Improving exploration efficiency in frontier basin using CSEM
Raghava TharimelaEMGS Asia Pacific, Suite 7.2 & 7.3, 7th floor, East Wing, Rohas PureCircle, No. 9 Jalan P. Ramlee 50250, Kuala Lumpur, Malaysia. Email: rtharimela@emgs.com
The APPEA Journal 60(2) 773-777 https://doi.org/10.1071/AJ19182
Accepted: 24 February 2020 Published: 15 May 2020
Abstract
In underexplored frontier offshore basins one of the key challenges is to identify areas with the greatest probability of success (Pg) within set budgetary and time constraints. Frontier exploration permits are generally large, with limited geophysical data and limited knowledge of a working petroleum system. Play concepts can be formulated using data at hand but will require augmenting by new datasets. The nature and extent of additional data is generally linked to budgetary constraints and exploration history of the area and will set the strategy to identify and manage key risks before major investment for block development. Often this preliminary evaluation does not address fluid-related risk which has a major impact on assessment of Pg. Seep evaluation could indicate presence of hydrocarbons in the system, but the absence of seeps cannot be a reason to condemn the area. Resistivity is a key attribute that has a reliable relation with hydrocarbon saturation. Subsurface resistivity imaging using the controlled source electromagnetic (CSEM) method, can indicate in situ saturated hydrocarbon accumulations and when correlated with available seismic data, absence of a resistive anomaly at the prospect location is a direct indication of a lack of significant hydrocarbons and associated leads/plays can be downgraded. The presence of a resistive anomaly could mean saturated hydrocarbons or other lithological effects that needs to be further evaluated. CSEM 2D data acquired along key seismic lines covering promising play types can be an effective means of screening the frontier block and identifying areas that should be the focus of further exploration activities.
Keywords: hydrocarbon saturation, non-seismic, offshore survey, probability of geological success, prospect de-risking, resistivity, scanning, sparse seismic.
Raghava Tharimela obtained his MS in Petroleum Engineering from the Technical University of Denmark, Copenhagen, with a specialisation in geophysics and rock mechanics. After working for 1 year in GEO Denmark, Raghava joined EMGS in 2008 as a geophysicist and since then has worked in several positions in EMGS business units in Norway and the US. Currently Raghava is working as a Technical Adviser for EMGS Asia Pacific Business Unit based in Kuala Lumpur, Malaysia. Raghava has worked in basins offshore Norway, US and Mexican part of the GOM, Brazil, India, Malaysia and Indonesia. |
References
Archie, G. E. (1942). The electrical resistivity log as an aid in determining some reservoir characteristics. (Society of Petroleum Engineers.) https://doi.org/10.2118/942054-GConstable, S. (2010). Ten years of marine CSEM for hydrocarbon exploration. Geophysics 75, 75A67–75A81.
| Ten years of marine CSEM for hydrocarbon exploration.Crossref | GoogleScholarGoogle Scholar |
Edwards, N. (2005). Marine controlled source electromagnetics: principles, methodologies, future commercial applications. Surveys in Geophysics 26, 675–700.
| Marine controlled source electromagnetics: principles, methodologies, future commercial applications.Crossref | GoogleScholarGoogle Scholar |
Eidesmo, T., Ellingsrud, S., MacGregor, L., Constable, S., Sinha, M., Johansen, S., Kong, F., and Westerdahl, H. (2002). Seabed logging (SBL), a new method for remote and direct identification of hydrocarbon filled layers in deepwater areas. First Break 20, 144–152.
Fanavoll, S., Gabrielsen, P., and Ellingsrud, S. (2014). CSEM as a tool for better exploration decisions: case studies from the Barents Sea, Norwegian Continental Shelf. Interpretation (Tulsa) 2, SH55–SH66.
| CSEM as a tool for better exploration decisions: case studies from the Barents Sea, Norwegian Continental Shelf.Crossref | GoogleScholarGoogle Scholar |
Granli, J. R., Veire, H. H., Gabrielsen, P. T., and Morten, J. P. (2017). Maturing broadband 3D CSEM for improved reservoir property prediction in the Realgrunnen Group at Wisting, Barents Sea. In ‘SEG International Exposition and 87th Annual Meeting’. Abstract 2205. (Society of Exploration Geophysicists.) https://doi.org/10.1190/segam2017-17727091.1
Senger, K., Birchall, T., Ohm, S., Ogata, K., and Olaussen, S. (2017). Review of geological controls on resistivity in uplifted basins: insights from the Norwegian Barents Shelf. In ‘AAPG/SEG International Conference & Exhibition, London, UK, 15–18 October’. Article 90310. (AAPG/SEG: Tulsa, OK, USA.)
