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A Layer-Stripping Method for 3D Near-Surface Velocity Model Building Using Seismic First-Arrival Times 被引量:6
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作者 Taikun Shi Jianzhong Zhang +1 位作者 Zhonglai Huang Changkun Jin 《Journal of Earth Science》 SCIE CAS CSCD 2015年第4期502-507,共6页
In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point (CMP) gather is assu... In order to improve the efficiency of 3D near-surface velocity model building, we develop a layer-stripping method using seismic first-arrival times. The velocity model within a Common Mid-Point (CMP) gather is assumed to be stratified into thin layers, and the velocity of each layer var- ies linearly with depth. The thickness and velocity of the top layer are estimated using minimum-offset first-arrival data in a CMP gather. Then the top layer is stripped and the second layer becomes a new top layer. After removing the effect of the top layer from the former first-arrival data, the new first-arrival data are obtained and then used to estimate the parameters of the second layer. In this manner, the velocity model, being regarded as that at a CMP location, is built layer-by-layer from the top to the bottom. A 3D near-surface velocity model is then formed using the velocity models at all CMP locations. The tests on synthetic and observed seismic data show that the layer-stripping method can be used to build good near-surface velocity models for static correction, and its computation speed is approximately hundred times faster than that of grid tomography. 展开更多
关键词 first-arrival time layer-stripping NEAR-SURFACE velocity model building static correction.
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Velocity Modeling and Inversion Techniques for Locating Microseismic Events in Unconventional Reservoirs 被引量:7
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作者 Jianzhong Zhang Han Liu +1 位作者 Zhihui Zou Zhonglai Huang 《Journal of Earth Science》 SCIE CAS CSCD 2015年第4期495-501,共7页
A velocity model is an important factor influencing microseismic event locations. We re- view the velocity modeling and inversion techniques for locating microseismic events in exploration for unconventional oil and g... A velocity model is an important factor influencing microseismic event locations. We re- view the velocity modeling and inversion techniques for locating microseismic events in exploration for unconventional oil and gas reservoirs. We first describe the geological and geophysical characteristics of reservoir formations related to hydraulic fracturing in heterogeneity, anisotropy, and variability, then discuss the influences of velocity estimation, anisotropy model, and their time-lapse changes on the accuracy in determining microseismic event locations, and then survey some typical methods for building velocity models in locating event locations. We conclude that the three tangled physical attributes of reservoirs make microseismic monitoring very challenging. The uncertainties in velocity model and ignoring its anisotropies and its variations in hydraulic fracturing can cause systematic mislocations of microseismie events which are unacceptable in microseismic monitoring. So, we propose some potential ways for building accurate velocity models. 展开更多
关键词 microseismic location velocity model building velocity error ANISOTROPY unconventional reservoir.
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Layer-Stripping Full Waveform Inversion with Damped Seismic Reflection Data 被引量:2
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作者 卞爱飞 於文辉 《Journal of Earth Science》 SCIE CAS CSCD 2011年第2期241-249,共9页
Full waveform inversion(FWI) directly minimizes errors between synthetic and observed data.For the surface acquisition geometry,reflections generated from deep reflectors are sensitive to overburden structure,so it ... Full waveform inversion(FWI) directly minimizes errors between synthetic and observed data.For the surface acquisition geometry,reflections generated from deep reflectors are sensitive to overburden structure,so it is reasonable to update the macro velocity model in a top-to-bottom manner.For models dominated by horizontally layered structures,combination of offset/time weighting and constant update depth control(CUDC) is sufficient for layer-stripping FWI.CUDC requires ray tracing to determine reflection traveltimes at a constant depth.As model complexity increases,the multi-path effects will have to be considered.We developed a new layer-stripping FWI method utilizing damped seismic reflection data,which does not need CUDC and ray tracing.Numerical examples show that effective update depth(EUD) can be controlled by damping constants even in complex regions and the inversion result is more accurate than conventional methods. 展开更多
关键词 full waveform inversion velocity model building layer-stripping strategy dampedwave equation sensitivity analysis.
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Seismic Imaging of Complex Structures in the Tarim Basin
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作者 Ning Guo Chao Wu Stuart Fagin 《Journal of Earth Science》 SCIE CAS CSCD 2015年第4期586-591,共6页
Conventional time imaging techniques are not capable of producing accurate seismic imaging of the subsurface in the mountain front of the Tarim Basin, China. Their imaged structures have led to some major drilling fai... Conventional time imaging techniques are not capable of producing accurate seismic imaging of the subsurface in the mountain front of the Tarim Basin, China. Their imaged structures have led to some major drilling failures before, bearing a disrepute that "their structural closures have wheels and their structural highs have springs". This article first lists the imaging challenges, and explains in a schematic why the time imaging techniques fail in this area. Then through a series of real data examples, it demonstrates that when there exist lateral velocity variations, depth imaging is the only solution to tackle the imaging challenges in this area. Depth imaging accounts for the complexity of the wavefield, therefore produces superior and geological plausible images. The core task in properly performing depth imaging is building the velocity model. This article stresses some the main aspects in this regard. 展开更多
关键词 time migration depth migration seismic image quality velocity model building anisotropy.
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