Journal of Geophysics and Engineering - Latest Papers

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Latest articles for Journal of Geophysics and Engineering
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Crustal structure beneath the Jiaodong Peninsula, North China, revealed with a 3D inversion model of magnetotelluric data

Thu, 08/02/2018 - 7:00pm
The Jiaodong Peninsula in North China is an important Chinese gold mining region, and deposits are mainly controlled by the northeast trending Sanshandao, Jiaojia, and Zhaoyuan–Pingdu faults. Most previous study results proposed the relationships of the known deposits, controlling faults and regional tectonics. One important tectonic belt, the Sulu Orogen, is thought to be related with mineralization and controlling faults. But debates remain concerning the orogeny boundary and tectonic process. We arranged 32 magnetotelluric stations in one line across the central and southern Jiaodong area to analyze the deep electrical structure of this orogeny. After the data collection (using Phoenix instruments) and pre-processing (Phoenix software), we carried out impedance analysis, data selection, static shift correction and three-dimensional inversion using our software. The results consequently proposed that the distribution of upwelling hydrous basaltic magma acts as conductor in the...

A new approach to history matching based on feature selection and optimized least square support vector machine

Sun, 07/29/2018 - 7:00pm
In this paper the latest approaches to automated history matching were applied to a real brown field with multiple responses, located in the south part of Iran. A modified support vector machine was employed to create a proxy model in which 44 model parameters were incorporated based on feature selection and the design of the experiment. A new algorithm was employed for parameter screening, based on feature selection, before commencing the proxy model construction. Thereafter, all model parameters were adjusted to reproduce the observed history within the created proxy model. A robust framework for building the proxy model was programmed with the ability to exchange data between commercial reservoir simulator software and the proxy model routine. Accordingly, the proposed proxy model was successfully constructed using 1086 samples based on an R 2 coefficient of about 0.9 for the trained and tested dataset. Finally, the process was optimized by two main algorithms for r...

A study on homogenization equations of fractal porous media

Sun, 07/29/2018 - 7:00pm
Fractal dimension can effectively describe the microstructure of self-similar fractal porous media, and it is of great significance to predict their macroscopic mechanical properties by different fractal dimensions. Based on fractal theory and the Mori–Tanaka method, homogenization equations of fractal porous media were deduced by tensors in this paper, and the parameters affecting the prediction results and the macro mechanical properties were discussed. The numerical results show that the homogenization equations are reliable, and the value of λ f ,min / λ f ,max has an influence on prediction results and the macro mechanical properties. When the pore fractal dimension is close to 1.4, the prediction results by fractal homogenization equations in this paper are more accurate. Meanwhile, the macro mechanical properties are enhanced with the increase of the solid parameters (Poisson’s ratio, elastic modulus), whereas they decrease ...

Study on mining failure law of the weak and weathered composite roof in a thin bedrock working face

Tue, 07/24/2018 - 7:00pm
In this paper, the occurrence characteristics of the weak and weathered overburden, and hydrogeological features, are first analyzed in a research coal field. The overburden failure law and the development of ‘Three Zones’ are studied through physical model tests, and the rupture pattern and rock failure are analyzed in the conditions of mining under a weakly cemented roof with longwall top coal caving. When coal mining is 5 meters thick, the developmental height of the caving zone and the water flowing fractured zone is calculated as 21 meters and 58 meters, respectively. Based on the geological and mining conditions, through discrete element numerical simulation, the overburden failure law and characteristics of strata pressure behaviors were studied under the weak and weathered composite roof during coal mining. The results show that under the conditions of the weak and weathered composite roof in a thin bedrock working face, the fracture length of old roof pressure will decr...

2D multiresolution automated system for detecting BSRs on seismic reflection images

Thu, 07/19/2018 - 7:00pm
This work presents an automation system for detecting the presence of bottom-simulating reflectors (BSRs) and other reflectors parallel to the sea bottom in real seismograms. The system uses automatic gain control to aid the thresholding method for edge detection and segmentation to calculate the sea bottom curve. After preprocessing the seismic reflection images, 2D multiresolution analysis methodology was used to develop the automated pattern recognition system which detects BSRs and other parallel reflectors in a robust manner. Synthetic and real seismic images were used to evaluate the proposed methodology, which showed excellent results in both cases.

