Thermal Alteration Index Research Articles

Palyno-petrographical Facet and Depositional Account of Gondwana Sediments from East Bokaro Coalfield, Jharkhand

Abstract: Palynological and petrological studies have been undertaken on the Gondwana coal and associated lithologies encountered in borehole EBM-2 of East Bokaro coalfield of Damodar Basin, India. The palynological investigation resulted in the recognition of Assemblage –III (Densipollenites, 27.9 m – 214.30 m), Assemblage – II (Striatopodocarpites + Faunipollenites, 225.00 m – 297.60 m) and Assemblage – I (Faunipollenites + Scheuringipollenites, 307.00m – 433.00 m). Lithofacies study was also done for better understanding of the preservation and abundance/paucity of the spores and pollen in different lithologies as the current borehole has significant thickness of mudstones, shales and siltstone. Palynofacies study and Petrographical studies of coal samples encountered in the borehole were used to determine the depositional environment of the coal precursor peat swamp. Palynological data has revealed the presence of younger Raniganj palynoflora between 27.00-214.30 m depth that is lithologically defined as Barren Measures Formation. This spore pollen study has proved that these sediments were deposited during late early Permian to late Permian period. Further the maceral analysis of organic sediments as well as the Thermal Alteration Index (TAI) has revealed that the coaly shale at 336.5 m depth has hydrocarbon generation potential.

Could the conventionally known Abu Roash “G” reservoir (upper Cenomanian) be a promising active hydrocarbon source in the extreme northwestern part of Egypt? Palynofacies, palaeoenvironmental, and organic geochemical answers

In different areas of the Western Desert of Egypt, the Abu Roash “G” Member exhibits either a reservoir or source affinity. Thus, thirteen cutting samples covering the Abu Roash “G” Member were selected from the Nest-1A well at Matruh Basin to investigate its hydrocarbon source potential. Palynological age dating of the section that is calibrated with foraminifera and ostracodes enabled a proper identification of the “G” Member. Detailed analysis of the vertical distribution of particulate organic matter of this member shows two palynofacies types. PF-1 reflects an outer middle shelf depositional environment of prevailed reducing (suboxic-anoxic) conditions for the organic-rich shales of the lower “G” Member (samples 1–8). While, PF-2 reflects a minor regression that resulted in deposition of another organic-rich shales of the upper “G” Member (samples 9–13) in an inner middle shelf setting under the same prevailing reducing (suboxic-anoxic) conditions.Organic geochemical analysis reveals good to very good potential of the “G” Member as a hydrocarbon source rock (1.8–2.41, avg. 2.15 total organic content wt %). It also shows good to very good petroleum potential (PP: 4.8–11 , avg. 8 mg HC/g rock). Pyrolsis and palynofacies analyses show kerogen type II for the lower “G” Member (samples 1–8), which is characterized by high Hydrogen index (HI: 396 and 329 mg HC/g TOC at depths 1500 and 1560 m) and very high dominance of oil-prone material (amorphous organic matter “AOM”, marine palynomorphs, and sporomorphs) and very rare occurrence of gas-prone material (brown phytoclasts). The upper “G” Member (samples 9–13) shows kerogen type II-III, which is characterized by a lower HI value of 213 mg HC/g TOC at depth 1340 m and it contains fewer amounts of gas-prone material and relatively lower AOM and marine palynomorphs in comparison to the upper “G” Member. Maturation parameters Tmax (430–433 °C), production index (PI: 0.1 mg HC/g rock), and thermal alteration index (TAI: 2+) indicate the lower “G” Member has already entered the early oil-window kitchen, and it is expected to produce oil. The upper “G” Member is expected to produce only oil with no gas shows, because it is marginally mature (Tmax 426 °C, PI 0.2, TAI 2). The source potential index (SPI: 5.3 t HC/m2) of the “G” Member shows it as currently generating moderate quantities of oil in the area of Nest-1A well.Consequently, the organic-rich shales of the “G” Member are suggested here as a promising, active oil source rock in that extreme northwestern part of the Western Desert of Egypt. However, for commercial oil recovery from the Abu Roash “G” Member, it is highly recommended to explore the depocentre of Matruh Basin at about 150 km east the Nest-1A well.

