Brazil Pre-Salt, Santos Basin: Feasibility Study for the Application of Borehole Gravity to Improve Reservoir Monitoring
- Zhijun Du (Silicon Microgravity) | Adrian Topham (Silicon Microgravity) | Jeremy Jez C. Lofts (Silicon Microgravity) | Ashwin A. Seshia (Silicon Microgravity)
- Document ID
- Offshore Technology Conference
- Offshore Technology Conference, 4-7 May, Houston, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2020. Offshore Technology Conference
- Brazilian Pre-salt reservoir, Borehole gravity, Reservoir characterization and monitoring, Three-axis gravity sensor, Time-lapse gravity survey
- 15 in the last 30 days
- 68 since 2007
- Show more detail
- View rights & permissions
Brazilian Pre-Salt reservoir characterization and monitoring is a challenge for surface geophysical methods due to the inherently minute observable signals from the reservoirs, located below the massive salt, in depth ranges > 5000 m.
The status of a program to develop a wireline deployed 3-axis gravity sensor with a target sensitivity of ~ 5 μGal is firstly introduced. This is followed by a feasibility study for the potential deployment as a time-lapse gravity survey (4D gravity monitoring) within the pre-salt. A conceptual pre-salt reservoir model for the Libra field, Santos Basin, the offshore of Brazil, is developed, built on available pre-salt knowledge provided from seismic imaging and well log data, including reservoir and production characteristics. The model is based on water substituting oil over 6 months within and through the reservoir, with adoption of an oil production rate for the field published in 2017 by the ANP. These data are used to forward model gravity to understand the potential for a detectable signal and thereby establish a baseline for a time-lapse gravity survey (4D gravity) that could be used to monitor the Libra Field.
A clear gravity response >80 μGal is observed over a six month period in the reservoir, due to water replacing oil, at the defined oil production rate. In a three-axis measurement the vertical axis is directly related to the magnitude of the fluid substitution and the two horizontal axes are sensitive to the fluid movement directions. Together, these suggest that an annual survey with a limited well stock could be effective in monitoring this type of reservoir and that a wireline deployed 3-axis gravity tool is likely to provide significant additional surveillance to constrain a reservoir production strategy through better appreciation of the direction of water movement. The follow-on step would be to model further field data and run a baseline survey to develop a novel reservoir surveillance method within the Pre-Salt.
|File Size||1 MB||Number of Pages||16|
Abelha, M. and Petersohn E, 2018. Brasil Pre-salt: Libra, AAPG 2018 Annual Convention & Exhibition, Salt Lake City, Utah, United States, May 20-23, 2018. DOI: 10.1306/30586Abelha2018.
Cainelli, C., and Mohriak, W., 1999, General Evolution of the Eastern Brazilian Continental Margin, The Leading Edge,18 (7), 800–805. DOI: 10.1190/1.1438387.
Du, Z and L. Macgregor, 2010. Reservoir characterization from joint inversion of marine CSEM and seismic AVA data using Genetic Algorithms: a case study based on the Luva gas field, EAGE Extended Abstract 2010; DOI: 10.1190/1.3513888.
Dyatlov, G., S. Lyngra, A. F. Marsala, A. M. Ton Loermans, D. T. Georgi, A. Vasilevskiy and C. M. Edwards, 2014. Reservoir monitoring of hydrocarbon-water flood front by gravimetry integrated with reservoir simulation. 2014 SPE Russian Oil and Gas Exploration & Production Technical Conference and Exhibition, Moscow, Russia, Society of Petroleum Engineers - SPE-171226-MS.
Formigli, J., Pinto, A. and Almeida, A., 2009, Santos Basin's Pre-Salt Reservoirs Development—the Way Ahead, OTC-19953 Offshore Technology Conference, Houston, Texas, USA, 4-7 May. DOI: http://dx.doi.org/10.4043/19953-MS.
Melo, M., Bender, A., Nib, C., and Mio, E., 2011, Giant Sub-Salt Hydrocarbon Province of the Greater Campos Basin, Brazil, OTC 22818 Offshore Technology Conference, Rio de Janeiro, Brazil, 4-6 October. DOI: http://dx.doi.org/10.4043/22818-MS.
Oliveira, L. C.; Fernandes, L. F.; Maul, A. R.; Rosseto, J. A.; Gonzalez-Farias, M. L. A.; Gonzalez-Sanchez, G. A. 2015. Geological Velocity Approach in Order to Obtain a Detailed Velocity Model for the Evaporitic Section — Santos Basin. Presented at the 14th International Congress of the Brazilian Geophysical Society, Rio de Janeiro, 03-06, August. http://dx.doi.org/10.1190/sbgf2015-273.
Penna, R, S. Ara*, A. Geisslinger, R. Sansonowskil, L. Oliveiral, J. Rosseto and M. Matos, 2019. Carbonate and igneous rock characterization through reprocessing, FWI imaging, and elastic inversion of a legacy seismic data set in Brazilian presalt province. The Leading Edge, 38, 11–19, doi: https://doi.org/10.1190/t1e38010011.1.
Santos Neto, E.V., Cerqueira, J.R., and Prinzhofer, A., 2012. Origin of CO2 in Brazilian Basins, AAPG Search and Discovery Article No. 40969. http://www.searchanddiscovery.com/documents/2012/40969neto/ndxneto.pdf.