4-D Seismic Feasibility Modeling of a Giant Offshore Oil Field

Martin Terrell¹*, Dez Chu¹, Shiyu Xu¹, Akmal Sultan², and Isao Takahashi^3
1ExxonMobil, USA
²Zadco
³JOGMEC, Japan
*[email protected]

Transferring successful 4-D seismic experience in siliciclastic reservoirs to more challenging carbonate reservoirs requires a disciplined and collaborative approach among national and international oil companies. Production at a giant offshore field in the Middle East is anticipated to be increased primarily through infill drilling and optimization of water-flood patterns. Acquiring 4-D seismic data to compare with a 2001 ocean-bottom cable (OBC) survey may help reach the production goal more efficiently through identification of fluid movement and improved reservoir characterization. Given the challenging rock physics and limited industry 4-D experience in carbonates, significant technical effort is required to appreciate the technical risks and potential improvement in the understanding the reservoir before implementing 4-D seismic technology at this field. A 4-D feasibility modeling study was undertaken to predict the 4-D seismic response from water saturation and pressure changes between 2001 and possible monitor surveys in 2008 and 2015. Full-field 4-D modeling consisted of: (1) determining petrophysical relationships from well logs and core analysis; (2) applying those relationships to the geologic and reservoir simulation models to create a 4-D seismic property model; (3) generating synthetic 4-D datasets for each timestep; (4) adding appropriate levels of 4-D noise; and (5) extracting attributes to determine the interpretability of the predicted 4-D response. The modeling results showed the expected change in seismic amplitude due to production within the reservoir will be less than 10–15%. Thus, a successful 4-D program will require highly repeatable data acquisition and processing, which is challenging in the shallow OBC environment for this field. Finally, the results showed that 4-D seismic will be able to help identify the main water-bank movements but will not be able to directly detect water movement in thin, high-permeability layers.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain