyzed. The simulation results showed that the button electrode had azimuth detection capability, and the proposed logging method was feasible. A surface simulation logging system was designed to carry out the indoor test of azimuth logging. The test found that this logging system may to achieve formation imaging and measure the formation dip angle, and the relative error between the test result and the actual formation dip angle is only 4.7%. The study showed that the proposed resistivity imaging LWD method is able to perform lateral resistivity measurements while drilling in oil-based drilling fluids, and make the measured resistivity imaging to obtain the reliable logging results.

     

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