scholarly journals Integration of the outcrop and subsurface geochemical data: implications for the hydrocarbon source rock evaluation in the Lower Indus Basin, Pakistan

2018 ◽  
Vol 9 (2) ◽  
pp. 937-951 ◽  
Author(s):  
Sajjad Ahmad ◽  
Faizan Ahmad ◽  
Abd Ullah ◽  
Muhammad Eisa ◽  
Farman Ullah ◽  
...  

Abstract The present study details the hydrocarbon source rock geochemistry and organic petrography of the outcrop and subsurface samples of the Middle Jurassic Chiltan Formation and the Lower Cretaceous Sembar Formation from the Sann #1 well Central and Southern Indus Basin, Pakistan. The total organic carbon (TOC), Rock–Eval pyrolysis, vitrinite reflectance (Ro) % and Maceral analysis techniques were used and various geochemical plots were constructed to know the quality of source rock, type of kerogen, level of maturity and migration history of the hydrocarbons. The outcrop and Sann #1 well data on the Sembar Formation reveals poor, fair, good and very good quality of the TOC, type II–III kerogen, immature–mature organic matter and an indigenous hydrocarbon generation potential. The outcrop and Sann #1 well data on the Chiltan Formation show a poor–good quality of TOC, type II–III kerogen, immature–mature source rock quality and having an indigenous hydrocarbon generation potential. The vitrinite reflectance [Ro (%)] values and Maceral types [fluorescent amorphous organic matter, exinite, alginite and inertnite] demonstrate that maturity in both Sembar and the Chiltan formation at surface and subsurface fall in the oil and gas generation zone to cracking of oil to gas condensate zone. Recurrence of organic rich and poor intervals within the Sembar and Chiltan formation are controlled by the Late Jurassic thermal uplift preceding the Indo-Madagascar separation from the Afro-Arabian Plate and Early Cretaceous local transgressive–regressive cycles. From the current study, it is concluded that both Sembar and Chiltan formation can act as a potential hydrocarbon source rock in the study area.

1985 ◽  
Vol 33 ◽  
pp. 239-252
Author(s):  
Birthe J. Schmidt

The Rhaetic - Jurassic - Lower Cretaceous sediments from the Børglum 1 and Uglev 1 wells have been investigated by coal petrographical methods to evaluate their hydrocarbon source rock potential. The methods include vitrinite reflectance analyses of maturity, optical qualitative rating of the composition of the dispersed organic matter in the sediments, along with an estimation of the total organic carbon content of the sediments. The composition of the sedimentary organic matter is highly influenced by the palaeogeographic conditions. In the Børglum 1 well the organic material is dominated by land-derived (mainly gas-prone) plant matter; this is also the case for the marine sediments due to introduction of plant material from the adjacent Fennoscandian Border Zone. The sediments in Uglev 1 also have a high content of terrestrial plant material, although there is more marine dominated (oil-prone) organic matter in the deposits of the Bream Formation. The most promising conditions tor generation of liquid hydrocarbons have been found in the Bream Formation in Uglev 1, but the investigated sediments are generally thermally immature, with a restricted potential tor hydrocarbon generation. The rank gradient for Uglev 1 (0.20 % Ro/km), which is situated over a deep-seated salt diapir is more than three times that of Børglum 1 (0.06 % Ro/km), which is placed more marginally in the Danish Subbasin. This is attributed to differences in the geothermal gradients (Børglum 1:19°C/km, Uglev 1: 32 and 37°C/km, uncorrected)


2017 ◽  
Vol 5 (2) ◽  
pp. SF225-SF242 ◽  
Author(s):  
Xun Sun ◽  
Quansheng Liang ◽  
Chengfu Jiang ◽  
Daniel Enriquez ◽  
Tongwei Zhang ◽  
...  

