1887

Abstract

Summary

Time-lapse (4D) seismic is an important technology for monitoring reservoir dynamics and overburden changes. At the Shearwater field, a High Pressure, High Temperature (HPHT) gas field in the Central North Sea, 4D seismic has been used to track reservoir compaction and overburden extension. These changes affect seismic velocities, leading to time-shifts between base and monitor surveys. This study highlights the impact of updating the monitor velocity model on 4D data quality. The methodology involves cross-correlating base and monitor surveys to measure 4D time-shifts, which are then used to update the velocity model. This updated model corrects for ray-path bending and lateral mis-positioning.

Traditional 4D processing workflows often neglect velocity changes, causing mis-positioning of post-production data. By incorporating velocity updates, the study demonstrates improved accuracy in 4D time-shift analysis and slightly improved imaging of 4D differences within the reservoir. These improvements are crucial for planning safe drilling operations to access remaining gas. The updated velocity models are also used to calculate velocity updates which provide another tool for measuring weakening and strengthening.

The results are important for future Shearwater development and of interest to the wider Geophysics community as it shows the remarkable impact of incorporating velocity changes into 4D processing.

© EAGE Publications BV
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/content/papers/10.3997/2214-4609.2025101240
2025-06-02
2026-02-13

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References

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/content/papers/10.3997/2214-4609.2025101240
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The Importance of Velocity Model Updating for 4D Seismic: A Case Study
Conference Proceedings 2025, 1 (2025); https://doi.org/10.3997/2214-4609.2025101240
/content/papers/10.3997/2214-4609.2025101240
/content/papers/10.3997/2214-4609.2025101240
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