Edinburgh Anisotropy Project

Edinburgh, United Kingdom

Edinburgh Anisotropy Project

Edinburgh, United Kingdom
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Alshangiti A.,University of Leeds | Chapman M.,Edinburgh Anisotropy Project | Wilson A.,Edinburgh Anisotropy Project | Clark R.,University of Leeds
72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010: A New Spring for Geoscience. Incorporating SPE EUROPEC 2010 | Year: 2010

Analysis of seismic data suggests that hydrocarbon bearing zones are often associated with high values of attenuation; this attenuation is associated with strong velocity dispersion. Due to dispersion, the impedance will be frequency-dependent. A frequency-dependent inversion has been carried out on synthetic data, and the results show that the impedance varies strongly with frequency in the dispersive medium but not in the elastic ones. We carried out this inversion on 2D PP field data, and the results show two consistent strong P and S impedance anomalies along the selected CMPs that might be interpreted as dispersive/reservoir zones. © 2010, European Association of Geoscientists and Engineers.

Chen S.-Q.,China University of Petroleum - Beijing | Wang S.-X.,China University of Petroleum - Beijing | Li X.-Y.,Edinburgh Anisotropy Project | Ji M.,Sinopec
Shiyou Diqiu Wuli Kantan/Oil Geophysical Prospecting | Year: 2010

In this paper the time matching between P-SV wave and P-P wave in pre-stack joint inversion was studied, it is believed that the matching effect is not great if the VP/VS ratio which is picked up from pre-stack time migration is used as VP/VS ratio in time matching between P-SV wave and P-P wave. By utilizing the datasets in mathematical model forward simulation in this paper, the VP/VS ratio scanning method could be used to correct the deviation in the matching between P-SV wave and P-P wave, based on the major makers in structural imaging the general time and velocity ranges in the scanning process can be determined, by selecting calculation window to conduct VP/VS ratio scanning the optimal VP/VS ratio factor was obtained, then the matching is completed. The workflow of the time matching between P-SV wave and P-P wave can be summarized as below: 1, To conduct P-P wave and P-SV wave velocity analysis and obtain VP/VS ratio; 2, Based on VP/VS ratio model the pre-stack the time gathers matching was conducted; 3, Evaluating the matching results, if satisfied then matching finishes, if not, continue the VP/VS ratio scanning, update the VP/VS ratio model and then go to step 2 and 4. Finishing the matching, outputting the matching gathers or stacking sections. The matching effects between the mathematical model data and field land seismic data demonstrated that the method described in this paper solved the time matching problem for a reflection event from same subsurface interface in the P-P wave and P-SV wave inversion process, providing the accurate gather data for the subsequent joint inversion.

Zhang S.-H.,China University of Petroleum - Beijing | Li X.-Y.,China University of Petroleum - Beijing | Dai H.-C.,Edinburgh Anisotropy Project
Applied Geophysics | Year: 2011

PS converted-waves (C-waves) have been commonly used to image through gas clouds but the C-wave imaging may also be degraded by the diodic effect introduced by the gas cloud. It may be compensated for using a velocity perturbation method which decouples the diodic moveout into two parts: the base velocity and the velocity perturbation. Gas clouds are widely distributed in the Sanhu area in the Qaidam basin of northwest China which is rich in natural gas. A land 2D3C seismic dataset is analyzed from the Sanhu area and significant diodic effects are observed in the data which harm the C-wave imaging. The diodic correction is applied to this data and the resultant C-wave imaging and the details of the reservoir structure are significantly improved. The diodic moveout plays an important role in working out the residual shear wave statics and the association of diodic correction and shear wave residual statics computation is a key step of C-wave high fidelity imaging in the gas cloud area. Finally, the new process workflow with diodic moveout is given. © 2011 Editorial Office of Applied Geophysics and Springer-Verlag Berlin Heidelberg.

Chen S.Q.,China University of Petroleum - East China | Li X.Y.,Edinburgh Anisotropy Project
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

In this paper, we have completed a case study of using VSP seismic data to improve surface seismic resolution. The P- and S-wave velocities are computed from the recorded three component (3C) VSP, from which other elastic parameters such as bulk modulus (K), Poisson's ratio (σ) are calculated. Using the down-going wavefield separated from the borehole VSP records, we obtain the Q model using the spectral ratio method. We then apply inverse Q filtering to a surface seismic dataset across the borehole using a stable inverse Q filtering method to improve the resolution of the surface seismic dataset. Correlating the corridor-stacked VSP seismic traces to surface seismic section before and after inverse Q filtering shows that the resolution of the surface seismic data and the matching of seismic events between the surface data and the VSP corridor stack are both significantly improved after the application of the VSP-derived inverse Q filtering.

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