基于柱坐标系下电场耦合势三维有限体积法研究方位随钻电磁测井响应

发布时间：2018-07-31 05:25

【摘要】：在现代油气勘探开发中,随钻测井(LWD)技术可应用于钻铤的实时监控和实现地质导向,以便有效提高大斜度井和水平井钻进成功率、油气采收率和单井产能。其原理是将测量装置安装在钻铤附近,使其能够在钻井过程中对钻铤周围地层进行有效测量并将测量结果实时传送到地面或储存起来。由于刚钻开的地层受泥浆侵入影响较小,随钻测井更容易获得地层真实参数。在经历了三十多年的发展以后,随钻测井已包含了电阻率、声波、中子与密度、核磁以及井壁成像等几乎所有的测井方法,不仅能够进行地质导向,而且还能够即时进行复杂油气储层综合评价。方位随钻电磁测井是一种新型随钻测井技术,能够更好地解决各向异性地层中复杂油气探勘开发问题,该仪器由安装在钻铤表面的倾斜线圈系组合成发射与接收系统,利用钻铤在钻进过程中的旋转,测量不同方位角上的电磁场,从中提取张量型电磁信号,不仅能够获取地层纵横向电导率、地层相对倾角与方位角信息,而且鉴于其交叉分量对地层边界更敏感的特点,能够更有效实现对地层边界的实时探测,进而更好地解决复杂油气储层评价与实时导向的问题。为了实现方位随钻电磁传播仪器相关参数的优化设计(包含线圈系间距、工作频率、倾斜线圈系的倾角等),并为随钻电磁资料的解释与反演提供可靠理论依据,本论文将根据随钻方位电磁传播测井仪器的结构特点,基于柱坐标系下电场矢势和标势耦合势方程研究建立与随钻方位电磁传播测井技术相配套的三维数值模拟算法和软件,并对其响应特征进行详细的考察。主要研究内容如下:第一章,简要介绍电法测井仪器的发展历程以及方位随钻电磁测井的研究背景与意义。回顾电法测井数值模拟中的解析、半解析以及多种数值模拟算法,并对其优缺点进行分析总结。最后,陈述本论文的主要研究内容与创新点。第二章,根据方位随钻电磁测井仪器的典型线圈系结构以及电磁叠加原理,通过引入完全各向异性地层中电偶极子并矢Green函数,给出倾斜发射线圈电场以及倾斜接收线圈上感应电动势的计算公式,并利用电场混合势(矢势和标势)克服电磁场数值模拟过程中的低感应数问题。针对圆柱状钻铤表面的特点,建立柱坐标系下Lebedev网格剖分方法,以提高数值模拟效率,即在?、z方向采用渐进网格、?方向用等间距网格并通过延拓虚点技术处理柱坐标系下电磁场的周期性问题。此外,利用标准均质化技术计算了控制单元的等价电导率以提高非均质网格上的离散精度。在此基础上,将应用柱坐标系下的三维有限体积法,进一步推导出电场矢势和标势Helmholtz方程与电流源离散方法,得到一个柱坐标系下交错网格节点上电场耦合势的大型稀疏方程,并利用不完全LU分解(ILUT)预处理与稳定双共轭梯度法(Bi CGSTAB)迭代法和Pardiso并行直接求解法这两种方法求解大型代数方程组。最后,利用数值结果对算法的可靠性进行检验。第三章,详细讨论了发射线圈的两种近似处理方法:叠加电偶极子与叠加磁偶极子,并对两种近似情况下的仪器响应进行对比。数值结果表明:不论发射线圈和接收线圈是否倾斜,用叠加电偶极子模拟发射线圈的测井响应更能保持较高的精度;而只有在发射线圈和接收线圈有一个保持轴向时、或者小钻铤的情况下,用叠加磁偶极子近似发射线圈的测井响应才能保持较高的精度。最终,得出结论:在方位随钻测井仪器测井响应的数值模拟中,用叠加电偶极子近似模拟发射线圈更有效。第四章,利用柱坐标系下有限体积法建立的三维数值模拟软件,具体考察了倾斜方位随钻线圈系(轴向收发线圈、轴向发射与倾斜接收线圈、倾斜发射与轴向接收线圈、倾斜收发线圈组合成的三线圈系或四线圈系测量方式)在钻铤旋转角固定不变,以及钻铤连续旋转时方位随钻电磁响应的变化特征,作为对比还考察了共面方位线圈系(三线圈、四线圈组合方式)在钻铤连续旋转时的电磁响应。在钻铤旋转角固定不变的情况下:垂直井中,井眼泥浆电导率对倾斜方位随钻线圈系(轴向收发线圈、轴向发射与倾斜接收线圈、倾斜发射与轴向接收线圈)随钻测井的影响会很小;泥浆电阻率对倾斜收发线圈系随钻测井响应的影响明显变大,且在层边界附近由于积累面电荷影响,幅度比和相位差曲线会出现明显“犄角”。而在倾斜井中,随着井眼倾角的增大,无论是轴向线圈还是倾斜线圈,井眼泥浆对测井响应均产生较大影响,且井眼泥浆对完全倾斜收发线圈系响应的影响更大。三线圈系在测井中会导致测井响应整体偏移,四线圈系由于具有对称的线圈系结构,消除了偏移。因此,四线圈系的测井响应更能精确反应层边界的位置。在钻铤连续旋转的情况下:均匀的各向异性地层中,幅度比和相位差随方位角变化并在180度时左右对称,且井眼倾角增大时方位角变化对测井响应的影响会更大。方位随钻电磁测井仪器的一个主要功能是具有较强的探边能力,从而达到实时地质导航的目的。为了比较不同结构仪器的探边能力,将不同结构的仪器倾斜穿过上下对称的三层地层模型,考察其对层边界的响应特征。不同深度点、不同仪器方位角下的仪器响应三维图显示:线圈偏移会导致单边仪器在层边界进、出位置有明显不同,并且在对称的地层模型中产生的幅度比和相位差响应不对称;而双边仪器由于采用了对称的仪器结构,在层边界的进、出位置几乎对称,整体的幅度比和相位差响应也几乎对称。此外,当工作频率降低时,幅度比响应和相位差响应变化相对减小。这说明工作频率越低,线圈方位角对方位随钻电磁测井影响越小。与采用倾斜线圈系的仪器相比,采用水平共面线圈系的仪器对层边界更敏感,具有更强的探边能力。第五章,对全文进行了总结并对下一步工作进行展望。
[Abstract]:In modern oil and gas exploration and development, the LWD technology can be applied to real-time monitoring and geological guidance of the drill collar, in order to effectively improve the drilling success rate, oil and gas recovery and single well productivity. The principle is to install the measuring device near the drill collar, so that it can be used in the drilling collar. Effective measurements are carried out and the results are transmitted to the ground or stored in real time. As the formation of the rigid drill is less affected by mud invasion, the real parameters of the formation are more easily obtained with the drilling well logging. After more than thirty years of development, the logging has included resistivity, acoustic wave, neutron and density, nuclear magnetic and well wall imaging, etc. All logging methods can not only carry out geological guidance, but also make a comprehensive evaluation of complex oil and gas reservoirs. Azimuth drilling electromagnetic logging is a new type of drilling well logging technology, which can better solve the problem of complex oil and gas exploration and development in the anisotropic formation. The instrument is composed of the inclined coil system installed on the drill collar. The synthetic emission and receiving system uses the rotation of the drill collar during the drilling process to measure the electromagnetic field on different azimuth angles and extract the tensor electromagnetic signal from it. It can not only obtain the longitudinal