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Summary We demonstrate 3D high-resolution seismic modeling and RTM imaging using velocities derived from the Eldfisk geologic model. Using calibration parameters for chalk, the Differential Effective Medium (DEM) method is used to derive P- and S-wave velocities from the imported porosity model. Once the velocity models are constructed, we run 3D finite-difference modeling followed by RTM imaging focused on the reservoir characterization and advanced acquisition design over the seismically obscured area (SOA) on Eldfisk.
- North America > United States (0.17)
- Europe > Norway (0.16)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.57)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/7 > Greater Ekofisk Field > Eldfisk Field > Tor Formation (0.98)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/7 > Greater Ekofisk Field > Eldfisk Field > Hod Formation (0.98)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/7 > Greater Ekofisk Field > Eldfisk Field > Ekofisk Formation (0.98)
A Method of Acquiring Full Azimuth Data for Carbonate Reservoirs Exploration in Tarim Basin, Western China
Liu, Yimou (China University of Petroleum) | Liang, Xianghao (Petrochina Tarim Oilfield Company) | Zhou, Yi (Petrochina Tarim Oilfield Company) | Wang, Yanfeng (BGP, CNPC) | Chen, Xueqiang (BGP, CNPC)
Summary Full azimuth (FAZ) data is essential to accurately imaging and characterizing of subsurface caves, holes and fractures, which is important in the successful exploration and development of fractured-cavernous carbonate reservoirs. However, FAZ acquisition is seldom carried out due to the much higher cost. Here we present a case study of obtaining near FAZ data in the carbonate reservoirs exploration in Tarim basin, western China, by orthogonally acquiring a second WAZ dataset over an existing WAZ data and combining them together. The results show that this method can improve the imaging of the reservoirs significantly and it is an economically feasible way of providing FAZ data for land seismic surveys.
Summary A detailed field study focused on constructively using the water surface multiples recorded in marine seismic VSP data for improved subsurface depth imaging is presented. Traditionally, up-going and down-going wavefields are separated during VSP signal processing and only the up-going wavefield is used to image the subsurface below the receivers. However with using the down-going wavefield, structures above the receivers are also imaged and wider horizontal coverage is achieved. Our field study consists of two perpendicular 2D walk away surveys: SW-NE and NW-SE. Images constructed using first order water surface multiples are presented and compared with each other as well as with the 3D surface seismic cube. VSP images have higher resolution than the 3D surface seismic image. Both VSP surveys image the shallower part of the subsurface very well. However, in the deeper parts of the sections, qualities of the VSP images are substantially different from each other. The SW-NE line images the deeper section of the subsurface rather well whereas the NW-SE line fails to image the deeper section of the subsurface. 3D ray tracing modeling shows that there are considerable amounts of unfocused and out-plane energies reflected from the deeper reflectors in NW-SE survey. This can explain why line NW-SE fails to image the deeper reflectors.
Summary A recent advance in single-well reflection imaging is the utilization of a dipole acoustic system in a borehole to radiate and receive elastic waves to and from a remote geological reflector in formation. This paper substantiates this dipole-acoustic imaging technology by numerically simulating the radiation and reflection of the wavefield generated by the borehole dipole source and analyzing the receiving sensitivity of the dipole system to the incoming reflection waves. The analyses show that a borehole dipole source can radiate a compressional wave (P wave) and two types of shear waves (i.e., SV and SH waves) into the formation. The SH wave has wide radiation coverage and the best receiving sensitivity, and is most suitable for dipole-shear imaging. In an acoustically slow formation, the dipole-generated P wave has strong receiving sensitivity and can also be utilized for reflection imaging. An important feature of dipole imaging is its sensitivity to reflector azimuth, which results from the directivity of the dipole source. By using a four-component data acquisition method to record the dipole-generated reflection signal, the reflector azimuth can be determined. The numerical simulation results provide a solid foundation for the dipole acoustic imaging technology.
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
SUMMARY Reverse-time migration can accurately image complex geologic structures in anisotropic media. Extended images at selected locations in the earth, i.e. at common-image-point gathers (CIPs), carry enough information to characterize the angle-dependent illumination and to provide measurements for migration velocity analysis. Furthermore, inaccurate anisotropy leaves a distinctive signature in CIPs, which can be used to evaluate anisotropy through techniques similar to the ones used in conventional wavefield tomography.
Summary Most well planning, formation evaluation, reservoir engineering, and production management can ultimately be condensed to analyze and utilize the nature and spatial distribution of rock and fluid properties. This observation provides the motivation for this paper’s objectives to: (1) re-examine and broaden the meaning of high resolution, (2) review the impact of seismic resolution on imaging, and (3) assess the advantage of high resolution for interpretation and reservoir characterization. Multi-dimensional (nD) processing techniques are first shown to enhance the seismic image by increasing signal to noise ratio and filling in missing data due to acquisition irregularity. Then a novel resolution enhancement technique is applied to the data post-stack, post-migration, and pre-migration to exam its impact in terms of multi-dimensional (nD) resolution and its benefits for seismic imaging, interpretation, and reservoir characterization. It is concluded that the applications of nD processing and nD resolution enhancement can significantly improve the quality of interpretation and reservoir characterization.
