Seismic Receiver Research Articles

The Value of Information From Horizontal Distributed Acoustic Sensing Compared to Multicomponent Geophones Via Machine Learning

Abstract Faults play an important role in recharging many geothermal reservoirs, and seismic information can image the locations of these faults. The value of information (VOI) metric is used to objectively quantify and compare the value of two types of seismic receiver data via a machine learning approach. The demonstrated VOI methodology is novel by including spatial models from seismic data and obtaining the information statistics from machine learning. Our two-dimensional numerical experiments compare images created from sparsely spaced (80 m), two-component geophone sampling to high spatial resolution (1 m), single-component DAS. We used a three-fold cross validation of a U-Net convolutional neural networks to achieve average classification statistics. The results suggest that when horizontal sources are utilized, geophones and DAS identify reflectors and non-reflectors at roughly the same rate. The average F1 score for horizontal DAS is 0.939 and 0.931 for geophones. For images created from a vertical source, DAS performed marginally better (F1 = 0.919) than geophones (F1 = 0.877). Our transferrable methodology can provide guidance on which acquisition scenarios can improve images of important structures in the subsurface and present an efficient method for obtaining reliability statistics from high-dimensional, spatial data.

Assessing the potential of passive seismic receiver functions for ore body exploration

ABSTRACTWe use a passive seismic high‐frequency receiver function method to image the shallow structure around a mine site. This is a relatively new application of a standard method for mapping major discontinuities in the crust and upper mantle at a scale small enough to be relevant in an exploration context. Data collected in a 21‐instrument array is inverted for isotropic velocity structure. The retrieved velocities in the south‐eastern part of the array match very well with available sonic log measurements in the top 800 m. Based on the differences in receiver function behaviour for stations across the array, recovered velocity profiles and their similarity to sonic log measurements, the target area is split into two separate regions along a north‐northeast trending line that correlates well to the strike of the dominant structure in the area – the Navan Fault. Our results demonstrate the ability of receiver functions to provide both qualitative and quantitative information in an exploration environment.

Repeat well logging using earthquake wave amplitudes measured by distributed acoustic sensors

Well-based technologies for seismic subsurface monitoring increasingly utilize fiber-optic cables installed in boreholes as distributed acoustic sensing (DAS) systems. A DAS cable allows measuring linear strain of the fiber and can serve as an array of densely spaced seismic receivers. The strain amplitudes recorded by the DAS cable depend on the near-well formation properties (the softer the medium, the larger the strain). Thus, these properties can be estimated by measuring relative variations of the amplitudes of seismic waves propagating along the well. An advantage of such an approach to subsurface characterization and monitoring is that no active seismic source is required. Passive sources such as earthquakes can be utilized. A synthetic data example demonstrates viability of the approach for monitoring of small-scale CO2 injection into an aquifer. Two field DAS data examples based on signal recordings from several distant earthquakes show that the relevant properties of the near-well formation can be estimated with an accuracy of approximately 5%.

ПОЛУЧЕНИЕ КАЧЕСТВЕННЫХ СЕЙСМИЧЕСКИХ ДАННЫХ НА ЗАБОЛОЧЕННЫХ ТЕРРИТОРИЯХ СЕВЕРА ПЕРМСКОГО КРАЯ

The study undertakes to solve the problem of obtaining reliable seismic data in swampy areas. Raw hydrocarbon deposits in the North of Perm Krai are a promising asset, but their geological survey is constrained due to problematic surface conditions. Seismic exploration is the most detailed and reliable remote method of geological subsurface studies, but any state-of-the-art seismic 3D survey requires covering a much larger surface area than an actual area of a targeted subsurface survey. Swamps tend to strongly attenuate seismic waves, thus complicate a further geological interpretation of obtained data, and significantly limit the choice of engineering tools and techniques of surveying. Also it is impossible to avoid the influence of hard surface conditions in territories extending over hundreds of square kilometers. In order to explore the possibility of obtaining high-quality data in such conditions, we offer a comprehensive pilot survey using various recording and seismic wave excitation facilities. We analyzed and explored the possibility of solving this problem by using advanced seismic exploration methods. The study looks into the technology of obtaining primary data and into the stage of information processing for its further geological interpretation. This is the first time that Geoton seismic pulse source and GSONE high-sensitivity seismic receivers have been used for these purposes. According to the findings, there is an obvious advantage of using the blast over pulse source, especially in the swamp bed itself. At the same time, Geoton proved to be highly eco-friendly and safe, which makes it possible to use it in seismic exploration works of inhabited areas. The results of processing the pilot survey data show that the single seismic receivers produce wave patterns with the best quality and accuracy. The paper offers the seismic exploration techniques in swampy conditions and in territories that have increased requirements to environmental protection and safety.

