Storage Appraisal - Appendix A5.6 - Exemplar Modelling and Dynamic Simulation of Bunter Sandstone Formation Closures in the Southern North Sea

Abstract:

This document is a supporting document to deliverable MS6.1 UK Storage Appraisal Final Report.<br /><br />The aim of this work was to build a 3D geocellular model of the reservoir and sealing formations for a closure in the Bunter Sandstone Formation which could be used to model CO₂ injection. A region in storage unit 139.000 (zone 4 Bunter Sandstone Formation) of 44.0 km by 25.2 km was chosen for detailed modelling. The target daughter storage unit 139.016 (Bunter closure 36) was chosen for modelling as:<ul><li>No faulting was visible on the seismic over the closure</li><li>The storage capacity was estimated to be large enough to store a sizable amount of CO₂</li><li>The area included three additional closures&nbsp; that could be used to study the impact of CO₂ injection on adjacent storage units</li><li>Data coverage was good over the chosen area</li></ul>The static geocellular model was constructed by BGS in PETREL^TM&nbsp; using PGS seismic surfaces, IHS well tops (from the EDIN database), well logs (for 12 wells) and core data for one well.<br><br>Some important findings arose from this study:-<ul><li>The storage capacity may be controlled by either the pressure (when the pressure increases above the maximum limit, the rate must be reduced), or the migration rate (if a high injection rate is maintained, CO₂ will reach the spill point more rapidly).</li><li>The pore volume utilisation and total capacity are quite sensitive to the assumed value for the fracture pressure gradient. A change in this gradient may switch the storage control from pressure-controlled to rate-controlled.</li><li>The storage capacity for an open model may be less than that for a closed system, if heterogeneity encourages a low pore volume utilisation.</li><li>It is import to monitor the pressure at the crest of a dome. Even when the injection rate is pressure controlled at the depth of the well completions, the pressure may rise above a safe limit in the crest.</li><li>It may be possible to increase storage capacity by controlling the injection rate. A lower rate will allow CO₂ more time to rise buoyantly and to dissolve in brine, before reaching the spill point.</li></ul><!-- CO2 -->

Publication Year:

2011

Publisher:

ETI

DOI:

https://doi.org/10.5286/ukerc.edc.000933

Author(s):

Bentham, M., Williams, J., Harris, S., Jin, M. and Pickup, G.