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1.
Blast damage to the tops of coal seams due to incorrect blast standoff distances is a serious issue, costing the industry in Australia about one open‐cut mine for every ten operating mines. The current approach for mapping coal‐seam tops is through drilling and pierce‐point logging. To provide appropriate depth control with accuracy of ±0.2 m for blast hole drilling, it is typically necessary to drill deep reconnaissance boreholes on a 50 m x 50 m grid well in advance of overburden removal. Pierce‐point mapping is expensive and can be inaccurate, particularly when the seam is disturbed by rolls, faults, and other obstacles.Numerical modelling and prototype‐field testing are used in this paper to demonstrate the feasibility of two seismic‐while‐drilling‐based approaches for predicting the approach to the top of coal during blast hole drilling: (i) reverse “walk‐away” vertical seismic profiling recording, in which the drill bit vibration provides the source signal and the geophones are planted on the surface near the drill rig, and (ii) in‐seam seismic recording, in which channel waves, driven by the coupling to the coal of the seismic signal emitted by the approaching drill bit, are guided by the seam to geophones located within the seam in nearby or remote boreholes. 相似文献
2.
A guided wave along a borehole is often observed in borehole radar measurements. These guided waves deform the antenna pattern and can cause artefacts in radar measurements. A water-filled borehole or a conducting logging cable can function as a waveguide for electromagnetic waves under some conditions. We describe the theoretical characteristics of such a guided wave in a borehole and compare them with our experiments. The measured signal discussed was obtained with a directional borehole radar. This radar uses a cylindrical conformal array antenna as receiver and is a model of a conducting structure in a borehole. The induced field around the borehole was compared with the theory. The most fundamental symmetrical and asymmetrical modes were TM01 and HE11, and they were identified in the measured signals using time–frequency distribution analysis and by observation of the azimuthal field distribution of the magnetic field. 相似文献
3.
Retrieving virtual reflection responses at drill‐bit positions using seismic interferometry with drill‐bit noise 
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下载免费PDF全文 In the field of seismic interferometry, researchers have retrieved surface waves and body waves by cross‐correlating recordings of uncorrelated noise sources to extract useful subsurface information. The retrieved wavefields in most applications are between receivers. When the positions of the noise sources are known, inter‐source interferometry can be applied to retrieve the wavefields between sources, thus turning sources into virtual receivers. Previous applications of this form of interferometry assume impulsive point sources or transient sources with similar signatures. We investigate the requirements of applying inter‐source seismic interferometry using non‐transient noise sources with known positions to retrieve reflection responses at those positions and show the results using synthetic drilling noise as source. We show that, if pilot signals (estimates of the drill‐bit signals) are not available, it is required that the drill‐bit signals are the same and that the phases of the virtual reflections at drill‐bit positions can be retrieved by deconvolution interferometry or by cross‐coherence interferometry. Further, for this case, classic interferometry by cross‐correlation can be used if the source power spectrum can be estimated. If pilot signals are available, virtual reflection responses can be obtained by first using standard seismic‐while‐drilling processing techniques such as pilot cross‐correlation and pilot deconvolution to remove the drill‐bit signatures in the data and then applying cross‐correlation interferometry. Therefore, provided that pilot signals are reliable, drill‐bit data can be redatumed from surface to borehole depths using this inter‐source interferometry approach without any velocity information of the medium, and we show that a well‐positioned image below the borehole can be obtained using interferometrically redatumed reflection responses with just a simple velocity model. We discuss some of the practical hurdles that restrict the application of the proposed method offshore. 相似文献
4.
