Scientists from Perm have discovered a method to reduce the greenhouse effect by injecting carbon dioxide into oil reservoirs.

According to a report by the World Meteorological Organization, the concentration of carbon dioxide in the atmosphere has risen by 11.4 percent in just the past 20 years. The levels of greenhouse gases are increasing, condemning the planet to rising temperatures for many years to come. One potential solution is the capture, utilization, and storage of carbon dioxide in oil wells, where the gas remains underground. However, the complex reactions occurring between the gas, rock formations, and the fluids in them are still not well understood. Researchers at Perm Polytechnic University have investigated the changes in the structure of rock layers when interacting with carbon dioxide and found that injecting CO2 into the rock leads to pore blockage, reducing their permeability by 60-70 percent, which in turn hampers oil extraction. These findings will aid in better understanding how to optimize the injection of carbon dioxide.

2025-02-20 10:00:18https://naked-science.ru/article/column/zakachki-uglekislogo-gaza

The article has been published in Chemical Engineering Journal. The research was conducted as part of the strategic academic leadership program "Priority 2030".

The greenhouse effect results in an increase in the planet's temperature by trapping solar heat. This is a natural process, but human activities significantly influence it. Fossil fuels, such as oil, remain the primary energy sources; however, their combustion releases greenhouse gases into the atmosphere. Among these is carbon dioxide, which exacerbates global warming, making its disposal essential.

A promising solution is the capture, utilization, and storage of this gas in oil reservoirs. It is purified from impurities, compressed, and injected at high pressure into the reservoir, where it mixes with the liquid inside. This also enhances the flow of oil and thereby increases its extraction. Although the technology is popular, the microscopic processes and how gas dissolution affects rock properties are still not sufficiently understood. Complex physicochemical reactions between carbon dioxide—dissolved carbon dioxide in water—and the rock can influence its physical properties: porosity, permeability, wettability, and more. These factors determine how much oil can be extracted from the reservoir.

Scientists from Perm Polytechnic University studied what happens when carbon dioxide is injected into rock formations for safe storage. They conducted an experiment on a core sample—20 millimeters long and 10 millimeters in diameter, cut from the rock. It was dried, tested for tightness, and scanned using a tomography machine, resulting in 3D images that allowed for the examination of pores. Subsequently, it was filled with distilled water saturated with carbon dioxide, after which a repeat scan was performed to observe and compare structural changes. During the experiment, the amount of liquid exiting the core was measured, and the liquid and sediment formed as a result of the reaction were studied.

It was found that injecting carbon dioxide affects the permeability of the reservoir—this parameter is crucial for oil extraction.

“The experiment showed that carbon dioxide leads to ambiguous changes in the pore structure. Dissolving in reservoir water, it undergoes a chemical reaction with the rock, thereby initiating two opposing processes. Initially, the gas breaks down thin walls between pores, enlarging them (due to the increase in voids through which liquid flows, permeability also increases): after 35 hours of reaction, porosity increased by almost two percent (from 14 to 16 percent). However, later in this reaction, potassium carbonate sediment forms in the form of crystals, which can block the pores and hinder oil extraction. This results in a sharp decrease in permeability,” comments Dmitry Martyushev, a professor in the Department of Oil and Gas Technologies at PNIPU, Doctor of Technical Sciences.

With further injection of carbon dioxide, magnesium carbonate begins to precipitate. Initially, it appears as a fluffy sediment with a loose structure and large pores—this structure temporarily improves the permeability of the rock. However, it then starts to form flaky crystals, complicating the flow of liquid again and continuing to block the pores. As a result, the permeability of the rock decreases by 60-70 percent compared to the initial state.

The research by scientists from Perm Polytechnic University will help to better understand how to safely inject carbon dioxide into reservoirs for storage and to extract more oil. This process has proven to be more complex, so before using gas to enhance oil recovery or disposal in reservoirs, polytechnic experts recommend conducting laboratory studies of its interaction with water and rock to eliminate negative consequences that lead to reduced extraction. In the future, scientists plan to conduct additional experiments with varying flow rates and pressures to study how these factors affect pore blockage.