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1

Noise suppression of distributed acoustic sensing vertical seismic profile data based on time-frequency analysis

Shao Dan, Li Tonglin, Han Liguo, Li Yue

Acta Geophysica

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2022

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Vol. 70, no 4

1539--1549

EN

Distributed acoustic sensing (DAS) technology is a novel technology applied in vertical seismic profile (VSP) exploration, which has many advantages, such as low cost, high precision, strong tolerance to harsh acquisition environment. However, the field DAS-VSP data are often disturbed by complex background noise and coupling noise with strong energy, affecting the quality of seismic data seriously. Therefore, we develop a time–frequency analysis method based on low-rank and sparse matrix decomposition (LSMD) and data position points distribution maps (DPM) to separate signals from noise. We adopt Multisynchrosqueezing Transform to construct the approximate ideal time–frequency representation of DAS data, which reduces the difficulty of signal to noise separation and avoids the loss of some effective information to a certain extent. The LSMD is performed to separate the signal component and noise component preliminarily. In addition, combined with the separated low-rank matrix and sparse matrix, we propose the DPM to improve the accuracy of signal component extraction and the recovery ability of the method for weak signals through the joint analysis of the maps in time domain and frequency domain. Both synthetic and field experiments show that the proposed method can suppress coupling noise and background noise and recover weak energy signals in DAS VSP data effectively.

2

Shear Wave Splitting Analysis to Estimate Fracture Orientation and Frequency Dependent Anisotropy

Gholami R., Moradzadeh A., Rasouli V., Hanachi J.

Acta Geophysica

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2016

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Vol. 64, no. 1

76--100

EN

Shear wave splitting is a well-known method for indication of orientation, radius, and length of fractures in subsurface layers. In this paper, a three component near offset VSP data acquired from a fractured sandstone reservoir in southern part of Iran was used to analyse shear wave splitting and frequency-dependent anisotropy assessment. Polarization angle obtained by performing rotation on radial and transverse components of VSP data was used to determine the direction of polarization of fast shear wave which corresponds to direction of fractures. It was shown that correct implementation of shear wave splitting analysis can be used for determination of fracture direction. During frequencydependent anisotropy analysis, it was found that the time delays in shearwaves decrease as the frequency increases. It was clearly demonstrated throughout this study that anisotropy may have an inverse relationship with frequency. The analysis presented in this paper complements the studied conducted by other researchers in this field of research.

3

On Choosing Effective Elasticity Tensors Using a Monte-Carlo Method

Danek T., Slawinski M. A.

Acta Geophysica

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2015

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Vol. 63, no. 1

45--61

EN

A generally anisotropic elasticity tensor can be related to its closest counterparts in various symmetry classes. We refer to these counterparts as effective tensors in these classes. In finding effective tensors, we do not assume a priori orientations of their symmetry planes and axes. Knowledge of orientations of Hookean solids allows us to infer properties of materials represented by these solids. Obtaining orientations and parameter values of effective tensors is a highly nonlinear process involving finding absolute minima for orthogonal projections under all three-dimensional rotations. Given the standard deviations of the components of a generally anisotropic tensor, we examine the influence of measurement errors on the properties of effective tensors. We use a global optimization method to generate thousands of realizations of a generally anisotropic tensor, subject to errors. Using this optimization, we perform a Monte Carlo analysis of distances between that tensor and its counterparts in different symmetry classes, as well as of their orientations and elasticity parameters.

4

Zastosowanie pomiarów PPS 3C do szczegółowego odwzorowania i interpretacji strefy okołootworowej

Bartoń R.

Nafta-Gaz

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2010

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R. 66, nr 7

561-572

PL

W niniejszym artykule opisano metodykę pomiarów PPS 3C oraz zaprezentowano sposób odwzorowania strefy okołootworowej przy wykorzystaniu pomiarów pionowego profilowania sejsmicznego PPS 3C – w wersji zero-offset oraz offset. Zamieszczono przykład wykorzystania pomiarów PPS 3C do dokładnego odwzorowania i interpretacji formacji polodowcowych (glacial deposits), zlokalizowanych w Kanadzie, na zachód od Saskatoon. Zasadnicza część artykułu dotyczy wyników przetwarzania PPS 3C zarejestrowanych w otworze Batycze-1, zlokalizowanym na obszarze badań sejsmicznych zdjęcia 3D Ujkowice-Batycze, w rejonie zapadliska przedkarpackiego. Otrzymane rezultaty potwierdzają zasadność wykonywania pomiarów PPS, które stanowią istotny element w kompleksowej interpretacji danych geofizycznych i sejsmicznych.

EN

This article presents methodology of VSP 3C measurement and the method of mapping of the near-wellbore zone with utilization of measurement of vertical seismic profile VSP 3C in zero-offset and offset option. The example of utilization of VSP 3C measurement to exact mapping and interpretation of glacial deposits, located in Canada at west Saskatoon was shown. The fundamental part of this article concerns the results of the VSP 3C processing measurement in the well Batycze-1, located in the area of 3D Ujkowice-Batycze seismic research in the region of the pre-Carpathian depression. Received results confirm the legitimacy of exercise of VSP measurement which makes the essential part in the complex interpretation of geophysical and seismic data.