Potential Hydrocarbon Source Rocks Research Articles

Hydrocarbon source rock potential of the Lower Eocene carbonates from the Abu Darag sub-basin, Gulf of Suez, Egypt: Integrated organic geochemical and petrographic analyses

Twenty-four subsurface samples from the Lower Eocene Thebes Formation in the north Gulf of Suez underwent organic geochemical and petrographic analyses. The aim is to evaluate the hydrocarbon source rock potential and understand the organic facies composition of this pre-rift formation, which received little attention. The Thebes Formation is a potential hydrocarbon source rock in the area of the GS 24–1 well with an average TOC of 1.52 wt% (range 0.51–4.23 wt%). The organic geochemical (HI/OI and Pr/Ph vs Pr/n-C17) and petrographic analyses revealed that the organic matter of this conventionally known marine source rock is made up of both marine and terrestrial sources in the Abu Darag sub-basin. The predominant kerogen type II is comprised mainly of liptinitic (dinoflagellate cysts and amorphous organic matter: AOM) and subordinate vitrinitic macerals, which produced mixed cyclo and normal alkanes and some aromatics when subjected to pyrochromatography. The average Tmax value of 428 °C and UV fluorescence of the palynomorphs and AOM indicate that the organic matter has entered the early oil-window stage. The tectonostratigraphic evolution of the Abu Darag sub-basin affected the Thebes Formation source rock quality. More exploration activities across this sub-basin are needed to fully explore the organic facies composition and hydrocarbon potential of the Thebes Formation.

Combining catalytic hydropyrolysis and GC–IRMS to reconstruct the geochemical characteristics of source rocks in the Baiyun deep-water area of the Pearl River Mouth Basin, China

Petroleum exploration has found that the Baiyun deep-water area of the Pearl River Mouth Basin (PRMB), China, holds abundant oil and gas resources with great prospects. However, conditions restricting offshore drilling in this area present significant challenges to the investigation of source rocks. Core samples are lacking, and any cuttings obtained are generally highly contaminated by drilling mud. As a result, the identification and evaluation of hydrocarbon sources in deep-water areas would be greatly aided by new techniques capable of reliably obtaining the geochemical characteristics of potential source rocks. This study combines catalytic hydropyrolysis (HyPy) and gas chromatography–isotope ratio mass spectrometry (GC–IRMS) to determine the carbon isotope composition of individual n-alkanes covalently bound in kerogen framework. Furthermore, it reconstructs the source and depositional environment of sedimentary organic matter in potential source rocks from the Baiyun deep-water area of the PRMB. The results indicate that the optimized degassing (i.e., degassing under high vacuum at 250 °C for 24 h) can effectively eliminate hydrocarbon contaminants in the kerogen. Determination by GC–IRMS of bound n-alkanes released from the degassed kerogen by HyPy can provide the molecular carbon isotope characteristics of the original organic matter in cuttings contaminated by drilling mud. The results improve the understanding of potential hydrocarbon source rocks in the Baiyun deep-water area of the PRMB.

PETROLEUM POTENTIAL OF MAE TEEP ORGANIC SEDIMENTS, NORTHERN THAILAND

The selected 7 organic sediment samples (3 oil shale samples from Upper Oil Shale, Lower Oil Shale and Oil Shale in Coal A sub-unit, 3 coal samples from Coal A, Coal B and Coal C sub-unit and 1 leonardite sample from Leonardite sub-unit) collected at the northern wall of Mae Teep coal mine were conducted the Hydrocarbon Analyzer with Kinetics (HAWK) pyrolysis in order to assess their petroleum source rock potential. The calculated HI, OI, PI, S2+S3 and Ro were then used to classify the kerogen type and to evaluate the thermal maturity stage of these 7 studied organic sediment samples. Results of the study indicate that all of the organic sediment sub-units of Mae Teep organic sediments have good to excellent hydrocarbon generation potential. HI vs Tmax and HI vs calculated Ro cross-plots results indicate that organic sediments of Coal A, Coal B, Coal C, Oil Shale in Coal A and Upper Oil Shale sub-unit are in the thermal immature stage, while the organic sediments of Lower Oil Shale and Leonardite sub-unit are in the early thermal mature stage. Mae Teep organic sediments are considered to be the high potential hydrocarbon source rock since they have high kerogen yield (S2) (21.49 - 69.8 mg HC/g rock) and their total hydrocarbon generation potential (S1+S2) are also high (22.13-72.12 mg HC/mg rock). These may contribute them to be a good to very good source rock if their maturity reaches the thermal mature stage.

