Flow pattern identification in oil wells by electromagnetic image logging

Petroleum production logging needs to determine the interpretation models first and flow pattern identification is the foundation, but traditional flow pattern identification methods have some limitations. In this paper, a new method of flow pattern identification in oil wells by electromagnetic image logging is proposed. First, the characteristics of gas-water and oil-water flow patterns in horizontal and vertical wellbores are picked up. Then, the continuous variation of the two phase flow pattern in the vertical and horizontal pipe space is discretized into continuous fluid distribution models in the pipeline section. Second, the electromagnetic flow image measurement responses of all the eight fluid distribution models are simulated and the characteristic vector of each response is analyzed in order to distinguish the fluid distribution models. Third, the time domain changes of the fluid distribution models in the pipeline section are used to identify the flow pattern. Finally, flow simulation experiments using electromagnetic flow image logging are operated and the experimental and simulated data are compared. The results show that the method can be used for flow pattern identification of actual electromagnetic image logging data.

Simulation Experiments in Electromagnetic Tomography Well Logging in Two-phase Flow

Electromagnetic Computer Tomography （ECT） is a method to probe the interior of an inhomogeneous medium via surface measurement in a non-linear way. Due to the great differences in conductivity and permittivity between oil and water in the well, Electromagnetic Tomography Well Logging （ETWL）, a new flow imaging measurement system, is proposed to describe the distribution and movement of oil/water two-phase flow in the well by scanning the detected region and applying a suitable data processing algorithm. The results of the numerical simulation and physical modeling show that the system could provide a clear image of the flow profile.

Numerical simulation and dimension reduction analysis of electromagnetic logging while drilling of horizontal wells in complex structures

Electromagnetic logging while drilling(LWD)is one of the key technologies of the geosteering and formation evaluation for high-angle and horizontal wells.In this paper,we solve the dipole source-generated magnetic/electric fields in 2D formations efficiently by the 2.5D finite diff erence method.Particularly,by leveraging the field’s rapid attenuation in spectral domain,we propose truncated Gauss–Hermite quadrature,which is several tens of times faster than traditional inverse fast Fourier transform.By applying the algorithm to the LWD modeling under complex formations,e.g.,folds,fault and sandstone pinch-outs,we analyze the feasibility of the dimension reduction from 2D to 1D.For the formations with smooth lateral changes,like folds,the simplified 1D model’s results agree well with the true responses,which indicate that the 1D simplification with sliding window is feasible.However,for the formation structures with drastic rock properties changes and sharp boundaries,for instance,faults and sandstone pinch-outs,the simplified 1D model will lead to large errors and,therefore,2.5D algorithms should be applied to ensure the accuracy.

The application of the high-frequency electromagnetic sounding method in the exploration of underground thermal water

High-frequency electromagnetic sounding is an electromagnetic exploration method using the natural high-frequency electromagnetic field as a field source. It has higher resolution and greater depth penetration than the direct current method and is especially fit for geothermal energy exploration and low- and mid-level groundwater detection. We introduce a successful application of high-frequency electromagnetic sounding for evaluating geothermal water resources. The high frequency electromagnetic system （MT-USA with a frequency range from 10 KHz to 1 Hz） is first applied to sample field data from China. A remote reference station is used to assure sampled data quality. We then perform 2D inversion image processing with the electrical method data. The results basically indicate the spatial distribution of underground geothermal water and provide favorable clues to finding the sources of the subsurface geothermal water in this area.

Logging while drilling electromagnetic wave responses in inclined bedding formation

For real-time inversion and fast reconstruction of formation true resistivity, the forward modeling of electromagnetic wave logging while drilling is usually based on the transversely isotropic formation model with vertical symmetry axis(VTI medium), but it only considers the horizontal and vertical resistivity. It has certain limitation during practical application. This paper presents a forward calculation method of electromagnetic wave logging while drilling in transversely isotropic(TTI) strata with inclined symmetry axis based on the Dyadic Green’s function. Anisotropic angle and azimuth are used to characterize TTI formation. The proposed algorithm is verified by numerical examples, the half-space electromagnetic wave reflection and transmission characteristics with different media are analyzed, and the necessity to use the new algorithm is pointed out. Numerical simulation also shows that there exist a critical borehole dip and critical anisotropic angle in TTI formation. Electromagnetic wave logging while drilling responses follows opposite rule before and after these two critical angles. Besides, the 'horns' at the interface are not only related to well deviation, resistivity contrast, but also related to anisotropic angle and anisotropic azimuth.

