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Course Level: Senior
The goal of this course is to obtain knowledge of the origins of petroleum and gas. An overview is given on the conditions that are needed for oil and gas to accumulate in reservoirs. Moreover, techniques to find and exploit these reservoirs are highlighted. The focus always is on the task of the petroleum geologist during the different phases of oil and gas exploration and production. After an introduction to the course including typical numbers and hystorical developments, essential terms and concepts like biomolecules and the carbon cycle are explained. A start is made with the geology with explaining source rocks and their maturation when forming oil and gas. After that, the composition of oil and gas and its application is eludicated on. How the oil travels from the source rock to the oil reservoir, where it is explored, is explained in the fourth lecture on migration. This lecture is followed by discussing the reservoir rock properties, like permeability and porosity. Moreover, it is explained how the oil or gas can be trapped inside the reservoir rock. Finally the exploration and production of different types of basins is discussed. In several of the lectures, non fictive case studies are presented in order to clarify the theory presented. In order to properly understand the course, prior knowledge in general geology and fluid flow in rocks is preferred.
- Lecture 1 - IntroductionIn this first lecture, a short introduction to the topic will be given. This is done in three parts. 1) The goal of the course is to obtain knowledge of the origins of petroleum and gas, of teh accumulation conditions and teh techniques to find and exploit hydrocarbons. The importance of this course is explained here. 2) Units like barrels and cubic feet are explained. Moreover, some interesting detailed facts are given like oil reserves of commercial and national companies, annual world oil consumption and the total number of gas and oil wells drilled up to today. These numbers are accompanied by several graphs. 3) Historical developments from the start up of petroleum geology around 1900 are summarized.
- Lecture 2 - The Carbon Cycle, Organic Matter and Maturation1) In this part, the carbon cycle is explained. First, the concepts of organic carbon, inorganic carbon adn phytoplakton are explained since these are crucial for understanding the carbon cycle. After that teh carbon cycle and moreover mass balances that go together with teh carbon cycle are preseneted as well. 2) The development of Flora and Fauna is explained by interpreting and partial pressure of several gases in teh atmosphere. 3) The composition of different biomolecules and their abundance in different organisms is explained. 4) Preservation of organic matter is first explained. It can be seen that source rocks are the main preservation zones, which indicates the low efficiency of the preservation process. The concepts of Total Organic Carbon (TOC) and kerogen as a content of that in source rocks are eludicated. 5) The conversion of kerogen in source rocks to hydrocarbons like oil and natural gas are explained. The "van Krevelen" diagram in used to illustrate this. Several types of maturation indicators, used to evaluate potential source rocks, are discussed.
- Lecture 3 - Composition of Oil and Gas1) The main hydrocarbon molecules present in crude oil, like paraffins, naphtenes and aromatics, are discussed. Structural formulas are shown as graphical representations. Moreover, the main method to analyze the composition of oil, gas chromatography, is explained. 2) After fractionating the crude oil by distillation, the main products are gas, gasoline, kerosine, diesel, oils and residuum. The applications of these fractions are all shortly discussed. For gasoline moreover, there are some extra production methods mentioned. 3) At the end of the lecture, everything is summarized shortly.
- Lecture 4 - Migration from Source to Reservoir1) We learned that oil results from kerogen, which in turn comes from organic matter. This oil is then present in source rocks. The source rocks get overpressured and oil moves from the source rocks to the reservoir rocks. Reservoir rocks can be imaged with seismic by geophysicists, and this is also where human get the oil from. Here it is explained why migration happens, and some evidence of see pages which prove migration is given. (In Petroleum Geoscience: paragraph 2.8 'See page of petroleum'). 2) Primary migration is the migration from the source rock to 'something else', which is badly understood in science. The contradiction on pore sizes in source rocks and the sizes of the migrating molecules is explained. Moreover four possible primary migration mechanisms are discussed. 3) Secondary migration is the migration from 'something else' to the reservoir rock. This is much better understood than primary migration. Buoyancy resulting from density differences is the driving force. Some migration pathways are presented, and seals which finally stop the migration are explained.
- Lecture 5 - Reservoir Rock Properties and Trapping1) The ability of a solid to transmit fluid is called permeability. This permeability is defined by Darcy's law an can be influenced by properties like grain size, grain sorting, grain roundness and the texture of the rock. An example of that is the fact that rounder grains lead to higher permeabilities. 2) The ability of a solid to store fluid is called porosity. Voids within the solid make it possible for liquid to be encapsulated by the solid. Processes like compaction decrease the porosity due to the effects of loading. All processes that can be undergone by a potential rock reservoir with burial are summarized as diagenesis. 3) Lateral and vertical changes in rock properties, called heterogenity, can result in changes of physical properties, called anisotropy. These layers, and with that the differences in reservoir quality, can be identified using well logs. 4) Petroleum geologists should use well data, seismic data and geological knowledge to build a 3D reservoir model. In Delft University of Technology, a process based simulation of barrier bar development as a function of fluctuating see levels. 5) The final part of the lecture is on carbonates, which are significantly different from classic reservoir rocks. One of the big differences is that most of the material is biogenic. It is not uncommon that carbonates are both the source and the reservoir rock. Carbonate depositional settings and a great variety of carbonate pore types, which influences the permeability, are discussed.6) A trap typically is the final place where oil an gas end up. The most important job for exploration geologists therefore is to find the traps. These traps can be either structural traps, caused by tectonic forces, or stratigraphic traps, which mainly has to do with the way the sediments have been deposited. The most typical traps, where 80-90% of the oil is trapped, are anticlines which are structural traps with arched upper surfaces. 7) To illustrate the theory further, some case studies on structural traps, stratigraphical traps, combination traps and dynamic traps are presented.
- Lecture 6 - Basin Types and Their Exploration and Production: Reserves and Resources (1)1) Basins are typically areas filled with sedimentary rocks. Three classes of basins, cathegorized by the way they are created, are proposed. Firstly cratonic basins due to the stretching of continental crust, secondly subductive troughs caused by tectonic collisions and finally basins occuring from plates drifting apart. Two types of filling such a basin with sediment are moreover presented: postdepositional and syndepositional. 2) In the final part of the course, some case studies regarding oil and gas fields are elaborated on. These are: the Golden lane (Mexico), the Niger Delta, the Gabon basin, the gulf of Mexico, the North Sea and finally the Alaskan North slope.
- Lecture 7 - Basin Types and Their Exploration and Production: Reserves and Resources (2)1) Basins are typically areas filled with sedimentary rocks. Three classes of basins, cathegorized by the way they are created, are proposed. Firstly cratonic basins due to the stretching of continental crust, secondly subductive troughs caused by tectonic collisions and finally basins occuring from plates drifting apart. Two types of filling such a basin with sediment are moreover presented: postdepositional and syndepositional. 2) In the final part of the course, some case studies regarding oil and gas fields are elaborated on. These are: the Golden lane (Mexico), the Niger Delta, the Gabon basin, the gulf of Mexico, the North Sea and finally the Alaskan North slope.