Depositional environment and hydrocarbon potential of marginal marine sediments of Eocene from western India: A palynofacies perspective

Palynofacies and palynological data from Eocene sediments documents a comprehensive picture of the nature (degraded, structured, non-structured, amorphous etc.) of organic matter, their distribution, and depositional setting for Matasukh lignite mines of Nagaur Basin in western India. Four Sporomorph Eco Groups (SEG) are defined based on the palynological data viz., Upland SEG, Lowland SEG, Coastal SEG and Tidally influenced SEG. Principal component analysis was used to categorize the organic matter into two palynofacies. Palynofacies-A is dominated by brown Phytoclasts (in particular cuticles) and Palynofacies-B is dominated by amorphous organic matter, mainly derived from terrestrially degraded material. In Palynofacies-B there is a reduced frequency of cuticles and high frequency of non-biostructured amorphous phytoclasts in comparison to Palynofacies-A. Further the Integration of Tidal limit index and Phytoclast preservation index suggest that the sediments were deposited in a proximal setting and were regularly influenced by brackish-marine water. The sand bed with current bedding in which the troughs are draped with lignitic clay indicate the tidal wave action. Tyson's ternary diagram indicates the deposition of these sediments in a sub-oxic to dysoxic condition, rich in Kerogen Type-II/III. Thermal alteration index (TAI) shows that the sediments of Matasukh lignite mine have attained maturation (the characteristic value reached by hydrocarbon generating sediments) to generate dry gas as majority of the organic matter is of Type-III Kerogen with few samples yielding Type-II. These sediments were deposited in deltaic plain, in particular, fluvial dominated marginal marine environment.

Late Cretaceous (Campanian) leaf and palynoflora from southern Skåne, Sweden

Abstract A Late Cretaceous (Campanian) leaf megaflora from the Vomb Trough in southern Skåne, Sweden, has been investigated on the basis of collections held at the Swedish Museum of Natural History. The main plant-bearing locality is Köpinge, but single specimens originate from Högestad, Ingelstorp, Rödmölla, Svenstorps mölla and Tosterup. The fossil flora is dominated by the angiosperm (eudicot) Debeya ( Dewalquea ) haldemiana (Debey ex de Saporta & Marion) Halamski. Other dicots are cf. Dryophyllum sp., Ettingshausenia sp., Rarytkinia ? sp., Dicotylophyllum friesii (Nilsson) comb. nov. and Salicites wahlbergii (Nilsson) Hisinger. Conifers are represented by cf. Aachenia sp. (cone scales), Pagiophyllum sp. and Cyparissidium sp. (leaves). Single poorly preserved specimens of ferns and monocots have also been identified. The terrestrial palynomorphs (the focus herein) clearly link to the megaflora, although with different relative abundances. The fern spore Cyathidites dominates along with the conifer pollen Perinopollenites elatoides and Classopollis . Angiosperm pollen comprise up to 15% of the assemblage, represented by monocolpate, tricolpate and periporate pollen and the extinct Normapolles group. The spores in the kerogen residue show a thermal alteration index (TAI) of 2+. The flora probably represents mainly a coastal lowland Debeya /conifer forest, and is similar to approximately coeval assemblages from analogous palaeo-communities described from eastern Poland, western Ukraine and Westphalia.

Paleoenvironment characteristics and hydrocarbon potential of the Lower Miocene bituminous shales in Sivas Basin (Central Anatolia, Turkey)

