Projects
Projects: Projects for Investigator |
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| Reference Number | NE/E006329/1 | |
| Title | Passive seismic emission tomography: The dynamics of a reservoir. | |
| Status | Completed | |
| Energy Categories | Fossil Fuels: Oil Gas and Coal(Oil and Gas, Enhanced oil and gas production) 100%; | |
| Research Types | Basic and strategic applied research 100% | |
| Science and Technology Fields | ENVIRONMENTAL SCIENCES (Earth Systems and Environmental Sciences) 100% | |
| UKERC Cross Cutting Characterisation | Not Cross-cutting 100% | |
| Principal Investigator |
Professor M (Michael ) Kendall No email address given Earth Sciences University of Bristol |
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| Award Type | R&D | |
| Funding Source | NERC | |
| Start Date | 01 March 2007 | |
| End Date | 28 February 2010 | |
| Duration | 36 months | |
| Total Grant Value | £218,619 | |
| Industrial Sectors | Transport Systems and Vehicles | |
| Region | South West | |
| Programme | Partnership Grants | |
| Investigators | Principal Investigator | Professor M (Michael ) Kendall , Earth Sciences, University of Bristol (100.000%) |
| Web Site | ||
| Objectives | The aim of this project is to use a state-of-the-art ocean bottom seismic network to monitor micro-earthquakes in an oil field and thereby derive constraints on the stress field and the nature of faulting in the region. The project will be a partnership with BP and use data from the Life of Field Seismic installation in the North Sea Valhall field. The key objectives of the project are: 1) Develop a 4D migration method to image microseismicevents in data continuously recorded by a dense 2D array of nearly 3000 4-component ocean-bottom sensors. A 3D anisotropic velocity model derived from depth migrations has been provided by BP and will be used to improve the accuracy of the event locations. 2) The imaged events will be used to image faults and their sense of failure and propagation. 3) The large aperture of the array compared to depth of reservoir events will allow accurate calculations of focal mechanisms using amplitude ratios. 4) Focal mechanisms will be then used to estimate stress tensor orientations. 5) Direct inversions for moment-tensor solutions will be developed. 6) Shear-wave splitting analyses will be used to infer fracture-induced anisotropy if the S-waveformsa re of sufficient quality. 7) The results will be integrated with the interpretation of time-lapse survey data. This will involve a close collaboration with staff at BP. 8) The results from a complementary project (IPEGG) that is integrating the geomechanical and fluid-flow properties of the Valhall reservoir with the seismic response will be integrated with the observations from this study.I PE GG involves petroleum engineers from the University of Leeds and geomechanical engineers from the University of Swansea. Input from IPEGG will help derive a better understanding of the microseismic behaviour of the reservoir. | |
| Abstract | In 2003 BP installed a dense array of seimic recording equipment on the sea bottom above the Vallhall oil field in the North Sea. Nearly 2500 state-of-the-art seismometers were attached to 120 km of cables that cover a 45 square km area and are connected to a recording platform. The installation is the first of its kind anywhere in the world and cost nearly US$45million. Such permanent monitoringallows the acquisition of ship-borne seismic surveys at regular intervals in time (so-called 4D seismics) for the life of the field (hence the name Life of Field Seismic or LoFS). Because the surveys are identical each time the data can be used to very accurately monitor changes in the reservoir, for example, the migration of oil due to production. The multicomponent sensors can also be used torecord less conventional data. For example, in this part of the North Sea shear-waves are much better than the conventional first arriving P-waves at imaging through the cloud of gas that lies above the reservoir. This new way of monitoring an oil field has dramatically improved reservoir management and productivity, and reduce costs in the long term. The sensors are continuously recording, evenwhen active-source (airguns) ship surveys are not being conducted. Thus there is great untapped potential in using these data to study small earthquakes in the subsurface. Such microseismic events are useful because they provide information about regional tectonics and production related forces. They provide information about fault locations and fluid migration, knowledge of which are of great importance to production. Furthermore, such stress releases can lead to well failure (borehole breakout), which costs the industry billions of pounds each year and can be quite dangerous. We areproposing a study of these micro-earthquakes by developing sophisticated imaging techniques that will use the sensors like eyes that can look in different directions into the Earth. Whilst these earthquakesa very small (they release roughly the same amount of energy as breaking a pencil) they can be accurately located and studied because of the redundancies afforded by such an immense amount of data. We can use standard techniques from conventional earthquake seismology to infer the orientation of fault planes and the stress field in the reservoir. A further synergy comes from the detailed informationabout the field that BP has at hand (e.g., velocity structure). We will work closely with BP staff and will be allowed to use their massive computing clusters to process the data. We are one of the very first organisations being allowed to look at this exciting dataset and the projectwill produce high-profile results. This is a unique and timely opportunity. | |
| Publications | (none) |
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| Final Report | (none) |
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| Added to Database | 08/09/08 | |