Boreholes present a potential hazard to mining in rock salt mines. The only rock salt mine in England was almost lost when they mined into an unknown borehole open to an aquifer. Rock salt is a good transmitter of VHF radar waves, so a good method of detecting boreholes is by using radar probing. This paper investigates theoretically the detection of a borehole in advance of mining using two different radar systems, Bravo II and Charlie II. Bravo II has a peak power of 20 kW at 230 MHz and Charlie II has 3 W at 440 MHz. The borehole detectability depends critically on the radar wave attenuation in salt, which is characterized by its loss tangent, tan δ. The backscattering cross section σ of the borehole is also important. These parameters are related in the radar signal-to-noise equation which determines the signal-to-noise ratio (S/N) for a given range in salt to the borehole. Theoretically, in salt with a tan δ of 10-3, Charlie II can detect (S/N= 3 dB) a 12.7 cm borehole 225 m in advance of mining while Bravo II, using only 100 W, can detect the same borehole 680 m ahead. These values are with the antenna E field parallel to the axis of the borehole. Theory shows this antenna orientation to be optimum for maximum detection probability. For salt with a tan δ of 2 × 10-5, the smallest value measured for salt, Bravo II can detect the borehole up to 15.3 km using maximum power of 20 kW. 相似文献
5.
Conversion of borehole Stoneley waves to channel waves was observed in data from a seismic cross-borehole experiment conducted between wellbores penetrating a thin coal layer at 2022 m depth, near Rifle, Colorado. Traveltime moveout observations show that borehole Stoneley waves underwent partial conversion to channel waves at the coal layer. The channel waves were detected directly in an adjacent borehole 35 m away at receiver positions within the coal. Stoneley waves, subsequently produced by partial conversion of channel waves, were also detected at receiver positions located up to 50 m above and below the coal layer in the adjacent borehole. We infer the channel wave to be the first-higher Rayleigh mode by comparing the observed group velocity with theoretically derived dispersion curves. Identifying the conversion between borehole and stratigraphically guided waves is significant because coal penetrated by multiple wells may be detected without placing a transmitter or receiver in the coal itself. 相似文献
6.
We revisit the equations governing the bending motions in thin rods and analyse the filtration of flexural waves in vertical drill strings pre‐stressed by gravity. The aim is to study transverse drill‐string vibrations at seismic frequencies for acoustic communication purposes and provide an algorithm for processing reflected and transmitted bending motions generated by downhole lateral vibrations. We obtain the dispersion equation, including attenuation due to a gravity pre‐stress gradient and frequency‐dependent reflection and transmission coefficients at the interface between subsequent tube intervals. We then develop a propagation‐matrix algorithm to simulate flexural waves in a drill string consisting in an assembly of multiple tube sections of different dimensions. The deflection vibrations are obtained at any arbitrary recording point in the drill string. The modelling is cross‐checked with a full‐wave grid algorithm. The analysis shows that the waves produced by a concentrated force are partitioned in standing and propagating modes, which are calculated by using the flexural impedance of the drill string. Moreover, the reflection coefficients weakly depend on the pre‐stress conditions and pre‐stress has important effects for far‐field signal transmission with variable weight on bit (WOB). We discuss the approximations and limits of the method with respect to realistic drilling conditions. 相似文献
7.
采用有限差分方法对基于圆弧片状声源和接收器的三维随钻反射声波成像测井进行模拟,研究了反射信号的幅度、相位等参数随方位和源距的变化规律,着重分析了利用该方法在水平井中对地层界面进行探测的可行性.研究结果表明,钻铤的存在使得圆弧片状声源能够向固定方位辐射声场,其主瓣三分贝角宽窄,旁瓣级低,向目的方位辐射的纵波场的幅度约为传统环状声源的0.6倍,适用于三维随钻反射声波成像测井;对于本文计算的井孔模型,反射波信号约为井孔导波信号的1/100;随着源距的增加,反射纵波幅度逐渐减小,转换波(P-SV、SV-P)的幅度先增加后减小,反射SV波的幅度增加,建议在实际应用中,选择合适源距的波形进行处理,并对其他非目的波动进行压制,以期获得更好的成像效果.本文模拟了在水平井中对地层上下界面进行探测的例子,结果显示,反射波纵波信号有较好的方位分辨率,能够准确获得井外波阻抗不连续界面的方位,而且对上、下界面的成像互不影响. 相似文献
8.