Palynology, palynofacies and organic geochemistry analysis of the late Eocene shale from Meghalaya, Northeast India

Here the depositional environment and hydrocarbon source rock potential of the Kopili Formation is investigated using palynological analysis and Rock-Eval pyrolysis on samples from a borehole section (Borehole BUM14) collected at Umphyrluh area in the Jaintia Hills, Meghalaya. In these Kopili shales, amorphous organic matter is often associated with structural terrestrial organic matter, biodegraded organic matter, charcoal, black carbon debris, dinoflagellate cysts, and spores. The palynotaxa are mainly composed of dinoflagellate cysts comprising eight genera and twelve referable species. Based on the palynological data, the sediments of the study area were deposited in a shallow marine setting under oxygen deficient conditions in an environment that received a continuous terrestrial influx throughout the succession. Rock-Eval pyrolysis and Total Organic Carbon (TOC) analysis determine the quantity, type, and thermal maturity of the associated organic matter. TOC values range from 0.03 to 0.45 wt.% (averaging 0.28 wt.%) and the Genetic Potential (GP) and Hydrogen Index (HI) values vary from 0.04 to 0.24 mg HC/g rock and 22–100 mg HC/g TOC, respectively. These values imply that all the shale samples have very low TOC values (< 0.5%), S1, S2, and Hydrogen Index (HI) values. Although most of the samples are in a mature stage as the average Tmax value is 428.16°C and the Production Index (average 0.16) indicates a potential for oil generation, low Genetic Potential (S1 + S2) and TOC concentrations suggest there is limited potential for oil generation. The HI vs. OI plot and HI vs. Tmax plot show that most of the shale samples fall in the predominantly gas prone domain (mostly Type III and Type IV), because the organic matter is generally derived from a terrestrial source. Thus, the source rock potential for the Kopili shales of the Umphyrluh area is considered to be poor for gaseous hydrocarbons.

Source Rock Potential of Chichali and Samana Suk Formations Deposits in Panjpir Oilfield Subsurface, Punjab Platform, Pakistan

By using total organic carbon (TOC) and Rock-Eval pyrolysis analysis measurements, the hydrocarbon source rock potential of Chichali and Samana Suk formations found in the subsurface of Panjpir oilfield in Punjab platform located in the eastern part of the middle Indus Basin was investigated. Twenty two core samples were collected from producing well. The analysed samples of Chichali formation contains TOC ranging between 0.99-4.61 wt.% having average TOC of 1.51 wt.% and the S2 values of Rock-Eval show the poor to fair generative potential with values ranging from 0.99-3.08 mg HC/g rock. The samples have low hydrogen index values ranging from 21-302 mg HC/g TOC and also most of the samples have low T_(max ) values ranging from 422-432 °C and have OI values ranging from 15-82 mg CO2/g TOC. Samana Suk formation samples have TOC ranging between 0.28-1.38 wt.% having average TOC of 0.84 wt.%. S2 values of Rock-Eval shows poor generative potential with values ranging from 0.05-2.99 mg HC/g rock. The samples have low hydrogen index values ranging from 13-322 mg HC/g TOC and T_(max) values ranging from 423-435 °C, and have OI values ranging from 41-182 mg CO2/g TOC. On the basis of analysis performed only one sample from Chichali and five samples of Samana Suk formations have entered early maturity zone, while all remaining samples lie in immature zone as indicated by HI vs T_(max) plot. HI vs OI plot and HI vs T_ (max) indicates the presence of kerogen Type III. All of the samples from Samana Suk formation shows poor generative potential as compared to Chichali formation having fair generative potential as indicated by S2 vs TOC plot. Hence, from the results some minor gas could be expected to have been generated from Chichali formation in Panjpir oilfield subsurface.&#x0D;

Evaluation of hydrocarbon source rock potential: Deep marine shales of Belaga Formation of Late Cretaceous-Late Eocene, Sarawak, Malaysia

