Algorithm simulates oil behavior for improved recovery techniques

Researchers have presented a new algorithm for molecular simulation of oil that will help optimize oil recovery and filtration strategies. The research was published in the journal Colloids and Surfaces A: Physicochemical and Engineering Aspects.

Molecular simulation of oil is essential for understanding its behavior in different environments, including porous structures. The lack of accurate models is one of the barriers to tackling this task. The common primitive single-component model simplifies the composition of oil, leading to unreliable results.

A team of researchers from Skoltech, MIPT, AIRI and MSU proposed a solution for building a reliable model of porous space in the Earth's interior. The scientists focused on determining the quartz-oil-brine contact angle and created an algorithm based on a complex 15-component oil model using experimental data.

In the new algorithm, a model cell has the shape of a slit pore formed by quartz plates with oil and water between them. The oil-water system in a pore was previously shown to form a droplet that looks like a flattened cylinder closed through cell boundaries. The projection of the liquid drop has four points of three-phase contact. The contact angle is calculated as the arithmetic mean of the angles at these points.

"The new numerical contact angle calculation method differs from the existing alternatives in that it uses linearly complex angle determination at each system step and does not need to fine-tune the algorithm for methane and water dissolved in water and oil, respectively," said Petr Khoventhal, the first author of the paper and a Petroleum Engineering Ph.D. student at Skoltech.

"This helps to speed up calculations and process large amounts of data, while making the calculation process easy to control."

The fact that the model includes multiple oil components—particularly asphaltenes and methane—is the key achievement of the study, ensuring a more accurate simulation of molecular interactions.

"Our research confirms the key role of asphaltenes in the study of wettability. Methane goes hand in hand with oil and can make up a significant portion of its composition, even by mass. Ignoring what could be the dominant component by mass will definitely affect the resulting simulation accuracy. In a single-component model, these components are completely ignored, which is contrary to reality," Ilya Kopanichuk, a senior researcher at the MIPT Computational Physics Center, explained.

The team used the new algorithm to study the effects of various factors on the contact angle. In the temperature simulation, the contact angle tends to decrease with increasing temperature. The higher the methane content, the larger the contact angle and the lower the wettability.

High brine salinity results in smaller angle values, while aromatic content and pressure variations have minimal effects on the angle size. Thus, the contact angle can be considered a function of temperature, methane content, pressure, and brine salinity. This discovery opens up new possibilities for controlling wettability in real environments, for example, by changing the composition of the injected brine.

Other advantages of the algorithm include low cost and the easy control of system parameters. For example, oil composition can be selected based on data from any oil field. The limitation is that it cannot simulate structures larger than 0.1 microns.

The results of the study show good agreement with experimental data. The algorithm is also useful for microfluidics research.

The next phase of the research will focus on developing a unified global standard for contact angle calculations. In the longer term, the team plans to create a universal digital oil model that will form the core of new production and refining technologies.

Provided by Skolkovo Institute of Science and Technology