Copyright by Nysha Chaderton 2009 - The University of Texas at ...

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eported. The Scotland reservoir rock outcrops onshore in several localities and has been the subject of preliminary work to understand the sedimentology, depositional environments and reservoir architecture. It is often steeply dipping and highly deformed complicating the details of its nature; however several outcrops do lend themselves to laterally extensive observations of facies distribution and surface relationships. The fine grained pelagic muds and marls of the Oceanic Formation are considered to be the broad regional seal of the petroleum system. Understanding the regional extent and distribution of the Oceanic Formation across the southern BAP will help us with our understanding of the BAP petroleum system as a whole. No source rocks are exposed onshore Barbados, nor have they been penetrated by offshore drilling or identified in seismic data. However, geochemical work carried out by geoscientists from the United States Geological Survey (USGS) suggests that Barbados oils are of uniform thermal maturity and originate from a Cretaceous source rock (Hill and Schenk, 2005). Fluid migration within accretionary prisms occurs along extension fractures, veins faults and also through sediment pores as a result of high fluid pressure created by the reduction of pore volume due to sediment burial (Moore, 2001). Within the BAP, mud volcanoes are associated with thrust faults. Fluid-rich mud that reaches the surface forms expulsion features, suggesting that these structural features are fluid migration pathways. This dissertation focuses on the defining the characteristics and distribution of the onshore reservoir the Scotland Formation and examining its potential distribution offshore Barbados. In addition the relationship with the Scotland Formation and its equivalents with the Oceanic Formation; which is the regional seal, will be examined. Source rock and migration pathway analysis was not undertaken as part of this study. 5
DATA AND METHODOLOGY Extensive work undertaken over the course of four field seasons of varying length offered the opportunity to revisit the previous geoscientists’ observations of fault frameworks and structural relationships. The field observations benefited from knowledge of the extensive 2D seismic data surrounding the island (Figures 1.3, 1.4). A number of faults are observed on the island and had to be taken into consideration when mapping stratigraphic relationships. The active tectonic setting has resulted in extensive post depositional modification of the Scotland Formation. The study area is characterized by seismic and outcrop scale thrust faulting and folding. Thrust faults, antiformal and synformal features observed in outcrop all have the NE-SW orientation noted by Speed, (1983). The lateral continuity of Scotland Formation sands were mapped across outcrops. Several measured sections were made at each large outcrop to analyze the stacking patterns, lateral continuity and geometries of beds. Facies descriptions, and sample collection for petrography was also undertaken in the field. A total of 44 samples were made into thin sections. The samples were left unpolished and without slip covers and were stained in two separate batches. The Houghton (1980) methodology that stains potassium feldspar yellow and plagioclase feldspar pink. All of the samples were examined under microscope. Ten samples were identified as representative and chosen for more in depth analysis for point counting and measurements. Only 10 samples were chosen for point counting because most were measured at one outcrop location. The selected samples were scattered across and so a smaller number of samples were scattered across the field area. Existing 2D seismic utilized in previous research (Chaderton, 2005) were available for further analysis and integration with field and subsurface observations. In addition 200 well logs from the Woodbourne oilfield were available for correlation and integration with field and seismic observations. 6
Page 1 and 2: Copyright by Nysha Chaderton 2009
Page 3 and 4: Sedimentation within the Tobago For
Page 5 and 6: Acknowledgements I would like to th
Page 7 and 8: Table of Contents List of Tables ..