Source-rock samples from the Upper Triassic Yanchang Formation in the Ordos Basin of China were geochemically characterized to determine variations in depositional environments, organic-matter (OM) source, and thermal maturity. Total organic carbon (TOC) content varies from 4 wt% to 10 wt% in the Chang 7, Chang 8, and Chang 9 members — the three OM-rich shale intervals. The Chang 7 has the highest TOC and hydrogen index values, and it is considered the best source rock in the formation. Geochemical evidence indicates that the main sources of OM in the Yanchang Formation are freshwater lacustrine phytoplanktons, aquatic macrophytes, aquatic organisms, and land plants deposited under a weakly reducing to suboxic depositional environment. The elevated [Formula: see text] sterane concentration and depleted [Formula: see text] values of OM in the middle of the Chang 7 may indicate the presence of freshwater cyanobacteria blooms that corresponds to a period of maximum lake expansion. The OM deposited in deeper parts of the lake is dominated by oil-prone type I or type II kerogen or a mixture of both. The OM deposited in shallower settings is characterized by increased terrestrial input with a mixture of types II and III kerogen. These source rocks are in the oil window, with maturity increasing with burial depth. The measured solid-bitumen reflectance and calculated vitrinite reflectance from the temperature at maximum release of hydrocarbons occurs during Rock-Eval pyrolysis ([Formula: see text]) and the methylphenanthrene index (MPI-1) chemical maturity parameters range from 0.8 to [Formula: see text]. Because the thermal labilities of OM are associated with the kerogen type, the required thermal stress for oil generation from types I and II mixed kerogen has a higher and narrower range of temperature for hydrocarbon generation than that of OM dominated by type II kerogen or types II and III mixed kerogen deposited in the prodelta and delta front.


2020 ◽  
Vol 10 (8) ◽  
pp. 3191-3206
Author(s):  
Olusola J. Ojo ◽  
Ayoola Y. Jimoh ◽  
Juliet C. Umelo ◽  
Samuel O. Akande

Abstract The Patti Formation which consists of sandstone and shale offers the best potential source beds in the Bida Basin. This inland basin is one of the basins currently being tested for hydrocarbon prospectivity in Nigeria. Fresh samples of shale from Agbaja borehole, Ahoko quarry and Geheku road cut were analysed using organic geochemical and palynological techniques to unravel their age, paleoecology, palynofacies and source bed hydrocarbon potential. Palynological data suggest Maastrichtian age for the sediments based on the abundance of microfloral assemblage; Retidiporites magdalenensis, Echitriporites trianguliformis and Buttinia andreevi. Dinocysts belonging to the Spiniferites, Deflandrea and Dinogymnium genera from some of the analysed intervals are indicative of freshwater swamp and normal sea conditions. Palynological evidence further suggests mangrove paleovegetation and humid climate. Relatively high total organic carbon TOC (0.77–8.95 wt%) was obtained for the shales which implies substantial concentration of organic matter in the source beds. Hydrocarbon source rock potential ranges from 0.19 to 0.70 mgHC/g.rock except for a certain source rock interval in the Agbaja borehole with high yield of 25.18 mgHC/g.rock. This interval also presents exceptionally high HI of 274 mgHC/g.TOC and moderate amount of amorphous organic matter. The data suggests that in spite of the favourable organic matter quantity, the thermal maturity is low as indicated by vitrinite reflectance and Tmax (0.46 to 0.48 Ro% and 413 to 475 °C, respectively). The hydrocarbon extracts show abundance of odd number alkanes C27–C33, low sterane/hopane ratio and Pr/Ph > 2. We conclude that the source rocks were terrestrially derived under oxic condition and dominated by type III kerogen. Type II organic matter with oil and gas potential is a possibility in Agbaja area of Bida Basin. Thermal maturity is low and little, or no hydrocarbon has been generated from the source rocks.


Author(s):  
Nasar Khan ◽  
Wasif Ullah ◽  
Syed M. Siyar ◽  
Bilal Wadood ◽  
Tariq Ayyub ◽  
...  