Summary There has been an increased interest in de-ghosting methods, which remove the effect of the sea-surface reflection, utilizing multi-component data. Various methodologies have proven that it is possible to successfully remove the ghost utilizing multi-component data. These methods are applied in the time domain at an early stage of a seismic imaging work-flow. This is appropriate for time-domain imaging. This presentation will show that the de-ghosting step is not necessary if multi-component data is available and the imaging is performed in the depth domain. The multi-component data can be used directly in a depth-domain imaging work-flow to remove any adverse effects of the ghost/sea-surface reflection. It is quite straight forward to realize this fact, since the wave-equation is a second order Partial Differential Equation, and access to both pressure and (particle) velocity components constitutes a complete set of initial/boundary conditions; hence the wave equation has a unique solution.
Summary We investigated the shallow subsurface at Barringer (Meteor) Crater, Arizona using seismic and gravity techniques. We found compressional (P)-wave velocities of 450-2500 m/s for a 55 m deep section from seismic refraction analysis. The low uppermost P-wave velocity layers thin away from the crater rim (toward the south). Shear (S)-wave velocities (estimated from ground-roll inversion) vary from 200-700 m/s for the top 16-20 m increasing to 900-1000 m/s at 38 m depth. The prominent change in S-wave velocities (around 500-600 m/s up to 20 m depth) is interpreted as the transition from the low-velocity ejecta blanket (a sheet of debris thrown out of the crater during the impact) to the bed-rock Moenkopi sandstone. This S-wave transition takes place at a depth range of 12-20 m near the crater rim with a thinning away from the crater rim. This consistent P- and S-wave layer is interpreted as the ejecta blanket. Near-surface reflection seismic analysis provided relatively deeper information indicating at least four sub-horizontal reflectors intersected by a number of faults. Staking velocity analysis estimates P-wave velocities up to 3500 m/s (for the top 500 ms) showing a similar P-wave thinning structure (especially for top 200 ms). Ultrasonic measurements on hand samples provide a range of P-wave velocities of 800-1600 m/s for the Moenkopi consistent with seismic refraction results. The estimated residual gravity profile also supports the identified thinning of the ejecta blanket in seismic analysis.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (1.00)
Summary Kirchhoff migration is routinely used for converted-wave (PS) imaging, partly because the suite of high-fidelity imaging algorithms available for PP seismic reflection data is not yet widely available for PS waves. This paper discusses the implementation issues of strong and weak TTI PS equations and presents application results for a new PS controlled-beam migration (CBM) algorithm working in the common-offset vector (COV) domain. CBM is a specialized version of Gaussian-beam migration aimed at signal-to-noise ratio enhancement.
- Europe (0.30)
- North America > United States (0.16)
- Europe > Norway > Barents Sea > Hammerfest Basin > License 100 > Block 7121/7 > Snøhvit Field > Stø Formation (0.99)
- Europe > Norway > Barents Sea > Hammerfest Basin > License 100 > Block 7121/7 > Snøhvit Field > Nordmela Formation (0.99)
- Europe > Norway > Barents Sea > Hammerfest Basin > License 100 > Block 7121/5 > Snøhvit Field > Stø Formation (0.99)
- (29 more...)
A Broadband Full Azimuth Land Seismic Case Study from Saudi Arabia Using a 100,000 Channel Recording System at 6 Terabytes Per Day: Acquisition and Processing Lessons Learned
Pecholcs, Peter I. (Saudi Aramco) | Al-Saad, Riyadh (Saudi Aramco) | Al-Sannaa, Muneer (Saudi Aramco) | Quigley, John (WesternGeco) | Bagaini, Claudio (WesternGeco) | Zarkhidze, Alexander (WesternGeco) | May, Roger (WesternGeco) | Guellili, Mohamed (WesternGeco) | Sinanaj, Sokol (WesternGeco) | Membrouk, Mohamed (WesternGeco)
Summary In 2010, a 100,000 channel point receiver acquisition system was mobilized together with 24 80,000 lb vibrators to improve the characterization of both conventional and unconventional reservoir properties. Using a low frequency sweep design with productivity rates exceeding 8,000 vibration points (VPs) per 24 hours significantly increased the seismic data volume and data rate. Over 6 Tb of seismic data were routinely acquired with critical quality control decision points to maintain the integrity and manage the significant increase in seismic data volume. To ensure that full azimuth signal amplitudes were preserved for all offsets and azimuths, carefully selected true amplitude processing parameters were applied. We present this case history and lessons learned, from this Saudi Arabia project, as part of an ongoing fully integrated broadband acquisition-to-rock mechanics interpretation project.