Hard-to-recover oil, which accounts for over 50% of Russian reserves, lies in the microscopic pores of dense rocks. Conventional technologies cannot ensure its flow due to high temperatures up to 160 °C and the complex structure of the formation. Acid fracturing is a method in which a solution is injected into the rock to dissolve minerals and form pathways for oil. However, traditional acids quickly lose their effectiveness: they dissolve only the most permeable rocks and pollute the formation.
The new composition, developed by scientists from Perm Polytechnic University and China, uses surfactants that make the acid "smart." It independently finds hard-to-reach zones, creating long channels for oil.
Surfactants in a 5-15% hydrochloric acid solution form a viscoelastic, environmentally friendly structure. How it works: when it enters the oil-bearing formation, the molecules form many particles that greatly increase the viscosity of the composition to 50 mPa·s, making it similar to a gel. Compared to analogues, it does not only go into highly permeable rocks, but evenly dissolves minerals and forms a network of fractures. After such treatment, under the influence of oil or formation water, the viscosity of the gel is maximally reduced to less than 10 mPa·s. This allows the solution to become more fluid, which in the future, when the well is put into operation, makes it easy to extract its residues without clogging the fractures and polluting the formation.
Experiments have shown that the new composition reduces solution loss by 55% compared to analogues. It also reacts more slowly with the rock, ensuring stable dissolution. The heat resistance is 14% higher: the acid retains its properties at 160 °C, while others are effective only up to 140 °C. This makes it suitable for deep formations.
The study is published in the journal Scientific Reports, 2025.
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