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油井内的钢铁质套管可视为大口径贺波导，为应用电磁波传播方法测量管内混合流体的持水率提供了可能性。本文通过分析油井套管构成的导波系统的电磁波传输特性，提出一种波导测量方法，并用数值模拟和物理模拟实验结果，考察方法的可行性。结果表明，波导法具有特殊优点和良好应用前景。 相似文献
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基于频域有限元方法仿真了精细地-电离层波导结构甚低频(VLF, Very Low Frequency)电磁波幅度和相位传播特性.首先给出了如何确定VLF波发射点和接收点传播路径所在大圆的方法，接着分析了获取波导结构中不同阶波导模式传播系数的耦合模理论，数值讨论了不同阶波导模式的衰减率和相对相速度随模式数和工作频率的变化关系，给出了波导不同结构参数对一阶模衰减率和相对相速度的影响.与文献结果对比验证了本文有限元方法模拟VLF波传播的正确性和高效性.最后利用实验和数值仿真结果，通过对电子密度国际电离层参考模型进行修正，讨论了澳大利亚—青岛台VLF波幅度和相位日变化的规律.本文工作为研究地-电离层波导结构VLF波电磁特性以及提高陆基超远程甚低频导航系统的精度，提供了新的思路和方法. 相似文献
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本文简要地介绍了地壳波导,电磁波在地壳波导中的传播特性以及我们采用的接收装置,然后分析研究了几年内观测结果。表明,大多数楚雄附近M_L≥3-4级地震,云南省内M_L≥5.0级地震以及远距离的大震前都记录到电磁波异常。这就显示了,利用电磁波异常预报中,强地震是可能的. 相似文献
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根据电磁波在地壳及大气波导层中传播的模拟实验,讨论了地震电磁信号在超低频及甚低频频段内的传播特征。用一块花岗岩板和两块铝板分别模拟地壳、电脑层和地下导电层,用海洋被铝薄膜覆盖的地图来模拟希腊群岛及其周围的海。为了弄清海洋对电磁波传播的影响,将从模拟震源发出的电磁波的传播强度标在地图上。我们得到了甚低频电磁波的长距离传播,而超低频电磁波传播从震中开始呈指数衰减。考虑波导的这一实验也许能够解释海洋对地 相似文献
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产油井套管变形断裂,造成油井的报废,这种现象影响了石油的生产。本文指出,由于开采石油,减低了含油层的孔隙压力,致使含油层被压缩,油层的压缩给固结在油层中的套管以一个纵向附加压力,当含油地层倾斜时,套管除受到纵向压力外,还受到一对横向水平剪力的作用。这种因油层压缩而产生的力,是造成套管变形的一种可能解释。 相似文献
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在石油工业的地质勘探方面,广泛应用放射性方法来研究油井地质剖面,和解决钻井、采油的工程问题.特别是研究已下套管的油井,唯一的办法,只有采用放射性测井;对高矿化度液体钻进的井及石灰岩地层中钻的井中,划分地层,判别油气水层,也具有重要的作用. 相似文献
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利用电磁波和地震波的性质以及目前对含流体多孔介质震电效应的认识，分析了电磁波对震电参数的分辨力，并与电磁波对电导率参数的分辨力进行了对比．据此指出了天然电磁场高分辨探测地下油气水地层的可能性． 相似文献
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Slip boundary condition is commonly utilized to model elastic wave propagation through layered earth media. The same approach is used here to characterize acoustic wave propagation along a cased borehole with various cement bond conditions. By modeling the cement layer between casing and formation as a viscoelastic slip interface with complex coupling rigidity parameters, one can not only reduce the complexity in the classical elastic wave modeling of the problem, but also efficiently model various complicated wave phenomena that are difficult for the existing modeling. More specifically, the new theory can well describe the effect of the cement bond condition change and the location of the change (i.e., whether it is in the first interface between casing and cement, or the second interface between cement and formation) on the acoustic waves, demonstrating the good modeling capability and predicting power. Application of the theory to field data shows that the theory can correctly model the acoustic wave characteristics and interpret the cement bond condition, thus providing a useful fundament theory for casing bond evaluation using acoustic logging. 相似文献
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为进一步了解井间地下介质结构及其电性特征,本文用时域有限差分方法(FDTD),实现了井间电磁场响应的数值模拟.激发源是探测深度相对磁偶极子更大一些的电偶极子,首先选择一个位于井轴上的垂直电偶极子作为场源,并假设参与计算的介质相对于发射井井轴是轴向对称的,这样可将研究区域作为二维问题处理.推导了二维井间电磁波传播时域差分公式.该方法适用于任何方向入射的电偶极子源,尤其善于解决频域差分方法所难以描述的宽频脉冲.给出了井间金属圆柱和矿体圆柱数值模拟2个例子,结果表明,时域有限差分方法能有效的模拟井间地下介质中电磁波的传播,揭示电磁波传播规律.该方法速度快、精度高、结果稳定,适合用于井间电磁场反演成像的正演响应计算. 相似文献
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Distinguishing oil and water layers by interpreting acoustic logging data with changing well diameters 