On the Coherence of Impulse Seismoacoustic Sources in Ice Conditions

Sparker and explosive-type marine seismoacoustic signal sources are described, which can be used to solve engineering seismic survey problems in water areas. The problem of surface wave excitation in water area conditions (moreover, in the presence of ice cover) is quite relevant due to the intensive development of surface-wave methods in land seismology. The paper presents the results of an in situ experiment in the ice conditions of Lake Ladoga, devoted to recording seismoacoustic signals in the water column (with hydrophones) and on shore (with a seismic receiver). Processing and analysis of experimental data demonstrated the possibility of applying the coherent integration procedure for a sparker impulse source in order to increase the signal-to-noise ratio of the initial hydroacoustic and seismic data. The waveforms of the signals received in the water column and on shore were obtained as the waves passed through a shore wedge in the presence of sheet ice. The coherence coefficient of signals generated by a sparker and airgun is estimated. The dependence of the signal-to-noise ratio on the number of summed pulses during coherent integration was analyzed. The results point to high quality of the sparker equipment developed at GEODEVICE and demonstrate the possibility in principle of using a sparker to generate seismic waves, including surface ones.

Aseismic mid-crustal magma reservoir at Cleveland Volcano imaged through novel receiver function analyses

Processes related to eruptions at arc volcanoes are linked by structures that transect the entire crust. Imaging the mid- to lower-crustal portions (here, ~5–15 km and >15 km respectively) of these magmatic systems where intermediate storage may occur has been a longstanding challenge. Tomography, local seismic source studies, geodetic, and geochemical constraints, are typically most sensitive to shallow (<5 km) storage and/or have insufficient resolution at these depths. Geophysical methods are even further limited at frequently-erupting volcanoes where well-developed trans-crustal magmatic systems are likely to exist, due to a lack of deep seismicity. Here we show direct evidence for mid-crustal magma storage beneath the frequently erupting Cleveland volcano, Alaska, using a novel application of seismic receiver functions. We use P-s scattered waves from the Moho as virtual sources to investigate S-wave velocities between the Moho and the surface. Our forward modeling approach allows us to provide direct constraints on the geometry of low velocity regions beneath volcanoes despite having a comparatively sparse seismic network. Our results show clear evidence of mid-crustal magma storage beneath the depths of located volcanic seismicity. Future work using similar approaches will enable an unprecedented comparative examination of magmatic systems beneath sparsely instrumented volcanoes globally.

Development of 3-axis Precise Positioning Seismic Physical Modeling System for Seismic Imaging and Data Processing

A seismic physical modeling system capable of automatic 3-axis positioning control of seismic sources and receivers was developed to allow more accurate seismic imaging and data processing. To verify the applicability of the system, data were acquired for sources and receivers at various depths. Comparison to numerical data showed that the acquired data showed similar reflected wave trends. A multi-channel seismic survey was performed at a salt dome model to determine the applicability of the seismic physical modeling system, and data processing such as velocity analysis and Kirchhoff migration was carried out. The seismic cross-section image acquired was consistent with that of the geological model, and the primary reflection, multiple reflection, and diffraction data obtained agreed with real wave propagation data. The seismic physical modeling system developed allows the acquisition of modeling data that is similar to field data in an economical and efficient manner. This data can be used for various purposes, such as to simulate seismic data acquisition, design seismic explorations, and investigate data processing algorithms.

