Thermal Evolution Characteristics and Discrimination of Reservoir Bitumen Based on Raman Spectroscopy
SI Shang-hua1, 2, YANG Zhe-heng1, 2, CHEN You-zhi3, SONG Li-jun1, 2, SHANG Xiao-qing1, 2, ER Chuang1, 2, LIU Chao1, 2
1. School of Earth Sciences and Engineering，Xi’an Shiyou University, Xi’an 710065, China
2. Shaanxi Key Laboratory of Hydrocarbon Accumulation Geology, Xi’an 710065, China
3. College of Resources and Environmental Engineering, Guizhou Institute of Technology, Guiyang 550003, China
Abstract：To determine the relationship between the thermal evolution degrees and Raman spectra of reservoir bitumens, bitumen from the reservoir in the Baiceng area of Southwest Guizhou Province was quantitatively analyzed using non-destructive Raman spectroscopy and fluid inclusion. Firstly, the homogenization temperature of fluid inclusions associated with the reservoir bitumen was obtained. The Raman spectrum of the bitumen was then obtained and compared with the maturity distribution standard for bitumen to determine the homogenization temperature, thermal evolution degree, and characteristics of the bitumen in the study. The results indicate that hydrocarbon reservoir charging events occurred in the Baiceng area of Southwest Guizhou in the Late Triassic (230 Ma) and Oligocene (30 Ma) and that the hydrocarbon-forming fluid had the characteristics of multi-stage hydrocarbon accumulation, these two oil and gas charging events are the ultimate source of reservoir bitumen in this area. Bitumen is the natural cracking product formed by the thermal metamorphism of oil. With the increase of burial depth, bitumen is continuously polymerized or carbonized. The formation of reservoir bitumen is accompanied by two stages of aqueous thermal fluid events, and the homogenization temperatures of aqueous inclusions are 93.5～96.7 and 101.2～103.7 ℃. The results show that the Raman shift range of D peak is 1 334～1 346 cm-1, the Raman shift range of G peak is 1 607～1 610 cm-1, the difference G-D is 264～275 cm-1, and the Dh/Gh value is 0.552～0.573. According to the bitumen maturity distribution chart, the bitumen in the reservoir has reached the over-mature stage. The energy intensity ratio of D peak to G peak (R1) is 0.573，the full width at a half ratio of D peak to G peak（R2） is 1.688～1.945，and the ratio of D peak to the (D+G) integral peak area (R3) is 0.68~0.72. The Raman spectrum analysis indicates that the fluid temperature of the regional paleo reservoir is 122.78~164.31 ℃. The reservoir bitumen in the Baiceng area of Southwest Guizhou is derived from allochthonous migration-type organic matter. The similarities in laser Raman spectrum characteristics indicate that the reservoir bitumen samples have the same origin. They are products of the transformation of oil and gas materials that escaped from the preexisting paleo reservoir along the ore-controlling structure in the study area. Finally, the relationship between the Raman spectrum and thermal evolution of bitumen is determined, providing a theoretical basis for studying the evolution of ancient reservoir oil into reservoir bitumen.
斯尚华，杨哲恒，陈友智，宋立军，尚晓庆，耳 闯，刘 超. 基于拉曼光谱的储层沥青热演化特征及其判别[J]. 光谱学与光谱分析, 2022, 42(03): 783-787.
SI Shang-hua, YANG Zhe-heng, CHEN You-zhi, SONG Li-jun, SHANG Xiao-qing, ER Chuang, LIU Chao. Thermal Evolution Characteristics and Discrimination of Reservoir Bitumen Based on Raman Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(03): 783-787.
