GIAO TRINH CHAPTER 8

Chapter 08: THE HABITAT OF HYDROCARBONS IN S EDIMENTARY BAS INS HCMUT-2011 Co nte nt Intro duc tio n 8.1-The S e dime ntary Bas in Co nc e pt 8.2-S e dime ntary Bas in Clas s ific atio n 8.3-Dis tributio n o f pe tro le um – ric h bas ins Intro duc tio n There are approximately 600 sedimentary rock basins in the world A quarte r o f the m are pro duc ing pe tro le um Before e xplo itating in a ne w are a, attemting to lo c ate drillabe pro s pe c ts , it is necessery to e s tablis h the type o f bas in, what pro duc tive ho rizo ns it may c o ntain and whe re the y may be broadly lo c ate d • Even though petroleum reserves can be found in rocks of all ages, mo s t g iant fie lds 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 S e dime ntary Bas in Co nc e pt • A g e ne ral te rm fo r any larg e are a o f te c to nic o rig in with a thic k ac c umulatio n o f s e dime ntary ro c ks • 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 thickerthan-everage sediments that fill it Fig: 03 Idealized pattern of a sedimentary basin Fig: 04 Sedimentation patterns over arch, shelf and basin Main c o nte nt: 1.Ge o me try o f S e dime ntary Bas ins 2.S e dime nt Fill 3.Te c to nic Pro c e s s e s and Timing 4.Bas in-Fo rming Me c hanis ms 5.S e dime ntary Bas in Clas s ific atio n 10 Fig: 47 Generalized cross-section through the Arabian-Iranian basin 75 Table 10.6 Downwarp Bas in • • • • • • • • • • A Ope n- related to pull-apart, passive margins B Clo s e d- related to foreland basins C Tro ug h- related to foreland basins Dis ting uis hing fe ature s basement and depositional downwarp dipping into small oceans, inland seas or linear suture zones; intermediate crust De po s itio nal His to ry mixed, interfingering shallow marine facies, either carbonate or clastic-prone Re s e rvo ir carbonate (C); or mixed (A,B) with sandstone (A) or carbonate (B) dominant S o urc e 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 Ge o the rmal Gradie nt normal to above average Hydro c arbo ns intermediate to mixed gravity crudes; sandstones more paraffinic, carbonates more aromatic; average to high natural gas Ris ks maturation; leakage; deformation too intense; igneous activity; poor reservoir properties Typic al Re s e rve s 4- 40 billion bbl hydrocarbon/basin (A); 10- >50 (B), 53 (C) 76 Tertiary Deltas In a sense, tertiary-age deltas are no t true bas ins but later overprints onto other basin types They can form in any coastal setting, and are found about equally over convergent and divergent margins 77 Fig: 48 Idealized pattern of a Tertiary age delta 78 Fig: 49 Major delta basins of the world 79 Fig 50: Generalized cross-section through the Niger delta of 80 west Africa Table 10.7 Te rtiary De lta   Dis ting uis hing fe ature s : circular depocenter basin; on plate triple junction where failed arm rift meets ocean basin, particularly at divergent or transcurrent margin De po s itio nal His to ry: prograding wedge of land-derived clastics with Type III kerogen Re s e rvo ir: sandstone (pro-delta facies) S o urc e : shale Cap: shale Trap: roll over anticlines; growth faults, mud or salt diapirs; sand lenses Ge o the rmal Gradie nt: low Hydro c arbo ns : paraffinic to paraffinic-naphthenic crude; very high natural gas Ris ks : small trap size, adequate caprock Typic al Re s e rve s : to 20 billion bbl hydrocarbon/basin; few fully developed 81 8-3-DIS TRIBUTION OF PETROLEUM – RICH BAS INS To g e the r the 25 s e dime ntary bas ins in the wo rld, whic h are the ric he s t in te rms o f kno wn pe tro le um re s e rve s , c o ntain ne arly 90% o f the wo rld's o il and g as 82 8-3-DIS TRIBUTION OF PETROLEUM – RICH BAS INS (c o nt.) A bre akdo wn o f the s e pe tro le um-ric h bas ins by bas in type s ho ws that e ig ht o f the m be lo ng to the wnwarp bas in c las s , and an additio nal s e ve n are larg e fo re land bas ins Of the re maining te n, thre e o f the bas ins are rifts and two are de ltas Finally, the re are five c o nve rg e nt marg in bas ins , inc luding thre e no narc , o ne bac k-arc , and o ne c o llis io n bas in type Only thre e bas in type s are no t fo und amo ng the wo rld's ric he s t pe tro le um bas ins : the inte rio r, the pull-apart, and the fo re -arc bas ins 83 Fig: 51 Richest petroleum basins 84 Fig: 52 85 Fig: 53 Histogram divides the total world sediment volume 86 Fig: 54 Dis tributio n o f P.re s e rve s with de pth fo r e ac h o f the bas in type s 87 Fig: 55 Pe rc e nt o f all P pro duc ing bas ins within e ac h bas in type that c o ntains g iant fie lds 88 Exercise 89 ...Co nte nt Intro duc tio n 8. 1-The S e dime ntary Bas in Co nc e pt 8. 2-S e dime ntary Bas in Clas s ific atio n 8. 3-Dis tributio n o f pe tro le um – ric h bas ins Intro... to its sediments 14 Bas in-Fo rming Me c hanis ms • Basins form as a result of large-scale vertical and horizontal movements within the earth's upper layers (fig 0 6-1 ) , which can be explained... but this is not necessarily true 11 Fig: 05 Non-coincidence of depocenters, topographic low and point of maximum 12 basement subsidence in a land-derived, prograding clastic wedge S e dime nt