Advanced Seismic Imaging Impacting Brazilian Offshore Brazil Fields Development

Abstract

Abstract This paper will focus on the strong impact that seismic technology has had on the production development of the Brazilian marine oil fields starting from the first oil discovery in 1968 (Guaricema field) to 2006, when the pre-salt new province was revealed in Santos basin. The evolution of three main knowledge areas of seismic technology will be detailed, namely: acquisition, processing and interpretation. Seismic acquisition technology has experienced an increase in " information density?? (seismic traces per square kilometer) which grew by one order of magnitude (from less than 100,000 to 1,024,000), from 1978 (first 3D in Brazil) to 2010. In the seismic processing domain, the improvement of seismic algorithms and methodologies has allowed for better seismic data quality, resolution and imaging. In particular, the algorithms/techniques of 3D multiple suppression and 3D depth migration have significantly evolved in recent years. In the seismic interpretation area, geological context-oriented seismic attributes algorithms/methodologies have made possible better reservoir characterization and monitoring in the deep and ultra deep-water Brazilian offshore basins. Advanced Seismic Imaging Impact This work will not limit the concept of Advanced Seismic Imaging-related technologies to the classic development of seismic migration-oriented methodologies and algorithms as traditionally perceived by the seismic processing area. It seems to us that the advanced seismic imaging technology capable of correctly impacting the development of oil reservoirs would be better understood if viewed as an integrated complex to include acquisition, processing and interpretation technologies. This will provide us with a more adequate and systemic view of the real impact of the evolution of these technologies on the development of Brazil's offshore oil fields. A brief historical evolution will be outlined below together with the identification of significant technological milestones in each of the respective seismic activity areas in the Brazilian coast. Greater emphasis will be placed on results of the last 10 years when Petrobras made the decision to invest in high-density data (>1,000,000 traces/km2) for use in the characterization and monitoring of turbidite reservoirs and also decided to invest in multicomponent seismic technology with a sizeable initial portfolio of 3C and 4C projects. We will also mention the company's initial efforts to improve the seismic imaging of the recently discovered (2006) reservoirs of the new pre-salt oil province. Huge efforts in seismic data acquisition and processing have been put forth both by Petrobras and service companies in this new oil province so as to enhance the seismic imaging of this area. The Brazilian pre-salt reservoirs have their own specific geological and geophysical characteristics which differ from those displayed by the sub-salt reservoirs of GOM and other sedimentary basins of the world. In view of this, new seismic technologies encompassing the three general knowledge areas namely, acquisition, processing and interpretation, will have to be rapidly developed to cope with the challenges posed by the massive dimensions of the energy resources discovered, and still to be discovered, in that new province. Acquisition Technologies Brazil's coast, with its 17 sedimentary basins spread over approximately 4,000,000 km2, has seen marine seismic acquisition projects since de 60's decade (Fig. 01). During that decade the pioneer marine acquisitions took place in very shallow waters (<100m) using streamers less than 1,000m long and analog recording techniques (Fig. 02). As a consequence, the resulting seismic imaging was rather rudimentary and limited to very shallow geologic prospects. The year of 1968 saw a very important company strategic decision which set a major milestone for the Brazilian oil industry: Petrobras made the decision to kick off an integrated seismic surveying effort to cover the entire Brazilian coast which represented a major enterprise due to the size of the area involved. These surveys were now performed with the use of multiple coverage reflection 2-D seismic technology and digital recording techniques (Fig. 03).