Mohammed Hail Hakimi

Organic geochemical characteristics and interpreted depositional environment of the Khatatba Formation, northern Western Desert, Egypt

The Middle Jurassic Khatatba Formation in the northern Western Desert of Egypt was evaluated in terms of organic matter abundance, type and thermal maturity, as well as for some organic petrographic characteristics. Depositional environments were interpreted based on organic geochemical (Rock-Eval pyrolysis, extract analysis, and biomarker distributions) and organic petrological methods. Organic carbon contents range between 1.0 and 32.5 wt. %. The Khatatba shale and coaly shale samples have hydrogen index values in the range of 63 to 261 mg hydrocarbon (HC)/g total organic carbon, with mixed types 2–3 and 3 kerogens. Mean vitrinite reflectance (Ro) between 0.77 and 1.07% is in reasonably good agreement with pyrolysis Tmax (temperature at maximum of S2 peak) data (438–459C). Organic-rich sediments of the Middle Jurassic Khatatba Formation have very good source rock generative potential and have obtained thermal maturity levels equivalent to the oil window. The main generation products are gas with very limited liquid HCs (oil or condensate). Seven shale and coaly shale samples from Khatatba Formation were characterized using gas chromatography (GC) and GC–mass spectrometry techniques. The Khatatba samples are characterized by the predominance of C14-C24 alkanes, a pristane/phytane ratio of less than 2, abundant C27 regular steranes, and the presence of tricyclic terpanes. These are consistent with the suboxic marine-environment conditions for the Khatatba source rock. Biomarker parameters for these samples generally indicate a mixture of land- as well as marine-derived organic-matter input. The maturity indicators based on C32 22S/(22S + 22R) homohopane and C29 20S/(20S + 20R) and /( + ) sterane ratios reveal that the Khatatba samples are thermally mature and have reached the peak oil-window maturity supporting the Ro data.

Biomarker characteristics of certain crude oils and the oil-source rock correlation for the Kurdistan oilfields, Northern Iraq

The study herein analysed crude oil and source rock samples from Kurdistan oilfields, northern Iraq using various biomarker ratios. Biomarker characteristics are used to provide information on source organic matter input, depositional environment and the correlation between crude oils and Chia Gara source rocks. The relevant data include normal alkane and acyclic isoprenoids distributions, terpane and sterane aliphatic biomarkers and distribution of the aromatic biomarkers naphthalenes, phenanthrenes, dibenzothiophene and methyldibenzothiophenes. The Kurdistan’s oils characterized by low Pr/Ph ratio (<1.0), a relatively high C35 homohopane index, high C27 regular steranes abundance, the presence of tricyclic terpanes and relatively high dibenzothiophene/phenanthrene ratios. These data indicated that the oils were derived from a carbonate source rock contain a mixture of aquatic (algal and bacterial) organic matter with a minor terrigenous organic matter contribution that were deposited in a marine environment under highly reducing conditions and generated at low maturity. The biomarker characteristics also suggest that the oils were derived from the Upper Jurassic–Early Cretaceous age Chia Gara carbonates.

Erratum to: Liquid hydrocarbon generation potential from Tertiary Nyalau Formation coals in the onshore Sarawak, Eastern Malaysia

Tertiary coals exposed in the north-central part of onshore Sarawak are evaluated, and their depositional environments are interpreted. Total organic carbon contents (TOC) of the coals range from 58.1 to 80.9 wt. % and yield hydrogen index values ranging from 282 to 510 mg HC/g TOC with low oxygen index values, consistent with Type II and mixed Type II–III kerogens. The coal samples have vitrinite reflectance values in the range of 0.47–0.67 Ro %, indicating immature to early mature (initial oil window). Tmax values range from 428 to 436 C, which are good in agreement with vitrinite reflectance data. The Tertiary coals are humic and generally dominated by vitrinite, with significant amounts of liptinite and low amounts of inertinite macerals. Good liquid hydrocarbons generation potential can be expected from the coals with rich liptinitic content ([35 %). This is supported by their high hydrogen index of up to 300 mg HC/g TOC and Py-GC (S2) pyrograms with nalkane/alkene doublets extending beyond C30. The Tertiary coals are characterised by dominant odd carbon numbered n-alkanes (n-C23 to n-C33), high Pr/Ph ratio (6–8), high Tm/ Ts ratio (8–16), and predominant regular sterane C29. All biomarkers parameters clearly indicate that the organic matter was derived from terrestrial inputs and the deposited under oxic condition.

Organic-geochemistry characterization of the Paleogene to Neogene source rocks in the Sayhut subbasin, Gulf of Aden Basin, with emphasis on organic-matter input and petroleum-generation potential

Paleogene Umm Er Radhuma and Ghaydah and Neogene Sarar source rocks from Sayhut subbasin in the Gulf of Aden Basin were studied to provide information such as organic-matter types, paleoenvironmental conditions, and petroleum-generation potential. This study is based on whole-rock organic-geochemical analyses and organic petrology. The total organic carbon (TOC) contents of the Paleogene to Neogene source rocks range from 0.43% to 6.11%, with an average TOC value of 1.00%, indicating fair to very good source-rock potential. The Paleogene Ghaydah and Umm Er Radhuma source rocks are relatively higher in genetic petroleum potential than Neogene Sarar source rocks. Mainly oil and gas are anticipated from the Ghaydah and Umm Er Radhuma source rocks with hydrogen index (HI) values ranging from 95 to 715 mg hydrocarbon (HC)/g TOC. This is supported by the presence of significant amounts of liptinite macerals in the Ghaydah and Umm Er Radhuma source rocks. The Sarar source rocks are dominated by vitrinitic type III kerogen (HI < 200 mg HC/g TOC) and are thus considered to be gas source rocks. The Paleogene to Neogene source rocks have vitrinite reflectance (R o) values in the range between 0.30% and 0.77% R o, and pyrolysis maximum temperature values range from 412°C to 444°C (774°F to 831°F), consistent with the immature to early mature oil window. Therefore, the present-day kerogen type in the Paleogene to Neogene source rocks is original and should not have been altered by thermal maturity. The biomarker of organic matter suggests that the Paleogene to Neogene source rocks were deposited in a marine environment under suboxic to anoxic conditions. The biomarkers also indicate that the Paleogene to Neogene source rocks contain a mixture of aquatic organic matter (planktonic and bacterial) and terrigenous organic matter, with increasing terrigenous influence to Sarar source-rock samples. Highly hypersaline reducing conditions are also evidenced in Ghaydah and Umm Er Radhuma source rocks, as indicated by the presence of the gammacerane biomarker, low pristane to phytane ratios, and homohopane distribution patterns.