High-frequency gravitational waves having large spectral densities and their electromagnetic response

Various cosmology models, brane oscillation scenarios, interaction of interstellar plasma with intense electromagnetic radiation, and even high-energy physics experiments （e.g., Large Hadron Collider （LHC）） all predict high frequency gravitational waves （HFGWs, i.e., high-energy gravitons） in the microwave band and higher frequency region, and some of them have large energy densities. Electromagnetic （EM） detection to such HFGWs would be suitable due to very high frequencies and large energy densities of the HFGWs. We review several typical EM detection schemes, i.e., inverse Gertsenshtein effect （G-effect）, coupling of the inverse G effect with a coherent EM wave, coupling of planar superconducting open cavity with a static magnetic field, cylindrical superconducting closed cavity, and the EM sychro-resonance system, and discuss related minimal detectable amplitudes and sensitivities. Furthermore, we give some new ideas and improvement ways enhancing the possibility of measuring the HFGWs. It is shown that there is still a large room for improvement for those schemes to approach and even reach up the requirement of detection of HFGWs expected by the cosmological models and high-energy astrophysical process.

Effective Electromagnetic Log Data Interpretation in Realistic Reservoir Models

This paper analyzes some specific features of the numerical interpretation of high-frequency electromagnetic logging data in vertical, deviated and horizontal boreholes entering oil- and water-saturated formations. The interpretation is based on numerical modeling for signals.

Comparison of marine controlled-source electromagnetic data acquisition systems by a reservoir sensitivity index:analyzing the effect of water depths

During the past ten years, a marine controlled source electromagnetic（CSEM） method has been developed rapidly as a technology for hydrocarbon exploration. For shallow water environments, two CSEM data acquisition systems： Seabed Logging（SBL） and towed streamer electromagnetics（TSEM） have been developed in recent years. The purpose is to compare the performance of the SBL and TSEM systems at different water depths. Three different methods for the comparison are presented. The first method is a quick one dimensional sensitivity modelling. As a result, the sensitivity of marine CSEM data increases with water depth for the SBL system. Further, the sensitivity decreases with the increasing water depth for the TSEM system. The two other methods use two dimensional synthetic data from a simple 2-D isotropic model. The second method is a reservoir sensitivity index（RSI） method which has been developed to provide a quick comparison of the two systems. The RSI is calculated as the amplitude of the scattered field dividing by data uncertainty. From the calculations, it is found that with the increasing water depth RSI increases for the SBL system, while it decreases for the TSEM system. The third method uses Occam＇s inversion, and applies an anomaly transverse resistance（ATR） ratio for evaluating the resulting resistivity image. In shallow water environments, the resolution of the CSEM inversion results is good for both the SBL and TSEM systems. In deep water environments, the resolution of the CSEM inversion is better for the SBL system than for the TSEM system. The ATR ratios of the resistivity images show the similar conclusion. The SBL data acquisition system has an advantage in deep water environments. The TSEM system, on the other hand, is preferable for the shallow water environments.

Efficient finite-volume simulation of the LWD orthogonal azimuth electromagnetic response in a three-dimensional anisotropic formation using potentials on cylindrical meshes

In this study,the cylindrical finite-volume method(FVM)is advanced for the efficient and high-precision simulation of the logging while drilling(LWD)orthogonal azimuth electromagnetic tool(OAEMT)response in a three-dimensional(3 D)anisotropic formation.To overcome the ill-condition and convergence problems arising from the low induction number,Maxwell’s equations are reformulated into a mixed Helmholtz equation for the coupled potentials in a cylindrical coordinate system.The electrical fi eld continuation method is applied to approximate the perfectly electrical conducting(PEC)boundary condition,to improve the discretization accuracy of the Helmholtz equation on the surface of metal mandrels.On the base,the 3 D FVM on Lebedev’s staggered grids in the cylindrical coordinates is employed to discretize the mixed equations to ensure good conformity with typical well-logging tool geometries.The equivalent conductivity in a non-uniform element is determined by a standardization technique.The direct solver,PARDISO,is applied to efficiently solve the sparse linear equation systems for the multi-transmitter problem.To reduce the number of calls to PARDISO,the whole computational domain is divided into small windows that contain multiple measuring points.The electromagnetic(EM)solutions produced by all the transmitters per window are simultaneously solved because the discrete matrix,relevant to all the transmitters in the same window,is changed.Finally,the 3 D FVM is validated against the numerical mode matching method(NMM),and the characteristics of both the coaxial and coplanar responses of the EM field tool are investigated using the numerical results.

