共查询到20条相似文献，搜索用时 46 毫秒
1.
M. Kulesh M. S. Diallo M. Holschneider K. Kurennaya F. Krüger M. Ohrnberger F. Scherbaum 《Geophysical Journal International》2007,170(2):667-678
We present an improved method for computing polarization attributes of particle motion from multicomponent seismic recordings in the time–frequency domain by using the continuous wavelet transform. This method is based on the analysis of the covariance matrix. We use an approximate analytical formula to compute the elements of the covariance matrix for a time window which is derived from an averaged instantaneous frequency of the multicomponent record. The length of the time-window is automatically and adaptively set to match the dominant period of the analysing wavelet at each time–frequency point. Then the eigenparameters are estimated for each time–frequency point without interpolation. With these key features, our method provides a suitable approach for polarization analysis of dispersive signals or overlapping seismic arrivals in multicomponent seismic data. For polarization analysis in the time domain, we show that the proposed method is consistent with existing polarization analysis methods. We apply the method to real data sets from exploration and earthquake seismology to illustrate some filtering applications and wave type characterizations. 相似文献
2.
Rosaria Tondi Roberto de Franco & Riccardo Barzaghi' 《Geophysical Journal International》2000,141(3):679-698
A new algorithm is presented for the integrated 2-D inversion of seismic traveltime and gravity data. The algorithm adopts the 'maximum likelihood' regularization scheme. We construct a 'probability density function' which includes three kinds of information: information derived from gravity measurements; information derived from the seismic traveltime inversion procedure applied to the model; and information on the physical correlation among the density and the velocity parameters. We assume a linear relation between density and velocity, which can be node-dependent; that is, we can choose different relationships for different parts of the velocity–density grid. In addition, our procedure allows us to consider a covariance matrix related to the error propagation in linking density to velocity. We use seismic data to estimate starting velocity values and the position of boundary nodes. Subsequently, the sequential integrated inversion (SII) optimizes the layer velocities and densities for our models. The procedure is applicable, as an additional step, to any type of seismic tomographic inversion.
We illustrate the method by comparing the velocity models recovered from a standard seismic traveltime inversion with those retrieved using our algorithm. The inversion of synthetic data calculated for a 2-D isotropic, laterally inhomogeneous model shows the stability and accuracy of this procedure, demonstrates the improvements to the recovery of true velocity anomalies, and proves that this technique can efficiently overcome some of the limitations of both gravity and seismic traveltime inversions, when they are used independently.
An interpretation of field data from the 1994 Vesuvius test experiment is also presented. At depths down to 4.5 km, the model retrieved after a SII shows a more detailed structure than the model obtained from an interpretation of seismic traveltime only, and yields additional information for a further study of the area. 相似文献
We illustrate the method by comparing the velocity models recovered from a standard seismic traveltime inversion with those retrieved using our algorithm. The inversion of synthetic data calculated for a 2-D isotropic, laterally inhomogeneous model shows the stability and accuracy of this procedure, demonstrates the improvements to the recovery of true velocity anomalies, and proves that this technique can efficiently overcome some of the limitations of both gravity and seismic traveltime inversions, when they are used independently.
An interpretation of field data from the 1994 Vesuvius test experiment is also presented. At depths down to 4.5 km, the model retrieved after a SII shows a more detailed structure than the model obtained from an interpretation of seismic traveltime only, and yields additional information for a further study of the area. 相似文献
3.
Multicomponent near-surface correction for land VSP data 总被引：1，自引：0，他引：1
Colin MacBeth Xinwu Zeng Xiang-Yang Li John Queen 《Geophysical Journal International》1995,121(1):301-315
Multicomponent seismic data collected using directional sources are degraded by the wave excitation process due to inaccurate control of the ground motion. unequal activation strengths or ground couplings between differently oriented sources, and misalignment of the pad. These acquisition uncertainties are exacerbated by the complicated near-surface scattering present in most seismic areas. Neither group of effects should be neglected in multicomponent analyses that make use of relative wavefield attributes derived from compressional and shear waves. These effects prevent analysis of the direct and reflected waves using procedures based on standard scalar techniques or a prima facia interpretation of the vector wavefield properties, even for the seemingly straightforward case of a near-offset vertical seismic profile (VSP). Near-surface correction, using a simple matrix operator designed from the shallowest recordings, alleviates many of these interpretational difficulties in near-offset VSP data. Results from application of this technique to direct waves from a nine-component VSP shot at the Conoco test-site facility, Oklahoma, are encouraging. The technique corrects for unexpected compressional-wave energy from shear-wave vibrators and collapses near-surface multiples, thus facilitating further processing for the upgoing wavefield. The method provides a simple and effective processing step for routine application to near-offset VSP analyses. 相似文献
4.