Page 9 and 10: List of Tables Table 2.1: Latitudes
Page 11 and 12: Figure 2.14: Planar parallel lamina
Page 13 and 14: Figure 2.42: Coarse, cobble and peb
Page 15 and 16: Figure A.3a: Chalky Mount Ridge mea
Page 17 and 18: 1. Development history of the south
Page 19: Formation. This interpretation requ
Page 23 and 24: DESCRIPTIVE METHODOLOGY Each sectio
Page 25 and 26: Two or more channel complexes stack
Page 27 and 28: These poorly sorted sands are later
Page 29 and 30: East Coast Road Although the East C
Page 31 and 32: succession of interlaminated siltst
Page 33 and 34: Mount All The beds of the Mount All
Page 35 and 36: Lobes are non-channelized bodies, 3
Page 37 and 38: Sandy units are the most resistant
Page 39 and 40: SUMMARY DEPOSITIONAL SETTING OF THE
Page 41 and 42: Chapter Three: Petrographic Analysi
Page 43 and 44: had not been buried deeply or long
Page 45 and 46: Feldspars Calcium Plagioclase Felds
Page 47 and 48: Authigenic Minerals Authigenic mine
Page 49 and 50: amounts of chlorite and kaolinite c
Page 51 and 52: Sample: WRA 16 This sample was take
Page 53 and 54: cementation is observed. A number o
Page 55 and 56: COMPARISON WITH PREVIOUS WORK Punch
Page 57 and 58: K feldspar preservation to slightly
Page 59 and 60: CONCLUSIONS 1. No quartz cementatio
Page 61 and 62: The highest point of the island, is
Page 63 and 64: STRATIGRAPHIC FRAMEWORK ONSHORE TO
Page 65 and 66: STRUCTURAL FRAMEWORK OF THE BARBADO
Page 67 and 68: Sandy material is primarily quartz
Page 69 and 70: esult of extension caused by flexur
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1994). The origin of the Oceanic Fo
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Oligocene-age sediments are deposit
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The observation of channel geometri
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Pudsey, (1982) interpreted smectite
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The interpretation of the Scotland
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Figure 1.2: Convergent margins arou
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NSF Study Lines Grenada St. Kitts S
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Figure 2.2: Generalized vertical se
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Figure 2.4: Detailed Geological map
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Figure 2.6: Photographs and illustr
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Figure 2.8: Bedsets on the channel
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S 50 m Figure 2.10: Photo-panorama
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Figure 2.13: Laminated silt and mud
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Figure 2.16a: Measured section at C
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Figure 2.16c: Measured section at C
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Figure 2.18: Correlation of section
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Figure 2.21: Parallel laminated sil
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Wach, Vincent and Chaderton March 2
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Page 109 and 110:
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Figure 2.24: Channel element identi
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WRB S N Fresh rock face exposed by
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Figure 2.28: Photograph of Diplocra
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Figure 2.31: Conglomerate with eros
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Figure 2.33: Thalassinoides trace f
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Figure 2.35: Mount All measured str
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Figure 2.37: Medium grained sand be
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Figure 2.38b: Inner Turner’s Hall
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Figure 2.38d: Inner Turner’s Hall
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Figure 2.39: Spa Hill measured stra
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Juniper Ridge, California Scotland
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Figure 3.1: Fractured quartz grain
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SGRF 1C SGRF 9C Figure 3.5: Measure
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Figure 3.8: Photo of sample SGRF 11
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Figure 3.10: Photo of sample SGRF 1
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Figure 3.12: Photo of sample WRA 16
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Figure 3.14: Photo of sample WRB 8
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Figure 3.16: Photo of sample ITR 9
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Figure 3.19: Photo of sample CMRA s
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Figure 3. 23: Composition of Scotla
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Figure 4.1: Base map showing seismi
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Figure 4.3: Channels within Unit Fi
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Figure 4.5: Seismic reflection prof
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Figure 4.7 Isochron maps of the old
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Figure 4.9: Illustration of the Spe
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Figure 4.11: Illustration of Hypoth
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necessary to clear a path. Keep to
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2006 Figure A.2a: Lidar Ridge measu
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Figure A.3b: Chalky Mount Ridge mea
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2006 Figure A.4a: Chalky Mount Ridg
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2006 Figure A.4c: Chalky Mount Ridg
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2006 Figure A.6: Chalky Mount Ridge
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Figure A.7b: Measured Section of Ch
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2006 Figure A.8a: Sleeping Giant Ri
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2006 Figure A.9: Sleeping Giant Rid
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2006 Figure A.11: Sleeping Giant Ri
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Figure A.13a: Sleeping Giant Ridge
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2006 Figure A.14a: Coast Road Below
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2006 Figure A.14c: Coast Road Below
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2006 Figure A.14e: Coast Road Below
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2006 Figure A.14g: Coast Road Below
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2006 Figure A.15: Ermy Bourne Ridge
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2006 Figure A.17: Spa Hill Fold Mea
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2006 Figure A.19: Ermy Bourne Ridge
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Figure A.20b: Walkers Ridge Measure
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Figure A.21: Walkers Ridge Measured
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Figure A.22b: Walkers Ridge Measure
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2007 Figure A.23b: Inner Turner’s
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2007 Figure A.23d: Inner Turner’s
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Framework grains Quartz Feldspar Ro
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CRIMES, T.P., 1977, Trace fossils o
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MONTGOMERY, S.L., BARKER, C.E., SEA
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RICHARDS, M., BOWMAN, M., and READI
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WEBER, J.C., DIXON, T.H., DEMETS, C
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