Laboratory Simulation of the Formation Process of Surface Geochemical Anomalies Applied to Hydrocarbon Exploration

• Published in: Acta geologica Sinica (Beijing) Vol. 90; no. 6; pp. 2149 - 2162
• Main Authors: WANG, Guojian, TANG, Yuping, CHENG, Tongjin, TANG, Junhong, FAN, Ming, LU, Li
• Format: Journal Article
• Language: English
• Published: Richmond Blackwell Publishing Ltd 01.12.2016; Wiley Subscription Services, Inc; Wuxi Research Institute of Petroleum Geology, Research Institute of Petroleum Exploration and Production, SINOPEC, Wuxi 214151, Jiangsu, China%College of Material & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, Zhejiang, China
• Edition: English ed.
• Subjects: 3D measurement; Anomalies; Buoyancy; Diffusion; Geochemistry; hydrocarbon microseepage; Hydrocarbons; Infiltration; laboratory simulation; Mathematical models; migration mechanisms and processes; Reservoirs; surface geochemical anomaly; 三维测量; 地球化学勘探; 地球化学异常; 地表; 实验室模拟; 扩散机制; 油气化探; 烃类微渗漏; laboratory simulation; 3D measurement; migration mechanisms and processes; hydrocarbon microseepage; surface geochemical anomaly
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.13028

The formation mechanisms and processes of geochemical anomalies used as proxies in surface geochemistry exploration （SGE） have not been well understood. Previous studies cannot realize 3D measurement of microseeping hydrocarbons from reservoirs to the surface, which made it difficult to understand the features and pathways of deep hydrocarbon microseepages. Understanding the processes of hydrocarbon microseepages will contribute to the acceptance and effectiveness of surface geochemistry. Based on a simplified geological model of hydrocarbon microseepages, including hydrocarbon reservoir, direct caprock, overlying strata and Quaternary sediments, this work established a 3D experimental system to simulate the mechanisms and processes of deep hydrocarbon microseepes extending to the surface. The dispersive halos of microseeping hydrocarbons in the subsurface were adequately described by using this 3D experimental system. Results indicate that different migration patterns of hydrocarbons above the point gas source within the simulated caprock and overlying strata can be reflected by the ratio of i-butane to n-butane （i-C4/n-C4）, which follow diffusion and infiltration （buoyancy） mechanisms. This is not the case for vertical measurement lines far from the point gas source. A vertical gas flow in the form of a plume was found during hydrocarbon microseepage. For sampling methods, the high-density grid sampling is favorable for delineating prospecting targets. Hydrocarbon infiltration or buoyancy flow occurs in the zones of infiltration clusters, coupling with a diffusion mechanism at the top of the water table and forming surface geochemical anomalies. These results are significant in understanding hydrocarbon microseepage and interpreting SGE data.