This study is based around Karayun which is in the Sivas Tertiary Basin, one of the important sedimentary basins in Turkey. The units observed in the study area and nearby are Oligocene Hafik, Lower Miocene Karayun and Lower-Middle Miocene Karacaoren Formations and Quaternary alluvium. This study focused on samples from the Karayun Formation due to the presence of alternations of bituminous shale levels in the formation. The studied bituminous shales are characterized by relatively high total organic carbon values up to 10.44 % and S2 values ranging from 0.01 to 89.02 HC/g rock, indicating fair to excellent source rock. Most of the bituminous shales are at the immature to early mature stage for hydrocarbon generation. Generally, genetic potential values are over 2 mg HC/g rock. The hydrogen index value of samples are between 9 and 887 mg HC/g total organic carbon (TOC) (on average 333.62 mg HC/g TOC). Oxygen index values vary between 17 and 557 mg CO2/g TOC (on average 135.35 mg CO2/g TOC). On the basis of Rock-Eval pyrolysis analysis, kerogens are type I/II and type II/III mixed. Dominant organic matter observed in this formation is algal amorphous organic matter. Thermal alteration index (TAI), Spore colour index (SCI), vitrinite reflectance values (Ro) and Tmax evaluations indicate that maturity of the unit is between diagenesis and the early mature zone, and at the beginning of the hydrocarbon-producing stage. As a result of a series of analyses, it was found that the Karayun Formation has organic facies of B, BC and C and limited hydrocarbon generation potential in the basin.

Acritarchs of the Ediacaran Frecheirinha Formation, Ubajara Group, Northeastern Brazil.

We report for the first time the occurrence of organic-walled microfossils in Ediacaran limestones and marls of the Frecheirinha Formation, Ubajara Group, and the first Precambrian acritarchs so far reported for northeastern Brazil. The assemblage of the Frecheirinha Formation represents a low-diversity microflora comprising Leiosphaeridia, Lophosphaeridium and subordinated Bavlinella (=Sphaerocongregus). Their thermal alteration index (TAI) between 4+ and 5, suggests metamorphic temperatures exceeding 200-250°C. Higher temperatures are probably related to intruding granitic plutons (Meruoca, Mucambo). Reported δ13C values of carbonates of -3.5 ‰ VPDB (Vienna-Peedee Belemnite) at the base, passing up section into a positive plateau of up to +3.7 ‰, and corresponding 87Sr/86Sr values between 0.7075 and 0.7080 suggest an Ediacaran age. The acritarch assemblage is comparable to the Late Ediacaran Leiosphere Palynoflora (LELP) or Kotlin-Rovno assemblage, in broad agreement with chemostratigraphic data. Macrofossils belonging to the Ediacara fauna were reported from the overlying Jaibaras Group, which would constrain even further the depositional age of the Frecheirinha Formation to within ca. 575-555 Ma. A more comprehensive palynological study of the Frecheirinha Formation is necessary to confirm this age assignment.

Les kystes de dinoflagelles et palynofacies de la transition Maastrichtien–Danien du stratotype El kef (Tunisie)

A palynological study of the Cretaceous–Paleogene (K–Pg) boundary deposits at the stratotype El kef, Tunisia, showed an exceptional richness of palynomorphs. Dinoflagellate cysts (dinocysts) are abundant, diversified and well preserved. The K–Pg boundary lies right after the last appearance of the Cretaceous species, Dinogymnium cretaceum, Dinogymnium acuminatum and Pterodinium cretaceum, and directly below the first appearance of the species markers of the basal Danian, such as Damassadinium californicum, Membranilarnacia? tenella, Senoniasphaera inornata, Carpatella cornuta, Eisenackia circumtabulata and Lanternosphaeridium reinhardtii. The age determined for these levels based on dinocysts is in agreement with that determined using planktonic foraminifera. The palynofacies study showed an organic matter dominated by marine palynomorphs, essentially dinoflagellate cysts, the sporomorphs are rare. Continental palynomorphs (Sporomorphs) and Amorphous Organic Matter (AOM) are present in all samples. The microplankton is dominated by peridinoid dinocysts with a progressive enrichment at Danian, mainly the Senegalinium group. The Total Organic Carbon (TOC) content is generally less than 0.6wt %. The TOC, Rock–Eval pyrolysis and palynofacies analyses indicate that the El Haria Formation presents immature organic matter of types II and III and a low Thermal Alteration Index (TAI).

