Experiment Study on Focal Mechanism Inversion of Shale Hydraulic Fracturing: Influence of Attenuation Changes

2017 ◽  
Author(s):  
Hongyu Zhai* ◽  
Xu Chang ◽  
Yibo Wang ◽  
Ziqiu Xue ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Focal Mechanism ◽  
Experiment Study

Microseismic search engine for real-time estimation of source location and focal mechanism

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. KS169-KS182 ◽  
Author(s):  
Xiong Zhang ◽  
Jie Zhang
Keyword(s):  
Hydraulic Fracturing ◽  
Real Time ◽  
Search Engine ◽  
Focal Mechanism ◽  
Input Data ◽  
Web Search ◽  
Solution Space ◽  
Web Search Engine ◽  
Fracturing Process ◽  
Microseismic Events

Similar to a web search engine, we have developed a microseismic search engine that can estimate an event location and the focal mechanism in less than a second to monitor the hydraulic fracturing process. The method was extended from a real-time earthquake monitoring approach for seismological applications. We first calculate the full waveforms of all possible microseismic events over a 3D grid with a known velocity model for a given acquisition geometry to create a database. We then index and rank all of the seismic waveforms in the database by following the characteristics of the phase and amplitude of the waveform through a computer fast search technology, specifically, the multiple randomized k-dimensional tree method. When a microseismic event occurs, the approximate best matches to the entry waveform are found immediately by comparing the characteristic features between the input data and the database. The method returns not just one but a series of solutions, similar to a web search engine. Thus, we can obtain a solution space that delineates the resolution and confidence level of the results. Also similar to a web search engine, the microseismic search engine does not require any input parameter or processing experience; thus, the solutions are the same for any user. Numerical tests suggest that the waveform search approach is insensitive to random and correlated noises. However, if the correlation values between the input data and best matches in the database are too low, suggesting unreliable results, the solution may be rejected automatically by applying a preset threshold. We have applied the method to real data, and found great potential for the routine real-time monitoring of microseismic events during hydraulic fracturing.

Microseismic moment-tensor inversion and sensitivity analysis in VTI media

Geophysics ◽  
2020 ◽  
pp. 1-74
Author(s):  
Han Li ◽  
Xu Chang ◽  
Xiao-Bi Xie ◽  
Yibo Wang
Keyword(s):  
Hydraulic Fracturing ◽  
Focal Mechanism ◽  
Moment Tensor ◽  
Staggered Grid ◽  
Inversion Method ◽  
Model Parameters ◽  
Seismic Moment Tensor ◽  
Tensor Model ◽  
Double Couple ◽  
The Impact

Through the study of microseismic focal mechanisms, information such as fracture orientation, event magnitude, and in-situ stress status can be quantitatively obtained, thus, providing a reliable basis for unconventional oil and gas exploration. Most source inversion methods assume that the medium is isotropic. However, hydraulic fracturing is usually conducted in sedimentary rocks, which often exhibit strong anisotropy. Neglecting this anisotropy may cause errors in focal mechanism inversion results. We propose a microseismic focal mechanism inversion method that considers velocity anisotropy in a vertically transverse isotropic (VTI) medium. To generate synthetic data, we adopt the moment-tensor model to represent microearthquake sources. We use a staggered-grid finite-difference (SGFD) method to calculate synthetic seismograms in anisotropic media. We perform seismic moment-tensor (SMT) inversion with only P-waves by matching synthetic and observed waveforms. Both synthetic and field datasets are used to test the inversion method. For the field dataset, we investigate the inversion stability using randomly selected partial datasets in the calculation. We pay special attention to analyze the sensitivity of the inversion. We test and evaluate the impact of noise in the data and errors in the model parameters ( VP0, ε, and δ) on the SMT inversion using synthetic datasets. The results indicate that for a surface acquisition system, the proposed method can tolerate moderate noise in the data, and deviations in the anisotropy parameters can cause errors in the SMT inversion, especially for dip-slip events and the inverted percentages of non-double-couple components. According to our study, including anisotropy in the model is important to obtain reliable non-double-couple components of moment tensors for hydraulic fracturing induced microearthquakes.

Joint inversion of source location and focal mechanism of microseismicity

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. KS41-KS49 ◽  
Author(s):  
Chuntao Liang ◽  
Yangyang Yu ◽  
Yihai Yang ◽  
Liang Kang ◽  
Chen Yin ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Focal Mechanism ◽  
Velocity Structure ◽  
Joint Inversion ◽  
Optimal Solution ◽  
Effective Property ◽  
Stress And Strain ◽  
Data Set ◽  
As Stress ◽  
Scanning Algorithm

The seismic focal mechanism (FM) is an effective property to indicate source physics, as well as stress and strain distribution in regional, local, and microscales. We have developed an algorithm to jointly invert for the FM and source locations. For a given velocity structure, all possible combinations of source locations ([Formula: see text], [Formula: see text], and [Formula: see text]) and FM (strike, dip, and rake) were used to compute traveltimes and polarities of waveforms. Correcting normal moveout times and polarities and stacking all waveforms, the ([Formula: see text], [Formula: see text], [Formula: see text], strike, dip, and rake) combination that gave the strongest stacking power was identified as the optimal solution. Compared with the traditional source scanning algorithm (SSA) that only scanned source locations, this algorithm was thereby called the joint source scanning algorithm (jSSA). The jSSA method was tested rigorously, and it was applied to a hydraulic fracturing data set. Our work determined several advantages against the SSA method: (1) The jSSA method could identify many shear sources that could not be detected by the SSA method due to polarity variation; (2) the jSSA almost always yielded more events than the SSA method, and the added events could often provide much better characterization of the hydraulic fracturing; (3) the statistics of source mechanisms could provide additional knowledge on the orientation of fractures, as well as the local and regional stress and strain field; and (4) for those events that were detected by both methods, the stacking power of jSSA was always higher than that obtained in SSA.