and transverse conductivity of the formation, the relative inclination and azimuth information of the formation, but also can be more effective in view of the more sensitive characteristics of the cross section to the boundary of the formation. In order to realize the optimization design of the related parameters of the azimuth drilling electromagnetic transmission instrument (including the coil distance, the working frequency, the inclination of the tilted coil system, etc.), and provide a reliable theory for the interpretation and inversion of the electromagnetic data of the drilled. According to the structure characteristics of the electromagnetic propagation logging tool with the drilling azimuth, the three-dimensional numerical simulation algorithm and software matching with the drilling azimuth electromagnetic propagation logging technology are established on the basis of the field vector potential and the potential coupling potential equation in the cylindrical coordinate system, and the response characteristics are investigated in detail. The main contents are as follows: In the first chapter, the development of the electrical logging tool and the background and significance of the azimuth drilling electromagnetic logging are briefly introduced. The analytical, semi analytical and several numerical simulation algorithms in the numerical simulation of electrical logging are reviewed, and their advantages and disadvantages are analyzed and summarized. Finally, the main contents and innovation points of this paper are stated. The second chapter, the root of this paper, is the root of the paper. According to the typical coil structure and electromagnetic superposition principle of azimuth drilling electromagnetic logging instrument, by introducing the electric dipole Green function in the fully anisotropic formation, the calculation formula of the electric field of the tilted launching coil and the induction electromotive force on the inclined receiving coil is given, and the number of electromagnetic fields is overcome by the mixed potential of the electric field (vector potential and the potential). According to the characteristics of the cylindrical drill collar, the Lebedev mesh generation method in cylindrical coordinate system is established to improve the efficiency of numerical simulation, namely, the gradual grid in the direction of Z, the direction of the equidistance grid and the periodic problem of the electromagnetic field in the cylindrical coordinate system by the extension virtual point technology. By using the standard homogenization technique, the equivalent conductivity of the control unit is calculated to improve the discrete precision on the heterogeneous grid. On this basis, the three-dimensional finite volume method in the cylindrical coordinate system is applied to further deduce the discrete method of the vector potential and the standard potential Helmholtz equation and the current source, and get a staggered grid node under a cylindrical coordinate system. The large sparse equations of the electric field coupling potential are used to solve large algebraic equations by using the two methods of incomplete LU decomposition (ILUT) preconditioning and stable dual conjugate gradient (Bi CGSTAB) iterative method and Pardiso parallel direct solution. Finally, the reliability of the algorithm is tested by numerical results. The third chapter discusses the launching coils in detail. Two approximate methods: superposition electric dipole and superimposed magnetic dipole, and comparison of the response of the instrument in the two approximate cases. The numerical results show that the log response of the emitter coil is more accurate, no matter whether the transmitting coil and the receiving coil are inclined or not. In the case of keeping an axial, or a