The Influence of Bitumen on Reservoir Physical Property and Its Recognition by Logging

• Published in: Pure and applied geophysics 2023-07, Vol.180 (7), p.2861-2878
• Main Authors: He, Xin, Chen, Shijia, Liu, Chaowei, Wang, Jian, Li, Yong, Fu, Xiaoyan, Mou, Feisheng, Dai, Linfeng, Lu, Yifan
• Format: Article
• Language: English
• Subjects: Bitumen; Bitumens; Bound water; Comparative analysis; Dissolution; Dissolving; Distribution; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Identification methods; Membrane permeability; Natural gas exploration; NMR; Nuclear magnetic resonance; Oil and gas exploration; Oil exploration; Permeability; Physical properties; Pore size; Pore size distribution; Porosity; Reservoirs
• ISSN: 0033-4553; 1420-9136
• DOI: 10.1007/s00024-023-03310-1

Bitumen is similar to oil and gas in logging, making it difficult to identify. It occupies the reservoir pores and affects the reservoir's physical properties. It is important to consider the influence of bitumen on reservoir physical properties and determine the logging identification method of bitumen for further oil and gas exploration. This article focuses on bitumen in the Mahu Depression. By carrying out bitumen dissolution experiments, comparative analyses of the physical property of bitumen-bearing samples before and after dissolution were made to quantitatively evaluate the influence of bitumen on the reservoir physcial properties. In addition, the NMR logging parameters of bitumen-bearing samples before and after dissolution of bitumen-bearing samples were compared and analyzed to quantify the correlation between bitumen content and NMR. The results showed that the porosity of the reservoir increased by 4.54% and the permeability increased by 15.17 mD after dissolution, and the pore size changed from a distribution mainly < 0.02 μm before dissolution to a distribution mainly between 2 μm and 20 μm after dissolution. The NMR T 2 relaxation times of bitumen and bound water are mainly in the range of 10 us to 6000 us, which supports the establishment of an identification model of bitumen by NMR logging. As the NMR porosity is considerably higher than that of gas measuring, an NMR-density porosity interpretation model of bitumen is established.