Volatile organic compounds (VOCs) are present in multiple water-bearing zones beneath and downgradient of Lawrence Livermore National Laboratory. This area is composed of interfingering unconsolidated alluvial sediments with hydraulic conductivities ranging over four orders of magnitude. The more permeable sediments exhibit moderate hydraulic interconnection horizontally and less interconnection vertically, and appear to consist largely of interconnected stream channel deposits. To optimize selection of monitoring well screened intervals in this complex environment, a technique that enables collection of saturated formation samples from each water-bearing zone without contamination from other VOC-containing zones was developed, tested, and implemented. The technique utilizes a wireline punch-coring system that allows the drill bit to be replaced with a core barrel without removing the drill rod from the borehole. To help ensure that a sample from one water-bearing zone is not contaminated by VOCs from another zone, the drilling fluid is replaced with new fluid before each sampling run. Overnight chemical analysis by gas chromatography enables field personnel to know the vertical distribution of VOCs as drilling proceeds. Since its first use in 1985, the technique has successfully characterized the presence or absence of VOCs in ground water in 123 of 140 wells, many with concentrations in ground water in the low parts-per-billion range. Our sampling technique is a cost-effective and rapid method of evaluating the vertical distribution of VOCs in ground water in a complex hydrogeologic environment. 相似文献
9.
10.
声波测井仪器的等效理论及其应用(英文) 总被引：3，自引：0，他引：3
在处理实际声波测井模式波数据或用模式波的反演地层参数时,必须考虑测井仪器对频散模式波传播的影响。本文介绍了一种用具有等效弹性模量的圆柱体来模拟声波测井仪器的等效理论,并将该理论推广应用到电缆、随钻多极子声波测井。在波长大于仪器半径的前提下,将井中的多极子声场与该等效仪器模型进行声导纳/阻抗匹配,便可导出这一理论。通过数值模拟和现场资料对该理论的有效性和实用性进行了验证,验证结果证明该理论既简单又足够精确。利用该理论模型处理实际资料时,通过调整仪器等效弹性模量和半径在给定频段标定仪器的影响,而不必考虑仪器的具体材料和结构。本文以电缆偶极子声波测井现场资料的频散校正为例,进一步证明了该等效理论处理现场资料的准确性和高效性。 相似文献
11.
《Journal of Applied Geophysics》2011,75(2):171-179
The efficacy of radio-wave imaging (RIM) in extended geological strata which are planar and regular, such as coal seams, continues to be questioned, because the electromagnetic wave excitation and propagation mechanisms remain unclear. To eradicate the doubts, a full-wave finite element simulation of a ‘realistic’ coal seam boundary value problem has been constructed and is described and analysed in this paper. The model is used to examine electromagnetic waves (near-fields) in the vicinity of the magnetic source and resonant modal patterns distant from it, for a range of electrical parameters for the coal medium and for a variety of possible boundary conditions. These studies suggest that only for very low loss seams can RIM be effective, and consequently a new guided electromagnetic wave (GEM) system has been proposed to circumvent the acknowledged deficiencies inherent in RIM. 相似文献
12.
本文对偶极横波远探测技术在随钻测井中的应用进行了探讨.对于随钻远探测而言,井中声源向井外地层中的辐射性能是它的主控因素.本文从井孔内外声场出发,考察了随钻和电缆测井中偶极声源的辐射效率,即声源产生的辐射波能流与沿井传播的导波能流之比;分析了声源的远场辐射指向性;基于声源辐射与接收之间的互易性,快速模拟和处理了随钻测井下SH和SV横波远探测波形.研究结果表明,随钻条件下SH和SV横波的最大辐射效率受钻铤的影响较电缆的情况降低了70%左右,且横波最大辐射效率对应的优势激发频率也从电缆的3.5kHz降为2.5kHz左右;虽然随钻偶极的横波辐射效率明显降低,但由理论模拟的随钻远探测数据的成像结果可知,声源辐射到地层中的横波能量仍足以探测井外反射体,表明随钻偶极远探测技术在理论上是可行的,本文结果为随钻偶极远探测测井提供了理论依据. 相似文献
13.