Biomarkers and inorganic geochemical elements of Late Jurassic-Early Cretaceous limestone sediments from Banik Village in the Kurdistan Region, Northern Iraq: implications for origin of organic matter and depositional environment conditions

Late Jurassic-Early Cretaceous limestone sediments from Banik Village in the Kurdistan Region, Northern Iraq, were analysed based on a combined investigation of elemental composition and biomarker characterisation. These investigations were used to define the origin, type of organic matters and their relation to the environment conditions during deposition. The bulk geochemical characteristics indicated that the Late Jurassic-Early Cretaceous limestone sediments were deposited in a marine environment with calcium-rich seawater. Their biomarkers provide evidence for a major contribution by aquatic organic matter with a minor terrigenous organic matter contribution. This is confirmed by normal alkanes, hopanoids, steroids and related compounds of the saturated hydrocarbons. Moreover, the salinity stratification and relatively reducing bottom water conditions are evidenced in the Late Jurassic-Early Cretaceous limestone sediments, as identified from Sr/Br, V/Ni and Pr/Ph ratios. The occurrence of gammacerane biomarker in the analysed samples is also a strong indicator of reducing and salinity stratification during deposition. Therefore, a stratified water column with salinity and relatively anoxic bottom water conditions contribute to organic matter (OM) preservation.

Geochemical Characteristics of Crude Oils, their Asphaltene and Related organic Matter Source Inputs from Fula Oilfields

The oils were derived from alga organic matter, which was sourced from sediments deposited in a lacustrine environment under suboxic to relatively anoxic conditions and were generated from mature source rock with a wide range of maturity ranging from early to peak oil window. This is indicated by biomarker compositions based on saturated and aromatic fractions and bulk geochemical characteristics. Previous work by Makeen et al. (2013) on the Abu Gabra shales in the basin shows similar organic matter characteristics, palaeo-depositional environment and maturity, suggesting that the Fula oils are derived from the early Cretaceous Abu Gabra shales. This genetic relationship is also confirmed by the similarities in the structural moieties of the Fula oil asphaltenes and Abu Gabra shale kerogens (Makeen et al., 2015).

Paleoenvironmental and paleoclimatic conditions during the deposition of the bauxite layer (Upper Cretaceous) using multi-proxy geochemical and palynological analyses, in the Zabirah Area, Northern Saudi Arabia

In this research, Cretaceous claystones in the Az Zabirah area, Northern Saudi Arabia were evaluated to investigate the paleoenvironmental and paleoclimatic conditions during deposition of the claystone sediments. Outcrop samples of claystone from the bauxite zone profile in the Az Zabirah area were analyzed using multi-proxy geochemical and coupled with palynological analysis. Palynological analysis suggested that the age of the Az Zabirah claystones is Maastrichtian of Upper Cretaceous. This evidence is valid due to the presence of microspore taxa Gabonisporis sp. The Az Zabirah claystones have abundant angiosperm taxa, indicating a large terrestrial influx in the interval of the claystone. This finding is confirmed from geochemistry of major and trace elements and mineral compositions. The high concentration of terrestrial detritus oxides, such as SiO2, Al2O3, and TiO2, infers that the Az Zabirah claystones were sourced from terrigenous origin. This is consistent with a significant amount of quartz and kaolinite in the Az Zabirah claystones. The claystones could be deposited under oxic paleo-redox and warm-humid with little aridity climatic conditions. This is indicated by their concentration of the trace element concentrations along with their geochemical ratios. Warm-humid climate condition is also largely supported by the presence of a significant amount of kaolinite.

Metamorphosis of Marine Organic Matter in the Jurassic Deposits from Sharab Area, Taiz Governorate of Southwestern Yemen: Thermal Effect of Tertiary Volcanic Rocks

The Tertiary volcanic rocks are widely exposed in the Sharab area of Taiz Governorate, southwestern Yemen. The Jurassic calcareous shale and black limestone deposits collected closely to theTertiary volcanic rocks were investigated to provide information regarding the thermal effects of Tertiary volcanic rocks on organic materials. The bulk geochemical results indicate that the analysed Jurassic deposits are organically lean with present-day TOC values less than 0.95% and very low HI values (< 50 mg HC/g TOC), with a predominantly Type IV kerogen (inert carbon). This is attributed to thermal effect on the original organic matter as indicated by high thermal maturity data, consistent with post-mature to metagenesis stage. The present study also suggests that the high thermal maturity of the Jurassic marine deposits is due to the presence of the alkali basalts which have invaded the Jurassic rocks during late Oligocene to early Miocene (~10 Ma). Thus, the heat flow caused by Tertiary basaltic rocks further increased the temperature level and led to metamorphosis of organic matter and converted it to graphitic materials (inert carbon).