Chapter 08: THE HABITAT OF HYDROCARBONS IN SEDIMENTARY BASINS HCMUT-2014 Content Introduction 8.1-The Sedimentary Basin Concept 8.2-Sedimentary Basin Classification 8.3-Distribution of petroleum – rich basins 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 01) 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) Fig: 01 • Worldwide reserves can be related to their location within a petroleum basin, regardless of its basin type (Figure: 02) Fig: 02 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 Fig: 03 Idealized pattern of a sedimentary basin Main content: Geometry of Sedimentary Basins Sediment Fill Tectonic Processes and Timing Basin-Forming Mechanisms Sedimentary Basin Classification 10 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 11 Table 10.6 Downwarp Basin • • • • • • • • • • A Open- related to pull-apart, passive margins B Closed- related to foreland basins C Trough- related to foreland basins Distinguishing features basement and depositional downwarp dipping into small oceans, inland seas or linear suture zones; intermediate crust Depositional History mixed, interfingering shallow marine facies, either carbonate or clastic-prone Reservoir carbonate (C); or mixed (A,B) with sandstone (A) or carbonate (B) dominant Source overlying, interfingering and basin-center shales; limestone and marls important in B Cap mostly shale; both shale and evaporites in B Trap anticlines; salt flow; combination; reefs, pinch-outs and unconformities Geothermal Gradient normal to above average Hydrocarbons intermediate to mixed gravity crudes; sandstones more paraffinic, carbonates more aromatic; average to high natural gas Risks maturation; leakage; deformation too intense; igneous activity; poor reservoir properties Typical Reserves 4- 40 billion bbl hydrocarbon/basin (A); 10- >50 (B), 5- (C) 89 Tertiary Deltas In a sense, tertiary-age deltas are not true basins but later overprints onto other basin types They can form in any coastal setting, and are found about equally over convergent and divergent margins 90 Fig: 48 Idealized pattern of a Tertiary age delta 91 Fig: 49 Major delta basins of the world 93 Fig 50: Generalized cross-section through the Niger delta of west Africa 94 Table 10.7 Tertiary Delta Distinguishing features: circular depocenter basin; on plate triple junction where failed arm rift meets ocean basin, particularly at divergent or transcurrent margin Depositional History: prograding wedge of land-derived clastics with Type III kerogen Reservoir: sandstone (pro-delta facies) Source: shale Cap: shale Trap: roll over anticlines; growth faults, mud or salt diapirs; sand lenses Geothermal Gradient: low Hydrocarbons: paraffinic to paraffinic-naphthenic crude; very high natural gas Risks: small trap size, adequate caprock Typical Reserves: to 20 billion bbl hydrocarbon/basin; few fully developed 95 IDENTIFICATION PARAMETERS OF BASIN MODELS • • • Continental or oceanic crust (basement) underlying basin Type of past plate movement involved in basin formation (divergent, convergent or transform motion) Basin/cycle position on plate and primary structural movement involved in basin origination 96 8-3-DISTRIBUTION OF PETROLEUM – RICH BASINS Together the 25 sedimentary basins in the world, which are the richest in terms of known petroleum reserves, contain nearly 90% of the world's oil and gas 97 8-3-DISTRIBUTION OF PETROLEUM – RICH BASINS (cont.) A breakdown of these petroleum-rich basins by basin type shows that eight of them belong to the downwarp basin class, and an additional seven are large foreland basins Of the remaining ten, three of the basins are rifts and two are deltas Finally, there are five convergent margin basins, including three non-arc, one back-arc, and one collision basin type Only three basin types are not found among the world's richest petroleum basins: the interior, the pull-apart, and the fore-arc basins 98 Fig: 51 Richest petroleum basins 100 Fig: 52 101 Fig: 53 Histogram divides the total world sediment volume 102 Fig: 54 Distribution of P.reserves with depth for each of the basin types 103 Fig: 55 Percent of all P producing basins within each basin type that contains giant fields 104 Exercise 105 [...]