Wave-equation based migration of primaries and free-surface multiples simultaneously with artifact suppressing

Wed, 07/18/2018 - 7:00pm
Free-surface related multiples exist widely in marine seismic data. Imaging with multiples rather than suppression has particular benefits because multiples have more information than primaries, such as wider illumination and higher vertical resolution. One-way wave-equation based pre-stack depth migration (OWPSDM) is an effective imaging tool with high calculation efficiency. By using an OWPSDM operator, primaries and multiples are imaged simultaneously. The artifacts caused by the cross-correlation between forward-propagated source and backward-propagated multiples can be suppressed by an approach with the following three steps: for the first step, the source is replaced by the recorded field data together with a wavelet and the data is the recorded field data. The imaging results contain both real structure images and artifacts. For the second step, the source is the wavelet and the data is replaced by the predicted free-surface related multiples. Artifacts can be obtained af...

Time domain full waveform inversion with low frequency wavefield decompression

Wed, 07/18/2018 - 7:00pm
Full waveform inversion (FWI) aims to recover the most accurate velocity components with full wave information. FWI produces nearly perfect results when the input seismic data contains enough low-frequency information. We first analyze the relationship between the gradient and the velocity perturbation based on the Born approximation. Compared with the frequency domain, the wavefield in the time domain contains a second-order time-derivative operator. For this reason, time-domain schemes are not very effective at recovering the very low wavenumbers, which are suppressed by the derivative operators. Accordingly, we propose a new method introducing a low-frequency decompression operator into the objective function to compensate for the high-passed filter effects in the time domain FWI. The objective function after low-frequency decompression has better convexity, thus converges to the global minimum more easily. We then compare the new approach with the classical FWI through an ap...

Sensitivity analysis and inversion processing of azimuthal resistivity logging-while-drilling measurements

Wed, 07/18/2018 - 7:00pm
We present systematic sensitivity analyses of logging-while-drilling azimuthal resistivity measurements (ARM). These analyses provide us the clear images of the sensitivities of the ARM to various formation parameters, such as bed boundary, current and shoulder layer formation resistivities, and dip angle. Optimized parameter bounds and initial values for inversion are also derived from these analyses. Furthermore, a fast-accurate, regularized Gauss–Newton inversion approach is developed to implement the inversion processing of ARM. Several strategies are applied to optimize and accelerate the inversion process: (1) a depth sliding window divides the 3D formation structure into a set of approximate ‘stitched’ 1D layered model, which is particularly useful for the interpretation in formation with lateral discontinuities; (2) a rank-one updating method approximates the Jacobian matrix to accelerate the inversion process. Examples are presented to validate the efficiency and robust...

Pore-scale identification of multi-phase spatial distribution of hydrate bearing sediment

Thu, 07/12/2018 - 7:00pm
The pore-scale location of hydrates exerts strong control on the macroscale physical properties of hydrate-bearing sediments. Many microfocus x-ray computed tomography (CT) devices have been used to detect the pore-scale spatial distribution of water, free natural gas, hydrate and sediment within the pore spaces of hydrate-bearing sediments. However, it is not easy to identify these four phases for intersection of grayscale intervals in CT images based on the usually obtained bimodal or trimodal histogram of grayscale in the threshold segmentation method, where four thresholds are required. To help deal with the overlapping areas of the grayscale in CT images, the Markov random field (MRF) is employed to promote the identification result of each phase, in the concept of maximum a posteriori (MAP) probability based on Bayes’ theorem. After validation in the example of Berea sandstone (voids and solid), this method behaves well in hydrate-bearing sediment, which is ...

Modeling of quantifying proppants for stimulation reservoir volume fracturing in a shale hydrocarbon reservoir

Thu, 07/12/2018 - 7:00pm
Massive hydraulic fracturing (MHF) technology is widely used to increase the stimulation reservoir volumes in the development of shale hydrocarbon reservoirs by pumping large amounts of fracturing fluids and proppants at a high injection rate. However, fresh water dissipation and the flowback fluid pollution created by this technology brings serious environmental problems. Moreover, the post-production of MHF is uncertain and some fractured wells keep a low production level all the time. It is therefore necessary to find an economical treatment size to satisfy the actual geology position of shale reservoirs, such as mountainous and water shortage regions. The amount of proppant for MHF are a key parameter of treatment size, which also effect the volume of fracturing fluids and injection rate directly. A proppant quantifying model for MHF in a shale hydrocarbon reservoir was developed. In this model, the complex fracture network was characterized as the enhanced permeability area...

