Study of Recording System and Objective Function for Microseismic Source Location

doi:10.13209/j.0479-8023.2016.091

Abstract

Abstract:

Through synthetic data tests, the influence on source location results of surface and downhole recording systems are discussed, as well as the combination of both. The results indicate that joint use of surface and downhole recording systems can significantly improve the location accuracy. With the downhole recording system, the location results obtained by adopting different objective functions in source location algorithm are compared. Moreover, a new objective function is also proposed. The effectiveness of the new objective function is tested on synthetic and real data sets. The results demonstrate that this objective function shows better convergency in both horizontal and vertical directions, and it can produce more reliable location results.

Key words: microseismic, source location, recording system, objective function

摘要：

通过模型试验, 分别讨论地面、井下观测系统以及二者的组合对于定位结果的影响。试验结果表明, 联合采用地面与井下观测系统能够有效提高震源定位精度。在采用井下观测系统的基础上, 对比几种常用目标函数的应用效果, 并在更有效的走时残差计算方法基础上, 提出一种新的目标函数。模型数据及实际资料的处理结果表明, 提出的目标函数在水平方向以及垂向上均具有较好的收敛性, 其震源定位结果也更准确、可靠。

关键词: 微地震, 震源定位, 观测系统, 目标函数

CLC Number:

P315

Luolan LI, Chuan HE, Yuyang TAN. Study of Recording System and Objective Function for Microseismic Source Location[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2017, 53(2): 329-343.

李罗兰, 何川, 谭玉阳. 微地震观测系统及震源定位目标函数研究[J]. 北京大学学报自然科学版, 2017, 53(2): 329-343.

Figures/Tables 19

Table 1 Comparison of the features of different microseismic recording systems

观测方式	仪器要求	检测周期	检测范围	数据质量	可操作性	成本花费
井下观测	高	短期	小	好	复杂	高
地面观测	低	短期/长期	大	较差	简便	低
浅井观测	低	长期	大	较好	较简便	较低

Fig. 1 Geometries of the surface (a) and downhole (b) recording systems and their corresponding objective function contour plots

Fig. 2 Geometries of different surface recording systems and their corresponding objective function contour plots

Fig. 3 Combinations of different recording systems and their corresponding objective function contour plots

Fig. 4 Contour plots of the objective functions (results of single layer model)

Fig. 5 Locations of the test grid points

Fig. 6 Calculated P-wave arrival times (a) and P-S separation times (b)

Fig. 7 Source location results of the synthetic data set

Fig. 8 Comparison of the means and variances of the location errors of different objective functions

Fig. 9 Multi-layer model and geometry of the source location and recording system

Fig. 10 Contour plots of the objective functions (results of multi-layer model)

Table 2 Layer model parameters

层位	D/m	v_P /(m · s^-1)	v_S/(m · s^-1)
1	0~1200	2000	1200
2	1200~1400	2400	1500
3	1400~1600	2800	1800
4	1600~1800	3200	2100
5	1800~2000	3600	2400

Fig. 11 Source location results of the synthetic data set

Fig. 12 Multi-layer model and geometry of the source location and recording system with the source moved right

Fig. 13 Multi-layer model and geometry of the source location and recording system with the source moved down

Fig. 14 Contour plots of the objective functions with the source moved right (results of multi-layer model)

Fig. 15 Contour plots of the objective functions with the source moved down (results of multi-layer model)

Fig. 16 Plan view of the source location results of the real data set

Fig. 17 Side view of the source location results of the real data set

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