Characteristics of the Triassic Source Rocks of the Aitutu Formation in the (West) Timor Basin

DOI:10.17014/ijog.v1i3.192The Triassic rocks of the (West) Timor Basin have been identified that was mainly deposited in the marine environment. The fine grained clastics and carbonate rocks of this Triassic marine facies are considered to be the most promising source rocks potential in this basin. In this paper we present geochemical and petrographic data from outcrop samples of the Triassic carbonate Aitutu Formation, due to emphasized the organic maturation, kerogen type of the organic matter and the origin of the organic matter. A representative of selected sample were subjected to the Rock-Eval Pyrolisis, vitrinite reflectance and thermal alteration index, bitumen extraction, were analyzed on the GC-MS. The samples were collected from marine deposit of the Triassic Sequence. The TOC values of the analyzed sample range between rich and rich organic richness (0.51% - 9.16%, wt.%, TOC), which consists mainly of type II and III kerogen and the organic matter consider to be predominantly oil/gas prone and gas prone potential. The thermal maturity assessed from Tmax, TAI, and vitrinite reflectance shows an immature to early peak mature stage of the organic matter. The GC-MS analyses of the biomarkers indicate mainly the organic matter derived from mixed source rocks facies containing alga debris and higher plant terrestrial origin.

Palynofacies characterization for evaluation of hydrocarbon source rock potential of Lower Paleogene (Thanetian-Ypresian) sub-surface sediments of Barmer Basin, western Rajasthan, India

This paper deals with the hydrocarbon source rock evaluation and depositional environment of Lower Paleogene sub-surface sediments from borehole MMK-26 of Barmer Basin, Rajasthan. Hydrocarbon potential of these sediments are estimated on the basis of plant derived Sedimentary Organic Matter (SOM) analysis. The palynofacies analysis indicate that the sediments are rich in organic matter with amorphous organic matter constituting the majority of the SOM in the lower part of the borehole where as the phytoclasts dominate in the upper part. The dominance of sapropelic facies (Amorphous Organic Matter) at a depth of 152 m and below suggests that these sediments are a good source for hydrocarbon generation. Further the categorized palynofacies components are plotted on Tyson's Amorphous Organic Matter-Phytoclast-Palynomorph diagram which reveal that the studied sediments are characterized by type-II (oil generating) and type – III kerogen deposited in a dysoxic – anoxic shelf. Thermal Alteration Index (TAI) values were determined to asses the organic maturity of the sediments and a maturation value of 2.80–3.0 for the lower part of the bore core suggest that the sediments have attained an optimum maturation level to produce hydrocarbons. The increasing frequency of marine palynomorphs in association with continental components indicates a transgressive phase of sea level during the deposition of the studied sediments.

Lower Cretaceous black shales of the Western Carpathians, Czech Republic: Palynofacies indication of depositional environment and source potential for hydrocarbons

Uppermost Jurassic and Lower Cretaceous strata of the Silesian Nappe of the Outer Western Carpathians contain large amounts of shale, which can, under favourable conditions, become source rocks for hydrocarbons. This study analysed 45 samples from the area of Czech Republic by the means of palynofacies analysis, thermal alteration index (TAI) of palynomorphs and total organic carbon (TOC) content to determine the kerogen type, hydrocarbon source rock potential, and to interpret the depositional environment. Uppermost Jurassic Vendryně Formation and Lower Cretaceous Formations (Těšín Limestone, Hradiště and Lhoty) reveal variable amount of mostly gas prone type III kerogen. Aptian Veřovice Formation has higher organic matter content (over 3 wt.%) and oil-prone type II kerogen. Organic matter is mature to overmature and hydrocarbon potential predisposes it as a source of gas. Aptian black claystones of the Veřovice Fm. are correlatable with oceanic anoxic event 1 (OAE1).