Offset-dependent characteristics of seismic scattering are useful for characterizing fractured reservoirs. We use two models that have different background medium properties and different azimuthal AVO responses to study elastic wave propagation and scattering in gas-saturated, heterogeneously fractured reservoirs. Heterogeneous fracture density distributions are built through stochastic modelling. Synthetic seismograms are generated by 3-D finite difference modelling, and waveforms along crack-normal and strike directions are considered in this paper. The multiple signal classification (MUSIC) frequency estimator is used in waveform estimation to provide frequency-domain attributes related to seismic wave scattering by fracture heterogeneity. Our results indicate that the strength of the scattering field is a function of the background medium. The strength also increases with increasing fracture scatterer density and with decreasing correlation length of spatial variations of fracture density. The scattering field is weak at the top of the fractured reservoir. The first-order results are dominated by velocity anisotropy of the mean fracture density field. However, the base of the fractured reservoir corresponds to a strong scattering field on which fracture heterogeneity has a larger effect and is characterized by the loss of coherence. 相似文献
5.
Detection of fluid migration pathways in seismic data: implications for fault seal analysis 总被引：2，自引：1，他引：2
J. H. Ligtenberg 《Basin Research》2005,17(1):141-153
A new and efficient method for fault seal analysis using seismic data is presented. It uses multiple seismic attributes and neural networks to enhance fluid migration pathways, including subtle features that are not detectable using single attributes only. The method may be used as a first estimate of fault seal or to calibrate results from other techniques. The results provide information about which faults and fault segments are sealing or leaking. Fluid flow along individual faults appears to be focused along zones of weakness, and fault seal research should thus be focused on finding such weak locations within fault zones, a task that is best done using three‐dimensional (3D) seismic data. Under certain conditions, it is suggested that fluids migrate along fault planes by a diapiric fluid flow mechanism. The results assist in calibrating the bulk hydraulic properties of faults and rock formations and can be used in basin modelling. 相似文献
6.
We have developed an inversion formuialion for velocity and attenuation structure using seismic attributes, including envelope amplitude, instantaneous frequency and arrival times of selected seismic phases. We refer to this approach as AFT inversion for amplitude, (instantaneous) frequency and time. Complex trace analysis is used to extract the different seismic attributes. The instantaneous frequency data are converted to t * using a matching procedure that approximately removes the effects of the source spectra. To invert for structure, ray-perturbation methods are used to compute the sensitivity of the seismic attributes to variations in the model. An iterative inversion procedure is then performed from smooth to less smooth models that progressively incorporates the shorter-wavelength components of the model. To illustrate the method, seismic attributes are extracted from seismic-refraction data of the Ouachita PASSCAL experiment and used to invert for shallow crustal velocity and attenuation structure. Although amplitude data are sensitive to model roughness, the inverted velocity and attenuation models were required by the data to maintain a relatively smooth character. The amplitude and t * data were needed, along with the traveltimes, at each step of the inversion in order to fit all the seismic attributes at the final iteration. 相似文献
7.
Mostafa AllamehZadeh 《Natural Resources Research》2011,20(4):367-375
A Quadratic Neural Networks (QNNs) model has been developed for identifying seismic source classification problem at regional
distances using ARMA coefficients determination by Artificial Neural Networks (ANNs). We have devised a supervised neural
system to discriminate between earthquakes and chemical explosions with filter coefficients obtained by windowed P-wave phase
spectra (15 s). First, we preprocess the recording's signals to cancel out instrumental and attenuation site effects and obtain
a compact representation of seismic records. Second, we use a QNNs system to obtain ARMA coefficients for feature extraction
in the discrimination problem. The derived coefficients are then applied to the neural system to train and classification.
In this study, we explore the possibility of using single station three-component (3C) covariance matrix traces from a priori-known
explosion sites (learning) for automatically recognizing subsequent explosions from the same site. The results have shown
that this feature extraction gives the best classifier for seismic signals and performs significantly better than other classification
methods. The events have been tested, which include 36 chemical explosions at the Semipalatinsk test site in Kazakhstan and
61 earthquakes (mb = 5.0–6.5) recorded by the Iranian National Seismic Network (INSN). The 100% correct decisions were obtained
between site explosions and some of non-site events. The above approach to event discrimination is very flexible as we can
combine several 3C stations. 相似文献
8.