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下载免费PDF全文 During surveys, water layers may interfere with the detection of oil layers. In order to distinguish between oil and water layers, research on the properties of well diameters and oil and water layers and their relation to acoustic logging rules is essential. Using Hudson's crack theory, we simulated oil and water layers with different well diameters or crack parameters (angle and number density). We found that when the well radius increases from 0.03 m to 0.05 m, the variation ratio of compressional wave amplitude for the oil layer is less than that for the water layer. The difference of Stoneley wave amplitude between the crack parameters (angle and number density) is greater in the case of the water layer than in the case of the oil layer. The response sensitivity of wave energy is greater for the water layer than that for the oil layer. When the well radius increases from 0.05 m to 0.14 m, the maximum excitation intensity for oil layer is greater than that for the water layer. We conclude that the propagation of an elastic wave is affected by medium composition and well diameter, and the influence has certain regularity. These results can guide further reservoir logging field exploration work. 相似文献
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Three‐dimensional controlled‐source electromagnetic modelling with a well casing as a grounded source: a hybrid method of moments and finite element scheme 下载免费PDF全文
下载免费PDF全文 Steel well casings in or near a hydrocarbon reservoir can be used as source electrodes in time‐lapse monitoring using grounded line electromagnetic methods. A requisite component of carrying out such monitoring is the capability to numerically model the electromagnetic response of a set of source electrodes of finite length. We present a modelling algorithm using the finite‐element method for calculating the electromagnetic response of a three‐dimensional conductivity model excited using a vertical steel‐cased borehole as a source. The method is based on a combination of the method of moments and the Coulomb‐gauged primary–secondary potential formulation. Using the method of moments, we obtain the primary field in a half‐space due to an energized vertical steel casing by dividing the casing into a set of segments, each assumed to carry a piecewise constant alternating current density. The primary field is then substituted into the primary–secondary potential finite‐element formulation of the three‐dimensional problem to obtain the secondary field. To validate the algorithm, we compare our numerical results with: (i) the analytical solution for an infinite length casing in a whole space, excited by a line source, and (ii) a three‐layered Earth model without a casing. The agreement between the numerical and analytical solutions demonstrates the effectiveness of our algorithm. As an illustration, we also present the time‐lapse electromagnetic response of a synthetic model representing a gas reservoir undergoing water flooding. 相似文献
