IOR/EOR Project Implementation Outcomes and Novel Insights in Extra-Heavy Oil Reservoirs in Eastern Venezuela Basin, Orinoco Oil Belt – Zuata Principal Field, Venezuela
Authors: Morales R. , Rodriguez F. , Bejarano C. , Belhaj H. , Alhameli F. , AlDhuhoori M. , Quintero E. 
Published: November 2024

This work presents a review of the exploitation schemes applied and envisioned for the next 25 years in the Exploitation Plan for the Zuata Principal Field, located in the Junín Block of "La Faja Petrolífera del Orinoco (FPO)", Venezuela. The relevance of Improved/Enhanced Oil Recovery (IOR/EOR) methods to increase the production/recovery factor of the area is highlighted, with recoverable reserves of 4,392 MMSTB and a current primary recovery factor of approximately 3.5% after more than 25 years of exploitation. In terms of field-scale IOR/EOR, the implementation of two main IOR projects is highlighted: Cyclic Steam Stimulation (CSS) and Downhole Electrical Heating (DEH) through an electro-resistive heating cable, executed between 2010-2018; as well as the visualization of the application of Chemical EOR (CEOR) methods (e.g., surfactants and polymers) in areas of the reservoir where the implementation of thermal methods is not feasible.

The comprehensive methodology of the CSS Project included well pre-selection, numerical reservoir simulation, infrastructure analysis, area prioritization, economic considerations, and implementation. Similarly, the DEH Project focus on selecting prospective wells based on criteria adapted to the study area, economic premises, and field implementation of the technology. Finally, for evaluating CEOR methods (surfactants and polymers), a first phase involved pilot area selection, fluid sampling, and laboratory testing. This will serve as the basis for the pilot field test feasibility evaluation phase.

The findings of this study indicate that 19 CSS activities were carried out during the 2013-2018 period, with cumulative injection volumes ranging from 7,500 to 10,000 tons/cycle. Production increases of up to 365% were observed, with thermal effect durations ranging from 12 to 16 months. The effectiveness of the CSS method was evaluated using two operational indicators: "Incremental Np" and "Steam to Oil Ratio (SOR)", both of which yielded favorable results. Furthermore, between 2010 and 2018, DEH systems were installed in 23 wells, which is considered a technological substitute as a pre-CSS scheme or in cases where CSS processes are not technically feasible. Incremental productions of 20% to 60% were achieved, with operating powers of up to 55 kW. Regarding the application of CEOR methods, the injection of polymers and surfactant-polymers could potentially increase hydrocarbon recovery in the area (up to 90% at the laboratory scale for the SP case) with a lower environmental impact compared to thermal methods, specifically in terms of water consumption (for steam generation) and acid gas emissions (e.g., CO2 and H2S). Depending on the type of chemical used, recovery mechanisms such as mobility control, interfacial tension reduction, ions exchange (low salinity of injected water), and/or changes in wettability could impact hydrocarbon recovery.

This novel study provides an exhaustive compilation of the experiences and best operational practices derived from the field applications of the main IOR/EOR projects executed in the Zuata Principal Field, allowing solid conclusions to be drawn about the oil-exploitation potential of the area. The optimization and/or application of new schemes in the implemented methods are also envisioned. Additionally, several outstanding studies concerning other IOR/EOR methods applicable to the area, such as Chemicals, Hybrids (e.g., thermo-chemicals), are listed, supporting their continuation.