small drill collar, the log response of a superimposed magnetic dipole is approximated by a superimposed magnetic dipole. Finally, the conclusion is that in the numerical simulation of the logging response of the azimuth logging instrument, the fourth chapter is used to simulate the launching coils. The three-dimensional numerical simulation software established by the finite volume method in the standard system is used to investigate the oblique azimuth with the drill coil system (axial transceiver coil, axial transmitting and tilting receiving coils, inclined launching and axial receiving coils, three coils or four coil measuring modes formed by the tilted transceiver coils), and the rotation angle of the drill collar is fixed and the drill pipe is fixed. As a contrast, the electromagnetic response of the coplanar azimuth coil system (three coils, four coils combined) in the continuous rotation of the drill collar is also investigated. Under the condition of fixed rotation angle of the drill collar, the electrical conductivity of the mud slurry in the borehole is in the direction of the axial transmission line (axial transmission line). The influence of the ring, the axial and the inclined receiving coils, the tilted and the axial receiving coils will be very small. The influence of the mud resistivity on the response of the slant receiving and receiving coil is obviously larger, and the amplitude ratio and the phase difference curve will appear obvious "horns" in the vicinity of the layer boundary due to the charge of the accumulation surface. In the well, with the increase of the angle of the borehole, both the axial and the inclined coils, the borehole mud has a great influence on the log response, and the well mud has a greater impact on the response of the fully inclined transceiver system. The three coil system will lead to the overall deviation of the log response and the four coil system has a symmetrical coil system. Therefore, the logging response of the four coil system is more accurate to the location of the reaction layer boundary. In the case of continuous rotation of the drill collar, the amplitude ratio and phase difference vary with the azimuth angle and are symmetrical at 180 degrees in homogeneous anisotropic formation, and the influence of the angle change on the logging response will be greater when the well angle is increased. One of the main functions of the electromagnetic logging tool is that it has strong edge detection ability to achieve the purpose of real-time geological navigation. In order to compare the edge detection ability of different structural instruments, the instruments of different structures are inclined through the upper and lower symmetrical three layer formation model to investigate the response characteristics to the layer boundary, different depth points and different instruments. The three-dimensional diagram of the instrument response in the azimuth angle shows that the coil offset will lead to the single side instrument in the layer boundary, and the output position is distinctly different, and the amplitude ratio and the phase difference in the symmetrical formation model are asymmetric. The amplitude ratio and the phase difference response are also almost symmetrical. In addition, when the working frequency is reduced, the amplitude is relatively smaller than the response and the phase difference response. This shows that the lower the working frequency, the smaller the influence of the coil azimuth to the electromagnetic logging. Compared with the inclining coil system, the horizontal coils system is used for the layer boundary. The fifth chapter summarizes the whole paper and looks forward to the next step.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O241.82;O441

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