Characterization of the Stratigraphic Column in an Extra Heavy Oil Field to Optimize Production Costs, From the Disposal of Wastewater Effluents to the Evaluation of Shallow Aquifers for Water Production. Cerro Negro Area, Venezuela.

Abstract

Abstract The Morichal reservoir at the Cerro Negro Extra Heavy Oil Field (Petromonagas JV) is starting its mature development phase after more than 18 years of production. In order to improve the current recovery factor which is around a value of 3%, maintain the production and reduce operational costs, two different strategies were defined: First, the use of the Jobo Member (overlaying sand deposits) to dispose the wastewater produced from the Morichal reservoir and second, the use of the shallow aquifer deposits of Las Piedras Formation as a water source for future massive implementation of EOR projects (Polymer and steam flooding), evaluating the potential origin of this water based on its physical and chemical properties. Both geological units are part of the drilled stratigraphic column of The Cerro Negro field, what brings technical and economical advantages such as high density of geological information available and the reuse of abandoned wells. This paper aims to describe the study case of the Cerro Negro Oil Field where on one hand, a static and dynamic characterization of Jobo Member was carried out in order to define the potential areas to be used as a wastewater disposal of the Morichal Member production. Based on the geological characterization, dynamic evaluation and surface facilities analysis, it was selected as the best area to dispose of more than 35,000 B/D of water derived from the production of 330 horizontal wells drilled; as well as, support the strategy of producing wells with high water cuts in zones of perched water and close to water contacts, where an important volume of oil is located which until now has been bypassed. On the other hand, the aquifer characterization of Las Piedras has allowed us to define the volume and composition of water available to use as a secure and probed water source during the EOR project implementation. As a result of the application of these strategies, the project management is expected to have an effect on saving in the infrastructure costs regarding the non-reconstruction/replacement of a 30 km pipeline connecting to an aquifer located outside of the field, in the El Salto Field (also located in the Orinoco Oil Belt), since the wastewater production would be disposed into the Jobo Member situated on Cerro Negro Field. Likewise, the definition of water volumes available from Las Piedras Formation support the massive implementation of the EOR projects planned for the next stage of the development of this field. It is expected that this study will open the possibility of considering a broader plan that could involve other extra heavy oil fields from the Orinoco Oil Belt, in order to use the whole geological column located in the same concession area, to reduce costs, minimize environmental risks, optimize production and make more viable extra heavy oil projects similar to this in Venezuela.