Age assessments and palynofacies of the Jurassic oil source rocks succession of North Iraq

Palynomorps of mainly dinoflagellate cysts are used in this study to assess age of Middle Jurassic (Bajocian–Bathonian) Sargelu, Upper Jurassic (Upper Callovian–Lower Oxfordian) Naokelekan, Upper Jurassic (Kimeridgian and Oxfordian) Gotnia and Barsarine, and Upper Jurassic–Lower Cretaceous (Beriassian–Tithonian) Chia Gara source rock Formations. Materials used for this palynological study are 85 core and cutting samples of five oil exploratory wells of Bj-1, Tk-3, Aj-8, K-109 and Tq-1 of selected North Iraqi oil fields. Palynofacies assessments are performed for this studied succession by ternary kerogen plots of the phytoclast, amorphous organic matters and palynomorphs. Accordingly, Chia Gara and Sargelu Formations are both deposited in distal suboxic to anoxic basin and can be correlated with kerogens classified microscopically as Type A and Type B, which comprised principally brazinophyte algae, dinoflagellate cysts, spores, pollen, foraminifera test linings and phytoclasts that could indicate affect of upwelling current. These deposits contain up to 18 wt% total organic matters that are capable to generate hydrocarbons within mature stage of thermal alteration index (TAI) range in Stalplin’s scale of 2.7–3.0 for the Chia Gara Formation and 2.9–3.1 for the Sargelu Formation.

Hydrocarbon potential and porosity types of the Geli Khana Formation (Middle Triassic), Northern Iraq

Hydrocarbon generation potential and porosity types of the Middle Triassic Geli Khana Formation in Jabal Kand-1 (JK-1) well and from outcrop section at Ora of northern Iraq are investigated. Total organic carbon, pyrolysis, and maturation assessment such as thermal alteration index (TAI) and vitrinite reflectance (Ro%) for 19 shale samples are conducted. The analyses showed a sufficient amount of organic matter (OM) occurs in JK-1 specifically. According to the obtained samples from the pyrolysis analysis of the studied samples, the existing organic matters in well (JK-1) are composed of a mixed of kerogen type II–III and III; while type IV in outcrop section which found in post mature state, indicating dry gas window. The estimated TAI for the studied section ranged between 3.3 in and 3.7 in JK-1 and 3.3–4 in Ora section. Additionally, the maturity derived information from vitrinite reflectance supported that the Geli Khana Formation is in dry gas window and post mature stage in both sections due to the average ratio of (Ro %) which is between 1.35 and 2 %. The porosity types in the carbonate successions of the formation include; fracture, moldic, intergranular, intramatrix, vuggy, intercrystalline, channel and fenestral birds-eye porosities. These types enhance the reservoir characteristics of the carbonate succession of the formation.

Source Rock Potential and Thermal Maturity of the Eocene Nanka Formation (Ameki Group) In Anambra Basin: An Appraisal of Ogbunike Reference Locality, South Eastern Nigeria

Source rock potential and thermal maturity of the Eocene Nanka Formation of Ogbunike,south eastern Nigeria was assessed in this research work.The rock-eval pyrolysis result recorded a value range of 0.04 to 0.11,0.44 to 1.32 and 0.44 to 0.49 forS1, S2 and S2/S3respectively. Production Index (PI) and Hydrogen Index (HI) results have a value range of 0.08 and 11.83 to 55.00 respectively. TheSoluble Organic Matter (SOM) has an average value of 0.013 wt. %(127.55ppm), while Total organic carbon (Toc) recorded a value range of 2.40wt. % to 4.50 wt. %. Thermal Alteration index (TAI) of +1 to -2 and Vitrinite reflectance (Ro %) of 0.2% to 0.3% was recorded. Particulate organic matter of the samples was also analysed. The results suggests that the studied area is a type 1VKerogen,immatured stage of thermal maturity, fair source bed,but has a high organic carbon that can generate oil

Sedimentary organic matter and source rock potential of the Paleocene Aaliji Formation in Qumar Oil Field, NE Iraq

