More than half of Russia's oil reserves are trapped in the microscopic pores of tight deep-layer rocks, making them difficult to extract using conventional methods. Unconventional techniques such as acid fracturing are employed, but traditional chemical compounds perform poorly under the extreme conditions of deep formations. Recently, scientists from Perm National Research Polytechnic University, in collaboration with Chinese colleagues, have developed a novel “smart” acid fluid. The related research was published in the journal Scientific Reports.

Today, hydrocarbons must be extracted from deep, tight rock formations where temperatures can reach 160°C, structures are complex, fluid permeability is extremely low, and oil flows very slowly. To create flow pathways, special acidic compounds are pumped in to dissolve the rock. However, conventional acid fluids become overly reactive at high temperatures, dissolving only the most permeable rock near the wellbore while failing to affect denser rock farther away. As a result, acid treatment efficiency drops significantly: the acid is neutralized near the wellbore and cannot create the necessary fractures deeper in the formation.

The special acid fluid developed by Perm Polytechnic experts together with Chinese partners is based on surfactants. It can penetrate hard-to-reach layers, creating long channels for oil flow without leaving harmful deposits in the formation during extraction. These compounds improve the contact between oil and rock surfaces. Fluids formulated with them can be used without unnecessary additives, readily decompose under the action of crude oil or natural gas, and cause no significant damage to the reservoir. Using such substances allows control of fracture height, increases fracture length, and reduces pipe friction, making them particularly suitable for stimulation operations in deep, high-temperature formations.

Vladimir Poplygin, Rector of the Kogalym Branch of the Philippine National Research and Petroleum University and Doctor of Engineering, explained that the surfactant forms a viscoelastic, environmentally friendly structure in a 5–15% hydrochloric acid solution. Upon entering the oil-bearing formation, the molecules aggregate into numerous particles, dramatically increasing the mixture's viscosity to 50mPa·s — similar to a gel. Compared to analogs, this formulation not only penetrates high-permeability rock but also uniformly dissolves minerals and creates a network of fractures. After treatment, in the presence of oil or formation water, the gel viscosity drops to below 10mPa·s, greatly improving fluid mobility. Once the well is put into production, residual material can be easily extracted without clogging fractures or contaminating the formation.

Laboratory experiments comparing the proposed acid with analogs showed that, thanks to the gel effect, the formulation reduces fluid loss by nearly 55%, prevents excessive consumption of the material, and allows the creation of significantly longer fractures in the formation. According to Vladimir Poplygin, the chemical reaction rate between the composition and the rock is slower than that of both the gel and conventional hydrochloric acid, enabling slower, more stable rock dissolution.

The experts highlight that the formulation exhibits excellent compatibility with hydrochloric acid and stable high-temperature performance, maintaining high viscosity even at 160°C (typical for deep reservoirs), while most existing acid systems remain effective only up to 140°C — representing a 14.3% improvement in reservoir temperature tolerance.

This new “smart” acid fluid enables high-quality hydraulic fracturing and is expected to become a key tool for increasing oil production under complex geological conditions, opening new opportunities for the development of hard-to-recover oil and gas reserves.