Surfactant-Polymer Flooding-Coupling the Development to a Previous Mobile-Modular Polymer Development
Authors: Serrano V. , Ojeda N. , Tosi A. , Guillen P. , Hernandez L. , Zurletti A. , Martinez D. , Campos H. , Ruiz A. , Juri J. E. , Legarto L. , Souto M. , Blanco H. 
Published: April 2024

The combination of alkali, surfactant, and polymer components within the ASP approach offered the potential to yield considerable value by extracting more oil from mature assets, potentially revitalizing fields once considered economically unviable. ASP has long held the promise not only of unlocking untapped reservoir potential but also reducing the project cost to 10-25 $/bbl compared to surfactant-polymer (SP) 15-30 $/bbl and extending 20 years the productive life of mature oilfields.ASP attempted to solve the challenge of cost-effectively recovering oil not only from reservoirs with high acid numbers but also reducing surfactant retention in reservoirs with low acid numbers, where chemical flooding showed technical promise but remained a commercial challenge.

The primary objective of ASP was to enable the efficient recovery of hydrocarbons through a process that combines the advantages of alkali flooding and surfactant injection. This synergy addresses the paradox in the alkali flooding approach: while the introduction of alkali agents leads to the formation of petroleum soaps that can be mobilized in the reservoir, these soaps inherently display hydrophobic behaviour. This contradiction hinders optimal reservoir performance (which is amplified because the dispersivity of heterogeneous reservoirs), as the salinity resulting from alkali addition typically exceeds the desirable salinity for efficient oil recovery. The innovative addition of a hydrophilic co-surfactant introduced to the ASP process, transforming the behaviour of petroleum soaps through the creation of mixed micelles by incorporating a co-surfactant, the optimal salinity range can be expanded to encompass both the salinity derived from alkali introduction and the original brine salinity (Nelson et al. 1984 SPE-12672). This effect is not sufficient, and the loss of mobility control is dominant at field scale which causes a more severe fingering therefore alkaline breakthurgh earlier leading to pump scaling and emulsion treatments in the topside. The promise of ASP that by adjusting the optimal salinity range, ASP demonstrated that water softening costs could be offset by reduced surfactant adsorption and polymer requirements and that the absence of divalent cations simplified formulation requirements, enhancing the feasibility of ASP is not such in practical implementations. Despite dispersivity analysis is established in groundwater science limited polymer pilot projects were overshadowed by economic constraints, preventing their widespread adoption to link it to the development plan.

This study presents a novel approach to enhance surfactant capabilities in oil recovery operations. By integrating a mobile surfactant injection unit with a mobile polymer development process, the transition from low to high dispersivity zones is facilitated. Initially, polymer injection into productive sweet spots, guided by 3D reservoir simulations, serves to identify suitable areas for subsequent surfactant injection, effectively countering dispersion issues. Unlike ASP, the behavior of SP demonstrates similarity to polymer, simplifying navigation through different media. Furthermore, polymer injection reveals significant differences in backproduced polymer and dispersivity, with polymer dispersion in the slug exceeding that in core reservoirs. Analysis of dispersivity data suggests the benefits of fewer simultaneous injectors, facilitating optimized deployment through modular solutions.