The organic matter content of the Paleocene Aaliji Formation has been studied from the Qm-1 well in the Qumar Oil Field, NE Iraq. A palynofacies analysis revealed the obvious domination of amorphous organic matter (AOM) in the samples studied in addition to the different ratios of palynomorphs, phytoclasts and opaque organic material. The deposition of the various percentages of organic matter components and types of palynomorphs appear to have occurred in a proximal suboxic–anoxic basinal environment. The samples analysed showed relatively low percentages of total organic carbon, indicating a generally poor source rock. The thermal alteration index for the palynomorphs (dinoflagellates) observed and identified ranged between 2, 2+ and 3−, indicating an immature to early stage of maturity for the section studied. No clear differentiation between the stages of maturity within the section was identified. The reflectance measured for a few vitrinite particles at a depth of 2,900 m showed uncertainly of 0.46 % Ro, indicating a still thermally immature stage. The values obtained from pyrolysis analysis also supported the formation being in the early stages of maturity, i.e. an immature condition, with T max values between 416 and 435 °C. The quality of the organic matter examined and analysed appeared to be mostly type III gas-prone kerogen, as discerned from the hydrogen index, oxygen index and other pyrolysis parameters. The parameters obtained and calculated from gas chromatography analysis performed on a sample at a depth of 2,900 m found marginally mature marine source organic matter.

Palynofacies, organic geochemical analyses and hydrocarbon potential of some Upper Jurassic-Lower Cretaceous rocks, the Sabatayn-1 well, Central Yemen

The current work investigates the hydrocarbon potentiality of the upper Jurassic–lower Cretaceous rocks in the Marib-Shabwah Basin, Central Yemen, through the Sabatayn-1 well. Therefore, palynological and organic geochemical analyses were carried out on 37 ditch cutting and 12 core samples from the well. Palynofacies analysis of the Madbi (late Oxfordian–early Tithonian) and Nayfa (Berriasian–Valanginian) Formations sediments indicates deposition of their organic-rich shale, calcareous shale and marl in middle to outer shelf environments under dysoxic–anoxic conditions, containing mainly kerogen of types II to III. However, the shales of the lower Sabatayn (Tithonian) Formation were deposited in an inner shelf environment of prevailing dysoxic–suboxic conditions, and show kerogen types III to II. Regional warm and relatively dry palaeoclimate but with local humid conditions developed near the site of the well is thought to have prevailed during deposition of the studied well sediments. The geochemical analyses of the Madbi Formation show higher total organic carbon content (TOC) than the overlying Sabatayn and Nayfa formations: it is varies between 1.2 and 7, and with average 4 wt% TOC, and the obtained S2 values (∼3–10, average 7 mg HC/g rock) indicates that the Madbi Formation is mainly good source rock. It shows a good petroleum potential of 4–11 mg HC/g dry rock, and the Rock-Eval pyrolysis indicates mainly kerogen types II to III (oil to gas prone) of hydrogen index values (132–258, and only one sample from Lam Member is of 360 and average 215 mg HC/g TOC). The thermal maturation parameters as T max (425–440 °C), production index (average 0.13 mg HC/g rock) and thermal alteration index (2 to 2+) reflected that this formation is present at margin of maturation to early mature stage oil window. So, the Lam Member (upper part) of the Madbi Formation is considered the main hydrocarbon (oil and gas) source rock in the Marib-Shabwah Basin. Accordingly, we predict that the Meem Member is an active source for gas and oil accumulations in the overlying sandstone reservoir of the Sabatayn Formation in the Sabatayn-1 well.

Potentiality of Paleocene source rocks and their contribution in generating the accumulated oil in the Eocene Pila Spi Reservoir in Taq Taq Oil Field, Kurdistan Region, Iraq

The organic matters within the Paleocene Aaliji and Kolosh Formations in the well TT-04, Taq Taq Oil Field in Kurdistan Region, NE Iraq have been studied optically and also analytically by means of pyrolysis, Gas Chromatography (GC), and Gas Chromatography/Mass Spectrometry (GC/MS). Amorphous organic matters seemed to be the dominant component of the extracted organic matters within the studied section with an obvious increase of the Phytoclasts at the upper part of Kolosh Formation. Thermal Alteration Index, vitrinite reflectance, pyrolysis, and gas chromatography data all indicated the maturity of the lower part from the studied layers (known generally as Aaliji/Kolosh) and within the early stages of oil generation. Oil–source correlation indicates the possibility of contribution of the Paleocene source rocks in generating the accumulated oil in the Eocene Pila Spi reservoir in the field which also appeared to be a mature and of marine-to-mixed carbonate source. Oil–oil correlation between the oil in Pila Spi and the oil in the Upper Cretaceous reservoirs showed the possibility of existence of more than one source for the two oils. GC/MS analysis for the Pila Spi oil indicated the effect of biodegradation which may be considered as one of the reasons for being the American Petroleum Institute (API) of this oil about 24° while the oil in the Cretaceous reservoirs is of more than 47° API.

