The CSEM method, which is frequently used as a risk-reduction tool in hydrocarbon exploration, is finally moving to a new frontier: reservoir monitoring and surveillance. In the present work, we present a CSEM time-lapse interpretation workflow. One essential aspect of our workflow is the demonstration of the linear relationship between the anomalous transverse resistance, an attribute extracted from CSEM data inversion, and the SoPhiH attribute, which is estimated from fluid-flow simulators. Consequently, it is possible to reliably estimate SoPhiH maps from CSEM time-lapse surveys using such a relationship. We demonstrate our workflow’s effectiveness in the mature Marlim oilfield by simulating the CSEM time-lapse response after 30 and 40 years of seawater injection and detecting the remaining sweet spots in the reservoir. The Marlim reservoirs are analogous to several turbidite reservoirs worldwide, which can also be appraised with the proposed workflow. The prediction of SoPhiH maps by using CSEM data inversion can significantly improve reservoir time-lapse characterization.

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Recent discoveries made in the presalt carbonates of southeast Brazil are among the most important in the past decade. This province, especially Santos Basin, contains large accumulations of oil with excellent quality and high commercial value. The latest seismic processing technologies, along with elastic inversion, have been used for reservoir characterization and in identifying carbonates with high-permeability intervals to model flow behavior of the reservoirs. One challenge encountered is identifying the occurrence of igneous bodies within the reservoir interval and their correct characterization as input into the reservoir modeling. Igneous rocks encountered in the Brazilian presalt can be of both intrusive and extrusive origin. They may present a variety of permo-porous reservoir properties ranging from being flow barriers to acting as high-permeability corridors if fracturing is high enough. The presence of igneous rocks is not common in Brazilian presalt carbonates; therefore, specific methodologies must be used, both in seismic processing and quantitative interpretation, in order to map and predict those occurrences.

Brazilian carbonate reservoirs contain huge oil-in-place volumes and are likely to have an important economic impact in global oil industry. Such carbonate reservoirs, both Albian and Aptian, are located offshore in deep water, which has an important role in development costs. In siliciclastic plays it is standard practice to use time-lapse (4D) seismic to locate wells in unswept areas, maximizing the recovery factor. However, in carbonate plays, time-lapse seismic monitoring remains challenging, with few cases of success published around the world. Carbonates differ from siliciclastic rocks in many aspects. With a varied chemical composition and complex pore connectivity, carbonates bring on a large diversity of facies, each one showing a specific seismic response. Moreover, the usually high incompressibility of the carbonate matrix reduces sensitivity to pressure and saturation changes, which are the main effects expected on a hydrocarbon field undergoing production. Considering both the economic relevance and the difficulties of using time-lapse seismic to monitor carbonate reservoirs, Petrobras created a strategic program to face this challenge, a time-lapse seismic (S4D) study of an Albian carbonate reservoir located in the Campos Basin offshore Brazil. Three legacy data were available: streamer–1987, streamer–2002, and ocean-bottom cable–2010. Extensive feasibility studies are performed as well as a meticulous prestack 4D simultaneous inversion based on the seismic data, preliminary cross-equalized to partially overcome the initial low repeatability. A multidisciplinary interpretation conducted by a team of geophysicists, geologists, and reservoir engineers finally lead to results overcoming expectations. Saturation and pressure changes are detected using P- and S-impedance attributes, consistent with production data. Results are opening perspectives for further monitoring other carbonate reservoirs, especially with new presalt Brazilian discoveries in the Campos and Santos Basins, which might have a huge economic impact.

fax 01-972-952-9435. AbstractThe 4D seismic technology has been successfully applied on numerous brown fields in order to optimize reservoir production and recovery. This paper will describe how we incorporated the 4D seismic results in the geological model and illustrate some applications in reservoir management decisions, thereby mitigating drilling risks in Marlim deepwater turbidite heavy oil field. It will highlight the repositioning of numerous planned wells and the improvement in the history match using the updated geological model.The Marlim giant field is located on the eastern Brazilian coast in water depths varying from 600 to 1200m (Figure 1). The reservoir is characterized by an unconsolidated sandstone turbidite related to the regressive mega sequence of the Brazilian eastern continental margin. It is the largest producing oilfield in Brazil (production peak: 615,000 bpd in 2002), with the original oil-in-place volume of 6.4 billion STB. Production started in 1991 and injection of water in 1994.Three seismic surveys cover the Marlim Field. The first one acquired in 1986, the others in 1997 and 2005. The most recent survey was specifically acquired for reservoir characterization and monitoring purposes. MARLIM Búzios Lagoa Feia 493 MARLIM SUL 5 0 m 1 0 0 m 4 0 0 m 1 0 0 0 m 2 0 0 0 m RONCADOR 2 3 0 0 m 2 6 0 0 m BARRACUDA 150 Km BOOKT23 Campos Macaé ALBACORA LESTE ALBACORA MARLIM LESTE MARLIM Búzios Lagoa Feia 493 MARLIM SUL 5 0 m 1 0 0 m 4 0 0 m 1 0 0 0 m 2 0 0 0 m RONCADOR 2 3 0 0 m 2 6 0 0 m BARRACUDA 150 Km