基于拉曼光谱的储层沥青热演化特征及其判别

为了明确储层沥青热演化程度与激光拉曼光谱的关系，利用拉曼光谱无损分析和流体包裹体方法，对黔西南白层地区储层沥青拉曼光谱进行了定量化描述，首先获取了储层沥青其伴生流体包裹体均一温度，然后获得了储层沥青拉曼光谱图，并对比标准沥青成熟度分布图，确定了储层沥青热演化程度及其特征。结果表明：黔西南白层地区存在晚三叠世（230 Ma）和渐新世（30 Ma）油气藏充注事件，成烃流体具有多期成藏的特征。这两次油气充注事件是该地区储层沥青最终来源，沥青是石油受热变质作用形成的天然裂解产物，沥青随着埋藏深度增加，不断发生聚合或增碳缩合作用。与储层沥青形成相伴生的有两期盐水热流体事件，其盐水包裹体均一温度为93.5～96.7和101.2～103.7℃。黔西南白层地区储层沥青拉曼光谱D峰拉曼位移变化范围为1 334～1 346 cm-1，G峰拉曼位移变化范围为1 607～1 610 cm-1，G-D差值为264～275 cm-1，D_h／G_h值为0.552～0.573，根据沥青成熟度分布图版判断：该储层沥青均已达过成熟演化阶段；测试样品的D峰与G峰能量强度的比值R₁变化0.552～0.573，D峰与G峰的半峰全宽比值R₂变化为1. 688～1.945，D峰与(D+G)峰积分面积之比R₃的变化为0. 68～0. 72，基于拉曼光谱分析结果计算得到区域古油藏储层流体温度为122.78～164.31 ℃。黔西南白层地区储层沥青属于异地迁移型有机质，相似激光拉曼光谱特征表明储层沥青具有相同成因，均为先存古油藏沿该区控矿构造发生逃逸的油气物质转化的产物。最后拟定了拉曼光谱与沥青热演化关系，为古油藏演化成储层沥青研究提供了理论依据。

Thermal Evolution Characteristics and Discrimination of Reservoir Bitumen Based on Raman Spectroscopy

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 D_h/G_h 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.