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地面电磁法在实际工作中在很大程度上受到了探测深度和分辨率的限制.为了克服这些缺点,出现了井间电磁法.井间电磁法指的是在两个(或多个)钻孔中分别发射或接收电磁波信号,利用电磁波信号进行成像并探测井间物理性质的地球物理方法.由于发射机和接收机可以分别放置在很深钻孔中,其具有大透距、大探测深度的特点,因而广泛应用于工程环境物探、矿产勘查、石油勘探等中.针对不同的应用,产生了各具特点的一些特殊方法,包括井间无线电波成像、跨孔雷达、井间电磁成像.井间无线电波成像仪目前只测量电场强度数据,工作频率低,一般是单频的电磁波,频率范围通常在1 kHz至10 MHz.由于缺少走时数据修正射线路径,井间无线电波成像主要是进行基于直射线追踪的衰减层析成像.井间无线电波成像既可用于工程与环境地球物理也可用于找矿.跨孔雷达是钻孔雷达的一种探测方式,用高频电磁脉冲探测两个井孔间介电常数和电导率的变化.跨孔雷达层析成像也叫地质雷达CT,既可进行走时成像,还可进行衰减成像.一般来说,地质雷达CT的电磁波工作频率较高,中心频率通常在10 MHz和1 GHz之间,因此在分辨率指标上占有优势,跨孔雷达主要用于工程与环境地球物理.井间电磁成像采用更低的频率,测量复电磁信号,适合油气储集层监测,是一种地球物理前沿技术.经过在多个试验区初步试验表明,井间电磁成像是油藏研究的有效手段,可用于分析剩余油分布,寻找油气富集区,进而达到提高钻探高效井成功率和提高采收率的目的.本文详细介绍对比了这三种方法在理论和实践中的一些特点,并对未来的发展进行了展望. 相似文献
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Electromagnetic fields in a non-uniform steel-cased borehole 总被引：1，自引：0，他引：1
Since most oil wells are cased in steel, electromagnetic (EM) signals undergo severe attenuation as they diffuse across the casing. This paper examines an effect of non‐uniform casing properties on EM fields measured in a steel‐cased well embedded in a layered formation. We use a finite‐element method for computing secondary azimuthal electric fields in a cylindrically symmetric model, and analytically obtain primary fields for a homogeneous casing in a homogeneous whole space. Although steel casing largely masks EM signals induced into a layered formation, the induced signal is more pronounced in phase than in amplitude. The effect of casing non‐uniformity is quite large in measured fields but is highly localized. When electrical conductivity varies rapidly in the casing wall, the resulting EM fields also vary rapidly. A cross‐correlation function of these variations has strong peaks at two points, the interval between them being equal to the source–receiver distance. The high‐frequency coherent noise event caused by the non‐uniform casing can be greatly suppressed by low‐pass filtering to enhance EM signals indicating formation conductivity. 相似文献
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针对套管井反射式超声波水泥固井质量检测问题，本文利用超声反射波频谱中套管共振透射窗内的复合反射系数，提出了定量反演套管-地层环空间内介质的波阻抗的方法. 利用复合反射系数中多个频率点的相移反正切函数主值，给出了波阻抗的计算公式，并把套管-地层环空间介质中波的相移的整、实特性作为波阻抗反演收敛的判据. 针对井下实际测井环境中超声换能器性能受温度和压力等的影响而发生变化，导致的声源波形（子波）和复合反射系数不确定的困难，提出了用井下原地（in situ）实测波形定量估计声源波形和复合反射系数的方法. 通过对合成数据的处理，分别考察了已知介质的声学和几何参数存在的偏差对套管-地层环空间内介质的波阻抗反演结果的影响. 本文对多组模型井检验数据进行了目的层介质的波阻抗反演与成像，成像结果与真实情况吻合，验证了反演方法的有效性. 最后对现场实测资料进行了套管-地层环空间内介质的波阻抗定量反演与成像. 相似文献
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多层套管井中的套管-水泥以及水泥-地层在径向上的分布较单层套管井界面多且径向分布范围更深.目前还未有针对多层套管井固井质量评价的有效方法,偶极子阵列声波测井具有工作频率低径向探测深的优势,本文通过实轴积分和三维有限差分计算了偶极子声源在不同胶结状况的双层套管井中激发的声场,旨在探讨偶极子阵列声波在双层套管井中评价外层套管和地层之间胶结状况的可行性.计算结果表明,在两层套管之间充填泥浆时,全波波形中可明显观测到地层弯曲波和套管弯曲波,若外层套管和地层之间充填水泥套管弯曲波的慢度明显高于充填泥浆时的慢度值;在外层套管和地层之间胶结的水泥出现缺失,套管弯曲波的频散曲线会处于完全胶结与完全无胶结之间,其变化量与水泥在外层环空的占比近似成线性关系,几乎不受水泥缺失的径向位置影响.由于偶极子声源的指向性,套管弯曲波的响应特征主要受与声源振动指向的方位扇区胶结状况的影响;在两层套管之间充填水泥时,若外层套管和地层之间充填泥浆,仍可观测到套管弯曲波,模拟波列提取的套管弯曲波的频散曲线与解析解计算的频散曲线吻合,两层套管通过水泥胶结在一起,其弯曲振动的传播速度稍有增加,类似单层套管厚度加厚的响应特征.两种模拟方法得到的结果均表明套管弯曲波对外层套管和地层之间的充填介质敏感,验证了偶极子阵列声波测井在双层套管井固井质量评价中应用的可行性. 相似文献
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大斜度井、水平井的固井质量评价需求,推动了基于随钻测井仪器的固井质量评价技术的发展.本文基于弹性波传播理论,建立柱状分层介质的套管井随钻测井模型,模拟了不同水泥胶结情况的随钻声场响应,特别是其波形特征.结果表明,套管井中随钻与电缆波形特征最大的区别在于随钻波列中存在隔声衰减后的钻铤波.特别是当水泥胶结较好时,钻铤波与套管波幅度大小相近,甚至钻铤波幅度更大,而时间域上两者波形重叠,该特点使得常规电缆声波(声幅/变密度)固井质量评价方法不适用于随钻测井环境.本文考察了不同水泥胶结程度下随钻波列中套管波幅度和衰减与胶结指数的关系,形成一种同时利用幅度和衰减的随钻声波胶结指数计算方法,为随钻声波固井质量评价提供理论指导. 相似文献