Unlocking trapped oil in Lamadian Oilfield's Class II reservoirs through the synergistic power of alkali, surfactant, and polymer
Imagine trying to drain every last drop of honey from a complex, porous sponge. No matter how much you squeeze, a significant amount remains trapped in the tiny pores. This is precisely the challenge petroleum engineers face in mature oil fields like Lamadian, where conventional extraction methods leave behind substantial amounts of recalcitrant crude oil.
As energy demands continue to grow and new discoveries become scarcer, the ability to extract more from existing fields has become increasingly vital.
Enter the ternary system—a sophisticated chemical cocktail that represents one of the most promising approaches in modern enhanced oil recovery.
This innovative technology doesn't rely on brute force but rather on clever chemistry to coax trapped oil from where it hides. Through the strategic combination of three specialized components, engineers can dramatically improve oil recovery rates in challenging Class II reservoirs that have already undergone conventional extraction methods. The implications extend beyond economics to environmental benefits, as maximizing output from existing fields reduces the need for new drilling operations .
At its core, a ternary system for enhanced oil recovery relies on the synergistic combination of three carefully selected components: alkali (A), surfactant (S), and polymer (P). Together, they form what engineers call an ASP flooding system—a sophisticated chemical approach that targets the physical forces trapping oil within rock formations .
When introduced into the reservoir, it reacts with natural acidic components present in the crude oil to generate surface-active substances right where they're needed most .
These specialized molecules dramatically lower interfacial tension—the cohesive force that keeps oil droplets from moving freely through pore throats .
These long-chain molecules significantly increase the viscosity of the injection fluid, creating favorable flow conditions and improving sweep efficiency .
| Component | Primary Function | Key Effect | Real-World Analogy |
|---|---|---|---|
| Alkali (A) | Generate surfactants in situ | Creates natural soaps from crude oil components | Like adding baking soda to grease to create natural cleansers |
| Surfactant (S) | Reduce interfacial tension | Allows oil droplets to deform and move through pores | Similar to how dish soap breaks grease apart in water |
| Polymer (P) | Increase solution viscosity | Improves sweep efficiency and mobility control | Comparable to using thicker cleaning solutions to cover more surface area |
"The synergistic effect of ASP includes sweep and oil washing. As for sweep, the swept volume is expanded by the interfacial reaction between the alkali and the acidic components in Daqing crude oil, and the polymer increases the viscosity of the system. As for oil washing, the surfactant generated by the alkali cooperates with surfactants to reduce the IFT to an ultra-low level, which promotes the formation and migration of oil-in-water emulsions" .
To truly appreciate the effectiveness of the ternary system approach, let's examine a revealing experiment that demonstrates its superiority over other chemical flooding methods .
The researchers first saturated a transparent chip model with crude oil from the Daqing Oilfield.
They injected water to simulate conventional oil recovery, continuing until no more oil was produced.
The team then injected one of the five chemical solutions while monitoring pressure changes.
For the ASP system specifically, they documented the formation and stability of oil-in-water emulsions.
They measured the additional recovery percentage achieved by each chemical solution.
Comparison of additional oil recovery (% OOIP) achieved by different chemical systems beyond water flooding alone.
| Chemical System | Key Observed Mechanism | Additional Oil Recovery (% OOIP*) | Limitations Observed |
|---|---|---|---|
| Alkali (A) Only | In-situ surfactant generation, some emulsification | Moderate improvement | Limited sweep efficiency, insufficient viscosity |
| Surfactant (S) Only | Interfacial tension reduction | Moderate improvement | Poor conformance, ineffective in small pores |
| Polymer (P) Only | Viscosity enhancement, improved sweep | Moderate improvement | Cannot mobilize isolated oil ganglia |
| SP Binary | Combined IFT reduction and viscosity improvement | Significant improvement (less than ASP) | Lacks in-situ soap generation capability |
| ASP Ternary | Synergistic IFT reduction, emulsification, and viscosity enhancement | 38.0% higher than water flooding | Most complex formulation required |
*OOIP: Original Oil In Place
The extraordinary success of the ASP system—achieving an impressive 38.0% higher oil recovery compared to water flooding alone—stemmed from its ability to simultaneously address multiple trapping mechanisms. While polymer flooding primarily improves macroscopic sweep efficiency, and surfactant flooding mainly enhances microscopic displacement, the ternary system successfully does both . This dual capability allows it to target both the continuous oil patches beyond the water-flooded zones and the disconnected oil droplets trapped within them.
Developing an effective ternary system for enhanced oil recovery requires careful selection of components based on the specific characteristics of the target reservoir and crude oil .
| Reagent/Material | Primary Function | Specific Example |
|---|---|---|
| Weak Alkali | Generate natural surfactants | Sodium Carbonate (Na₂CO₃) |
| Surfactant | Reduce oil-water interfacial tension | Heavy Alkylbenzene Sulfonate |
| Polymer | Increase viscosity and improve sweep efficiency | Hydrolyzed Polyacrylamide (HPAM) |
| Core Models | Mimic reservoir conditions | Transparent Micromodels |
| Interfacial Tensiometer | Measure oil-water interfacial tension | Spinning Drop Interfacial Tensiometer (TX-500C) |
The selection of sodium carbonate as the preferred alkali represents an important evolution in ternary system design. Earlier approaches used stronger alkalis, but these caused problematic scale formation and clay swelling in reservoirs .
This surfactant consistently achieves the ultra-low interfacial tensions necessary for mobilizing trapped oil, while remaining cost-effective for large-scale field applications .
Under reservoir flow conditions, it exhibits viscoelastic properties that help to "pull" oil droplets from rock surfaces—a mechanism that further enhances recovery .
By enabling more efficient oil recovery, this technology effectively reduces the carbon footprint per barrel of produced oil.
Maximizing recovery from existing operations represents a sustainable approach to petroleum extraction.
The integration of pre-crosslinked particle gels (PPG) with chemical flooding systems represents a promising direction 4 .
The successful implementation of ternary system technology extends far beyond immediate production increases from mature fields. As governments and industries worldwide grapple with energy transition challenges, maximizing recovery from existing operations represents a sustainable approach to petroleum extraction.
The environmental dimension of ternary systems deserves particular attention. Ongoing research focuses on developing more eco-friendly surfactant alternatives and biodegradable polymer options to further minimize environmental impact.
As research continues, the fundamental understanding of ternary system mechanics continues to refine. Advanced simulation techniques and improved thermodynamic modeling—drawing from ternary phase diagram approaches used in other fields 6 9 —are helping researchers optimize chemical formulations for specific reservoir conditions.
The development of ternary system technology for enhanced oil recovery represents a fascinating convergence of chemistry, physics, and engineering. By understanding and manipulating the fundamental interactions between fluids and reservoir rocks, petroleum engineers have created an approach that can significantly extend the productive life of mature oil fields.
The story of ternary system development serves as a powerful reminder that innovation in the energy sector continues to evolve, finding novel solutions to long-standing challenges. As this technology progresses from laboratory experiments to widespread field application, it carries with it the potential to reshape what's possible in petroleum extraction while setting new standards for efficiency and environmental stewardship in the energy industry.