Fractures can be observed in micro or macro scale at outcrops and many oil/gas reservoirs can be fractured as well. A good understanding of the fracture network is hence critical for reservoir development since it could have significant impact on fluid flow. Full azimuth 3D seismic data provides a means of detecting and characterizing fractures before drilling. Seismic anisotropy investigation for fracture detection has been carried out in a carbonate oil field located in offshore United Arab Emirates (U.A.E). Target reservoirs are lower cretaceous carbonates mainly consisting of limestone with alternating porous and dense intervals which become dolomitic with depth. A large 3D-2C OBC seismic data sets was acquired over this giant oil field with orthogonal patch geometry covering all azimuths in 2001. The seismic data was reprocessed in 2006 to improve mainly pre-stack data quality and maintain azimuthal integrity. Velocity and amplitude analysis by ellipse fitting for the azimuthal anisotropy intensity and the direction have been conducted on seismic super CMP gathers, PreStack Migrated (PrSTM) partial stacked data and azimuthally picked velocities. A multi-line walkaway and walk-around VSP survey from a single point of well control was also used to analyze and to verify 3D seismic results. The VSP amplitude and AVOAz results around the well show harmonic amplitude variation with offset and azimuth. However, amplitude analysis on partial stack data shows relatively high seismic anisotropy intensity especially in noisy data areas and the direction is not consistent with the other results. The azimuth direction of partial stacked amplitude is close to the receiver line orientation and thus appears susceptible to acquisition geometry and processing applications. On the other hand, all velocity analysis results show a NE-SW high velocity anisotropy trend. This is consistent with the regional ZAGROS stress field which also has a NE-SW as SHmax, consistent with FMI and core interpreted open fracture data. Six core and FMI data sets were used in this study to verify the results. The velocity analysis result is consistent with the core & FMI data at 5 of the 6 well locations in terms of the azimuthal direction. These results of this study highlight the importance of reviewing multi-sources of information when available, evaluating pros and cons of the datasets with specific attention paid to data volume, noise sensitivity and resolution.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn Abu Dhabi Offshore areas, the development of Lower Cretaceous fractures carbonate reservoir is a challenge that can be achieved using fracture characterization modelling approach.
An Ocean Bottom Cable (OBC) 3D/4C seismic survey covering 2730 square kilometers and spanning 23 months has been undertaken by ADMA-OPCO. This survey covers 2 offshore congested producing fields, plus several exploration areas currently planned for development in the near future. This large acquisition when coupled with two previously acquired 3D OBC surveys (in 2000 and 2007) offers 4580 square kilometers of continuous 3D OBC converage. Coordination and intensive communications between 6 shareholders, 14 ADMA-OPCO divisions and 4 governmental agencies were required to facilitate this survey. The initial survey design (used for 2 months) used Distance Separated Simultaneous Source (DS3) acquisition but was revised to Managed Source and Spread (MSS) acquisition for improved fold, offset and acquisition efficiency. During the course of survey acquisition, 3 different test data sets were also acquired for technical analysis. A short history on the feasibility and complicated process leading up to the start of the survey will be offered, as well as samples of the onboard processing from the various areas will be presented. This survey was acquired in a little over half the time of previous OBC surveys in offshore Abu Dhabi. The data, based on limited onboard fast processing, is of high quality and illuminates deeper gas bearing structure and stratigraphy. Formal onshore processing has begun and promises excellent results. This innovative acquisition has provided more efficient data acquisition saving time and money, reduced HSE exposure in busy fields and will in conjunction with previous surveys provided one of the largest continuous offshore 3D datasets in the Arabian Gulf.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.