Origin of the Magnetic Signature of Hydrocarbons

航磁调查表明，一些油气藏周围存在较大的磁异常。对委内瑞拉、中国和美国岩心的直接采样揭示了这些异常中存在丰富的独特的磁铁矿框体，但我们仍然不清楚这些磁性矿物是如何形成的，以及它们与油气的关系。如果我们能够了解这些磁铁矿框体的形成机制和环境，以及它们的运移行为，那么这将有助于我们更好地理解油气藏。这项跨学科的建议旨在了解这些过程。在一项初步研究中，为了测试这些磁性特征的普遍性，我们已经研究了多塞特Wytch农场油田附近的油砂露头，来自爱丁堡BGS北海岩芯储存库的样品，来自加拿大阿尔伯塔盆地的Athabasca和哥伦比亚的Llanos前陆。在这些样品中，我们发现了磁性框体，以及由磁化率和有机质含量决定的磁性矿物的丰度之间的直接关系。然而，如果我们要将矿物磁学技术应用于油气研究，还有一些关键问题尚未得到解答，这些问题是重要的：1)磁性矿物的来源是什么？2)石油的生物降解状态与磁性特征之间的关系是什么？3)磁性矿物是否会迁移，如果是的话，4)我们能确定迁移距离吗？作为这项提案的一部分，我们计划回答这些问题。为了实现我们的目标，我们打算用Wytch Farm钻芯(位于Keyworth的BGS芯店)和英国什罗普郡著名的焦油隧道的沥青来补充我们的样品套件。什罗普郡的样品将从不同的区段采集，以便评估迁移路径。研究计划将样品的磁学、扫描和透射电子显微镜结合起来，通过气相色谱-质谱分析和其他化学分析确定磁性矿物的丰度、形态、粒度和矿物学。迁移过程将通过对油层进行采样来确定。如果磁性矿物迁移，那么较大的框体很可能会比较小的框体移动更远的距离。考虑到磁性高度依赖于磁性颗粒的大小，我们的目标是确定一个磁性指标来识别迁移距离。

From aeromagnetic surveys there is evidence of large magnetic anomalies around some hydrocarbon reservoirs. Direct sampling of cores from Venezuela, China and the US has revealed the presence of an abundance of distinctive magnetite framboids at these anomalies, however, we still do not understand how these magnetic minerals form and how they relate to the hydrocarbons. If we can understand the formation mechanisms and environment, and the migration behaviour of these magnetite framboids, then this has the potential to will help us to better understand hydrocarbon reservoirs. This cross-disciplinary proposal aims to understand these processes.In a preliminary study, to test for the universality of these magnetic signatures, we have already studied samples from the oil sand out-crops near Wytch Farm oil field, Dorset, from the North Sea core repository at the BGS in Edinburgh, from Athabasca, the Alberta basin, Canada, and Llanos Foreland, Columbia. Within these samples we have found magnetic framboids and a direct correlation between the abundance of magnetic minerals determined by the magnetic susceptibility and organic matter content. However, there are a number of key questions, which as yet remain unanswered, which are important if we are to apply mineral magnetic techniques to hydrocarbon research: 1) What is the origin of the magnetic minerals?, 2) What is the relationship between the biodegradation state of oil and the magnetic signature?, and 3) Do the magnetic minerals migrate, and if so, 4) can we identify the migration distance? As part of this proposal we plan to answer these questions.To address our objectives, we aim to complement our suite of samples with samples Wytch Farm drill cores (BGS core store at Keyworth) and with bitumen from the celebrated Tar Tunnel in Shropshire, UK. The samples from Shropshire will be collected from a different sections so that migration paths can be assessed.The plan of research plan combines magnetic and scanning and transmission electron microscopy of the samples to determine the abundance, morphology, size and mineralogy of the magnetic minerals, with gas-chromatography mass spectrometry and other chemical analysis. Migration processes will be determined by sampling through an oil reservoir. If the magnetic minerals migrate, then it is likely that the greater framboids will travel a greater distance than the smaller ones. Given that magnetic properties are highly dependent on magnetic grain-size, we aim to determine a magnetic proxy to identify migration distance.