In the Sibu-Tatau region of Sarawak, the Belaga Formation (Late Cretaceous- Late Eocene turbidites) is interpreted in relation to a submarine fan model deposited in the extinct ocean basin of the proto-South China Sea. A number of clastic rocks, which include sandstone, siltstone, mudstone, and black shale, define the formation. While it is considered one of the Rajang group's extensive and well-studied formations, yet no comprehensive studies have been carried out on the shales in Sarawak, Malaysia, to interpret their importance as a source rock to oil and gas fields. The present study highlights the prominent lithofacies in addition to the detailed source rock characterization of each member of Belaga Formation to discuss the potential source rock intervals present in these Cretaceous to Eocene rock units. Four major types of shales and mudstones facies were observed in the field, i.e. (i) Variegated colored shale facies (VSF), (ii) Black “Papery” shale facies (BSF), (iii) Gray to black mudstone facies (GMF), (iv) Silty/sandy shale facies (SSF). They show hemipelagic settling in a calm environment to turbiditic deposition at levees as well as distal lobe depositional environment. In this study primary geochemical studies such as Rock-Eval pyrolysis and Total Organic Carbon (TOC) analysis were used to classify the thermal maturity, organic matter richness, and kerogen type of the studied shales. Forty-six selected shale samples were studied from the formation, including samples from members of the Layar (Upper Cretaceous), Kapit (Paleocene to Early Eocene), Pelagus (Early to Middle Eocene), Metah (Middle to Late Eocene) and Bawang (Eocene). The shales of Belaga Formation typically display low to moderate source rock potential, which is obvious by low TOC contents between 0.14 wt% and 7.22 wt% (average of about 2.97 wt%) and show a wide range of maturity (immature to over mature) evident from very low to very high Tmax values ranging from 293 °C to 610 °C. The results show that the kerogen is of type IV, with some units can be potential sources of gas.

Hydrocarbon source-rock potential of the Jurassic succession in eastern part of the North Western Desert, Egypt

The hydrocarbon potential is determined by the quantity and quality of organic matter encountered in the Jurassic sediments in two wells at the Northern Western Desert. It utilizes to define the zones of oil and gas using the well logging data for calculates the total organic carbon (TOC). The evaluation of source rock has been based on two steps; the first one depended on the geochemical parameters including TOC, S1, S2, Tmax, and Vitrinite reflectance (Ro %) of two wells JG-1 and JD-4. The second step was to calculate (TOC) from wireline logs. The well log types utilized in such kind of analysis are the density log, sonic log, resistivity log and gamma-ray log. The stratigraphic sequence, in the studied wells ranges in age from Paleozoic to Recent. The present work focuses on the Jurassic rocks represented by Khatatba Formation as they include the main source horizon. Based on the obtained results, Jurassic sediments called as fair to excellent source rock potential. The genetic type of organic matter can be identified through the study of pyrolysis data, which indicate that is rich in mixed oil and gas-prone kerogen except few samples reflect type I organic facies.

Distribution and geodynamic setting of the Late Neoproterozoic– Early Cambrian hydrocarbon source rocks in the South China and Tarim Blocks

Abstract The Late Proterozoic–Early Cambrian, one of the most critical intervals in Earth’s history, is characterized by dramatic tectonic, climatic, oceanic and biological changes. In China, thick black mudstones and shales formed in intracontinental rifts during this period, associated with interglacial and postglacial phases of the Neoproterozoic global-scale glaciations. Previous studies have shown these black mudstones and shales were potential hydrocarbon source rocks that contributed to the Proterzoic-Early Paleozoic oil and gas discoveries. However, less work has been done to systematically characterize these important source rocks. In the South China Block, these excellent source rocks (~30–200 m) were discovered in the Nanhua (Cryogenian), Sinian (Ediacaran), and Lower Cambrian Systems, with total organic carbon (TOC) contents of 2–10%. In contrast, black mudstones in the Nanhua and Sinian Systems in the Tarim Basin had low TOC contents (0.3–1.5%) perhaps affected by intense weathering, whereas excellent source rocks (TOC ~ 6–18%) existed in the Cambrian Yuertusi Formation (12–80 m). Our study indicates the formation and distribution of excellent source rocks were mainly controlled by the Late Proterozoic–Early Cambrian rifts, which was supported by a decrease in thickness towards marginal areas especially for the Nanhua and Sinian Systems. The Early Cambrian source rocks occurred pervasively due to a global marine transgression and those formed under deep-water anoxic conditions at slope areas were of the best quality with TOC up to 15%. These source rocks could be focuses for future exploration in the deep or ultra-deep depths in the studied blocks as well as their peripheral areas.

