Before committing to a 4D seismic monitoring programme, an operator must be reasonably certain that the data obtained would contribute materially to efficient reservoir management, cost-reduction through better well-placement and increased recovery. Subsurface feasibility modelling is a valuable aid in predicting the commercial value of 4D monitoring.
To assist decision-making, Ikon Science will perform a 4D seismic modelling study to provide answers to a number of pertinent questions, including:
- Will water-influx and a rising OWC produce interpretable time-lapse seismic anomalies?
- What pressure-change would be required to produce significant anomalies?
- Would 4D seismic reveal un-drained reservoir compartments?
- Would 4D seismic be effective in monitoring a water-flood?
- How strongly does this depend on sweep efficiency (residual So)?
- Is the seismic resolution adequate to distinguish differential saturation/pressure changes in different reservoir zones?
- Is the S/N ratio of the existing 3D seismic data high enough for it to be used as the baseline survey?
The study will be carried out using a selection of techniques, including our RokDoc® and RokDoc-ChronoSeis™ software, drawing reservoir information from an Eclipse® simulation of the field, combined with our extensive knowledge and experience in this area.
Experience
Ikon employees have carried out 4D work in a wide range of locations:
- Campos Basin, Brazil
- Williston Basin, Canada (CO2 injection to displace oil in a carbonate reservoir)
- Norwegian Sector of North Sea (Gullfaks Oil and Sleipner )
- West of Shetlands (Schiehallion)
- Offshore Western Australia
- Offshore West Africa, Mauritania
- Gulf of Mexico
Plus have experience writing joint-inversion code for CO2 pressure and saturation (used in Sleipner gas field, Norway), extended research on CO2 related equations of state (EoS), Statistical Associating Fluid Theory (SAFT) in particular, and created molecular dynamics simulations to validate EoS for CO2 in reservoir settings.
Examples
1. Magnus Field; Time-lapsed seismic was used to verify the flow simulator and used to predict fluid movements.References to this work:
Gawith, D.E. & Gutteridge, P.A. 1994 Seismic validation of reservoir simulation using a shared earth model. Paper presented at EAPG Vienna 1994 & published in Petroleum Geoscience, Vol 2. 1996, pp 97-103.
Watts, G.F.T., Jizba, D., Gawith, D.E. & Gutteridge, P.A. 1996 Reservoir monitoring of the Magnus Field through 4D time-lapse seismic analysis. Petroleum Geoscience, Vol 2, pp 361-372.
2. Nelson Field; In this project time-lapsed seismic was used with a ‘stochastic matching’ process to aid the interpretation of fluid movements. This process uses a detailed geological model to help extract valid information from the data.
Reference to this work:
Gawith, D.E. & Gutteridge, P.A, 2001 Model-based Interpretation of Time-Lapse Seismic, Using Stochastic Matching. Paper presented at the EAGE Amsterdam 2001.
Publications and papers include:
Rock physics analysis for time-lapse seismic at Schiehallion Field, North Sea4D seismic pressure-saturation inversion at Gullfaks field, Norway
Estimation of Reservoir Pressure and Saturations by Crossplot Inversion of 4D Seismic Attributes
4D seismic data processing issues and examples
Seismic monitoring of CO2 geo-sequestration: realistic capabilities and limitations
Developing the Rock Physics Model - Improved Carbon Dioxide Mixing Rules for Carbon Capture and Storage