Seismic modulation model and envelope inversion with smoothed apparent polarity

Mon, 07/09/2018 - 7:00pm
The seismic modulation model analyzes a seismogram from the low and high-frequency information, which is different from the traditional convolution model. In the modulation model, a seismogram is regarded as a modulated signal and its envelope is the amplitude-modulation component containing the low-frequency information. On this foundation, the envelope of seismograms can be used to recover a very smooth background structure. However, amplitude demodulation methods can only obtain the absolute value of the envelope, which cannot reflect the polarity changes of the amplitude information in seismograms. To solve this problem, we consider the low-frequency modulation from both the amplitude and polarity points of view. We extract a modulator signal with smoothed apparent polarity, which contains the amplitude and polarity information in seismograms. The new approach can broaden the modulation model theory for seismic signals. Good results from examples for application to envelope ...

Development of machine learning predictive models for history matching tight gas carbonate reservoir production profiles

Mon, 07/09/2018 - 7:00pm
History matching (HM) is an important task that is performed once a reliable reservoir model is constructed during numerical reservoir simulation studies. This HM process requires modification of uncertain reservoir parameters in order to match historical production data. As a result of these modifications, HM has been a long-standing industrial challenge in terms of computational cost and time consumption and furthermore, it requires much experience from the modeler. The tight gas production profiles of a damaged formation used in this study have been difficult to match due to the complex flow mechanism, computational expensiveness and minimal interaction between production wells. In addition, incorporating complex fracture networks due to stress sensitivity into the field’s reservoir model for prediction is also a major challenge. Therefore, this paper proposes supervised machine learning predictive data analytics techniques of multivariate adaptive regression splines (MARS), ...

A field experiment with self-developed broadband recorders and a preliminary characteristic analysis of the data records

Mon, 07/09/2018 - 7:00pm
Field experimental studies are mostly conducted from a technological approach, which helps to advance technological improvements in instrumentation and data processing schemes. In combination with a project initiated to explore the deep structures beneath South China led by the Institute of Geology and the Chinese Academy of Geological Sciences, the field experiment in this study was utilised to perform a contrast experiment between the self-developed GEI broadband seismic recorder and the universal Reftek 130 broadband seismic recorder. The power spectral densities (PSDs) and cross-correlation functions of ambient noise observed at ten self-developed broadband seismographs were calculated and analysed. The results obtained through the noise PSDs show the following: (i) strong diurnal variational characteristics of the high-frequency noise PSDs agree well with regular daily human activities, indicating that the high-frequency components of noise are generated by human activities...

Soil–rock mixture shear strength measurement based on in situ borehole pressure-shear tests

Mon, 07/09/2018 - 7:00pm
The shear strength of a soil–rock mixture is an important parameter in geotechnical engineering design and the stability analysis of large-scale geotechnical engineering structures such as earth-rock dams and slopes. To solve the problem of the large disturbances that are encountered in laboratory and in situ direct shear testing of soil–rock mixtures, a new method referred to as borehole pressure-shear testing was developed for the measurement of the shear strength of a soil–rock mixture. The mechanical and mathematical models used for the proposed in situ borehole pressure-shear test were established based on the principles of borehole shearing technology. The shear strengths of similar materials were measured by borehole pressure-shear tests and direct shear tests, respectively, and the test results were used to calibrate the working parameters of the apparatus for the borehole pressure-shear test. The borehole pressure-shear test was then applied to the on-site...

Ground stability evaluation of a coal-mining area: a case study of Yingshouyingzi mining area, China

Mon, 07/09/2018 - 7:00pm
Ground subsidence is a very common phenomenon in mining areas, especially for those with a long mining period. After nearly half a century of mining activity, the concomitant disasters of Yingshouyingzi mining area gradually accumulated and have frequently occurred in recent years. In this work, the ground disaster situation and ground subsidence range appearing in the survey area were determined using field investigation and D-InSAR monitoring technology. Geophysical exploration technology (seismic prospecting and transient electromagnetic methods) and geological drilling exploration was adopted to ascertain the distribution of the underground goaf. The results show that the No. 4 and No. 6 coal seam goafs and second mining affected area were developed in the study area. Additionally, ten influencing factors were selected to evaluate the ground stability. According to the grading of each evaluation factor, the survey area was divided into four regions: unstable region, basic un...

