Application of Modern Reservoir Characterization in Mature Fields to Unravel Hidden Reserves
Authors: Rodriguez M. , Abad F. , Rodriguez L. , Gaibor J. , Moran M. , Verdezoto A. 
Published: November 2015

This paper discusses the successful, fully integrated, three-dimensional (3D) earth modeling (EM) and dynamic reservoir simulation of the Hollin formation in the Lago Agrio field within an operator's first producer field in Ecuador. Early feedback of reservoir heterogeneity helped to understand key reservoir issues and methods undertaken to solve various problems. The implementation of cutting edge reservoir modeling techniques contributed to improving production rates and enhancing recovery.

Improved understanding of the sedimentological model, diagenetic events, and capillary pressure analysis helped to identify eight rock types (RTs), which were then adequately propagated into a 3D geocellular model. This geocellular model overcomes a previous paradigm that reservoir heterogeneities and effectiveness upon convergence and nonmatching of dynamic reservoir simulation must be honored. Instead, a balanced result was achieved by making insightful changes in terms of upscaling the population model by replicating production history. This allowed pinpointing barriers, coning, and preferential aquifers layering to control bypassed oil, thereby helping to identify potential zones corroborated with new wells.

Inexorable production decline in mature fields requires solutions to improve production rates and enhance recovery factors using reservoir modeling techniques. Typical characterization involves integration of EM and production performance to estimate reserves and develop optimal production. However, for mature fields, this process can be challenging when accelerated field development impacts fluid distribution and bypassed reserves.

Early feedback of reservoir heterogeneity was used to understand key reservoir issues. Integration of sedimentological and petrophysical studies with reservoir simulation yielded information regarding complexities affecting rock quality, barriers, and baffles controlling water influx.

Limited 3D seismic field coverage hindered reliable seismic interpretation because of the merging of two-dimensional (2D) lines and 3D seismic volume to populate a 3D structural grid. Gathering core porosity measurements using different methods with unappropriated net mean stress required homologate data for consistent overburden confining pressure using compressibility rock test relationships for rock typing.

Finally, the innovative idea of modeling the fluvial, tidal, and shallow marine domains of the Hollin formation separately, which are in hydraulic connectivity with an infinite aquifer, allowed successful dynamic performance, accurately mimicking reservoir productivity and allowing water breakthrough prediction. This new approach provided robust analysis for a strong reservoir model, helping optimize the drilling development plan.

Successful, fully integrated 3D EM and dynamic reservoir simulation of an operator's first producer field in Ecuador are discussed in this paper. This improved understanding of key reservoir issues and methods for solving various problems enables engineering solutions for improving production rates and enhancing recovery factors through the implementation of cutting edge reservoir modeling techniques.