Biodegraded bitumens dispersed in Vendian (Neoproterozoic) rocks of the Khatyspyt Formation, Northeastern Siberia

The organic matter of the Vendian (Neoproterozoic) Khatyspyt Formation was investigated. The new data obtained from the GS and GS-MS analyses include: high UCM humps andheightened peaks of steranes and terpanes against the backdrop of C27+ alkanes on chromatograms of saturated hydrocarbons fractions of five samples; predominance of С21-С26 in n-alkanes distribution; the presence of 12- and 13-monomethylalkanes on chromatograms and demethylatedterpanes on filtered chromatograms (m/z 191 and 177). Besides, dispersed bitumens with biodegraded hydrocarbons have been for the first time identified in carbonate and carbonate-siliceous rocks of the Khatyspyt Formation. Also 8,14-sekohopanes resistant to biodegradation and gammacerane were established. The revealed features of the composition and distribution of hydrocarbons showed that their source was the autochthonous (syngeneic) organic matter of the Khatyspyt Formation,one of the potential hydrocarbon source rock of Northeastern Siberia. The composition and content of bitumen are found to be controlled by the inputs of primary organisms (eukaryotes and prokaryotes)which lived in Vendian seas, by changing redox conditions of sediment deposition and transformation, as well as by relatively little effect of temperature and high degree of biological oxidation in hypergenesis. The patterns of bitumen distribution throughout the section show, that besides the overlying deposits,their accumulations canbe discoveredin the Khatyspyt Formation.

Redox conditions on the Anadarko Shelf of Oklahoma during the deposition of the “Mississippian Limestone”

A multiproxy approach, including stable nitrogen isotopes and redox sensitive trace elements, was employed in order to evaluate the impact of depositional redox conditions on organic matter accumulations within the Mississippian Limestone interval in the Anadarko Shelf of Oklahoma and also to investigate hydrocarbon source rock potential of the Mississippian Limestone in the study area. Nitrogen isotopes (δ 15 N), total organic carbon (TOC), and concentrations of redox-sensitive trace elements (Cu, Mn, Mo, Ni, U, V) were measured on samples from a core drilled in Canadian County, Oklahoma. Values of TOC are between 0 and 2.5 wt. % and average 0.8 wt. % in the studied interval of the core. The δ 15 N data (3‰–14‰, average 8 ± 1‰) indicate sediment deposition under oxic to suboxic water conditions. This interpretation of depositional redox conditions is supported by elemental redox proxies which show no enrichment relative to average carbonate. Our geochemical data suggest that the Mississippian Limestone is unlikely to be an oil source rock due to pervasively oxic to suboxic depositional redox conditions which would have resulted in oxidation of organic matter. • Water column and benthic redox conditions at time of deposition were oxic-suboxic. • Depositional redox does not influence organic matter accumulation in study site. • Mississippian Limestone sediments have poor oil source rock potential due to oxygenated conditions during deposition.

Sedimentary environment and organic matter accumulation of Neoproterozoic black shale in the North China Craton: A case study of the Tonian Baishugou Formation in the Luonan area

With acceleration of “oil exploration near the source” in the petroleum industry, black shales (BS) play an increasingly important role in oil and gas exploration. Meso-Neoproterozoic BS are well developed in the North China Craton (NCC), China, many of which are identified as potential hydrocarbon source rocks. Although BS from the Mesoproterozoic Era has been widely investigated, few studies were focused on the Neoproterozoic BS so far. Based on petrology and geochemistry analysis, the sedimentary environment, provenance and organic matter accumulation of two BS layers in the Tonian Baishugou Formation from Sujiacun section, Luonan Area, southern NCC were investigated. It suggests that the lower BS (LB) was deposited in a shallow and non-stratified cratonic-interior sea environment with unstable dysoxic or suboxic conditions. The seawater salinity increased from brackish to marine facies conditions due to the decrease of runoff caused by climate cooling. The Upper BS (UB) was deposited in an open paleomarine environment with stable suboxic conditions and brackish salinity in continuously humid and hot paleoclimate. Both BS were derived from granitoids formed by the ca.2.5 Ga collisional-thermal events in the NCC. The OM accumulation rate of UB is higher than that of UB while LB records lower OM loss rate. On these bases, two developmental modes for the BS from the Baishugou Formation were established.

