Chapter Two - A biophilic material in petroleum exploration and production: iodine

Abstract

All of the waters of the oil and gas production basins of the world are not saline, but all of them are rich in iodine. Hydrocarbons and iodine-rich waters may be derived from the oil or gas reservoirs in the subsurface to surface by geological events. Surface hydrocarbons seeps, which are direct indicators of a petroleum system in the subsurface may be degraded or volatilizable by atmospheric effects. But iodine is a stable biophilic element and does not volatilize. It is the main reason why iodine is an excellent surface exploration material. Iodine-rich waters provide proving from the surface or near-surface levels of the presence of oil or gas deposits in the subsurface. Iodine-rich waters are rich in mature petroleum hydrocarbons at the same time. Therefore all organic geochemical analyses performed on rock and gas samples can be applied to these hydrocarbons-rich waters. Iodine-rich waters are an especially unique geochemical tool for petroleum exploration in basins/regions, where source rocks are not exposed at surface as outcrops (covered basins) or have been exhausted (depleted). Thus it is a more suitable integrated usage of reservoir-targeted iodine geochemistry (water and soil) and oil in water analysis than the source rock-targeted organic rock and gas geochemistry for oil and gas exploration in active tectonic and geologically complex basins. Also, the integrated method has another significant advantage in the sampling richness for exploration in the basin/regions where a large number of water resources are available. Furthermore, the method identifies the presence of oil and gas deposits from a large number of samples. Through this feature of iodine-rich waters, the chances of discovering commercial hydrocarbon accumulations are increased. By performing iodine analysis on mud samples during drilling, it may be possible to determination whether there is commercial oil or gas in the well. Moreover, the zone(s) perforated in the well and the prediction of the volume of oil produced from it may also be determined. Iodine contents of reservoir waters (petroleum saturation, oil/water ratio) are high in petroliferous basins where source rocks are found containing high organic matter. In this case, the water saturation (water % ratio) of production wells will decrease. Reserves of oilfields increase as the iodine contents of reservoir waters increase. In this chapter, we focused the relationships between iodine and petroleum systems, the usage of iodine hydrogeochemical and pedogeochemical methods in petroleum exploration and production, case studies, and recent advances.