含油砂岩抽提物中含氮化合物指标的有效性分析

Effectiveness of nitrogen compound indices of oil-bearing sandstone extracts

朱楠 王爱国 郭凯 吴春燕 李春雨 杨泽光 何森森

ZHU Nan WANG Aiguo GUO Kai WU Chunyan LI Chunyu YANG Zeguang HE Sensen

1. 西北大学 地质学系, 西安 710069; 2. 西北大学 大陆动力学国家重点实验室, 西安 710069; 3. 陕西延长石油(集团)有限责任公司 研究院, 西安 710075

1. Department of Geology, Northwest University, Xi'an, Shaanxi 710069, China; 2. State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, Shaanxi 710069, China; 3. Research Institute of Yanchang Petroleum(Group) Co. Ltd., Xi'an, Shaanxi 710075, China

在油样匮乏地区鲜见利用含氮化合物示踪油气运移的报道，究其原因是含油砂岩抽提物中含氮化合物指标的有效性还不清楚，为此，设计了2组、5种抽提方法的对比实验，探讨了含氮化合物指标的有效性。实验结果显示，随着抽提强度的增大，抽提物的1-/4-甲基咔唑和1,8-/2,7-二甲基咔唑的比值逐渐减小，但始终高于对照石油；苯并咔唑［a］/［c］比值则保持相对稳定并接近对照石油。分析认为，导致这些现象的根本原因是咔唑类异构体吸附能力的差异。在地表条件下，该差异导致咔唑类异构体在游离烃—吸附烃之间发生分馏；在抽提时，该差异还导致它们在抽提物—岩石之间发生分馏。这2种分馏作用控制了含油砂岩抽提物中含氮化合物指标的变化。相较于1-/4-甲基咔唑和1,8-/2,7-二甲基咔唑，苯并咔唑［a］/［c］受这2种分馏作用的影响较小，比值的变化主要受控于运移分馏作用，所指示的油气运移方向也符合地质实际，因而成为含油砂岩抽提物中有效的含氮化合物指标，可将其用于油样匮乏地区的石油运移示踪研究。

Reports on the utilization of nitrogen compounds to trace oil and gas migration in oil-scarce regions are limited. This scarcity can be attributed to the lack of clarity regarding the effectiveness of nitrogen compound indices in oil-bearing sandstone extracts. To address this knowledge gap, two sets of experiments were designed, encompassing five extraction methods, to evaluate the validity of nitrogen compound indices. The results showed that as the extraction intensity increased, the ratios of 1-/4-methylcarbazole and 1,8-/2,7-dimethylcarbazole in the extracts gradually decreased but remained consistently elevated compared to the control oils. The benzocarbazole ［a］/［c］ ratio remained relatively stable and closely aligned with the control oils. Upon analysis, it was concluded that the observed variations could be attributed to the differing adsorption capacities of carbazole isomers. These differences lead to the fractionation of carbazole isomers between free and adsorbed hydrocarbons under surface conditions, as well as between the extracts and rocks during the extraction process. In comparison to 1-/4-methylcarbazole and 1,8-/2,7-dimethylcarbazole, the benzocarbazole ［a］/［c］ ratio is less susceptible to these two fractionations, with its variations primarily governed by migration fractionation. Additionally, the indicated direction of oil and gas migration aligns with geological realities. Therefore, the benzocarbazole ［a］/［c］ ratio can be considered an effective nitrogen compound index in oil-bearing sandstone extracts, suitable for oil migration tracing studies in oil-scarce regions.

国家自然科学基金(41402115)和陕西省自然科学基础研究计划(2020JQ-591)联合资助。

https://doi.org/10.11781/sysydz202402393