Early Diagenesis of Lacustrine Carbonates in Volcanic Settings: The Role of Magmatic CO2 (Lake Dziani Dzaha, Mayotte, Indian Ocean)

Lacustrine carbonates formed in rift settings are increasingly studied not only as archives of Earth chemical and climatic history but also as potential hydrocarbon source rocks and/or reservoirs. The role of magmatic gases in their formation and diagenetic evolution, hence in their reservoir properties, remains unclear. We studied the first meter of carbonate sediment of the Dziani Dzaha volcanic crater lake (Mayotte Island) and developed a reactive-transport model with CrunchFlow software that allows the quantification of diagenetic reactions by considering depth-dependent burial rates and sediment compaction. The model is constrained by the previously documented solid-phase compositions of the lake sediment and new data consisting of 14C dating of plant macroremains to characterize the sediment age model, chemical composition of sediment pore waters, and chemical and isotopic composition of gases dissolved and bubbling through the lake. These new data reveal a massive magmatic CO2 contribution to the dissolved inorganic carbon of the lake, which fuels the primary productivity and carbonate formation. A pH value of 9 in the surface sediment pore waters induces supersaturation relative to aragonite, hydromagnesite, and saponite. At 1 m depth in the sediment, our model predicts that magmatic CO2 inflows and organic matter degradation account for 22 and 2 mol % dissolved inorganic carbon, respectively. The magmatic CO2 inflows result in a pH decrease at depth, leading to the destabilization of hydromagnesite, while saponite and aragonite remain stable. These results demonstrate the role of magmatic CO2 in fueling carbonate production and controlling the diagenetic evolution of sediment mineralogy.

Microfossil assemblages (diatoms, calcareous nannofossils, and silicoflagellates), paleoenvironment, and hydrocarbon source rock potential of the Oligocene Ruslar Formation at Karadere, Bulgaria

The Oligocene Ruslar Formation, an equivalent of the Maykop Suite, is a potential hydrocarbon source rock in the western Black Sea Basin. In contrast to the offshore areas, the depositional environment and hydrocarbon source rock potential of onshore Bulgaria sediments are largely unknown. Hence, a 14-m-thick section of the Ruslar Formation, exposed near Karadere (Black Cape) along the Black Sea coast, provides an excellent opportunity to study the upper part of the Ruslar Formation. Here, laminated diatomrich mudstones with frequent thin sandstone beds and a prominent concretion horizon are exposed. Furthermore, the fossil diatom assemblages provide a key component to understand the paleoenvironment. Overall, Paleogene diatoms are understudied in the Black Sea Basin and therefore only a genus-level study is undertaken here. The studied Ruslar Formation contain remarkably diverse and wellpreserved diatom assemblage with 23 different genera. The most frequent genera are Paralia, Distephanosira, and Stephanopyxis. Common genera include Coscinodiscus, Hemiaulus, Pseudopodosira, Rouxia, and Xanthiopyxis. Rare taxa include Actinoptychus, Asterolampra, Azpeitia, Delphineis, Distephanosira, Diploneis, Eunotogramma, Eurossia, Lyrella, Liradiscus, Plagiogramma, Radialiplicata, Rutilaria, Saeptifera, and Triceratium. The diatom assemblages together with calcareous nannoplankton, silicoflagellates, and the presence of rare foraminifera indicate a fully marine neritic environment without major salinity variations. The calcareous nannoplankton investigated can be assigned to biozone NP23 (Early Oligocene). The exposed fragment of the Ruslar Formation was deposited after the low salinity Solenovian event, which represents the maximum isolation of the Paratethys present in the lower part of the NP23. Bulk geochemical parameters from 35 samples (avg. TOC: 1.80% wt.; avg. HI: 226 mg HC/g TOC) show that the exposed part of the Ruslar Formation contains type II-III kerogen and a fair to good hydrocarbon potential. The Ruslar Formation is immature (avg. Tmax: 424 °C), but may generate about 0.5 tons of hydrocarbons per square meter if mature. Biomarker proxies support the low maturity and are characterized by diatom-related biomarkers (24-norcholestane; C25HBI alkanes and thiophenes). Land-plant-derived biomarkers suggest a significant input of angiosperms. Based on biomarker ratios, the depositional environment was oxygen-depleted but probably not strictly anoxic. Reworking of biomass by chemoautotrophic bacteria is suggested by the presence of 28,30-bisnorhopane.