Small offsets in hard coal seams can be detected with the aid of seam (channel) waves. Transmission and reflection of seam waves depend, among other parameters, upon the symmetry properties of the sequence rock/coal/rock. Two typical unsymmetrical sequences are found in European coal deposits: (i) coal seams with roof and floor of differing acoustic impedance and (ii) coal seams interlayered with rock and soil. Two-dimensional analog models with appropriate impedance contrasts are used to study the effect of the unsymmetrical layers upon the propagation of Rayleigh seam waves. Data analysis is based upon amplitude measurements both parallel and perpendicular to the layers and dispersion curves. The effect of unsymmetrical roof (rock 1) and floor (rock 2) was studied with models containing homogeneous coal seams. Leaky mode wave groups with phase velocities (cR) in the range between the SV-wave velocities (βr1, 2) of the two rock materials, i.e. βr1≥cR > βr2, form a characteristic part of the Rayleigh seam wave signal. Using Knott's energy coefficient calculations it is shown that in that range energy leakage into the surrounding rock by refracted SV-waves is restricted to only one of the two interfaces, namely coal/rock 2. At the other interface, coal/rock 1, all waves are totally reflected. Thus, the high amplitudes of these leaky mode wave groups are explained by “quasi-normal mode” features. The influence of a dirt bed on wave propagation was studied in models where the roof and the floor have the same elastic properties. The maximum thickness of the dirt bed did not exceed 20% of the total seam thickness. The effect of the bed's location within the seam was also investigated. For all recorded normal-mode wave groups either the total seam or the coal layers could be regarded as wave guides. This was shown by the fact that the phases could be associated with the phase velocity dispersion curves calculated for the symmetrical sequence rock/coal/rock. These curves are relevant under the condition that the thickness of the coal layer assumed under the calculation coincides with the thickness of the effective wave guide of the respective wave groups. Wave groups guided in the total seam are not influenced by either the thickness or the position of the dirt bed. On the other hand, for wave groups guided in the coal layers, the quotient of signal amplitudes in the coal layers is influenced by the position of the dirt bed. 相似文献
14.
作为一种典型的强阻抗差低阻抗薄层,煤层中孔隙含流体时是否会引起地震反射产生明显的异常是回答地震检测流体是否可行的根本.为此,本文针对强阻抗差薄层模型,基于Biot双相介质理论,通过弹性波有限差分法数值模拟,与各向同性单相介质假设的煤层反射对比,探讨了反射复合波受煤层孔隙度及流体性质变化的影响程度.模拟分析发现：由于薄层孔隙度和孔隙流体属性的变化在Biot理论中表现为纵波速度的变化,PP波反射AVO（Amplitude Versus Offset,振幅随偏移距变化）特征对薄层是否含流体相对敏感;综合使用PP与PS波对比有利于薄层中流体的预测;孔隙度一定时,PP波反射振幅随着含气饱和度的增加而增大;受薄层调谐作用的影响,孔隙和流体变化对煤层反射的频谱特征影响不大,近似于单相介质时的情况. 相似文献
15.
煤层隐伏小断层在煤田地质勘探期间能否查明,是影响煤矿安全生产的主要地质因素.煤层中传播的地震槽波,非常适用于探测煤田异常构造.本文利用谱元法模拟计算了含断层模型Rayleigh型地震槽波的产生、传播过程,对于直达槽波、反射槽波、透射槽波进行了波场特征分析,频散特征分析,频谱特征分析.根据不同小落差断层模型（垂直断距分别为1/4、1/2、3/4、1个煤厚;断层倾角分别为90°、60°、45°）,分析了Rayleigh型槽波传播过程中断层对反射槽波、透射槽波能量、频谱的影响效应.基于以上分析,对于小断层模型中的Rayleigh型地震槽波取得了一些规律性认识,并对Rayleigh型地震槽波的勘探应用做了一些探讨. 相似文献
16.
