1 1 Chapter 08 Chapter 08 THE THE HABITA OF HABITA OF HYDROCARBONS IN HYDROCARBONS IN SEDIMENTARY BASINS SEDIMENTARY BASINS 2 2 Introduction There are approximately 600 sedimentary rock basins in the world. A quarter of them are producing petroleum Before exploitating in a new area, attemting to locate drillabe prospects, it is necessery to establish the type of basin, what productive horizons it may contain and where they may be broadly located • Even though petroleum reserves can be found in rocks of all ages, most giant fields and most of the world's reserves occur in sequences, of Late Mesozoic and Cenozoic age ( Figure ) . Paleozoic rocks probably had potential to generate hydrocarbons equal to that of these younger rocks, but there has been more time in which to destroy all or part of the petroleum through uplift and erosion (Halbouty et al, 1970). 3 3 4 4 • Worldwide reserves can be related to their location within a petroleum basin, regardless of its basin type (Figure ) 5 5 6 6 8.1-The Sedimentary Basin Concept • A general term for any large area of tectonic origin with a thick accumulation of sedimentary rocks. • A basin is a geological structure with a unique sequence of rocks that are dissimilar to those outside the basin. • A low area with no exterior drainage. • Include both depression itself and the thicker-than- everage sediments that fill it 7 7 Idealized pattern of a sedimentary basin 8 8 Sedimentation patterns over arch, shelf and basin 9 9 Main content: • Geometry of Sedimentary Basins • Sediment Fill • Tectonic Processes and Timing • Basin-Forming Mechanisms • Sedimentary Basin Classification 10 10 Geometry of Sedimentary Basins Geometry of Sedimentary Basins It is tempting to believe that a sedimentary basin was deepest where its sediments are thickest, but this is not necessarily true [...]... • MID-OCEAN RIDGES • SUBDUCTION ZONES AND SUTURES • TRANSCURRENT FAULTS 27 8. 2-Sedimentary Basin Classification • Many different basin classification schemes have been proposed, as geological thought has evolved from the geosyncline concept to plate tectonics • In the petroleum industry, a classification is needed that emphasizes the role of the sedimentary basin as a container for oil and gas 28 There... separate class because of their unique petroleum features 29 Basin classification 30 Idealized pattern of an Interior basin 31 Generalized cross-section through the Williston basin of the USA and Canada 32 Geometry of the world;s interior basins 33 Major interior basins of the world Major interior basins of the world 34 Table 10.1 Interior Basin (Intracratonic, sag) • Distinguishing features simple,... 10.1 Interior Basin (Intracratonic, sag) • Distinguishing features simple, single cycle; no uplands; in continental interiors • Depositional History mature, shallow water to non-marine sediments (clastic or carbonate prone); non-depositional or nonmarine late stage • Reservoir equally sandstone or carbonate • Source shale • Cap shale, less commonly evaporite • Trap basement uplift arches and anticlines;...Non-coincidence of depocenters, topographic low and point of maximum basement 11 subsidence in a land-derived, prograding clastic wedge Sediment Fill Basins can be characterized by the sediments that fill them They can be dominated by continental, shallow... nature and timing of tectonic processes • The types of folds and faults that develop within a basin are partly due to deformation mechanisms and partly to its sediments 13 Basin-Forming Mechanisms • Basins form as a result of large-scale vertical and horizontal movements within the earth's upper layers, which can be explained through the widely accepted theory of plate tectonics 14 • The earth's outermost... lithospheric plates, showing relative velocity and direction of plate separation and convergence in centimeters per 17 year Initiation of rifting and ocean floor spreading over continental crus Pre-rift domal bulge 18 Innitial radial rift 19 Early separation stage 20 21 MODEL OF A DIVERGING PLATE BOUNDARY The separated continents are now far apart, and basins develop along their passive margins 22 MODEL... combination and stratigraphic • Geothermal Gradient low to normal • Hydrocarbons low S, high gravity crude low natural gas • Risks adequate traps; presence of shale for source and cap • Typical Reserves . the petroleum through uplift and erosion (Halbouty et al, 197 0). 3 3 4 4 • Worldwide reserves can be related to their location within a petroleum basin, regardless of its basin type (Figure ) 5 5 6 6 8. 1-The. drainage. • Include both depression itself and the thicker-than- everage sediments that fill it 7 7 Idealized pattern of a sedimentary basin 8 8 Sedimentation patterns over arch, shelf and basin 9 9 Main. though petroleum reserves can be found in rocks of all ages, most giant fields and most of the world's reserves occur in sequences, of Late Mesozoic and Cenozoic age ( Figure ) . Paleozoic