Technology of bitumen characterization in unconventional rocks presented in new paper
The Laboratory of Enhanced Oil Recovery published its research in Fuel.
"Shale rocks, especially such as the Bazhenov formation and Domanik deposits, are rich in organic matter and have been actively studied in recent years by both scientists and oil industry specialists. However, studying such rocks remains a difficult task. Oil, bitumen, kerogen and water coexist in very small pores, which complicates their identification and quantitative assessment. At the same time, traditional analysis methods, such as Rock-Eval pyrolysis or extraction, require lengthy preparation, destroy the sample and work with very small amounts of matter," explains first author Marsel Fazlyyakhmatov.
The technology is based on a method invented and patented by KFU for determining the amount of kerogen and recoverable hydrocarbon raw materials in rock using low-field NMR relaxometry, a method based on the phenomenon of nuclear magnetic resonance and allowing to determine the relaxation times of nuclear magnetization.
"We are developing our method based on low-field NMR relaxometry and allowing us to capture signals from hydrogen nuclei in various components of rock," says Fazlyyakhmatov. "With the help of a special combination of FID (free induction decay) and CPMG (Carr-Purcell-Meiboom-Gill) signals, we can see almost all hydrogen nuclei in a core sample measuring 8.5 by 13.5 millimeters, including those contained in solid bitumen and even in kerogen. This is a significant achievement, because these components are traditionally invisible to standard NMR methods."
In order to find out how much kerogen and bitumen the shale rock contains, the researchers used a solvent—deuterated chloroform. With its help, bitumen dissolves and turns into a liquid state without affecting solid kerogen.
"We proposed a new pulse sequence, and then supplemented the study by introducing a solvent—deuterated chloroform (CDCl3)," adds Senior Research Associate Boris Sakharov.
The development allows differentiating kerogen, asphaltenes, resins, aromatic and saturated hydrocarbons.
"Unlike pyrolysis, where the sample is destroyed, our technology can be used to study a whole core (this is especially important for rare or valuable samples), without grinding, and does not require a significant amount of chemical reagents. This approach can be used both in laboratory and field conditions—for a quick preliminary assessment of the quality of shale rocks and making decisions on the feasibility of their further study or development," elaborates Dr. Sakharov.
According to the authors, their technology is necessary in the early stages of oil exploration, when it is critical to know how much organic matter the rock contains, what type it is and how mature it is, since this determines whether the shale rock will produce oil.
"Today it is important to study and obtain the characteristics of oil source samples and other objects related to reserves of hard-to-recover hydrocarbons as fully as possible. The method we propose, with less time expenditure, compared to all other existing methods, allows not only to determine the quantity and type of hydrocarbon raw materials, but also provides information on its detailed fractional composition, properties, and water content within a single measurement. We have successfully applied it to the study of very different objects and are confident that it will be useful in the industry," sums up Director of the Small Tonnage Chemical Technology Park Mikhail Varfolomeev.
More information:
A low-field NMR relaxometry-based technology for organic matter and bitumen characterization in unconventional reservoir rocks
www.sciencedirect.com/science/ … ii/S0016236125019325
Provided by Kazan Federal University
