Reducing the Risk of EOR in Early Cretaceous Eolian Sanstone Reservoirs: The Impact of Geological Heterogeneity (Huitrin Formation, Chihuido de la Sierra Negra Field, Neuquen Basin, Argentina)

Morettini, Elena; Thompson, Anthony R.; Ancheta, Daniela; Dufour, Sophie; Lopez Gibson, Andres; Ruyu, Bruno; Valenzuela, Marta; Delshad, Mojdeh

The challenge in up-scaling chemical ASP (alkali-surfactant-polymer) floods to a field pilot or commercial project, is to ensure coreflood results will be replicated in the field, in this case Chihuido de la Sierra Negra (ChSN), Argentina's largest on-shore oilfield.

The objective of the study was to evaluate the potential and risks of an ASP flood by honoring geological detail and subsequently to demonstrate commercial viability.

Completing a laboratory coreflood, history matching results and applying these parameters to the modelling of a five spot pattern in a chemical simulation program is a known process. However, Cretaceous aeolian sandstone of the Troncoso Member (Huitrín Formation) in ChSN represents highly heterogeneous deposits. Such heterogeneity required additional geological and sequence stratigraphic studies to constrain dynamic simulation forecasts.

High computational requirements for chemical flooding processes made simulation with enough grid cells to represent the geology over the entire commercial project area impossible to run. To overcome this issue, several 3-D multiscale static and dynamic models based on integrated workflows were built; these incorporating varying levels of geological detail from a comparatively coarse 300 well sector model through to fine layered small cell models to account for geological heterogeneity and chemical dilution effects. In addition, coreflood models were used to simulate the laboratory microemulsion flood.

Forecast recoveries for ASP Flooding from single pattern tertiary simulations based on models not constrained by a history match varied significantly. By integrating results from the history matching of the coarser models, the range in estimated recoveries was reduced.

It was demonstrated that for every robust history-matched scenario, ASP flooding was economic. Also geological heterogeneity affected the attractiveness of a chemical flood, even in good reservoir. Results have been used to justify a pilot for 2013.

Even in a comparatively homogenous sand, the success of a pilot is closely linked to geological heterogeneity. Construction of multiscale models, while ensuring consistency between these models enables detailed geological parameters to be considered even in a fine cell model designed to minimize chemical dilution.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013