《Basin Research》2018,30(Z1):210-227
Gas chimneys are common in offshore petroliferous basins, but little known on land where seismic columnar anomalies are often attributed as poor data quality or processing artefacts. This study utilizes high‐quality 3D seismic data to document a seismic columnar anomaly penetrating through the Miocene heterolithic submarine fan‐deltaic infill of the Carpathian Foredeep. The interpreted gas chimney exhibits vertically clustered velocity push‐down features throughout the attenuated amplitude column accompanied by gas shows in well tests, has its root in gas‐bearing Palaeozoic interval and culminates in an anomalous geochemical gas record at soil level. The chimney system, ca 2 km in height and 500‐m wide, begins above the flank of a rotational bedrock fault‐block and extends vertically along a fault‐controlled conduit. At shallower levels, it passes upwards into amplitude wipeout zones that spread laterally around and partly across thin, gas‐charged reservoirs showing bright spots associated with an AVO response. At shallow levels, gas pathways through muddy slope and deltaic clinoforms are not imaged in low‐fold regions of the seismic volume. The surface geochemical anomalies, in contrast to the microbial methane signature of the Miocene succession, show significant enrichment in higher alkanes and alkenes with C2H6/C3H8 ratios indicative of a deep‐sourced, thermogenic gas or gas condensate. These anomalies form a semi‐enclosed halo around the chimney. Despite the juxtaposition of biogenic and thermogenic methane, the chimney structure imaged on seismic data supports a causal link of gases derived from Palaeozoic source rocks ascending to the surface. 相似文献
9.
Given enormous capital costs, operating expenses, flue gas emissions, water treatment and handling costs of thermal in situ
bitumen recovery processes, improving the overall efficiency by lowering energy requirements, environmental impact, and costs
of these production techniques is a priority. Steam-assisted gravity drainage (SAGD) is the most widely used in situ recovery
technique in Athabasca reservoirs. Steam generation is done on surface and consequently, because of heat losses, the energy
efficiency of SAGD can never be ideal with respect to the energy delivered to the sandface. An alternative to surface steam
generation is in situ combustion (ISC) where heat is generated within the formation through injection of oxygen at a sufficiently
high pressure to initiate combustion of bitumen. In this manner, the heat from the combustion reactions can be used directly
to mobilize the bitumen. As an alternative, the heat can be used to generate steam within the formation which then is the
agent to move heat in the reservoir. In this research, alternative hybrid techniques with simultaneous and sequential steam-oxygen
injection processes are examined to maximize the thermal efficiency of the recovery process. These hybrid processes have the
advantage that during ISC, steam is generated within the reservoir from injected and formation water and as a product of oxidation.
This implies that ex situ steam generation requirements are reduced and if there is in situ storage of combustion gases, that
overall gas emissions are reduced. In this research, detailed reservoir simulations are done to examine the dynamics of hybrid
processes to enable design of these processes. The results reveal that hybrid processes can lower emitted carbon dioxide-to-oil
ratio by about 46%, decrease the consumed natural gas-to-oil ratio by about 73%, reduce the cumulative energy-to-oil ratio
by between 40% and 70% compared to conventional SAGD, and drop water consumption per unit oil produced. However, oil recovery
is between 25% and 40% below that of SAGD. Design of successful hybrid steam–oxygen processes must take into account the balance
between injected steam and amount of injected oxygen and combustion gas products that dilute injected and in situ-generated
steam in the depletion chamber by lowering its partial pressure, and thus its saturation temperature which in turn impacts
production rates and recovery. 相似文献
10.
Analysis of seismic data suggests that hydrocarbon deposits are often associated with higher than usual values of attenuation, but this is generally ignored during amplitude-versus-offset (AVO) analysis. The effect can be modelled with equivalent medium theory based on the squirt flow concept, but the excess attenuation is associated with strong velocity dispersion. Consequently, when we study reflections from the interface between such an equivalent medium and an elastic overburden we find that the reflection coefficient varies with frequency. The impact of this variation depends on the AVO behaviour at the interface; class I reflections tend to be shifted to higher frequency while class III reflections have their lower frequencies amplified. We calculate synthetic seismograms for typical models using the reflectivity method for materials with frequency dependent velocities and attenuations, and find that these effects are predicted to be detectable on stacked data. Two field data sets show frequency anomalies similar to those predicted by the analysis, and we suggest that our modelling provides a plausible explanation of the observations. 相似文献
11.
Andrew A. Skabar 《Natural Resources Research》2011,20(3):143-155
Assuming a study region in which each cell has associated with it an N-dimensional vector of values corresponding to N predictor variables, one means of predicting the potential of some cell to host mineralization is to estimate, on the basis
of historical data, a probability density function that describes the distribution of vectors for cells known to contain deposits.
