Published by the DTI Oil & Gas Directorate for the reservoir engineering and IOR community in the UK.
Send comments on this issue and contributions for next issue to iornewsletter@senergyltd.com by 15 August 2002.

Improving Oil Recovery Using 4D Seismic

Contact: Prof. Colin MacBeth

Over the past five years 4D seismic has gained a well-deserved reputation, within both the reservoir engineering and the seismic communities, as a tool capable of widespread application in monitoring production, secondary recovery processes, and locating compartments of by-passed oil. This has been exemplified by recent figures from certain North Sea fields suggesting increases in recovery of up to 10%. Advances in the seismic acquisition method such as seabed sensors continue to reward us with additional benefits and push the frontiers of reservoir description still further.

With a view to assessing the benefits of new generation seismic techniques, the Edinburgh Time-Lapse Project (ETLP) at Heriot-Watt has recently completed an analysis of seismic data from a permanent installation of multi-component seabed sensors in the shallow water of the Gulf of Mexico. In principle, such data offer additional control on the reservoir's 4D signature by combining both PP and PS recordings. Heriot-Watt's contribution to the project was to investigate new ways of cross-equalising both the legacy and OBC surveys to reduce non-repeatable noise influences and enhance the coherent 4D signal. This procedure revealed additional reservoirs on the neighbouring fault blocks that were connected to production in the main sand (see figure). The implications of these findings are currently under investigation using in-house software that can calculate the seismic response of the history-matched reservoir model. Heriot-Watt work continues on the Teal South with a study to discriminate production and compaction-related events using multi-component data.

Improvements in acquisition remain only one of the keys to using 4D seismic effectively in the future. To determine high resolution snapshots of dynamic reservoir parameters, seismic interpretation and management must become more quantitative than they have traditionally been in the past. The challenge set by the Edinburgh Time-Lapse Project at Heriot-Watt is to target weak links in workflows, and to refine the seismic processing and interpretation tools to achieve this capability. Progress towards this goal is being made possible by building an understanding of the 4D signature through careful integration of petrophysics, rock physics, seismic modelling, processing, interpretation and reservoir engineering.

4D signal for the 4500' sand of the Teal South field, processed by cross-equalisation of seismic data from the legacy and second OBC surveys. Most of the anomalies are caused by gas coming out of solution due to a drop in reservoir pressure after almost two years of production. Although the major concentration is on the lower fault block penetrated by the producing well, there are a number of associated hydrocarbon accumulations on the neighbouring fault blocks. (Click for a larger image)

The Edinburgh Time-Lapse Project is an academic research consortium based at Heriot-Watt University. It is now in the second year of its first three-year phase of activity, and is currently sponsored by 8 companies. New entrants are welcome to join the sponsorship group at any point throughout the programme. More details on this project can be obtained by contacting: Professor Colin MacBeth, Reservoir Geophysics Group, Department of Petroleum Engineering, Heriot-Watt University, or http://www.pet.hw.ac.uk/research/etlp

Disclaimer: The material available on this website is designed to provide general information only. Whilst every effort has been made to ensure that the information provided is accurate, it does not constitute legal or other professional advice.
Please note: The Department of Trade and Industry cannot be held responsible for the contents of any pages referenced by an external link.