Abstract
Hydrocarbon (HC) reservoirs leak to the surface over time and produce discernible physio-chemical and mineralogical transformations on the surface, which are described within microseepage theory. Microseepage-induced surfaces are characterized by (1) anomalous gas concentration; (2) microbial and geobotanical anomalies; (3) mineralogical changes such as clay alterations, and the formation of carbonates, sulfides, and elemental sulfur; (4) bleached facies; (5) electrochemical changes; (6) magmatic iron oxides and sulfides; and (7) radiation anomalies. Many of these mineral collections (e.g. clays, carbonates, and iron oxides) show diagnostic spectral features within visible-near infrared and shortwave infrared wavelengths. Accordingly they have been the subject of many remote sensing-based studies. Despite the many attempts to develop a fast, and cost-effective remote sensing (RS) tool for target generation, play evaluation, and risk reduction, there is still a large gap between the capability of RS, the achieved results, and the demand of industry. Iran holds one of the largest reserves of onshore HCs in the world, while being ruled by semi-arid climate. As a result, most of its HC-prone expanses have exceptionally well-exposed bedrocks. Considering the Qom sedimentary basin in Iran as a control area, this research aims to employ state-of-the-art technology in a multi-scale framework to reveal the presence of HC on the surface, understand the chemical and physical processes responsible for lithological alteration, assess the effects of climate and weathering, and then establish HC-induced mineralogical indicators that would be detectable by RS approaches. To achieve such objectives, this work will integrate evidence from (1) broad-scale alteration maps extracted from ASTER, Landsat, and WorldView-3 satellite datasets, (2) field investigation and extensive sampling scheme, (3) close-range spectroscopy, and (4) analytical geochemistry. To build up a clear picture of the changes, the mineralogy, geochemistry, and petrography of the seep-affected facies will be contrasted with intact outcrops.There are several lines of evidence that suggest similarities in mineralogy between exhumed HC reservoirs and microseepage-induced facies. To have a deeper understanding of such indications, and to draw an analogy between these two phenomena, we have devised a second study case in the Anhembi area, in southeastern of Brazil, within which a series of close-range spectral measurements, as well as far-range WorldView-3 orbital data is incorporated.Given the level of exposure of the bedrock lithology in the Qom study area and large extent of red beds, it is an ideal laboratory to study seepage phenomenology on outcrop to reservoir scale and establish representative models and methods that could be used worldwide in areas that are geologically poorly known, or where accesses to the bedrock is limited by environmental constraints.
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