Hydrocarbons generation potential of the Jurassic–Lower Cretaceous Formation, Ajeel field, Iraq

Organic geochemical analysis and palynological studies of the organic matters of subsurface Jurassic and Lower Cretaceous Formations for two wells in Ajeel oil field, north Iraq showed evidences for hydrocarbon generation potential especially for the most prolific source rocks Chia Gara and Sargelu Formations. These analyses include age assessment of Upper Jurassic (Tithonian) to Lower Cretaceous (Berriasian) age and Middle Jurassic (Bathonian–Tithonian) age for Chia Gara and Sargelu Formations, respectively, based on assemblages of mainly dinoflagellate cyst constituents. Rock-Eval pyrolysis have indicated high total organic carbon (TOC) content of up to 18.5 wt%, kerogen type II with hydrogen index of up to 415 mg HC/g TOC, petroleum potential of 0.70–55.56 kg hydrocarbon from each ton of rocks and mature organic matter of maximum temperature reached (Tmax) range between 430 and 440 °C for Chia Gara Formation, while Sargelu Formation are of TOC up to 16 wt% TOC, Kerogen type II with hydrogen index of 386 mg HC/g TOC, petroleum potential of 1.0–50.90 kg hydrocarbon from each ton of rocks, and mature organic matter of Tmax range between 430 and 450 °C. Qualitative studies are done in this study by textural microscopy used in assessing amorphous organic matter for palynofacies type belonging to kerogen type A which contain brazinophyte algae, Tasmanites, and foraminifera test linings, as well as the dinoflagellate cysts and spores, deposited in dysoxic–anoxic environment for Chia Gara Formation and similar organic constituents deposited in distal suboxic–anoxic environment for Sargelu Formation. The palynomorphs are of dark orange and light brown, on the spore species Cyathidites australis, that indicate mature organic matters with thermal alteration index of 2.7–3.0 for the Chia Gara Formation and 2.9–3.1 for the Sargelu Formation by Staplin's scale.

The potential of hydrocarbons generation in the Chia Gara Formation at Amadia area, north of Iraq

Sixteen rock samples of outcrop of Chia Gara Formations from the type locality area, south of Amadia, North Iraq showed evidences for hydrocarbon generation potential by palynological studies. These analyses include age assessment of Upper Jurassic (Tithonian) to Lower Cretaceous (Berriasian) age based on assemblages of mainly dinoflagellate cyst constituents. Qualitative studies are done in this study by textural microscopy used in assessing amorphous organic matter for palynofacies type belong to kerogen type A of Thompson and Dembiki (Int J Coal Geol 6:229–249, 1986) which contain brazinophyte algae, Tasmanites, and foraminifera test linings, as well as the dinoflagellate cysts and spores, deposited in dysoxic–anoxic environment. The palynomorphs are of dark orange and light brown, on the spore species Cyathidites australis, that indicate mature organic matters with thermal alteration index of 2.7–3.0 by Staplin’s scale. These characters and total organic carbon of 0.5–8.5 wt% have rated the succession as a source rock for high efficiency for generation and expulsion of oil with ordinate gas that charged mainly oil fields of Tawqi. Some oil is released from the Chia Gara Formation to charge the Cretaceous–Tertiary total petroleum system.

