Challenges of the 4D Seismic in the Reservoir Management of Marlim Field

Abstract

Abstract The seismic 4D (Time-lapse seismic), has been globally used as an effective tool in reservoir management. At Petrobras its use is still incipient. A 4D seismic acquisition is being performed in the Marlim field, Campos Basin, Brazil. The main objective is to identify the fluid flow and the undrained areas in order to optimize the infill drilling wells. The Marlim giant field is located on the eastern Brazilian coast in water depths varying from 600 to 1100m. The reservoir is characterized by an unconsolidated sandstone turbidite related to the regressive megasequence of the Brazilian eastern continental margin. The average porosity and permeability are 30% and 2000mD, respectively. The production started in 1991 and the water injection in 1994. The production is done through seven platforms. There are two seismic surveys covering the area. The first one, acquired in 1986, has a poor vertical resolution compared to the second one, registered in 1997. The shooting directions of these two 3D surveys are not the same. For the new survey the parameters was quite the same of the 1997 acquisition. The studies of technical and economical viability have been showing that it will be a challenge to monitor the front progress of water in the field since the impedance contrast among the remaining oil (19 to 24 degree API) and the water injected is not very high. Another challenge in this acquisition is the overcoming of the amount of production structures, that act as obstacles to the conventional seismic acquisition. This work presents the feasibility studies for 4D seismic acquisition, the acquisition planning and the expectations of its use in the reservoir management.