In the mid-to-late stages of oilfield development, particularly during phases characterized by high water cut and high recovery degree, the core challenge facing the industry is how to extract more crude oil from increasingly dispersed remaining oil. Welan gum, a biopolymer produced through microbial fermentation, is playing an irreplaceable role in key tertiary recovery technologies, especially in the composite "enhanced foam + gel" profile control and displacement system, where its application details and advantages are particularly prominent.
I. Key Application Details in Production
On the oilfield site, welan gum does not operate alone but serves as the core "viscosifying and foam-stabilizing" component within the system. Its application details are primarily reflected in the synergistic coordination with foaming agents and the precise control of injection processes.
Compatibility and System Construction: Oilfield formation water often exhibits high salinity, which poses a severe challenge to the stability of displacement systems. The advantage of welan gum lies in the stability of its molecular structure. When combined with specific foaming agents, it forms "enhanced foam" with performance far superior to single-agent systems. During on-site preparation, operators must strictly control the dissolution and hydration time of welan gum to ensure its molecular chains are fully extended, forming a uniform and stable gel solution. This is then mixed with surfactants such as foaming agents at predetermined ratios. In this process, welan gum not only increases viscosity on its own but, more importantly, adsorbs onto the foam liquid film, significantly enhancing foam toughness.
The Craftsmanship of Slug Injection: The displacement system is not simply injected into the subsurface all at once. Field operations employ a "small slug, multiple rounds" injection strategy. Engineers alternately and batchwise inject the welan gum-enhanced foam system and the gel system into the reservoir in stages. This sophisticated injection method functions like a "pulse-style" flushing of the underground oil layer. Each small slug of the welan gum foam system can continuously adjust its flow direction in deep heterogeneous reservoirs, expanding sweep volume and thereby improving displacement efficiency. Experimental studies have shown that this refined injection approach yields significantly higher ultimate recovery rates compared to single large-slug injection.
II. Core Advantages Derived from Welan Gum's Properties
The key role that welan gum plays in displacement systems stems from its unique physicochemical characteristics.
Exceptional Viscosifying and Suspending Capacity: Welan gum can impart extremely high viscosity to aqueous solutions even at low concentrations. This property enables it to effectively increase the "apparent viscosity" of the displacing phase, slowing down the breakthrough velocity of the displacing fluid in high-permeability channels during the displacement process, and forcing subsequent fluids to divert toward medium- and low-permeability zones with higher oil saturation, thereby significantly improving sweep efficiency.
Remarkable Rheological Properties—Shear Thinning: Welan gum solutions exhibit typical pseudoplastic rheological behavior. This means that when passing through porous media or downhole tubular goods under high shear rates, the solution viscosity temporarily decreases, facilitating pumping and injection. Once it enters deep into the formation where shear rates drop, viscosity quickly recovers, continuing to exert its excellent sand-carrying and profile-control capabilities. This characteristic of "weakening when stressed, strengthening when at rest" represents a perfect combination of efficient oil displacement and engineering practicality.
Robust Temperature and Salt Resistance: Deep reservoirs are often accompanied by harsh conditions of high temperature and high salinity. Welan gum's unique molecular structure endows it with excellent thermal stability and tolerance to high concentrations of calcium and magnesium ions. Under high-temperature, high-salinity formation conditions, the viscosity variation of its aqueous solution is far smaller than that of conventional polymers, ensuring that the displacement system maintains effective performance over long-distance migration, delivering its "combat effectiveness" precisely where it is most needed.
Environmentally Friendly Attributes: As a biodegradable product derived from natural fermentation, welan gum and its displacement system components are environmentally friendly, non-toxic, and harmless, causing no damage to the formation. With increasingly stringent environmental regulations, this advantage paves the way for its large-scale application.
Through precise formulation in enhanced foam displacement systems and careful slug injection processes, welan gum—leveraging its outstanding viscosifying, shear-thinning, temperature-resistant, salt-tolerant, and environmentally friendly characteristics—effectively addresses the challenge of tapping remaining oil in high-water-cut oilfields, making it a key technological tool for significantly enhancing crude oil recovery.
On the oilfield site, welan gum does not operate alone but serves as the core "viscosifying and foam-stabilizing" component within the system. Its application details are primarily
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