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Microseismic Monitoring Events Classification Based on Waveform Clustering Analysis and Application
ZHAI Shang, YU Zhichao, TAN Yuyang, HUANG Fangfei, LIU Ling, HU Tianyue, HE Chuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (3): 406-416.   DOI: 10.13209/j.0479-8023.2020.018
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Based on the difference of waveform similarity between different types of microseismic monitoring events and combined with their characteristics in occurrence location, traveling time and polarization direction etc., a method for classifying microseismic monitoring events based on waveform clustering analysis is proposed. Firstly unclassified events can be identified rapidly using conventional microseismic event detection methods, then similar events are grouped based on waveform clustering analysis, finally the types of microseismic events or noise events are determined combining the attribute characteristics. Classified microseismic events can be further used for template matching technique to finely detect similar events with low signal-to-noise ratio. Meanwhile the global optimization approach which aims to improve the accuracy of arrival time picking can be also performed by taking similar microseismic events as a whole. 
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Seafloor Deformation Monitoring Based on Tiltmeters for Natural Gas Hydrate Production
ZHANG Xin, ZHANG Hongliang, ZHOU Lei, HE Tao, LIANG Qianyong, DONG Yifei, HE Chuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (4): 635-642.   DOI: 10.13209/j.0479-8023.2019.054
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We present and establish a seafloor deformation model for gas hydrate exploitation in the sea area based on Okada’s linear elasticity theory. The seafloor deformation field is simulated by using high precision tiltmeters, and the model parameters are inverted by simulated annealing method. The results show that the accurate information of dip, azimuth and volume of hydrate dissociated zone can be obtained by tiltmeters. The test results at different noise levels show that the model parameter inversion method has good anti-noise performance. In addition, the feasibility of tiltmeter monitoring in practical application is analyzed according to the hydrate exploitation test in Shenhu area of South China Sea in 2017, and the results show that the type of decline in production has advantages in seabed stability.
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Automatic Microseismic Event Detection and Arrival Picking Based on Waveform Cross-Correlation
WEI Mengyi, TAN Yuyang, MAO Zhonghua, FENG Gang, HU Tianyue, HE Chuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (2): 361-372.   DOI: 10.13209/j.0479-8023.2017.079
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Generally, a cluster of seismic events which share similar source locations and focal mechanisms will show similar waveforms on the record. Based on this assumption, a method have been developed for microseismic event detection and arrival picking based on waveform cross-correlation. This method achieves moveout correction for the seismic records based on cross-correlation functions, then calculates a multi-channel semblance coefficient to identify the microseismic events. Meanwhile, the seismic records after moveout correction are superposed. The STA/LTA method is adopt to pick the arrivals for the stacked traces, the arrival times of the microseismic events are then automatically obtained. The performance of the method is evaluated using both synthetic and real datasets. Analysis of the results demonstrates that the proposed method can not only detect the microseismic events, but also obtain relatively accurate arrival picks at the same time.

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Velocity Model Inversion for Microseismic Monitoring Based on Occam Inversion Algorithm
ZHAO Zhong,TAN Yuyang,ZHANG Hongliang,HE Chuan
Acta Scientiarum Naturalium Universitatis Pekinensis   
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In order to accurately locate the microseism sources, a thorough knowledge of the velocity model between the treatment well and monitoring well is essential. A new method is developed to invert the velocity model based on Occam inversion algorithm. Instead of the travel times, this method adopts the moveouts of the first arrivals to invert the velocity models, so it can overcome the limitation of conventional approaches when the perforation origin times are unavailable or measured inaccurately. The feasibility of this method is examined on synthetic datasets. The results demonstrate that although the velocity models obtained using this method show some discrepancies, which are caused by the picking errors, they can locate the perforation shots back to their expected positions, so the inverted velocity models can be used to locate the microseism sources.
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Simulated Annealing Based Inversion of Hydraulic Fracture Parameters
ZHANG Hongliang,HE Chuan,TAN Yuyang,ZHANG Bo,ZHANG Baoping
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract781)      PDF(pc) (612KB)(376)       Save
The authors propose a simulated annealing (SA) based inversion method to calculate hydraulic fracture parameters. A synthetic tilt data is used to demonstrate the accuracy of this new approach when inversing the hydraulic fracture parameters such as central position, azimuth, dip and volume. Compared with conventional gradient-based approaches or Bayesian inversion method, the new SA-based method can not only estimate the fracture parameters effectively, but also enlarge the objective function’s convergent region significantly. It relieves the accuracy requirement on initial guess, so that its applicable scope is extended significantly, and any prior fracture information to start with is unnecessary. This study provides algorithmic foundation for the real-time calculation of fracture parameters during hydraulic fracturing.
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