《Ground Water Monitoring & Remediation》1985,5(4):70-73
Noncontaminating procedures were used during the hollow-stem auger installation of 12 observation wells on three hazardous waste sites in Kansas. Special precautions were taken to ensure that water samples were representative of the ground water in the aquifer and were not subjected to contamination from the land surface or cross contamination from within borehole. Precautions included thorough cleaning of the hollow-stem auger and casing, keeping drill cuttings from falling back into the borehole while drilling, and not adding water to the borehole. These procedures were designed to prevent contamination of the ground water during well installation.
Because the use of water during well installation could contaminate the aquifer or dilute contaminants already present in the aquifer, two methods of well installation that did not introduce outside water to the borehole were used. The first method involved using a slotted 3/4-inch coupling that was attached to the bit plate of the hollow-stem auger, allowing formation water to enter the auger, thereby preventing sand-plug formation. This method proved to be adequate, except when drilling through clay layers, which tended to clog the slotted coupling. The second method involved screened well swab that allowed only formation water to enter the hollow-stem auger and prevented sand from plugging the hollow-stem auger when the bit plate was removed. 相似文献
Because the use of water during well installation could contaminate the aquifer or dilute contaminants already present in the aquifer, two methods of well installation that did not introduce outside water to the borehole were used. The first method involved using a slotted 3/4-inch coupling that was attached to the bit plate of the hollow-stem auger, allowing formation water to enter the auger, thereby preventing sand-plug formation. This method proved to be adequate, except when drilling through clay layers, which tended to clog the slotted coupling. The second method involved screened well swab that allowed only formation water to enter the hollow-stem auger and prevented sand from plugging the hollow-stem auger when the bit plate was removed. 相似文献
17.
M. Fred Strauss Steve L. Story Norman E. Mehlhorn 《Ground Water Monitoring & Remediation》1989,9(2):63-71
Dual-wall reverse-circulation drilling uses flush-threaded double-wall drill pipe and high-pressure air to provide continuous return of formation and water samples. Cuttings and formation waters are not contaminated with drilling additives or mixed with other borehole material. Up-hole velocity of about 70 ft/sec provides reliable logging of water, mineral or contaminant-bearing strata. Water samples representative of specific strata may be airlifted or bailed to the surface.
In the percussion hammer system, dual-wall drill pipe is advanced through chiefly unconsolidated material by the percussion action of an above-ground pile hammer. The borehole is drilled and temporarily cased in one pass. Wells or monitoring devices are installed as the drill pipe is hydraulically retracted during construction. A rotary head may be adapted as an option to allow dual-wall rotary drilling into consolidated or crystalline formations through a percussion hammer drill string temporarily left in place as a conductor.
The complex geology and variety of geoenvironmental problems in southern California has provided a testing ground for dual-wall drilling on hazardous material site investigations. Several case histories have demonstrated the capabilities and versatility of this method, including: (1) the installation of 4-inch and 6-inch diameter gasoline monitoring and recovery wells through gravels and cobbles at a filling station where hollow-stem auger drilling failed; (2) the confirmation of a dry borehole initially drilled by direct rotary at a landfill; and (3) multiple installations of monitoring devices through municipal refuse at a city of Los Angeles landfill. 相似文献
In the percussion hammer system, dual-wall drill pipe is advanced through chiefly unconsolidated material by the percussion action of an above-ground pile hammer. The borehole is drilled and temporarily cased in one pass. Wells or monitoring devices are installed as the drill pipe is hydraulically retracted during construction. A rotary head may be adapted as an option to allow dual-wall rotary drilling into consolidated or crystalline formations through a percussion hammer drill string temporarily left in place as a conductor.