Source‐Independent Passive Seismic Reverse‐Time Structure Imaging With Grouping Imaging Condition: Method and Application to Microseismic Events Induced by Hydraulic Fracturing

AbstractSeismic imaging with active seismic sources can be used to image subsurface structures such as faults, fractures, and layer interfaces with higher resolutions than tomographic methods. However, for characterizing large‐scale three‐dimensional structures, oftentimes it is too expensive and thus impractical to conduct active seismic survey. Seismic imaging using passive sources has been used to image structures through the “pseudoactive” source imaging by assuming source information is known. However, in practice there exist some uncertainties on source information including location, origin time, source time function, and radiation pattern, which can inevitably affect the final imaging result. In this study, we propose a new source‐independent passive seismic imaging method based on reverse‐time imaging with converted waves and a new imaging condition. This method uses the interference between P and S waves at conversion points for structure imaging by back‐propagating seismograms recorded by all receivers. Since no forward modeling is needed in this method, source information is not needed. A new grouping imaging condition is proposed to improve the image resolution, in which seismic receivers are divided into several groups and the separated P and S wavefields of different groups are multiplied and then stacked over time to get an image. We test the new method on both synthetic and real data sets based on a downhole microseismic system that is used for monitoring a shale gas hydraulic fracturing treatment. The results show that the proposed passive seismic imaging method does not depend on knowing source information and can achieve higher imaging resolution.

ОБОСНОВАНИЕ ПАРАМЕТРОВ СИСТЕМЫ ПОЛЕВЫХ НАБЛЮДЕНИЙ МОГТ 2D

When performing seismic observations, 2D seismograms of a common shot point are represented as a discrete function of two variables, i.e. time and receiver – source offset. When recording a wave field using single seismic receivers placed small distance apart (UniQ technology), two goals are pursued : maintaining high frequencies of reflected signals by eliminating the effect of microstatics and fulfilling the Kotelnikov sampling theorem when discretizing a continuous field with respect to a spatial variable, thereby eliminating the effect of spatial aliasing of regular interference waves. At the stage of digital processing, this allows to solve the problem of extracting useful signals and suppressing noise more effectively. Taking the idea of a close array of receivers as a whole, it is proposed to optimize the profile observation system by source – receiver spacing combining analog and digital grouping of seismic receivers. In this case, the spatial sampling of the field is determined by the distance between the centers of receiver groups, and the parameters of the analog – digital grouping are calculated from the condition of suppressing spatial aliasing frequencies. Based on the analysis of static corrections obtained during processing of previous seismic studies, a method is proposed for assessing the effect of lateral microstatics variations on the results of analog grouping.

ФОРМА СЕЙСМИЧЕСКОГО ГОРИЗОНТА НА ВРЕМЕННОМ РАЗРЕЗЕ И ГОДОГРАФА ОБЩЕЙ ТОЧКИ ВЗРЫВА ОТРАЖЕННОЙ ВОЛНЫ В ПЕРЕХОДНОЙ ЗОНЕ ДЛЯ СЛУЧАЯ, КОГДА ПОКРЫВАЮЩАЯ ЦЕЛЕВОЙ ГОРИЗОНТ СРЕДА ОСЛОЖНЕНА НАРУШЕНИЕМ

The paper is devoted to study of reflection pattern (seismic horizon) and CSP travel time curve of reflected wave when the base of seismic oscillations receivers is within transition zone, i.e. the portion of base is in one flank while the other part is already in the next flank. The equation has been derived for travel time curve of zero-offset survey, i.e. reflection pattern) for the case when target horizon cover is complicated by fault. The other equation derived is the equation of traveltime curve of CSP of reflected wave, which upgoing rays are refracted on the fault line. For this, we have used the equation of traveltime curve of normal reflections refracted on the fault line. Based on derived formulae we have calculated traveltime curves of CSP for various models of environment. Analysis of these models has shown that while passing through seismic waves receiver base over the faulted zone the travel time curve is divided into two cuts with differing curvature and various time offsets relative to each other depending on velocity section difference from the fault line leading to the impression that these two cuts are not the sections of the same travel time curve.

Analysis of blasting seismic impact on underground mining workings under the conditions of the Magnezitovaya mine

Seismic impact of technological explosions on underground mining workings of the Magnezitovaya mine was assessed. Seismic stability of rocks of the Magnezitovaya mine was determined and safe distances from technological explosions have been calculated by the admissible seismic effect for rocks. URAN and Minimate Plus seismic recorders with three-component seismic receivers were used to establish the dynamic impact on the mine workings. Based on comparison of calculated values and experimental measurements, the recommendations are given for explosive mass limitation at a slowing-down stage at a level of minimum dangerous values for technological explosions in underground mine. It is established that the blasting operations carried out at the Magnezitovaya mine of PAO Magnezit Combine with fan longhole stopping were performed with the seismic impact safety of underground technological explosion and will not lead to the loss of rock mass stability near the underground workings. Relevance of these studies is to ensure industrial safety of underground mining operations.