Earthquake source parameter analysis shows hydraulic fracturing induced events are consistent with fault reactivation under regional stress in northeastern British Columbia, Canada

2020 ◽  
Author(s):  
Marco Pascal Roth ◽  
Alessandro Verdecchia ◽  
Kilian B. Kemna ◽  
John Onwuemeka ◽  
Rebecca M. Harrington ◽  
...  
Keyword(s):  
British Columbia ◽  
Hydraulic Fracturing ◽  
Focal Mechanism ◽  
Seismic Moment ◽  
Parameter Analysis ◽  
Active Time ◽  
Regional Stress ◽  
Seismic Stations ◽  
Stress Orientation ◽  
Time Periods

<p>An increasing number of M3+ earthquakes have been associated with Hydraulic Fracturing (HF) injection activity in low-permeable tight shale formations in the Western Canada Sedimentary Basin (WCSB) in the last decade. These include a M<sub>w </sub>4.6 on 08/17/2015 near Ft. St. John, a M<sub>L</sub> 4.5 on 11/30/2018, and two M<sub>L</sub> 3.2 on 10/05/2019, 10/08/2019 near Dawson Creek, British Columbia. Increased seismic activity in the Dawson-Septimus area prompted a temporary deployment of seismic stations in a joint effort between McGill University and the Ruhr University Bochum in order to perform higher-resolution monitoring relative to the regional seismic station coverage. Here, we use waveform data from that deployment of 22 (dominantly broadband) stations in close proximity to numerous HF wells in an area of roughly 60 x 70 km<sup>2</sup>, between July 2017 and August 2019, as well as records from 6 additional seismic stations northwest of the study area. In total, we detect 6222 local earthquakes, of which 5325 surpass a quality control criterion of having a horizontal location error ≤ 3 km. An investigation of the spatial and temporal correlation between injection and earthquake initiation using a cross-correlation based event similarity analysis during seismically active time periods reveals a high degree of event similarity within various clusters and a strong correlation with individual injection episodes at specific HF wells. In addition, event clusters also exhibit similar patterns in daily cumulative seismic moment, independent of differences in waveform characteristics.</p><p>As individual clusters may represent the activation of specific geological structures, we perform double-difference relative relocation of seismicity to identify fault orientations. In addition, we invert for focal mechanism solutions per event cluster to check consistency with structures inferred with relocated hypocenters, and perform spectral fitting for source parameter analysis. Event relocations are performed on individual families, where the total catalog is divided into subsets corresponding to 24 seismic active time periods where 43 event families are active. Relocating each earthquake family separately allows us to successfully relocate 4571 out of the total 5325 events. The relative relocations align in two dominant orientations, with one roughly perpendicular to the maximum horizontal regional stress orientation, and the other at low angles to the maximum regional stress orientation on a regional scale around individual HF wells. Focal mechanism estimates for events with M > 2.0 result in two primary groups of faulting mechanisms: strike-slip deformation on faults implied by lineations striking at low angles to S<sub>H</sub>, and thrust-faulting deformation on faults implied by lineations perpendicular to S<sub>H</sub>. Seismic moment and corner frequency estimates from single spectrum and spectral ratio fitting as well as scaling relations will be presented.</p>

scholarly journals Multisource stress data constraints on Cretaceous—present regional tectonic stress field evolution in the southern Jinzhou area, North China Craton

2021 ◽  
Vol 18 (6) ◽  
pp. 1007-1021
Author(s):  
Chengwei Yang ◽  
Chenghu Wang ◽  
Mingruo Jiao ◽  
Yujiang Li ◽  
Pu Wang
Keyword(s):  
Stress Field ◽  
Hydraulic Fracturing ◽  
Focal Mechanism ◽  
North China Craton ◽  
North China ◽  
Tectonic Stress ◽  
Strike Slip ◽  
Stress Fields ◽  
Focal Mechanism Solutions ◽  
Regional Tectonic

Abstract Regional tectonic stress fields are key crustal stress elements that drive tectonic movements and are associated with regional tectonics and geological resources. Regional tectonic stress field evolution of the Jinzhou area, located in the eastern block of the North China Craton (NCC), may provide a deeper understanding of tectonics of western Liaoning and the NCC. This work conducted borehole television, hydraulic fracturing and focal mechanism solutions to invert the paleo and present regional tectonic stress fields. Four groups of tensile fracture in the southern Jinzhou area were identified via borehole television, and their azimuths were NNW–SSE, NWW–SEE, nearly W–E and NE–SW in temporal order representing four stages of extensional tectonic events. Hydraulic fracturing and focal mechanism solutions showed that the stress status was normal fault and strike-slip, revealing that the southern Jinzhou area is undergoing NEE–SWW-oriented compression and nearly N–S-oriented extension in accordance with the strike-slip mechanism. From the Early Cretaceous to the present, the direction of the regional extensional stress in the southern Jinzhou area has evolved counterclockwise and sequentially from NNW–SSE to NWW–SEE, W–E, NE–SW and nearly N–S, and the regional tectonic mechanism has transited from extension to extension-strike-slip to strike-slip, leading to the current tectonic framework.

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