Application of polymer flooding in the revitalization of a mature heavy oil field

• Published in: Journal of petroleum science & engineering Vol. 204; p. 108695
• Main Authors: Lamas, L.F., Botechia, V.E., Schiozer, D.J., Rocha, M.L., Delshad, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2021
• Subjects: Mature fields; Polymer flooding; Reservoir management; Reservoir simulation; Revitalization of fields; Reservoir management; Revitalization of fields; Polymer flooding; Mature fields; Reservoir simulation
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2021.108695

Polymer flooding is a chemical enhanced oil recovery that aims to improve mobility control, by increasing the viscosity of injection brine and thus reducing the mobility ratio. Starting the polymer injection as early as possible brings the best economic results because it prevents the formation of viscous fingering and sweeps more efficiently the reservoir. It is possible, however, to obtain gains with polymer flooding even after massive waterfloods. In this work, three different model-based approaches are developed to revitalize mature oilfields and tested considering the use of water and polymer as injection fluid. These strategies were tested using a synthetic reservoir model based on data from an offshore field in Brazil. The reservoir is sandstone (average permeability = 1650mD, average porosity = 20%). The oleic phase is heavy viscous oil (~70 cP, 14° API). The first simulation approach considered a strategy based on a standard waterflood until its economic limit. For this case, the maximum net present value (NPV) was reached after 15 years of production with a recovery factor of 25%. The revitalization strategy of this field considers an abandonment status for all wells. To emulate the time necessary to install all new facilities, all wells were assumed to be closed for six months. The first approach consists simply of reopening the injectors by changing the injection fluid to an aqueous polymer solution. The second approach has an additional degree of freedom: it allows all wells to be converted from injectors to producers and vice-versa. Finally, the third approach consists of the addition of new wells. Equations for quality maps for placing injectors and producers are presented. Using these equations, new producers and injectors could be placed at the best locations to produce the remaining oil spots. All three approaches increased the oil recovery factor. The additional oil recovery and variations in NPV were higher for the polymer flooding when compared with the standard waterflood, ensuring a longer productive life. This significant increase in oil production means that, for the selected case, producers needed to be closed in the water flooding period, due to economic performance, leaving a significant amount of oil still in the reservoir. The methodologies presented in this paper are easy to apply and can allow mature fields to economically produce more oil. The conversion of old wells by changing from producers to injectors or vice-versa allows new and creative production strategies. This can be done in onshore and dry completed offshore fields demanding small budgets and intervention times. This paper shows that it is possible to increase both the recovery factor and net present value of fields in the later stages of production life. •Creation and application of three methodologies for revitalization of mature fields.•Revitalization of fields using polymer flooding.•Creation of equations for quality maps for placing producers and injectors.•Comparison of strategies for polymer and water flooding.