Print this pagePushing the Limits: Putting Seismic to Work from the Brazil BC-10 Ostra Field Development
Through seismic processing, inversion and detailed interpretation that integrates the well data, it is possible to use 3D seismic in a much more rigorous way than has been common in the industry. The 3D seismic has utility in all phases from exploration, appraisal and development and can provide reasonable accuracy that is tested by development drilling.
At OSTRA Field development, the seismic data is routinely used to accurately map the depth structure. Using a PSDM for imaging and vertical depth conversion with check shots, the data was tied to existing exploration and appraisal wells with a good relative precision. This resulted in development wells with tops that on average tie within +/- 2meters, but can be as much as 10m out. In contrast, the real-time directional drilling tools exhibited reasonable variances (+/- 6m vertical), but in one case there was a large 30m lateral survey error that resulted in an apparent mis-tie with the seismic.
Seismic inversion data provides net to gross and seismic facies data within the reservoir interval that is used for static modeling. By calibrating to the well data, multiple seismic volumes are used to provide better seismic reservoir facies estimates that are limited by the detectability and resolution of the seismic data. The 3D data has provided generally accurate net-to gross reservoir estimates, but lack the ability and precision to detect thin shales that make horizontal drilling difficult.
Throughout the well execution process, seismic based data is used to guide and optimize the drilling of our long reach deviated production boreholes. For several years now, well data and the inversion results have been integrated to provide more detailed interpretations of lithologies along the total well path. Interpretation of hard streaks, marls and soft wet sands in the shallow build-up sections has provided additional information, confidence and control to drillers in this difficult environment. Real-time monitoring of the well paths with seismic data was used to ensure that paths were accurate, and to optimize the well paths to the target locations.
With calibration and integration the seismic can be used to drill successful horizontal wells and provide useful information for geosteering within the reservoir. This paper discusses the integration of the seismic and well data that was used to develop the OSTRA field to optimize and drill production wells.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil