Time difference-based velocity model inversion for microseismic event location

Tan, Yuyang; He, Chu; Zhang, Hongliang

doi:10.1190/segam2013-0165.1

Cited by 4 publications

(3 citation statements)

References 3 publications

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“…Because a perforation shot position is generally very well known, it can be relocated iteratively to reduce the location error. However, existing iterative techniques mainly rely on picking of P and S wave arrival times (Bardainne and Gaucher, 2010;Pei et al, 2008Pei et al, , 2009Tan et al, 2013;Jiang et al, 2016), meaning that seismograms with high signal-to-noise ratios (S/N) are required. This approach is suitable for borehole monitoring arrays; however, for microseismic monitoring at the surface, the seismograms of perforation shots tend to have low S/N ratios, and existing velocity model optimization methods do not perform well.…”

Section: Introductionmentioning

confidence: 99%

Velocity model optimization for surface microseismic monitoring via amplitude stacking

HaiYu

Wang

Zeng

et al. 2016

Journal of Applied Geophysics

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Section: Introductionmentioning

confidence: 99%

Velocity model optimization for surface microseismic monitoring via amplitude stacking

HaiYu

Wang

Zeng

et al. 2016

Journal of Applied Geophysics

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“…Moreover, log data may be incomplete, which naturally reduces the accuracy of the initial model. Methods based on searching for a local optimal solution (Pei et al 2008;Tan et al 2013) are not suitable for this task.…”

Section: Introductionmentioning

confidence: 99%

“…However, the method still faced the problem that perforation shot origin times are generally inaccurate. Tan et al (2013) proposed an inversion method based on time differences calculated from picked arrival times, which circumvented the issue of origin time inaccuracies. However, their method was still sensitive to the initial model.…”

Section: Introductionmentioning

confidence: 99%

Velocity calibration for microseismic event location using surface data

et al. 2016

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Because surface-based monitoring of hydraulic fracturing is not restricted by borehole geometry or the difficulties in maintaining subsurface equipment, it is becoming an increasingly common part of microseismic monitoring. The ability to determine an accurate velocity model for the monitored area directly affects the accuracy of microseismic event locations. However, velocity model calibration for location with surface instruments is difficult for several reasons: well log measurements are often inaccurate or incomplete, yielding intractable models; origin times of perforation shots are not always accurate; and the non-uniqueness of velocity models obtained by inversion becomes especially problematic when only perforation shots are used. In this paper, we propose a new approach to overcome these limitations. We establish an initial velocity model from well logging data, and then use the root mean square (RMS) error of double-difference arrival times as a proxy measure for the misfit between the well log velocity model and the true velocity structure of the medium. Double-difference RMS errors are reduced by using a very fast simulated annealing for model perturbance, and a sample set of double-difference RMS errors is then selected to determine an empirical threshold. This threshold value is set near the minimum RMS of the selected samples, and an appropriate number of travel times within the threshold range are chosen. The corresponding velocity models are then used to relocate the perforation-shot. We use the velocity model with the smallest relative location errors as the basis for microseismic location. Numerical analysis with exact input velocity models shows that although large differences exist between the calculated and true velocity models, perforation shots can still be located to their actual positions with the proposed technique; the location inaccuracy of the perforation is \2 m. Further tests on field data demonstrate the validity of this technique.

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Microseismic velocity model inversion and source location: The use of neighborhood algorithm and master station method

Tan

Mao

2018

GEOPHYSICS

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The accuracy of the velocity model strongly affects the accuracy of microseismic source location and hence the reliability of fracture imaging. We have developed a systematic methodology for microseismic velocity model inversion and source location. A new misfit function is used for both problems, which yields more reliable result than the conventional ones. Using the same measure of misfit, the location errors resulting from the use of different misfit functions are eliminated. The neighborhood algorithm and master station method (MSM) are adopted for calculating the velocity model and source location, respectively. The reason for using the neighborhood algorithm is that it has fewer tuning parameters and is easy to be tuned, whereas the advantage of the MSM is that it can automatically remove the mispicks. The performance of the proposed methods is illustrated using the ball-hit events with known locations, and the validity of the inversion results is verified by the relocations of these events. We also used the inverted velocity models to locate the microseismic events detected from the monitoring data. The location result indicates that the fractures have an average half-length of 280 m and height of 55 m and the fracture azimuth is approximately N77°W.

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Time difference-based velocity model inversion for microseismic event location

Cited by 4 publications

References 3 publications

Velocity model optimization for surface microseismic monitoring via amplitude stacking

Velocity model optimization for surface microseismic monitoring via amplitude stacking

Velocity calibration for microseismic event location using surface data

Microseismic velocity model inversion and source location: The use of neighborhood algorithm and master station method

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