Chemical Enhanced Oil Recovery (CEOR) Applications for Extra-Heavy Oil Reservoirs in the Eastern Venezuela Basin: The First Surfactant-Polymer Pilot Test

Abstract Sustainable oil production and water management in the Eastern Venezuela Basin, where the largest world oil reserves are located, represents a great challenge. In the Orinoco Oil Belt or "La Faja Petrolífera Del Orinoco", the injection of polymer and surfactant (SP) has been envisioned as a strategy to control water mobility/viscous instabilities and mobilize residual oil. The objective of this article is to evaluate the feasibility of SP injection in a reservoir of the Zuata Principal Field-Junín Block to increase oil production with current recovery factors of < 5%. For the evaluation of surfactant and polymer injections in the area Zuata Principal, a cluster with a simple horizontal well configuration was chosen for the injection and future monitoring of the CEOR process. Four coreflood tests have been performed in the selected area (crude oil 9°API and 4,500 cP at 50°C), both on Bentheimer outcrops and on a real reservoir rock (unconsolidated sandstone), at the reservoir temperature of 50°C, using polymer injection (HPAM3630S) and a tailored SP alkaline-free formulation to avoid operational problems such as the formation of complex emulsions and/or scales. The history matching of laboratory tests was carried out, and a development/optimization plan was proposed for the evaluated cluster considering different injection and production scenarios. History matching of experimental tests using polymer and surfactant as a mixture is discussed in detail in this article. High recoveries were observed after SP injection in secondary conditions, with final oil saturations of less than 10% at the core scale. The importance of recovery mechanisms such as mobility control, reduction of interfacial tension, wettability alteration, microemulsion effect, and possible ions exchange due to the low salinity of the injected brine is highlighted. Additionally, a development/optimization plan is presented for the evaluated cluster system considering different chemical concentrations, injection and production scenarios. This article shows the potential of the injection of surfactants and polymers to increase production of highly viscous crude oils from the Eastern Venezuela Basin, being the first case of SP pilot application in Venezuela. The need to carry out additional studies for the optimization of chemicals and type of polymer is indicated, as well as considering economic aspects (OPEX and CAPEX) and possible operational issues associated with mobility control, high chemical losses, fluid separation, emulsion formation, water treatment, among others.