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2 ORAL SESSIONS 4 GS 33: Geochemistry: new understanding provides Geochemical characterization of Upper Cretaceous source new opportunities rocks in Morocco Chair: N. Cameron, A. Morabet Chakor Alami ONHYM, Rabat, Morocco Hydrocarbon generation modelling in the Atlantic margin basins of Morocco : the effect of water pressure The Upper Cretaceous source rocks in Morocco range in age from Cenomanian to Maastrichtian and they are Andy Carr encountered in most Moroccan sedimentary basins. They Advanced Geochemical Systems Ltd., Loughborough, outcrop in the Rif / Pre-Rif area at the North, in the middle Atlas Leicestershire, UK in the centre and in Tarfaya Basin in the South. Where they Hydrocarbon exploration has largely been controlled by the outcrop they occur as oil shale deposits. They have high TOC necessity to ensure the presence of a mature source rock values, high petroleum potential (S2) and are generally capable of generating either oil or gas. Current geochemical immature. models claim that hydrocarbon generation is controlled Upper Cretaceous source rocks were also encountered in primarily by temperature, and basins with deeply buried source exploration wells in the Tadla Basin in the central region, the rocks are therefore most likely to be gas-prone. However the Boujdour area in the south of Morocco and in the Moroccan evidence from deepwater basins appears to contradict this Atlantic offshore. All the geochemical data (TOC, Rock-Eval, understanding in that deepwater exploration in the Gulf of GC, GC-MS and isotopes) from ONHYM’s data base will be Mexico shows that oils appear to have been generated presented, together with oil-oil correlations and Oil-Source relatively recently even though the Upper Jurassic source rocks Rock correlations. A synthesis of all the geochemical studies have been buried at depths often exceeding 7 to 8 km of rock made at ONHYM will be presented and discussed. cover. In the Atlantic margin basins ,of Morocco, the oil-prone Central Atlantic Petroleum Systems source rocks range in age from Lower Jurassic to Upper Nick Cameron, John Zumberge and Harold Illich Cretaceous in age (Jabour, 1993) and appear to be deeply GeoMark Research Ltd., Houston, Texas, USA buried (> 5 km) along the Moroccan Atlantic margin. The Jurassic source rocks in particular will either be gas or Multiple Petroleum Systems characterise the Atlantic overmature using the current approach to predicting margins of NW Africa (Senegal to Morocco), SW Europe hydrocarbon generation from source rocks. Physical theory (Portugal and Spain) and the Eastern Americas (USA and however differs from geochemical theory in that physical Canada). With much of this region remaining underexplored, chemists predict that water pressure should retard maturation application of this information provides a cost effective means and hydrocarbon generation reactions (Atkins and de Paula, of reducing risk in wildcat exploration. 2002). If this retardation occurs then oil generation would Offshore sources are predominantly associated with could still from source rocks buried to depths at which the Jurassic and Cretaceous clastics with reservoirs positioned current geochemical models would predict either gas up-dip of the kitchens or in the cover succession. An generation or no generation. equivalent to the Jurassic to early Cretaceous sourced gas Laboratory pyrolysis using water pressure show that fairway of Nova Scotia remains to be found in NW Africa. hydrocarbon generation is indeed retarded by water pressure DSDP coreholes suggest mid-Cretaceous, oil-prone sources as predicted by physical chemical theory (Carr et al., 2007). may be restricted to NW Africa. Biomarker correlations suggest Applying the water retardation model to the Atlantic margin carbonate sources associated with the Jurassic shelf edge basins of Morocco shows that there is significant potential for bank in NW Africa and SW Europe are more abundant than oil generation in the offshore basins. currently envisaged. So far Triassic lacustrine sourced oils derived from the syn-rift succession are only known from the Atkins P. and J. de Paula, 2002. Atkins’ Physical Chemistry. 