AbstractThe present study aims to investigate the origin, type, thermal maturity and hydrocarbon generation potential of organic matter and paleo-depositional environment of the Early Paleocene (Danian) Hangu Formation outcropped in the Kala-Chitta Range of Northwest Pakistan, Eastern Tethys. Organic-rich shale and coal intervals were utilized for geochemical analyses including TOC (total organic carbon) and Rock–Eval pyrolysis coupled with carbon (δ13Corg) and nitrogen (δ15Norg) stable isotopes. The organic geochemical results showed that the kerogen Type II (oil/gas prone) and Type III (gas prone) dominate the investigated rock units. The TOC (wt%) and S2 yield indicate that the rock unit quantifies sufficient organic matter (OM) to act as potential source rock. However, the thermal maturity Tmax°C marks the over maturation of the OM, which may be possibly linked with the effect attained from nearby tectonically active Himalayan Foreland Fold-and-Thrust Belt system and associated metamorphosed sequences. The organic geochemical analyses deciphered indigenous nature of the OM and resultant hydrocarbons. The δ13Corg and δ15Norg stable isotopic signatures illustrated enrichment of the OM from both marine and terrestrial sources accumulated into the Hangu Formation. The Paleo-depositional model established using organic geochemical and stable isotopic data for the formation supports its deposition in a shallow marine proximal inner shelf environment with prevalence of sub-oxic to anoxic conditions, a scenario that could enhance the OM preservation. Overall, the formation holds promising coal and shale intervals in terms of organic richness, but due to relatively over thermal maturation, it cannot act as an effective source rock for liquid hydrocarbon generation and only minor amount of dry gas can be expected. In implication, the results of this study suggest least prospects of liquid hydrocarbon generation potential within Hangu Formation at studied sections.


2020 ◽  
Vol 4 (2) ◽  
pp. 48-64
Author(s):  
Swar Al-Atroshi ◽  
Govand Sherwani ◽  
Srood Al-Naqshbandi

The Middle–Late Jurassic Sargelu, Naokelekan, and Barsarin formations of northwestern Iraq have been investigated in the Shaikhan oilfield (well Shaikhan-8) to assess their potential for hydrocarbon generation.The results of total organic carbon analysis and rock-eval pyrolysis revealed a good-to-excellent hydrocarbon content and suggest that the depositional conditions were suitable for the production and preservation of organic matter. The thermal maturity proxy indicates that the studied formations were at the start of the hydrocarbon generation period. Most of the samples from the Sargelu and Barsarin formations belong to kerogen type II, whereas those of the Naokelekan Formation belong to kerogen type II/III. The Pr/Ph, Pr/n-C17, and Ph/n-C18 ratios of the extracted bitumen indicated that the organic matter originated from marine sources under reducing conditions. The stable carbon isotope composition of the saturated and aromatic hydrocarbon fractions ranged from –28.3 to –27.7 ‰ and –28.0 to –27.7 ‰, respectively. The biomarker results show a high contribution of marine organic matter that was preserved under relatively anoxic conditions. The profiles of the burial and thermal maturity history show that the simulated generation zones, based on the calculated vitrinite reflectance, indicate immature (0.44%–0.6%)-to-early oil generating (0.6%–0.75%) source rock. The low thermal maturity of the studied formations relative to the depth may be attributed to the low geothermal gradient and heat flow.


Author(s):  
Nazan Yalcin Erik ◽  
Faruk Ay

AbstractWith this study, the hydrocarbon generation potential of Miocene aged coals around Arguvan-Parçikan in the northern district of Malatya province was evaluated with the aid of petrological and organic geochemical data. According to organic petrography, coal quality data, and low thermal maturity, the Arguvan-Parçikan coals are of high-ash, high-sulfur subbituminous B/C rank. The organic fraction of the coals is mostly comprised of humic group macerals, with small percentages derived from the inertinite and liptinite groups. The mineral matter of the coals is comprised mainly of calcite and clay minerals. The total organic carbon (TOC, wt%) values of the shale and coal samples are between 2.61 wt% and 43.02 wt%, and the hydrogen index values are between 73 and 229 mg HC/g TOC. Pyrolysis (Tmax, PI), huminite/vitrinite reflectance (Ro, %), and biomarker ratios (CPI, Pr/Ph ratio, Ts/(Ts + Tm) ratio, C32 homohopane ratio (22S/22S + 22R) and C29ββ/(ββ + αα sterane ratio) indicate that the organic matter of the studied coals is thermally immature. When all these data are taken together, Miocene aged coals around Arguvan are suitable for hydrocarbon generation, especially gas, in terms of organic matter type (Type III and Type II/III mixed), organic matter amount (> 10 wt% TOC), however, low liptinitic macerals (< 15%–20%), low hydrogen index (< 200 mg HC/g TOC) and low thermal maturity values inhibit the hyrocarbon generation.