Reliable workflow for inversion of seismic receiver function and surface wave dispersion data: a \u201c13 BB Star\u201d case study

Non-linear inverse problems arising in seismology are usually addressed either by linearization or by Monte Carlo methods. Neither approach is flawless. The former needs an accurate starting model; the latter is computationally intensive. Both require careful tuning of inversion parameters. An additional challenge is posed by joint inversion of data of different sensitivities and noise levels such as receiver functions and surface wave dispersion curves. We propose a generic workflow that combines advantages of both methods by endowing the linearized approach with an ensemble of homogeneous starting models. It successfully addresses several fundamental issues inherent in a wide range of inverse problems, such as trapping by local minima, exploitation of a priori knowledge, choice of a model depth, proper weighting of data sets characterized by different uncertainties, and credibility of final models. Some of them are tackled with the aid of novel 1D checkerboard tests—an intuitive and feasible addition to the resolution matrix. We applied our workflow to study the south-western margin of the East European Craton. Rayleigh wave phase velocity dispersion and P-wave receiver function data were gathered in the passive seismic experiment “13 BB Star” (2013–2016) in the area of the crust recognized by previous borehole and refraction surveys. Final models of S-wave velocity down to 300 km depth beneath the array are characterized by proximity in the parameter space and very good data fit. The maximum value in the mantle is higher by 0.1–0.2 km/s than reported for other cratons.

Crustal density structure of the northwestern Iranian Plateau

We present a new 2D crustal-scale model of the northwestern Iranian plateau based on gravity–magnetic modeling along the 500 km long China–Iran Geological and Geophysical Survey in the Iranian plateau (CIGSIP) seismic profile across major tectonic provinces of Iran from the Arabian plate into the South Caspian Basin (SCB). The seismic P-wave receiver function (RF) model along the profile is used to constrain major crustal boundaries in the density model. Our 2D crustal model shows significant variation in the sedimentary thickness, Moho depth, and the depth and extent of intra-crustal interfaces. The Main Recent Fault (MRF) between the Arabian crust and the overriding central Iran crust dips at approximately 13° towards the northeast to a depth of about 40 km. The geometry of the MRF suggests about 150 km of underthrusting of the Arabian plate beneath central Iran. Our results indicate the presence of a high-density lower crustal layer beneath Zagros. We identify a new crustal-scale suture beneath the Tarom valley between the South Caspian Basin crust and Central Iran and the Alborz. This suture is associated with sharp variation in Moho depth, topography, and magnetic anomalies, and is underlain by a 20 km thick high-density crustal root at 35–55 km depth. The high-density lower crust in Alborz and Zagros may be related to partial eclogitization of crustal roots below about 40 km depth. The gravity and magnetic models indicate a highly extended continental crust for the SCB crust along the profile. Low observed magnetic susceptibility of the Kermanshah ophiolites likely indicates that the ophiolite rocks only form a thin layer that has been thrust over the sedimentary cover.

Assessment of the permanent seismic sources for borehole seismic monitoring applications: CO2CRC Otway Project

In the CO2CRC Otway Project, seismic monitoring has evolved from traditional campaign-based seismic acquisition using a large array of seismic receivers and mobile sources, towards the techniques u...