This density estimate can then be employed to predict the mineralization likelihood of other cells in the study region. However,
owing to the curse of dimensionality, estimating densities in high-dimensional input spaces is exceedingly difficult, and
conventional statistical approaches often break down. This article describes an alternative approach to estimating densities.
Inspired by recent work in the area of similarity-based learning, in which input takes the form of a matrix of pairwise similarities
between training points, we show how the density of a set of mineralized training examples can be estimated from a graphical
representation of those examples using the notion of eigenvector graph centrality. We also show how the likelihood for a test
example can be estimated from these data without having to construct a new graph. Application of the technique to the prediction
of gold deposits based on 16 predictor variables shows that its predictive performance far exceeds that of conventional density
estimation methods, and is slightly better than the performance of a discriminative approach based on multilayer perceptron
neural networks. 相似文献
12.
The subsurface imaging using conventional seismic reflection technique is challenging in areas where high velocity rocks such
as basalts are underlain by low velocity rocks. The seismic image quality worsens in the presence of intercalated sediments
within the basaltic layers. In the recent years, the multicomponent seismic exploration technique has drawn great attention
because it reduces the ambiguity in seismic imaging, enlarges the S-wave information, and improves the prediction and identification
of reservoir fluids. Improvements in sub-basalt imaging techniques could hold highly significant geologic implications such
as resource exploration and identifying permanent geochemical trapping potential (such as for carbon sequestration studies).
In this article, we examine the possibility of utilizing mode-converted (P-SV) waves for sub-basalt imaging as well as likely
complicacies one may expect in such processes. 相似文献
13.
Reserve estimation for hydrocarbon reservoirs can be improved by incorporating values extracted from three-dimensional (3-D)
seismic data with those obtained from more conventional data sources of data, such as drill-core and well-log data. An example
of this improved method is illustrated by an application to the QW pool located in the Buohaiwan Basin in eastern China. Parameter
values extracted from 3-D seismic data extend the knowledge about the spatial distributions of such reservoir parameters as
net thickness, porosity, and oil saturation. To assist in the extraction of these values, different pattern-recognition techniques
can be applied. The results that are obtained by this method offer a more reliable and more credible approach to reserve estimation
and can be applied at every stage of resource extraction from exploration to development. 相似文献
14.
Jay Lee Junfang Gong 《International journal of geographical information science》2017,31(6):1154-1177
We examined three different ways to integrate spatial and temporal data in kernel density estimation methods (KDE) to identify space–time clusters of geographic events. Spatial data and time data are typically measured in different units along respective dimensions. Therefore, spatial KDE methods require special extensions when incorporating temporal data to detect spatiotemporal clusters of geographical event. In addition to a real-world data set, we applied the proposed methods to simulated data that were generated through random and normal processes to compare results of different kernel functions. The comparison is based on hit rates and values of a compactness index with considerations of both spatial and temporal attributes of the data. The results show that the spatiotemporal KDE (STKDE) can reach higher hit rates while keeping identified hotspots compact. The implementation of these STKDE methods is tested using the 2012 crime event data in Akron, Ohio, as an example. The results show that STKDE methods reveal new perspectives from the data that go beyond what can be extracted by using the conventional spatial KDE. 相似文献
15.
K. David Newell 《Natural Resources Research》2007,16(1):55-66
Drill cuttings can be used for desorption analyses but with more uncertainty than desorption analyses done with cores. Drill
cuttings are not recommended to take the place of core, but in some circumstances, desorption work with cuttings can provide
a timely and economic supplement to that of cores. The mixed lithologic nature of drill cuttings is primarily the source of
uncertainty in their analysis for gas content, for it is unclear how to apportion the gas generated from both the coal and
the dark-colored shale that is mixed in usually with the coal. In the Western Interior Basin Coal Basin in eastern Kansas
(Pennsylvanian-age coals), dark-colored shales with normal (∼100 API units) gamma-ray levels seem to give off minimal amounts
of gas on the order of less than five standard cubic feet per ton (scf/ton). In some cuttings analyses this rule of thumb
for gas content of the shale is adequate for inferring the gas content of coals, but shales with high-gamma-ray values (>150
API units) may yield several times this amount of gas. The uncertainty in desorption analysis of drill cuttings can be depicted
graphically on a diagram identified as a “lithologic component sensitivity analysis diagram.” Comparison of cuttings desorption
results from nearby wells on this diagram, can sometimes yield an unique solution for the gas content of both a dark shale
and coal mixed in a cuttings sample. A mathematical solution, based on equating the dry, ash-free gas-contents of the admixed
coal and dark-colored shale, also yields results that are correlative to data from nearby cores. 相似文献
16.