Middle and Upper Jurassic hydrocarbon potential of the Zagross Fold Belt, North Iraq

Structured organic matters of the Palynomorphs of mainly dinoflagellate cysts are used in this study for dating the limestone, black shale, and marl of the Middle Jurassic (Bajocian–Bathonian) Sargelu Formation, Upper Jurassic (Upper Callovian – Lower Oxfordian) Naokelekan Formation, Upper Jurassic (Kimeridgian and Oxfordian) Gotnia and Barsarine Formations, and Upper Jurassic – Lower Cretaceous (Tithonian-Beriassian) Chia Gara source rock Formations while spore species of Cyathidites australis and Glechenidites senonicus are used for maturation assessments of this succession. Materials' used for this palynological study are 320 core and cutting samples of twelve oil wells and three outcrops in North Iraq.Terpane and sterane biomarker distributions, as well as stable isotope values, were determined for oils potential source rock extracts of Jurassic-Lower Cretaceous strata to determine valid oil-to-source rock correlations in North Iraq. Two subfamily carbonate oil types-one of Middle Jurassic age (Sargelu) carbonate rock and the other of mixed Upper Jurassic/Cretaceous age (Chia Gara) with Sargelu sources as well as a different oil family related to Triassic marls, were identified based on multivariate statistical analysis (HCA & PCA). Middle Jurassic subfamily A oils from Demir Dagh oil field correlate well with rich, marginally mature, Sargelu source rocks in well Mk-2 near the city of Baiji. In contrast, subfamily B oils have a greater proportion of C28/C29 steranes, indicating they were generated from Upper Jurassic/Lower Cretaceous carbonates such as those at Gillabat oil field north of Mansuriyah Lake. Oils from Gillabat field thus indicate a lower degree of correlation with the Sargelu source rocks than do oils from Demir Dagh field.Palynofacies assessments are performed for this studied succession by ternary kerogen plots of the phytoclast, amorphous organic matters, and palynomorphs. From the diagram of these plots and maturation analysis, it could be assessed that the formations of Chia Gara and Sargelu are both deposited in distal suboxic to anoxic basin and can be correlated with kerogens classified microscopically as Type A and Type B and chemically as Type II. The organic matter, comprised principally of brazinophyte algae, dinoflagellate cysts, spores, pollen, foraminifera test linings, and phytoclasts in all these formations and hence affected with upwelling current. These deposit contain up to 18 wt% total organic matters that are capable to generate hydrocarbons within mature stage of thermal alteration index (TAI) range in Stalplin's scale (Staplin, 1969) of 2.7–3.0 for the Chia Gara Formation and 2.9–3.1 for the Sargelu Formation. Case study examples of these oil prone strata are; one 7-m (23-ft) thick section of the Sargelu Formation averages 44.2 mg HC/g S2 and 439 °C Tmax (Rock-Eval pyrolysis analyses) and 16 wt% TOC especially in well Mk-2 whereas, one 8-m (26-ft) thick section of the Chia Gara and 1-m (3-ft) section of Naokelekan Formations average 44.5 mg HC/g S2 and 440 °C Tmax and 14 wt% TOC especially in well Aj-8. One-dimension, petroleum system models of key wells using IES PetroMod Software can confirm their oil generation capability.These hydrocarbon type accumulation sites are illustrated in structural cross sections and maps in North Iraq.

Palynofacies characterization for hydrocarbon source rock evaluation in the Subathu Formation of Marhighat, Sirmaur district, Himachal Pradesh

This paper deals with the hydrocarbon source rock evaluation of the Subathu Formation exposed at Marhighat on Sarahan–Narag road in Sirmaur district of Himachal Pradesh. Hydrocarbon potential of these sediments is estimated on the basis of palynofacies analysis and thermal alteration index (TAI) values based on the fossil spores/pollen colouration. The analyses are based on the classification and hydrocarbon generation potential of plant derived dispersed organic matter present in the sediments. The palynofacies analysis of Subathu Formation in the area reveal moderate to rich organic matter, with amorphous organic matter constituting the bulk of the total organic matter, followed by charcoal, biodegraded organic matter, fungal remains, spores/pollen and structured terrestrial organic matter. The TAI value for the organic matter in these sediments has been ascertained as 3.00. A dominance of the sapropelic facies (amorphous organic matter) and the measured TAI values for the Subathu sediments in the Marhighat area suggests a good source-rock potential for the hydrocarbon generation.