Geophone Equivalent Circuit for Simulation Tasks in SPICE Packages

Introduction. In modern electronic equipment the inductive seismic receivers (geophones) are the most widespread as sensors for registration of seismic signals. In developing seismic receiving devices, the most significant attention is paid to input amplifiers, which are directly connected to the geophones. Depending on the type of seismic research it is necessary to allocate specific ranges of input frequencies. For filtration and frequency response form correction to geophone is adding additional circuits. Therefore, the work of the geophone should be considered in conjunction with the input cascades of the seismic waves receiver. The main part. The main parameters from the documentation of geophones are analyzed and parameters for the assess of created model adequacy are selected. The analysis was carried out on an example of the model GS-ONE produced by Geospace (USA). The structure of the geophone and the principle of electromechanical analogies for equivalent circuit creating are considered. The equivalent circuit, taking into account parasitic parameters, and the measuring and calculating methods ofthe schemeelements are given. The influence on the work of the geophone of the shunt resistance connected to the output geophone terminals is considered.The calculation of the circuit elements according to the following method is carried out on the example of the GS-ONE geophone, the amplitude and phase frequency responses as the results of simulation in the package of NI Multisim are introduced. The simulation results are assessed according to their similarity with geophone parameters from documentation. Conclusions. The accuracy of the given model is increased compared to known models due to the consideration of the presence of the output geophone branch in the form of inductance coil and its parasitic parameters. This method can be used for equivalent circuit parameters calculation and for modeling in electronic simulation packages. The model does not take into account absolutely all processes in geophone, which leads to deviation in the amplitude values of amplitude frequency response to 8% and the deviation of phase frequency response to 2 degrees. However, further additions to the model will complicate its use in engineering practice and from this point of view it is not expedient.

Multicomponent ferroactive materials for low-frequency applications: Features of the crystal and grain structure, macro-responses

Abstract Two-stage solid-phase synthesis followed by sintering according to the usual ceramic technology prepared high-density solid solutions of the composition ( Pb 1 − α 1 − α 2 Sr α 1 Ba α 1 ) [ Ti x Zr y ( Nb 2 / 3 Zn 1 / 3 ) ( Nb 2 / 3 Mg 1 / 3 ) 1 − x − y ] O 3 , with α1 = 0.02 ÷ 0.12; Δα1 = 0,02, α2 = 0.0036 ÷ 0.073; x = 0.385 ÷ 0.430, y = 0.402 ÷ 0.447. The laws governing the formation of the crystal structure, grain landscape, macroresponses (dielectric, piezoelectric, ferroelastic) and correlation links between them have been established. A group of solid solutions with promising electrophysical parameters for low-frequency applications was identified. The conclusion about the expediency of taking into account (accounting) the results obtained in the development of low-frequency devices (hydrophones, microphones, seismic receivers, etc.) was made.

A case study on receiver-clamping quality assessment from the seismic-interferometry processing of downhole seismic noise recordings

For downhole microseismic monitoring of hydraulic fracturing, the acquisition is performed using a set of three-component (3C) seismic receivers attached firmly to the borehole wall by a clamping mechanism. Such an acquisition cannot be repeated, and it is focused on recording weak signals. Thus, proper installation of the receivers is especially crucial for microseismic applications. We have developed a case study of using a seismic-interferometry approach for assessing the receiver’s installation quality from ambient-noise records. Crosscorrelation of one vertical receiver noise records with the others allows us to retrieve the direct body wave propagating along the receiver array. Our observations indicate that the inability to retrieve the direct body wave is an indicator of clamping issues. Our case study does not support the emergence-frequency hypothesis reported in the literature (that higher frequencies present in the retrieved body-wave spectrum imply better clamping quality). Another conclusion is that seismic-interferometry processing provides a stable assessment of the clamping quality only for the vertical receivers. Thus, one gets only partial diagnostics of the clamping quality for the 3C downhole tool. This is important because the horizontal components may be affected more by the clamping issues compared with the vertical components. The overall conclusion is that seismic-interferometry processing of noise records is recommended for the assessment of the downhole receiver installation prior to microseismic monitoring. It does not provide complete diagnostics but comes for free (does not need any additional technological operations or extra time).

Inverting Rayleigh surface wave velocities for crustal thickness in eastern Tibet and the western Yangtze craton based on deep learning neural networks

