Innovative EOR & 4D seismic achievement in the deep offshore

Tuesday, 09 September 2014 Read 7243 times
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The field, located deep offshore Angola in Block 17, is composed of confined and unconfined unconsolidated turbidites sands aged from Miocene. The field was discovered in 1997 and production started in December 2006. On Block 17, seismic data are of very good quality with a vertical resolution of 7 metres.

After 30 development wells, a first 4D seismic survey was acquired in order to monitor these development wells, understand reservoir communications, but also prepare the next development and infill wells. Due to the fact that sands are very unconsolidated and with a low burial, 4D effects are very strong: time shifts larger than 10 ms are observed due to fluid changes. Post-stack processing and interpretation techniques were optimized in order to fully interpret 4D and integrate it into the reservoir model.

EOR studies were launched very early in the development of the field, typically 3 years before firts oil, that concluded to a phased polymer injection, starting with one well injectivity test, then one reservoir upon four before deciding any extension. The Dalia specificities (large spacing and low BSW at polymer injection start up) imply a late response if usual EOR monitoring techniques are applied. Various monitoring options have been considered in order to verify the injected polymer solution properties in-situ. The studies concluded on a recommendation to drill a well and sample the injected viscosified water behind the water front to a distance of approximately 100 m from an injector. The 4D seismic interpretation provided a detailed water flood performance inside the reservoir that has been used to locate and design this sampler well with two main objectives:
- Sample the viscosified water in top layer swept by water,
- Produce the bottom layers still unproduced.

About the Author

Renaud GAUCHET Geosciences Director , Total E&P Russia. Renaud Gauchet is graduated from ENSAM (Arts & Metiers) engineering school in 1989. He first held several R&D positions (University of Texas at Austin in Texas and in Elf Aquitaine Production in France) working mainly on two-phase flow behavior and wettability research projects. Then, Renaud moved to Reservoir Engineering positions for Elf Aquitaine E&P in Italy, Cameroon; Reservoir Manager positions for Total E&P in Indonesia and Libya. Then he took the Geophysics, Geology and Reservoir responsibilities of the Dalia Asset (deep offshore Angola) before being nominated Geosciences Director in Total E&P Russie in 2010. Renaud is author or co-author of ~ 20 international publications and is an active member of EAGE and SPE organizations (regular member of program committees).

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