Improved horizontal well logging porosity calculation for a gas reservoir in the Northern Ordos Basin, China

Mon, 07/09/2018 - 7:00pm
The porosity calculation is the basis for the estimation of permeability and fluid saturation, which plays a significant role in hydrocarbon production. Acoustic logging is a critical method for porosity calculation but it suffers from partial distortions in horizontal wells. In addition, owing to high costs and imperfect technology, the horizontal logging data are always insufficient in the Northern Ordos basin, China. Therefore, porosity calculations based on partially distorted acoustic logs and insufficient horizontal logging data complicate the well logging interpretation. In this study, the abnormal acoustic log phenomena were analyzed based on the stratigraphic correlation and several influencing factors resulting in abnormal acoustic slowness in horizontal wells were summarized. Based on a detailed analysis, we proposed a novel porosity calculation model in which the normal acoustic log was combined with the compensated neutron log. Based on accurate porosity estimations...

Fast multi-trace impedance inversion using anisotropic total p-variation regularization in the frequency domain

Thu, 06/28/2018 - 7:00pm
In this article, we find that the transformational matrix between the natural logarithm of the acoustic impedance and the reflection coefficient is a Toeplitz matrix. As a result, we can convert the matrix multiplication into convolution operation according to properties of the Toeplitz matrix. In this way, we calculate the convolution of matrices through a dot product operation in the frequency domain based on the convolution theorem. Thus a fast multi-trace impedance inversion method by using two dimensional fast Fourier transform in the frequency domain is proposed, which can greatly improve the inversion speed. Considering the non-convex Lp(0 ≤ p < 1) quasi-norm is more suitable for sparse optimization than the L1 norm, anisotropic total variation regularization based on the Lp quasi-norm is used to improve the inversion result. Synthetic seismic data and field data inversion results show that the proposed method improves the inversion speed more than ten times co...

Effects of solid backfilling on overburden strata movement in shallow depth longwall coal mines in West China

Thu, 06/28/2018 - 7:00pm
Overburden strata movement can create problems in longwall coal mines at shallow depths located in the West of China, due to surface subsidence affecting the surface structures and sensitive land features. Solid backfill mining (SBM) has been successfully used in several mines to solve many subsidence related problems, including coal extraction under buildings, water bodies and railways, and protecting the sensitive landscape. Due to the relatively shallow depth of coal seam, however, the solid backfilling materials must have high compactibility (i.e. be stiff). Based on the longwall working face 15 061 in the Dong Ping coal mine, the different size of the backfill gangue and the affects of porosity, stress and strain, strain energy density and strain were obtained in the laboratory. The deformation and energy absorb of the gangue with different particle size during compaction were analyzed. A multi-layer, composite and elastic foundation mechanical model of the key layers in th...

Reflection and transmission coefficients of poroelastic thin-beds

Thu, 06/28/2018 - 7:00pm
Based on Biot’s poroelasticity theory for low-frequency range and Deresiewicz’s boundary conditions, we first derive propagator matrices of multi-layered isotropic poroelastic media for elastic waves defined by displacement functions. Then we give the reflection and transmission coefficients of a thin-bed where there is only a fast P-wave incident. The reflection and transmission coefficients are functions of incidence angle, thin-bed thickness, frequency, Biot’s elastic parameters and rock properties. Numerical simulations and comparisons with the solid-phase models show that, for models of a water-saturated thin-bed embedded by two water-saturated porous solid half-spaces, the reflections of fast P-wave, slow P-wave and converted S-wave versus incidence angle are of great difference. Not only do the thin-bed thickness and porosity affect the reflection coefficients’ amplitudes and phases of the porous thin-bed, but also the existence of fluid further complicates amplitude-vers...

Study of ultrasonic wave characteristics of shale in triaxial compression tests

Thu, 06/28/2018 - 7:00pm
Changes in the velocity, amplitude and attenuation of ultrasonic waves are accompanied by physical changes during rock failure. A large number of triaxial compression tests were performed to study the progressive failure of shale rock according to these physical properties. The tested shale samples had different bedding planes and were subjected to different confining pressures. During the experiments, ultrasonic wave testing was used to monitor the progressive failure process and to evaluate different characteristic points. Variations were interpreted by analyzing the ultrasonic velocity and amplitude. Failure points cause velocity drops that are greater in the P than in the S waves. The percentage wave amplitude decrease at dilatancy point was determined and that of the P wave is double that of the S wave, which indicates that the P wave is more sensitive. The shale sample attenuation was analyzed, and the results show that samples with high density and high homogeneity tend t...

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