北京市居住用地特征价格的空间分异特征 总被引：2，自引：0，他引：2
基于2004-2009年北京市居住用地出让地块微观交易数据,利用特征价格模型,研究了地块所在区域的社会属性特征对地价的影响以及地块特征价格的空间分异特征。研究显示:①居住用地价格存在显著的空间依赖效应,轨道交通和公园绿地便利性及合理的土地混合利用能够显著提升地价。②人口密度、租用公共住房比例和居住用地开发强度等地块所属社会经济属性对价格影响显著。③居住用地的空间依赖效应、周围商业办公用地溢出效应、轨道交通和公园便利性的特征价格随着就业可达性、教育状况、租用公共住房比例、犯罪率和居住用地出让比例等地块所属社会经济属性特征的变化,存在较大的分异。 相似文献
17.
1 Introduction Automated extraction of drainage features from DEMs is an effective alternative to the tedious manual mapping from topographic maps. The derived hydrologic characteristics include stream-channel networks, delineation of catchment boundaries, catchment area, catchment length, stream-channel long profiles and stream order etc. Other important characteristics of river catchments, such as the stream-channel density, stream-channel bifurcation ratios, stream-channel order, number… 相似文献
18.
Bougrain Laurent Gonzalez Maria Bouchot Vincent Cassard Daniel Lips Andor L. W. Alexandre Frédéric Stein Gilbert 《Natural Resources Research》2003,12(3):173-181
This study is concerned with understanding of the formation of ore deposits (precious and base metals) and contributes to the exploration and discovery of new occurrences using artificial neural networks. From the different digital data sets available in BRGM's GIS Andes (a comprehensive metallogenic continental-scale Geographic Information System) 25 attributes are identified as known factors or potential factors controlling the formation of gold deposits in the Andes Cordillera. Various multilayer perceptrons were applied to discriminate possible ore deposits from barren sites. Subsequently, because artificial neural networks can be used to construct a revised model for knowledge extraction, the optimal brain damage algorithm by LeCun was applied to order the 25 attributes by their relevance to the classification. The approach demonstrates how neural networks can be used efficiently in a practical problem of mineral exploration, where general domain knowledge alone is insufficient to satisfactorily model the potential controls on deposit formation using the available information in continent-scale information systems. 相似文献
19.
Conventional oil and gas productions in Louisiana has been in decline for four decades, but in recent years, new technology
and capital investment have opened up a significant new resource play in the Haynesville shale, reversing Louisiana’s gas
production decline. The need for long-term forecasting has become more important for state planning and for facilitating efficient
regulatory development and incentive programs, as the largest oil and gas fields diminish in productivity and the promise
of unconventional resources are realized. The purpose of this article is to present a hydrocarbon production forecast for
Louisiana using disaggregate resource classes and a transparent analytic framework. A field-level evaluation is employed for
producing fields categorized by primary product, resource category, geographic area, and production class. Undiscovered fields
are classified according to conventional and unconventional categories and are modeled using a probabilistic and scenario-based
forecast. The analytic framework is described along with a discussion of the model results and limitations of the analysis.
Louisiana is in the early stages of transitioning to a primarily gas-producing state, and the manner in which the Haynesville
shale develops will play a critical role in deliverability and economic prospects in the future. 相似文献
20.
Jason A. McLennan Weishan Ren Oy Leuangthong C. V. Deutsch 《Natural Resources Research》2006,15(2):119-127
The application of steam-assisted gravity drainage (SAGD) to recover heavy oil sands is becoming increasingly important in
the northern Alberta McMurray Formation because of the vast resources/reserves accessible with this mechanism. Selecting the
stratigraphic elevations of SAGD well pairs is a vital decision for reservoir evaluation and planning. The inherent uncertainty
in the distribution of geological variables significantly influences this decision. Geostatistical simulation is used to capture
geological uncertainty, which is used can be transformed into a distribution of the best possible well pair elevations.
A simple exhaustive calculation scheme is used to determine the optimum stratigraphic location of a SAGD well pair where the
recovery R is maximized. There are three basic steps to the methodology: (1) model the uncertainty in the top continuous bitumen (TCB)
and bottom continuous bitumen (BCB) surfaces, (2) calculate the recovery at all possible elevation increments within the TCB
and BCB interval, and (3) identify the elevation that maximizes R. This is repeated for multiple TCB/BCB pairs of surfaces
to assess uncertainty. The methodology is described and implemented on a subset of data from the Athabasca Oilsands in Fort
McMurray, Alberta. 相似文献