Guided and Direct Wave Evaluation of Controlled Source Electromagnetic Survey Using Finite Element Method

Deep target hydrocarbon detection is still challenging and expensive. Direct hydrocarbon indicators (DHIs) in seismic data do not correspond to economical hydrocarbon exploration. Due to unreliability in seismic data for the detection of DHIs, new methods have been investigated. Marine controlled source electromagnet (MCSEM) or Sea bed logging (SBL) is new method for the detection of deep target hydrocarbon reservoir. Sea bed logging has also the potential to reduce the risks of DHIs in deep sea environment. Modelling of real sea environment helps to reduce the further risks before drilling the oil wells. 3D electromagnetic (EM) modelling of seabed logging requires more accurate methods for the detection of hydrocarbon reservoir. Finite element method (FEM) is chosen for the modelling of seabed logging to get more precise EM response from hydrocarbon reservoir below 4000 m from seabed. FEM allows to investigate the total electric and magnetic fields instead of scattered electric and magnetic fields, which shows accurate and precise resistivity contrast below the seabed. From the modelling results, It was investigated that Hz field shows higher magni- tude with 342% than the Ex field. It was observed that 0.125 Hz frequency can be able to show better resistivity contrast of Hz field (31.30%) and Ex field (16.49%) at target depth of 1000 m below seafloor for our proposed model. Hz and Ex field delineation was found to decrease as target depth increased from 1000 m to 4000 m. At the target depth of 4000 m, no field delineation response was seen from the current electromagnetic (EM) antenna used by the industry. New EM antenna has been used to see the EM response for deep target hydrocarbon detection. It was investigated that novel EM antenna shows better delineation at 4000 m target depth for Ex and Hz field up to 10.3% and 15.1% respectively. Novel EM antenna also shows better Hz phase response (128.4%) than the Ex phase response (38.3%) at the target depth of 4000 m below the seafloor.

Electromagnetic Response Studies of the Antenna for Deep Water Deep Target CSEM Environments

The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electromagnetic field response of an antenna is unable to detect deep hydrocarbon reservoirs due to a weak electromagnetic signal response in the seabed logging environment. This work premise deals with the comparison of the electromagnetic signal strength of a new antenna with a straight antenna and the orientation of an antenna for deep target hydrocarbon exploration. Antenna position and orientation (Tx and Ty) was studied using Computer Simulation Technology software (CST) for deep targets in marine CSEM environments. The model area was assigned as (40 ′ 40 km) to replicate the real seabed environment. From the results, the new dipole antenna shows an 804% and 278% increase in electric and magnetic field strength than the straight antenna. An electric (E) and magnetic (H) field component study was done with and without the presence of a hydrocarbon reservoir. Ex and Hz field component responses with the new antenna at the1 kmtarget were measured in a deep water environment. It was analyzed that the antenna shows 53.10% (Ex) and 83.13% (Hz) field difference in deep water with and without a hydrocarbon reservoir at the30 mantenna position from the sea floor. From the antenna orientation results, it was observed that, the electric field Ex and magnetic field Hz responses decreased from 18% to 12% and 21% to 16%, respectively but was still able to detect the deep target hydrocarbon reservoir at the4 kmtarget depth. This EM antenna may open new frontiers for the oil and gas industry for deep target hydrocarbon detection (HC).

