An Example of a Steam Drive Pilot Project Management With 3D Seismic Survey in Northeast Brazil

Abstract

Estreito field contains heavy oil and has been successfully cycled withsteam since 1984. The first steam drive pilot was initiated in November 1998 inthe standard pattern of the field. A seismic survey to monitor the steam front was acquired six months afterthe pilot had begun. This work intends to present the integration of the pilot results, theseismic survey and the numeric flow simulation as a way to manage a steam driveprocess. The paper shows also the importance of 3D seismic activities to support thesteam drive management in a large scale, creating possibilities of improvementsand optimization. Introduction Estreito oil field is located in northeast Brazil (figure 1) with an area ofabout 40 Km2. The main reservoir is near 200 meters deep andcontains oil that ranges from 1,000 to 6,000 cp at reservoir conditions. The Açu Formation was deposited on Superior Cretaceous and is constituted bycoarsening and conglomeratic sandstones, interbedded with thin shales inalluvial to fluvial fans environment. Due to its characteristics of high viscosity and low °API, the Estreito oilreservoir is adequate for applying a recovery thermal method. The chosenprocess was steam cycling (huff and puff). A steam drive pilot project wasstarted on November 1998 on a 10-acre spacing, containing two injectors andseven producers in two five-spot patterns. A seismic survey was performed in order to help the project management.Initially it was planned to be 4D and intended to monitor the steam drivefront. However, due to the characteristics of the reservoir and fluidsinvolved, only one seismic image was enough to monitor the steamflood. Thisimage was obtained six months after the project had started. After two years of production, a numerical flow simulation model was run tostudy the effects of the steam drive project. One of the main goals of this paper is to compare the steam drive frontbehavior based on seismic survey with maps of reservoir temperature, obtainedfrom the numerical simulation model using appropriate geostatisticalcharacterization of the pilot area. Steam Drive Pilot Project The principal production mechanism of Estreito is fluid expansion assistedby bottom aquifer, occurring on most part of the AÇU100 Zone.