7th eastern seaboard of the USA. Edition. Oxford University Press, Oxford. Contributing onshore source rocks range from Lower Carr A.D. et al., 2007. An experimental study into the effect of water Paleozoic to Miocene in age with the greatest variety occurring pressure on maturation and hydrocarbon generation; the implications for modelling hydrocarbon generation in geological basins. Meeting in Morocco. As is the case offshore, Jurassic and Cretaceous abstracts, AAPG Hedberg Conference, The Hague, 6-9 May 2007. horizons dominate. These include both clastic and carbonate sources, the former tending to be associated with the mid- Jabour H., 1993. Source rock characterisation of the Atlantic Cretaceous highstands, the latter with lagoonal settings continental margin of Morocco. Bulletin AAPG, 77, 2, p. 326. inboard of the carbonate bank. Silurian sources are developed regionally in Morocco and they offer, in conjunction with Ordovician, Devonian and Carboniferous sources, a range of The First MAPG International Convention, Conference & Exhibition 5 Marrakech Convention Center, October 28 - 31, 2007 opportunities, both within the Palaeozoic and as migration Genesis of the source rocks and reservoir hydrocarbons of products into the Mesozoic. The Neoproterozoic of the the Scotian shelf and slope, offshore Eastern Canada Taoudeni Basin (Mauritiania) is attracting attention as a Prasanta K. Mukhopadhyay (Muki) source/seal/reservoir interval. Global Geoenergy Research Ltd., Halifax, Nova Scotia, Canada Deep-water prospectivity along the NW African margin: an integrated, remotely sensed technique to assess The genesis of the petroleum systems from Jurassic- Tertiary sediments of the Abenaki Subbasin, LaHave Platform, hydrocarbon potential and Sable Subbasin within the Scotian Basin, Eastern Canada Pedro Barreto and Mike Oehlers indicate presence of an (a) active and mature lacustrine, NPA Group. Edenbridge, Kent, UK marine, and mixed marine/terrestrial source rocks of kerogen It is often rewarding and desirable to high-grade Types I, II, II-III, and III within Bajocian to Tertiary age and (b) exploration acreage offshore by taking an integrated on- and numerous clastic and carbonate reservoirs within the Jurassic- offshore approach and in this paper we look at how onshore Cretaceous Mic Mac, Missisauga, Logan Canyon, and Banquereau (slope) formations that are filled with light oil, structures and seepage patterns surrounding the Agadir Basin condensate, and gas. in western Morocco, can be extrapolated into the offshore using GIS and interpretative, remote sensing techniques. Organic-rich oil-prone source rocks are not restricted only to the Verrill Canyon Formation but occur in various other Landsat Geocover, Shuttle Radar Topographic Mission intervals within the Early Jurassic to Tertiary sediments. No (SRTM) and geological mapping from published sources form widespread anoxic events have been recognized in the Upper the bases for the onshore component and Free Air Gravity, Jurassic sediments. More than 90% of the condensate- and bathymetry, geology maps and sections from published gas-prone source rocks occur within the mid-shelf areas in sources were added into the offshore realm. both subbasins, whereas oil-prone source rocks are concentrated in the more distal part and on the early rifting The onshore satellite imagery and DEM data were phase of the Scotian Basin. There are considerable variations interpreted using established photo-geological principles. in the maturity of various sections from the basin that are Onshore seep locations derived from public domain data were closely connected with the variations in heat flux due to salt added and compared to the structural trends and integrated movement and major crustal fractures. into the GIS model. Based on petroleum geochemical parameters (aromatic Similar techniques were used in the offshore where data biomarkers, pyrolysis-gas chromatography-mass allowed: published seismic and map data were linked with the spectrometry, and stable carbon isotopes), the genetic classes observed onshore trends and extended into the offshore. and the maturity of liquid hydrocarbons within the Scotian Seepage patterns were then interpreted using backscatter Basin (shelf and slope regions) have been formally defined. The intensity data derived from satellite radar (SAR) data. Once following five distinct hydrocarbon families could be recognized natural film slicks and pollution slicks had been removed from within the shelf and slope regions of the Scotian Basin the sample, repeating and higher ranked single seepage slicks although the hydrocarbons show a wide range of maturities with each family. were isolated and related to both onshore seepage patterns and regional structure. Family 1 - Condensates and gases with the Jurassic and Cretaceous (Mississauga and Mic Mac sandstone reservoirs; The results revealed some interesting correlations between example – Venture and Thebaud fields, Sable Subbasin): seepage distribution patterns and interpreted offshore originated from kerogen Type III and Type IIB terrestrial organic structural trends to the offshore Malm Carbonate Bank Front matter from the Mic Mac/Missisauga Formation, which are the and the Neocomian-Aptian Delta Front play fairways. terrestrial equivalent of Jurassic and Cretaceous Verrill Canyon Furthermore, geochemical