随钻中继式电磁波传输技术及应用研究

针对随钻条件下无线电磁波传输技术信号衰减大、传播距离短、信号频率低以及传输速率慢的难题,文章设计了基于准横电磁波(Transverse Electromagnetic Wave,TEM)激励模式的随钻中继式电磁波传输技术。该技术以钻杆作为传输载体,将电磁波在井内的随钻传输模型类比同轴线传输模型,通过使用多组载波频率,在提高传输速率的同时,利用中继接力扩展传输距离。该技术已通过不同地层环境的现场验证,是井下数据传输未来发展的重要方向。

神府矿区采空区精细化综合勘探技术研究

为精细化查明神府矿区亿源煤矿井田内原不明小煤窑采空区,为采空区治理提供科学依据,需开展瞬变电磁法、钻探及测井等综合勘查技术工作,以明确采空区分布范围及富水情况。结果表明:从测井曲线中可以看出煤岩层物性稳定,曲线形态明显,煤层具有高电阻率、低密度、低伽玛特性,煤层属导电性较差的高阻层(最高大于1000Ω·m),其他泥岩、砂质泥岩、砂岩等呈现相对低阻特征,煤层与围岩物性差异明显;瞬变电磁法采用280 m矩形发射线框、发射频率25 Hz、增益2^(2)~2^(5)之间、发射电流8 A、积分时间15 s的参数组合进行探测,对已知采空区反映明显,推断3^(-1)煤层房柱式采空区总面积0.985 km^(2);通过钻探揭露了2^(-2)煤和3^(-1)煤房柱式采空区,验证了物探推断的3^(-1)煤采空区。测井、瞬变电磁法探测、钻探相互依托、相辅相成,达到了精细化综合勘探的目的。

电磁波传播测井地层介电常数测量应用分析

受地层水矿化度的影响,复杂油气储层电性特征复杂,采用电阻率测量方法难以对复杂储层流体进行准确评价与识别;但介电常数受地层水矿化度影响小,并且水的介电常数远大于油气介电常数,通过电磁波传播测井仪测量地层介电常数可有效准确区分油气储层与水层,且其地层响应转换图版的精准性对复杂储层流体的准确评价至关重要。本文基于等效磁偶极子模型推导了层状介质中1 GHz电磁波传播计算公式,提出了将测量探头几何工程参数融入有限元的精确仿真方法,采用COMSOL Multiphysics建立1∶1有限元仿真模型,分析了探头几何工程参数对地层转换图版的影响。搭建实验系统验证了理论仿真的准确性,测量结果显示基于精确仿真方法得到介电常数与真实值的相对误差约为1%。研制出电磁波传播测井仪,并在某油田开展了非常规页岩油气测井应用,为油田复杂油气储层的评价提供了一种有效的测量方法。

模块化随钻电磁波测井仪器结构对测量信号的影响

常规的随钻电磁波测井是一种重要的地层流体评价方法,但其不具有方位特性。为此,提出了一种具有较好方位探测特性的新型模块化随钻电磁波测井仪器结构。为准确了解模块化随钻电磁波测井仪器结构对测量电压信号的影响情况,采用有限元法建立了三维模型,探究了仪器各部分的影响规律。研究得出:随着钻铤和天线槽填充物电阻率增大,接收电压信号出现了突变区间且与仪器的频率和几何尺寸密切相关;盖板材料的电阻率对接收信号强度的影响较大,盖板应选择电阻率比金属稍低的材料,而测量信号随传感器本体电阻率增大而增大,因此传感器本体应选择非金属材料;钻铤和填充物的电阻率较小时,接收电压信号有明显的衰减,填充物电阻率较大时其影响可以忽略;通过扣除空气介质中的仪器响应,可以较好地消除仪器结构的影响,扣除仪器结构影响后线圈中磁通量减小,导致仪器信号低于扣除前。该研究结果可为实际测井仪器的设计制造提供理论依据。

三轴各向异性层状介质磁偶极子源电磁场递推算法及应用

为快速、精确模拟复杂三轴各向异性介质中的电磁波测井响应规律,研究了一种适用于水平层状地层的磁偶极子源电磁场伪解析递推算法。该算法通过双重傅里叶变换,将空间域的三维电磁场正演转换为一系列对一维谱域场的求解,将地层上、下界面位置引入谱域电磁场通解公式,克服了传统方法存在的数值溢出问题;进一步利用传播矩阵方法,递推获得各个地层界面处的幅度系数;针对积分核函数存在的强烈振荡问题,提出了一种双重正余弦数值滤波积分方法,实现了谱域到空间域电磁场的准确、快速转换。模拟结果表明:三轴各向异性导致电测井响应更为复杂,传统各向异性电测井解释模型不再适用。新递推算法是复杂各向异性储层测井响应分析的基础,也为电性参数准确提取和精准地质导向提供了正演手段。