... Basin types and details 37 Stable continental plates: • Interior Basin 38 Fig: 17 Idealized pattern of an Interior basin 39 Fig: 18 Generalized cross-section through the Williston basin of the USA and Canada 40 Major interior basins of the world Fig: 20 Major interior basins of the world 42 Table 10.1 Interior Basin (Intracratonic, sag) • Distinguishing features simple, single cycle; no uplands; in. .. occurring along continent-ocean margins They may also be grouped according to the stability and movement of this underlying crust, as either; •cratonic basins, developed on the stable parts of continents away from continental margins; •divergent-margin basins, formed along continental margins where the sea floor is spreading and rift-drift (extensional) movements occur; or, •convergent-margin basins, formed... Non-coincidence of depocenters, topographic low and point of maximum 12 basement 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 marine, or deep marine sediments, depending on their elevation and the interplay between the rate of subsidence and the rate of sedimentation 13 Basin-Forming... apart, and basins develop along their 24 passive margins MODEL OF SUBDUCTING PLATE MARGIN Fig: 12 At a subduction zone, the leading edge of one plate overrides another, and the overridden plate is dragged down into the mantle and consumed 25 MODEL OF A COLLISIONAL PLATE MARGIN, COLLISION BETWEEN OCEAN PLATE AND A CONTINENTAL MARGIN Fig: 13 26 MODEL OF A COLLISIONAL PLATE MARGIN, CONTINENT – CONTINENT COLLISION... 14 27 Transcurrent faulting along the conver plate margin in California Fig: 15 28 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 30 • Petroleum enrichment, the incidence of giant fields, and the habitat of petroleum within sedimentary basins can be related to structural,... settings, which can be used to describe a number of petroleum basin types • There are several general ways in which sedimentary basins can be grouped 31 32 They can be divided on the basis of their underlying material or crust: •continental crust, which is relatively light, granitic and underlies most continental areas; or, •intermediate crust, compositionally between granite and basalt and occurring... emphasizes the role of the sedimentary basin as a container for oil and gas 34 There are a total of ten basin types: • two that are related to stable continental plates; • two that develop through plate divergence; • four that relate to plate convergence • two other types, basins that downwarp (Open & closed) into small oceans, form a separate class because of their unique petroleum features 35 Basin classification... composed of dense basaltic rocks • The rigid lithosphere overlies a less viscous layer called the asthenosphere 17 Fig: 06-2 The earth's outermost layers 18 Initiation of rifting and ocean floor spreading over continental crus Fig: 08 Pre-rift domal bulge Fig: 09 Initial radial rift 20 Fig: 10 Early separation stage Fig: 11 21 MODEL OF A DIVERGING PLATE BOUNDARY Fig: 12 The separated continents are... basins, formed along continental margins where continents and/or oceans are in collision and some ocean crust may be consumed 33 For the purpose of petroleum exploration, however, we need a finer-tuned classification scheme such as the ten-part basin classification scheme based on the work of Huff (1980) and Klemme (1980), which is summarized in Figure 16 In the petroleum industry, a classification... Basin-Forming Mechanisms • Basins form as a result of large-scale vertical and horizontal movements within the earth's upper layers (fig 06-1) , which can be explained through the widely accepted theory of plate tectonics 15 • The earth's outermost shell is a rigid layer called the lithosphere, which consists of crust and uppermost mantle Topographic lows form on the earth's surface where the crust is thin, ... pattern of a sedimentary basin Main content: Geometry of Sedimentary Basins Sediment Fill Tectonic Processes and Timing Basin-Forming Mechanisms Sedimentary Basin Classification 10 Geometry of Sedimentary. .. basins of the world Fig: 20 Major interior basins of the world 42 Table 10.1 Interior Basin (Intracratonic, sag) • Distinguishing features simple, single cycle; no uplands; in continental interiors...Content Introduction 8.1-The Sedimentary Basin Concept 8.2 -Sedimentary Basin Classification 8.3-Distribution of petroleum – rich basins Introduction There are approximately 600 sedimentary rock basins