Author(s):  
Listriyanto Listriyanto ◽  
Sugeng Widada ◽  
Basuki Rahmad ◽  
Salatun Said ◽  
Hendaryono Hendaryono

<p class="western" style="text-indent: 0.5in; line-height: 115%;" align="justify"><span style="font-family: Times New Roman,serif;"><span style="font-size: small;">Identifikasi interval batuan yang mungkin berpotensi sebagai batuan induk merupakan langkah awal eksplorasi yang penting, oleh sebab itu perlu dilakukan penelitian tentang potensi batuan sedimen yang mengandung bahan organik dengan kadar tertentu, yang oleh panas dan waktu dapat menghasilkan hidrokarbon dalam bentuk minyak atau gas secara tepat. Penelitian ini bertujuan untuk mengidentifikasi fasies dan potensi batuan induk hidrokarbon Formasi Gumai di Talang Padang, Cekungan Sumatra Selatan. </span></span><span style="font-size: small; font-family: 'Times New Roman', serif; text-indent: 0.5in;">Analisis geokimia guna mengetahui potensi dan kualitas batuan induk dilakukan pada serpih penyusun Formasi Gumai. Hasil analisis potensi dan kualitas Batuan Induk menunjukkan kandungan TOC 3,55 termasuk “sangat baik”. Rock-Eval menunjukkan bahwa serpih berpotensi “sedang” sebagai batuan induk hidrokarbon (S2 = 4,32 kg/ton). Angka Ro (&lt;0,6) menunjukkan tingkat pematangan hidrokarbon belum tercapai. Nilai HI yang relatif tinggi mencerminkan bahwa batuan ini jika mencapai kematangan akan cenderung menghasilkan minyak. Nilai HI antara 456 mgHC/g umumnya berasal dari kerogen tipe II yang secara dominan mengandung unsur organisme laut dan darat.</span></p><p class="western" style="text-indent: 0.5in; line-height: 115%;" align="justify"><em style="text-indent: 0.5in;">Rock Identification intervals that might be as potential source rocks is an important initial exploration step, therefore it is necessary to conduct research on the potential of sedimentary rocks containing certain levels of organic material, which by heat and time can produce hydrocarbons in the form of oil or gas appropriately. This study aims to identify the facies and potentials of the Gumai Formation hydrocarbon source rock in Talang Padang, South Sumatra Basin. Geochemical analysis to determine the potential and quality of the source rock is carried out on the Gumai Formation shale. The results of the analysis of the potential and quality of the Parent Rock showed that the TOC content of 3.55 was "very good". Rock-Eval shows that shale has the potential to be "medium" as a hydrocarbon source rock (S2 = 4.32 kg/ton). Ro (&lt;0.6) indicates the level of hydrocarbon maturation has not been reached. The relatively high HI value reflects that if these rocks reach maturity they will tend to produce oil. HI values between 456 mgHC/g are generally derived from type II kerogen which predominantly contains marine and terrestrial organisms.</em></p>


2014 ◽  
Vol 18 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Jude E. Ogala ◽  
Mike I. Akaegbobi