Abstract. Crustal thickness is an important factor affecting lithospheric structure and deep geodynamics. In this paper, a deep learning neural network based on a stacked sparse auto-encoder is proposed for the inversion of crustal thickness in eastern Tibet and the western Yangtze craton. First, with the phase velocity of the Rayleigh surface wave as input and the theoretical crustal thickness as output, 12 deep-sSAE neural networks are constructed, which are trained by 380 000 and tested by 120 000 theoretical models. We then invert the observed phase velocities through these 12 neural networks. According to the test error and misfit of other crustal thickness models, the optimal crustal thickness model is selected as the crustal thickness of the study area. Compared with other ways to detect crustal thickness such as seismic wave reflection and receiver function, we adopt a new way for inversion of earth model parameters, and realize that a deep learning neural network based on data driven with the highly non-linear mapping ability can be widely used by geophysicists, and our result has good agreement with high-resolution crustal thickness models. Compared with other methods, our experimental results based on a deep learning neural network and a new Rayleigh wave phase velocity model reveal some details: there is a northward-dipping Moho gradient zone in the Qiangtang block and a relatively shallow north-west–south-east oriented crust at the Songpan–Ganzi block. Crustal thickness around Xi'an and the Ordos basin is shallow, about 35 km. The change in crustal thickness in the Sichuan–Yunnan block is sharp, where crustal thickness is 60 km north-west and 35 km south-east. We conclude that the deep learning neural network is a promising, efficient, and believable geophysical inversion tool.

Lateral variation in crustal structure along the Lesser Antilles arc from petrology of crustal xenoliths and seismic receiver functions

We reconstruct crustal structure along the Lesser Antilles island arc using an inversion approach combining constraints from petrology of magmatic crustal xenoliths and seismic receiver functions. Xenoliths show considerable island-to-island variation in xenolith petrology from plagioclase-free ultramafic lithologies to gabbros and gabbronorites with variable proportions of amphibole, indicative of changing magma differentiation depths. Xenoliths represent predominantly cumulate compositions with equilibration depths in the range 5 to 40 km. We use xenolith mineral modes and compositions to calculate seismic velocities (vP,vS) and density at the estimated equilibration depths. We create a five-layer model of crustal structure for testing against receiver functions (RF) from island seismic stations along the arc. Lowermost layer (5) comprises peridotite with physical characteristics of mantle xenoliths from Grenada. Uppermost layer (1) consists of 5 km of volcaniclastics and sediments, whose physical properties are determined via a grid inversion routine. The three middle layers (2) to (4) comprise igneous arc crust with compositions corresponding to the xenoliths sampled at each island. By inversion we obtain a petrological best-fit for the RF on each island to establish the nature and thicknesses of layers (2) to (4).Along the arc we see variations in the depth and strength of both Moho and mid-crustal discontinuity (MCD) on length-scales of tens of km. Moho depths vary from 25 to 37 km; MCD from 11 and 32 km. The Moho is the dominant discontinuity beneath some islands (St. Kitts, Guadeloupe, Martinique, Grenada), whereas the MCD dominates beneath others (Saba, St. Eustatius). Along-arc variability in MCD depth and strength is consistent with variation in estimated magmatic H2O contents and differentiations depths that, in turn, influence xenolith lithologies. A striking feature is steep, along-arc gradients in vP similar to those observed at other oceanic arcs. These gradients reflect abrupt changes in rates and processes of magma generation in the underlying crust and mantle. We find no evidence for large, interconnected bodies of partial melt beneath the Lesser Antilles. Instead, the crustal velocity structure is consistent with magma differentiation in vertically-extensive, crystal mush-dominated reservoirs. Along-arc variation in crustal structure may reflect heterogeneous upwelling within the mantle wedge, itself driven by variation in slab-derived H2O fluxes.

A Heuristic-Learning Optimizer for Elastodynamic Waveform Inversion in Passive Seismics

This paper explores (full-) waveform inversion in passive seismics to simultaneously optimize the source parameters of seismic events together with the properties of the medium of wave propagation. A heuristic optimization algorithm inspired in iterative design is proposed, which incorporates ideas from particle swarm optimization and variable projection. The algorithm is designed to accelerate convergence, improve stability and robustness, and minimize the number of user-defined parameters. The performance of the algorithm is illustrated with a real data example of hydraulic stimulation monitoring using a surface array of seismic receivers. In this example, only the locations of the receivers are known. The inversion is targeted to jointly optimize the parameters of a viscoelastic velocity model, associated models of receiver residual statics, wavelet signatures for direct compressional and shear arrivals, spatiotemporal locations of the input seismic events, and their corresponding moment tensors. Velocity model and locations are compared to estimations of the same parameters previously obtained through a well-established workflow using decoupled inversions. Results from both approaches show consistency. The main advantage of the joint approach is, therefore, the possibility of incorporating additional unknowns into the optimization to obtain self-consistent solutions using a single inversion process.