Investigation of Eccentric PM on High-frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

This study investigates the negative influence of an eccentric permanent-magnet(PM)design on high-frequency electromagnetic vibration in fractional-slot concentrated-winding(FSCW)PM machines.First,an analytical expression for the sideband current harmonics was derived using the double Fourier series expansion method.Then,the characteristics of the flux-density harmonics are studied from the perspective of the space-time distribution and initial phase relationship.The influence of the eccentric PM design on high-frequency electromagnetic and concentrated forces was studied based on the electromagnetic force modulation effect.Consequently,an eccentric PM design is not conducive to reducing the 2pth-order high-frequency electromagnetic forces.Finally,two FSCW PM machines with conventional and eccentric PM designs are manufactured and tested to verify the theoretical analysis.The results show that the eccentric PM design worsens high-frequency vibrations.

水平井瞬变电磁边界远探测数值模拟与响应特征分析

为克服频率域电磁感应远探仪器过长的缺点,提出采用瞬变电磁远探测方法进行边界探测,给出了均匀地层中响应解析计算方法,基于COMSOL Multiphysics有限元数值软件,建立了层状地层水平井瞬变电磁远探测响应计算模型,并对其在地层界面识别时的响应特征进行了分析。结果显示:双对数坐标系下,均匀地层中瞬态电磁远探测响应随采集时间呈线性衰减规律,且地层电阻率越大,响应衰减越快,同时刻采集的响应值越小;在两层地层中,定义背景地层响应与层状地层响应差异为边界场响应,岩层边界会导致边界场产生局部极值,该极值点对应的时间与岩层电阻率对比度、探边距离以及仪器倾斜角度密切相关,增大收发线圈间距可导致边界场响应极值向晚期时刻移动;在三层地层中,瞬变电磁远探测响应同时包含岩层上边界和下边界的信息,在边界场响应中形成两个局部极值点。研究成果为瞬变电磁远探测打下良好基础。

无线电磁波随钻测量系统的发展与展望

无线电磁波随钻测量系统是煤矿地质透明、智能钻孔探测的重要组成部分。无线电磁波随钻测量、随钻数据传输技术能够将孔内的数据传输到孔外,有效解决煤矿钻孔探查信号传输“最后一公里”的技术难题。中长距离碎软煤层定向钻进及在钻孔中开展地球物理探测是未来煤矿井下物探技术发展的方向。孔中探测能够极大地减少外界干扰,也能够简化解释地质模型。本文介绍了无线电磁波测量系统的构成、技术性能、应用场景和技术发展现状,列举了技术装备存在的一些不足,重点分析了无线传输系统中发射部分的绝缘短节和基础单元轨迹测量短节的稳定性,并对无线电磁波随钻测量系统的未来测量短节类型及技术发展趋势、高速率数据传输,多学科协同创新等方面进行了展望。

基于物理驱动的超深随钻方位电磁波测井深度学习反演

超深随钻方位电磁波测井反演是表征地层参数信息的重要技术。基于正则化(物理驱动)的电磁波测井反演方法广泛应用于现场解释,但迭代过程中需要多次调用正演,计算耗时长且不能获得实时反演结果,因此迫切需要一种高效的反演方法对随钻电磁波测井资料进行实时反演。近些年,基于深度学习(数据驱动)的电磁波测井反演算法在油气勘探领域受到了广泛关注,但该算法过度依赖于数据本身,训练过程未考虑麦克斯韦理论,所以在数据集不完备的情况下,深度学习反演效果不佳。文中针对二维各向异性地层,提出了一种耦合物理驱动和数据驱动的混合反演流程:基于超深随钻方位电磁波测井数据,随机生成无断层和断层模型数据集进行网络训练;基于训练好的网络,实现模型预测。与传统深度学习方法相比,文中方法预测精度显著提高。对含有不同噪声水平的数据进行测试,结果表明:基于物理驱动的深度学习反演方法的电阻率模型反演效果良好,具有较强的鲁棒性,泛化能力更强。