Standards Development

Scope

This document specifies the phase behavior test method of surfactant-based chemical flooding system with oil.

This document is applicable to the chemical flooding system of surfactant-polymer, alkali/salt-surfactant and alkali/salt-surfactant-polymer.

This document includes principle, reagents and materials, instruments, procedures, experiment result and informative annex.

Purpose

Phase behavior is a key performance indicator in surfactant-based chemical flooding system. Three primary phase types are commonly observed: Winsor Type I (oil-in-water microemulsion), Winsor Type II (water-in-oil microemulsion) and Winsor Type III (middle-phase microemulsion). The middle-phase microemulsion (Winsor Type III) offers distinct advantages, as it can achieve ultra-low interfacial tension with both the oil and water phases. It also exhibits a critical state analogous to mutual solubility. The displacement efficiency of this phase type can exceed 90%, leading to a significant improvement in oil recovery.

Research and application of phase behavior have played an important role in the advancement of enhanced oil recovery (EOR) technologies. In the 1970s, micellar flooding with surfactant concentration above 2% was widely used to form microemulsions. However, due to the high costs associated with chemical consumption, this method was gradually discontinued in industrial practice. In the 1980s, alkali–surfactant–polymer (ASP) and surfactant–polymer (SP) floodings were developed using surfactant concentrations around 0.3%. These methods successfully reduced oil–water interfacial tension to ultra-low levels, forming Winsor Type II microemulsions. The technology was economically feasible and achieved commercial application in field operations. In recent years, the development of high-efficiency EOR surfactants has accelerated due to improve the understanding of surfactant structure–activity relationships and advances in synthesis technology. Modern formulations allow dilute systems (approximately 0.3% surfactant concentration) to form middle-phase microemulsions (Winsor Type III) with ultra-low interfacial tension. Compared to conventional commercial surfactant systems, oil displacement efficiency has improved more than 10% further promoting the advancement of ASP flooding technology. Phase behavior tests have been extensively applied in the in the United States, China, India, Oman, Indonesia, Venezuela, and Malaysia to optimize surfactant formulations and provide scheme design parameters of chemical flooding for different reservoir conditions. The pilot tests have achieved remarkable oil recovery results, emphasizing the importance of phase behavior in petroleum industry.

However, there is no internationally recognized standard for phase behavior test method of surfactantbased chemical flooding system. The lack of a universal protocol leads to inconsistencies in data interpretation and limits comparability across research and industrial applications.

The establishment of a standardized phase behavior testing method is essential and would provide the following benefits:

1. Provide internationally recognized experimental protocols and technical foundation for phase behaviour of surfactant-based chemical flooding system.

2. Help surfactant manufacturers align their products with specific technical requirements from different oilfields.

3. Provide accurate technical parameters for feasibility assessments and chemical flooding program design.

4. Ensure the effectiveness and economic benefits of chemical flooding projects.

5. Facilitate international collaboration, also promote global development and extension of chemical flooding technologies.