The complex geology and variety of geoenvironmental problems in southern California has provided a testing ground for dual-wall drilling on hazardous material site investigations. Several case histories have demonstrated the capabilities and versatility of this method, including: (1) the installation of 4-inch and 6-inch diameter gasoline monitoring and recovery wells through gravels and cobbles at a filling station where hollow-stem auger drilling failed; (2) the confirmation of a dry borehole initially drilled by direct rotary at a landfill; and (3) multiple installations of monitoring devices through municipal refuse at a city of Los Angeles landfill. 相似文献
18.
We use different interferometry approaches to process the seismic signals generated by a drill‐bit source in one well and recorded by seismic receivers located both in a second borehole and at the surface near the source well. We compare the standard interferometry results, obtained by using the raw drill‐bit data without a pilot signal, with the new interferometry results obtained by using the drill‐bit seismograms correlated with a reference pilot signal. The analysis of the stationary phase shows that the final results have different S/N levels and are affected by the coherent noise in the form of rig arrivals. The interferometry methods are compared by using different deconvolution approaches. The analysis shows that the results agree with the conventional drill‐bit seismograms and that using the reference pilot signal improves the quality of the drill‐bit wavefields redatumed by the interferometry method. 相似文献
19.
幅度大的钻铤波掩盖地层信号是困扰随钻声波测井技术的难题,认识钻铤波特性对于消除或有效降低钻铤波至关重要.记录岩石动电效应引起电磁场的随钻动电测井,被认为有望彻底解决钻铤波干扰问题.本文采用有限差分法,模拟不同钻铤、不同井孔结构的随钻声场,对比分析了单极源钻铤波的传播特性,阐明存在伴随钻铤波动电信号的原因.结果表明:钻铤声波在沿钻铤传播时向外部介质辐射能量,透过井壁进入地层的具有视钻铤波速度的声波,与地层纵横波一样可发生动电转化,因而可导致随钻动电测井时产生钻铤波速度的电磁信号.计算还表明,高频情况下,随钻声波测井钻铤波呈现两阶模式:具有低频截止频率的高阶钻铤波幅度较小,其速度略低于钻铤纵波速度;无截止频率的低阶钻铤波幅度较大,其波速在高频时甚至低于钻铤横波速度.这种频散特性和多阶模式特性,是径向多分层开波导结构的导波属性. 相似文献
20.
K. M. Strack 《Surveys in Geophysics》2014,35(1):157-177
For hydrocarbon applications, seismic exploration is the workhorse of the industry. Only in the borehole, electromagnetic (EM) methods play a dominant role, as they are mostly used to determine oil reserves and to distinguish water from oil-bearing zones. Throughout the past 60 years, we had several periods with an increased interest in EM. This increased with the success of the marine EM industry and now electromagnetics in general is considered for many new applications. The classic electromagnetic methods are borehole, onshore and offshore, and airborne EM methods. Airborne is covered elsewhere (see Smith, this issue). Marine EM material is readily available from the service company Web sites, and here I will only mention some future technical directions that are visible. The marine EM success is being carried back to the onshore market, fueled by geothermal and unconventional hydrocarbon applications. Oil companies are listening to pro-EM arguments, but still are hesitant to go through the learning exercises as early adopters. In particular, the huge business drivers of shale hydrocarbons and reservoir monitoring will bring markets many times bigger than the entire marine EM market. Additional applications include support for seismic operations, sub-salt, and sub-basalt, all areas where seismic exploration is costly and inefficient. Integration with EM will allow novel seismic methods to be applied. In the borehole, anisotropy measurements, now possible, form the missing link between surface measurements and ground truth. Three-dimensional (3D) induction measurements are readily available from several logging contractors. The trend to logging-while-drilling measurements will continue with many more EM technologies, and the effort of controlling the drill bit while drilling including look-ahead-and-around the drill bit is going on. Overall, the market for electromagnetics is increasing, and a demand for EM capable professionals will continue. The emphasis will be more on application and data integration (bottom-line value increase) and less on EM technology and modeling exercises. 相似文献