The authors report an additional oil recovery (AOR) of 36.04% using Pseudoxanthomonas taiwanensis biosurfactant in sand-pack columns, positioning this as strong evidence of the biosurfactant’s suitability for MEOR. However, this figure is presented without sufficient methodological rigor to support its scientific or industrial relevance. A standard deviation of ±21.34%, over half the mean value—indicates not just experimental noise, but a lack of reproducibility significant enough to undermine the reliability of the result. In field-oriented MEOR research, where recovery improvements are often marginal and cumulative, such variability renders the data operationally meaningless unless tightly constrained and statistically verified.
Furthermore, the paper provides no information on porosity, permeability, or wettability characteristics of the sand-pack system. These are fundamental parameters in oil recovery studies. Without them, the oil displacement data cannot be contextualized or compared to any standard or real reservoir condition. The assumption that these sand-pack results translate into field performance is unjustified, especially in the absence of pressure gradient data, capillary pressure effects, or mobility ratio analysis, all of which govern actual biosurfactant flooding efficacy in porous media.
More critically, the core flooding result (12.92% AOR) is also reported without replicates or statistical treatment, and lacks key physical parameters such as core length, porosity, brine/oil saturation, and pressure drop across the core, making it impossible to assess the hydrodynamic or physicochemical relevance of the result. The claim that this confirms the biosurfactant’s applicability to real-world MEOR settings is not scientifically supportable under such conditions.
In its current form, the data may indicate that the biosurfactant has promising properties in isolation (e.g., IFT reduction), but the claim of MEOR readiness is premature and unsupported. A field-facing MEOR study requires not just a displacement percentage, but a complete physicochemical and flow characterization with reproducibility, uncertainty quantification, and sensitivity to reservoir conditions.
In my opinion, while the comment raises valid concerns about reproducibility and methodological rigor, it’s important to recognize that the study was designed as a foundational investigation to demonstrate the biosurfactant’s potential under controlled conditions. Key parameters for the core flooding test, such as core length (72.17 mm), porosity (13.25%), and permeability (36.41 mD), were indeed provided, which partially addresses the need for system characterization. The reported AOR values are not positioned as definitive field predictions, but rather as indicators of promise, especially considering the biosurfactant’s strong performance in IFT reduction, wettability alteration, and environmental stability.
That said, an important issue remains unaddressed: although the authors optimize the emulsification index (EI24) using a Box-Behnken design, they do not establish a direct correlation between emulsification performance and oil recovery under flow conditions. Without connecting EI24 values to flow dynamics or capillary number behavior, the mechanistic link to actual displacement efficacy in porous media remains speculative.