<p>The concentration and distribution of aromatic biomarkers in coals and shales from five boreholes penetrating the Maastrichtian Mamu Formation of the Anambra Basin, southeastern Nigeria, were investigated by gas chromatography-mass spectrometryto assess the thermal maturity and organic matter input. The study focused on the variations of the relative abundances of naphthalenes, phenanthrenes, and monaromatic and triaromatic steroids identified on the mass fragmentograms. Trimethylnaphthalene(TMN) is the most abundant member of the naphthalene family while methylphenanthrene (MP) is the most abundant phenanthrene family member. The total of phenanthrenes and their isomers was greater than that of naphthalenes. The distribution of these aromatic hydrocarbons and their akyl derivatives was strongly controlled by a selective expulsion mechanism and thermal maturation of organic matter. The low dibenzothiophene/phenanthrene (DBT/PHEN) ratios (0.01-0.06), as well as the enhanced concentrations of 1,2,5-TMN relative to 1,2,7- TMN,indicates organic matter derived mainly from higher plants,and the extract ternary plot of C<sub>27</sub>, C<sub>28</sub> and C<sub>29</sub> monoaromatic steroids suggests a Type III and mixed Type II/III kerogen. The calculated mean vitrinite reflectance (%R<sub>m</sub>), determined from the distributions of the isomers of methyldibenzothiophene ratio (MDR) in the rock extracts, ranged from 0.51 to 1.43. These maturity values indicate that the coal and shale extracts are marginally mature for hydrocarbon generation.</p><p> </p><p><strong>Resumen</strong></p><p>La concentración y distribución de biomarcadores aromáticos en carbones y esquistos de cinco perforaciones en la formación Maastrichtian Mamu de la cuenca de Anambra, en el sureste de Nigeria, fueron analizados a través de un estudio de espectometría cromatográfico y de masa del gas para medir la madurez termal y la entrada de material orgánico. El estudio está enfocado en las variaciones de la abundancia relativa de naftalinas y fenantrenos, y en los esteroides monoaromáticos y triaromáticos identificados en los fragmentogramas de masas. La trimetinaftalina (TMN) es la más abundante de la familia de las naftalinas mientras el metilfenantreno (MP) es el más abundante de los fenantrenos. El tota de los fenantrenos y sus isómeros fue mayor que el de las naftalinas. La distribución de estos hidrocarbones aromáticos y sus alquilos derivados fue controlada ampliamente por un mecanismo de expulsión selectiva y de la maduración térmica de material orgánico. La baja proporción dibenziotofeno/fenantreno (DBT/ PHEN) (0.01-0.06), al igual que las concentraciones mejoradas de 1,2,5-TMN relativas de 1,2,7-TMN indican que la materia orgánica se deriva principalmente de plantas mayores, y del diagrama terniario de los esteroides monoaromáticos C<sub>27</sub>, C<sub>28</sub> y C<sub>29</sub> sugiere un tipo III mezclado con tipos II/III de querógenos. El valor calculado de la reflectancia de vitrinita (%Rm) determinado de la proporción de isómeros de metildibenziotofeno (MDR) en los extractos rocosos oscila de 0.51 a 1.43. Estos valores de madurez indican que los extractos de carbones y esquistos son marginalmente maduros para la generación de hidrocarbono.</p><p> </p>


2021 ◽  
Vol 11 (4) ◽  
pp. 1679-1703
Author(s):  
Liyana Nadiah Osli ◽  
Mohamed Ragab Shalaby ◽  
Md. Aminul Islam

AbstractA comparative analysis on source rock properties has been carried out on the Miocene-Pliocene formations as well as the Quaternary terrace deposits using Rock–Eval pyrolysis results and organic petrography as well as some biomarkers results. Samples were obtained from outcrops of the Quaternary terrace deposits, Pliocene-aged Liang Formation together with the Miocene Miri and Setap Shale formations in Brunei-Muara district, with sample lithologies ranging from coal, coaly shale, shale and lignitic sand. High total organic carbon (TOC) and S2 values ranging from 41.8 to 62.4% and 7.40 mg HC/g rock to 122 mg HC/g rock, respectively, are identified in coals of the terrace deposit, Liang and Miri formations, making these as the best potential source rock due to the “good to excellent” generating potential. Meanwhile, a “fair to poor” potential is exhibited for the coaly shale, shale and lignitic sand samples as a result of their low TOC, HI and S2 values. The organic matter is composed of kerogen type III (gas prone) and type II-III (mixed oil and gas prone). Organic matter in all studied formations originate from a terrestrial-source, as proven by the abundance of huminite. Organic petrographical and biomarkers studies suggest that the coals and lignitic sand samples were deposited in a mangrove-type mire in a lower delta setting, under oxic and limnic to limnotelmatic conditions, except sample DD2-1, which is deposited in a less water-saturated environment. The samples display the presence of bi-modal and normal distribution of n-alkanes. For all of the samples, the dominating plant types in the palaeomire are of soft, herbaceous plants and this is supported by the low vegetation index and moderate Paq values. All the studied samples are thermally immature to early mature, as exhibited by the Tmax values that range from 300 to 437 °C and vitrinite reflectance readings of 0.22% to 0.46%.


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