- One of the first questions to be addressed in a frontier exploration area is if there is a working petroleum system. One of the indicators for working petroleum system is presence of hydrocarbon occurrences, which could be surface seeps, hydrocarbon shows in existing wells, or existing accumulations for example. Identification of potential source rock presence is very important. Often, however, the potential source rocks are situated at very deep levels, may not be recognizable on seismic and may not have outcrops or well cores. In these cases, global source rick distribution models could be used to define the characteristics of the source rocks. We'll discuss these topics in a little more detail in the following slides. In addition to identifying presence of a source rock, it is very important to be able to assign reasonable source rock characteristics like richness and type or organic matter in the source rock, distribution and thickness or the source rock and maturity. If there is information available, for example, from existing wells, cored wells, outcrops, production, it is important to identify genetic relationships between elements of the petroleum system using source rock, oil correlations, oil-oil correlations, oil, solid hydrocarbon correlations. All the studies performed during the exploration stage have the purpose to address the question What are the RISKS related to presence of source rock, petroleum charge, type of generated fluids, oil verses gas? By addressing questions like, is the source rock maturity now, to generate hydrocarbons. What type of hydrocarbons are likely generated, mainly oil or mainly gas? Are there any migration indicators? What is the risk for trap leakage and smaller volumes to be found in potential accumulation. What is the risk for biodegradation and poorer fluid properties? Ultimately, all of this information is used to perform economic analysis and rank the potential cost benefits of different exploration prospects. benefits of different exploration prospects. Hydrocarbon Occurrences are important indicators of a working petroleum system in the basin. Therefore, we should be looking for any indications of seeps onshore or offshore. That could be gas, oil, or fluids like Offshore they could be also oil seeps or a piston core surveys available. And onshore, geochemical soil surveys could be useful. We should be looking also at existing wells in the basin. Any hydrocarbon discoveries as well as dry well analysis should be used to build the petroleum system model. Existing accumulations in the basin are very important and should be used to calibrate the basin modeling output results on predicted distribution of accumulations by size and fluid type meaning oil versus gas. Potential source rock presence could be evaluated based on source rock distribution models. These models are based on a large number of studies and accumulated knowledge. Some favorable conditions for source rock formation include, high bio-productivity, which is related to warm, humid, climate, typical for low to middle paleo-latitudes. Also to upwelling zones which provide nutrients and ultimately results in high bio-productivity. Structural basin forms like platforms, circular and linear sags provide the majority of most prolific source rock formations. Sea level changes are also important, especially the transgressions which can be linked to the position of major black shale formations. Preservation of organic matter in bottom sediments is favored by anoxic bottom conditions which often relates to ocean hydrodynamics. The figure on the left presents a correlation between stratigraphic occurrences of major source rocks and various geologic factors considered to be favorable for deposition of source rocks. There are six main stratigraphic levels where prolific source rocks are found. Those are, Silurian, Late Devonian, Pennsylvanian-Late Permian, Late Jurassic, Middle Cretaceous, and Oligocene-Miocene. Most of the source rock intervals, Silurian, Late Devonian, Late Jurassic, Middle Cretaceous, are associated with warm climates, high sea levels, anoxic events, and sediment deposition on broad marine platforms, which favor accumulation of marine organic matter and formation of predominantly oil-prone source rock. During Pennsylvanian-Early Permian and Oligocene-Miocene times, the climates were cooler and severe marine regressions, sea-level drops, occurred globally. The deposition was mainly in foreland basins and deltaic systems favorable for accumulation of gas and oil-prone organic material in the source rocks. During Pennsylvanian-Early Permian time, formation of wide-spread forests and swamps was very favorable for accumulation of thick coal beds and gas-prone organic matter in the source rocks. It should be noted that Jurassic-Cretaceous periods are very special because more than 2/3 of the known petroleum resources were generated from source rocks formed during these times. The figure on the right illustrates distribution of Upper Jurassic major source rock formations on a paleo-reconstructed map of the world during this time. Now, let's look at the back of source rock characteristics on expelled volumes and type of hydrocarbons. The figure shows on the left-hand side the source rock qualifier and on the right-hand side the impact. So, presence of source rock, actually, identifies a petroleum system component. The richness of the source rock here is in fact on the chart, is specifically the volumes of hydrocarbons generated. The effective thickness and areal distribution of the source rock also suggest on the chart, specifically on the volume of the hydrocarbons. The type of organic matter in the source rock the richness versus marine, influence the type of hydrocarbons fluids that could be generated oil versus gas. The source of maturity has a matching the type of hydrocarbon fluids as well as the volumes. The source rock lithology, carbonate versus clastic, shares an impact of fluid properties, and a presence of solid hydrocarbons. The source rock depositional environment and facies could be used as a proxy for type of organic matter and type of fluids, oil versus gas. This is an example to illustrate the impact of Source Rock Richness on Volumes of Expelled Oil and Gas, as discussed in the previous slide. The figure represent three different scenarios where the only parameter that is varied is the RICHNESS of the source rock expressed as total organic carbon. All other control factors are kept the same Marine type II oil-prone kerogen, temperature history, heating rate, Hydrogen index, source of rock effective thickness, are kept as constant parameter as seen in the model. The figures show the volumes of expelled oil and gas with increasing temperature, which is used here as a proxy for maturity. The results illustrate the dramatic effect of source rock richness on the expelled volumes of generated oil and gas. This is an example to illustrate the impact of Source Rock effective thickness on Volumes of Expelled Oil and Gas. The figure again represents three different scenarios where the only parameter that is varied is the effective THICKNESS of the source rock. All other control factors are kept the same Marine type II oil-prone kerogen, temperature history, heating rate, Hydrogen indedx and a TOC of 10 weight percent. The results illustrate the significant impact of increasing the source rock effective thickness on the expelled volumes of generated oil and gas. These examples clearly illustrate the importance of source rock characteristics, especially because they are used as input parameters in basin models. If there are uncertainties about the source rock characteristics, especially in frontier exploration areas, then the best way would be to run several scenarios and define a range of most probable output results.