Integrated IOR/EOR Screening of an Offshore Oilfield in Trinidad

Abstract

An integrated benchmarking and screening study of IOR/EOR technologies used in analogous reservoirs worldwide was performed in the Southwest Soldado (SWS) Field offshore Trinidad, in order to establish the top three methods which could be implemented in this field to increase the recovery factor after more than 30 years producing under primary conditions. The evaluation of IOR/EOR processes for the Southwest Soldado Field was done in 2 stages. Stage 1 included screening of processes to identify the top 3 methods to be used. Stage 2 involved the detailed evaluation of the top 3 processes. For Stage 1, the National Petroleum Council EOR Screening Method was used along with innovative techniques recommended by industry literature (Taber et al., 1997, Pérez-Pérez et al., 2001). In Stage 2, standard statistical methods were applied to the compiled database of successful IOR/EOR projects in offshore sandstone reservoirs. That information was used to establish a predicted recovery factor for the top 3 IOR/EOR methods selected. A theoretical description of the selected methods and their relationship with Southwest Soldado characteristics was done. Finally, considerations for pilot projects with recommended facilities, required logistics and cost estimates were analyzed and the best options were recommended. Given the characteristics of the Southwest Soldado field, Water Alternate Gas (WAG) injection resulted with the highest score based on the benchmarking exercise; Carbon dioxide (CO2) injection and water injection were selected in second and third place respectively. In the case of CO2, it was recommended as Huff and Puff in order to delineate transition zones, for ease of application in existing wells and facilities and for comparatively low cost. This method also generates high oil recoveries in a relative short period of time. Finally, it was recommended that for the implementation of a pilot project, Huff and Puff CO2 injection should be tested prior to WAG injection due to the many advantages in evaluating the reservoirs, quick execution and rapid production results at the lowest investment cost from the other 2 methods evaluated. This paper presents the steps taken to benchmark an offshore field in Trinidad using the field's actual data. It lays the foundation for further development of heavy oil reserves in Southwest Soldado, highlights the challenges based on infrastructure, technology and economics requirements and provides a roadmap to further increase the recovery factor of these offshore heavy oil reservoirs.