Hydrocarbon generation potential of the uppermost Jurassic—basal Cretaceous Sulaiy formation, South Iraq

Arabian Journal of Geosciences (Impact Factor: 1.22). 02/2011; 4(1):53-58. DOI: 10.1007/s12517-009-0064-y


Organic geochemical analysis, palynology, and PetroMod software for the organic matters of subsurface Tithonian to Valanginian Sulaiy formation of six wells in Basrah Region, South Iraq showed evidences for hydrocarbon generation potential. These analyses include quantitative studies such as pyrolysis, fluorescence spectroscopy, and total organic carbon (TOC), while the qualitative studies are the textural microscopy used in evaluating amorphous organic matter for palynofacies analysis leading to hydrocarbon assessments. High TOC content of up to 7.3 wt.%, kerogen type II of mesoliptinic type with hydrogen index of up to 466 mg HC/g TOC, and mature organic matter along with dysoxic-anoxic environment and stratigraphic framework have rated the succession as a source rock for oil with ordinate gas, not only in Iraq but also in neighboring Kuwait and Saudi Arabia. This case study is also inferred for hydrocarbon generation and expulsion by PetroMod software which confirmed the source potential.


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    [Show abstract] [Hide abstract] ABSTRACT: 1D (Petromod) hydrocarbon charge modeling and source rock characterization of the Lower Cretaceous and Upper Jurassic underlying the prolific Cretaceous and Tertiary reservoirs in the Basra oilfields in southern Iraq. The study is based on well data of the Majnoon, West Qurna, Nahr Umr, Zubair, and Rumaila oil fields. Burial histories indicate complete maturation of Upper Jurassic source rocks during the Late Cretaceous to Paleogene followed by very recent (Neogene) maturation of the Low/Mid Cretaceous succession from early to mid-oil window conditions, consistent with the regional Iraq study of Pitman et al. (Geo Arab 9(4):41–72, 2004). These two main phases of hydrocarbon generation are synchronous with the main tectonic events and trap formation associated with Late Cretaceous closure of the neo-Tethys; the onset of continent–continent collision associated with the Zagros orogeny and Neogene opening of the Gulf of Suez/Red Sea. Palynofacies of the Lower Cretaceous Sulaiy and Lower Yamama Formations and of the Upper Jurassic Najmah/Naokelekan confirm their source rock potential, supported by pyrolysis data. To what extent the Upper Jurassic source rocks contributed to charge of the overlying Cretaceous reservoirs remains uncertain because of the Upper Jurassic Gotnia evaporite seal in between. The younger Cretaceous rocks do not contain source rocks nor were they buried deep enough for significant hydrocarbon generation.
    Full-text · Article · Oct 2013 · Arabian Journal of Geosciences
  • [Show abstract] [Hide abstract] ABSTRACT: The purpose of the present work was to discuss the composition and hydrologic framework of modern continental sabkha in northwest El Fashn area, Western Desert, Egypt, and its possibilities as a source to generate hydrocarbons. The continental sabkha occupies the low topography of a closed basin fringed with sand dunes and Middle Eocene rocks. The site receives the excess of discharged irrigated water, sourced from a well within the limestone rocks (>40-m depth), in addition meteoric water from sand dune aquifers. The capillary rise powered by evaporative pumping mechanism is responsible for continuous feeding of the surface area. Four sedimentological zones are discriminated for sabkha: elevated temporary dry marginal, temporary wet saline mudflat broad, hypersaline pool and permanent saline pan zones. Halite, gypsum, anhydrite, sinjarite, bloedite and bischofite minerals predominate. The non-evaporative minerals are quartz, calcite, plagioclase, hematite and clay minerals. The upward increase in salinity with Na+ and Cl− ions supports the evaporative pumping mechanism that plays a significant role in the upward movement of brines and formation of the evaporative salts under arid conditions. The repeated cycles of salt precipitation reflect the complexity of the diagenetic history in both mineralogy and sedimentary textures. Total organic carbon content confirmed high organic richness. The kerogen content of the organic matter is believed to be derived from algal and biomass, together with microbial content that accumulated under saline to hypersaline and moderately to highly reducing conditions. Thermal maturity of the organic matter is generally low grade hydrocarbons. This result favors the conclusion that the study examples of sabkha are analogs of a possible generation of hydrocarbons. KeywordsSabkha complex sequence–Hydrocarbon exploration–Hydrochemistry–Organic matter–Evaporative pumping mechanism
    No preview · Article · Oct 2011 · Carbonates and Evaporites
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    [Show abstract] [Hide abstract] ABSTRACT: a b s t r a c t Thirty one crude oil samples from Lower Cretaceous reservoirs in southern Iraq were analyzed using bulk property and molecular methods to determine their maturity and biomarker characteristics, as well as to obtain information on their respective source rocks. All the oils are unaltered, non-biodegraded, have high sulfur content and API gravity is in the range for light to heavy oil (19–40° API). They are character-ized by low Pr/Ph values, even/odd predominance and front-end biased n-alkane distributions. Based on these parameters the oils were generated and expelled from a marine carbonate source rock bearing Type II-S kerogen. Compositional similarities of hopane and sterane biomarkers with those from potential source rocks allowed identification of the Upper Jurassic–Lower Cretaceous Sulaiy and Yamama carbon-ate succession as the effective source beds. A similar composition of normal and isoprenoid hydrocarbons among the oils suggests an origin from a common source rock. However, biomarker maturity ratios indi-cate a wide range of maturity. This appears to result from the type of burial history of the source rock, characterized by a slow passage through the liquid window interval during an extended period of geo-logic time.
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