Source rock potential and depositional environment of the Lower Oligocene İhsaniye Formation in NW Turkey (Thrace, Karaburun)

The Lower Oligocene succession of the Ihsaniye Formation, exposed at Karaburun on the Turkish (Thrace) coast of the Black Sea, provides insights into potential hydrocarbon source rock extent in the southwestern part of the Black Sea Basin. Presently, no detailed study of the Ihsaniye Formation exists with regards to organic matter content and type. We analyzed 78 fine-grained samples from a c. 70-m-thick section near Karaburun. Relatively high total organic carbon (TOC) contents (average 1.45 wt.%) are present in the lower part of the Ihsaniye Formation; the hydrogen index values reach a maximum of 252 mg HC/g TOC, indicating the presence of type III-II kerogen, and the organic matter is thermally immature (Tmax 418 °C). The presence of foraminifera and TOC/S ratios below 2.8 confirm a fully marine environment. Elevated TOC contents and very low pristane/phytane ratios indicate an oxygen-depleted environment during deposition of the lower part of the Ihsaniye Formation. The quartz/clay minerals ratio suggests a deepening trend in the lower part of the succession and a shallowing trend in the upper part. Peculiarly, the low salinity Solenovian Event (in nannofossil zone NP23) is not developed although Sr isotope ratios indicate that the basin was only connected to the Mediterranean for short periods during deposition of the Ihsaniye Formation.

Hydrocarbon source rock potential of Miocene diatomaceous sequences in Szurdokpüspöki (Hungary) and Parisdorf/Limberg (Austria)

Abstract Diatomaceous sediments are often prolific hydrocarbon source rocks. In the Paratethys area, diatomaceous rocks are widespread in the Oligo-Miocene strata. Diatomites from three locations, Szurdokpüspöki (Hungary) and Limberg and Parisdorf (Austria), were selected for this study, together with core materials from rocks underlying diatomites in the Limberg area. Bulk geochemical parameters (total organic carbon [TOC], carbonate and sulphur contents and hydrogen index [HI]) were determined for a total of 44 samples in order to study their petroleum potential. Additionally, 24 samples were prepared to investigate diatom assemblages. The middle Miocene diatomite from Szurdokpüspöki (Pannonian Basin) formed in a restricted basin near a volcanic silica source. The diatom-rich succession is separated by a rhyolitic tuff into a lower non-marine and an upper marine layer. An approximately 12-m thick interval in the lower part has been investigated. It contains carbonate-rich diatomaceous rocks with a fair to good oil potential (average TOC: 1.28% wt.; HI: 178 to 723 mg HC/g TOC) in its lower part and carbonate-free sediments without oil potential in its upper part (average TOC: 0.14% wt.). The composition of the well-preserved diatom flora supports a near-shore brackish environment. The studied succession is thermally immature. If mature, the carbonate-rich part of the succession may generate about 0.25 tons of hydrocarbons per square meter. The diatomaceous Limberg Member of the lower Miocene Zellerndorf Formation reflects upwelling along the northern margin of the Alpine-Carpathian Foreland. TOC contents are very low (average TOC: 0.13% wt.) and demonstrate that the Limberg Member is a very poor source rock. The same is true for the underlying and over-lying rocks of the Zellerndorf Formation (average TOC: 0.78% wt.). Diatom preservation was found to differ considerably between the study sites. The Szurdokpüspöki section is characterised by excellent diatom preservation, while the diatom valves from Parisdorf/Limberg are highly broken. One reason for this contrast could be the different depositional environments. Volcanic input is also likely to have contributed to the excellent diatom preservation in Szurdokpüspöki. In contrast, high-energy upwelling currents and wave action may have contributed to the poor diatom preservation in Parisdorf. The hydrocarbon potential of diatomaceous rocks of Oligocene (Chert Member; Western Carpathians) and Miocene ages (Groisenbach Member, Aflenz Basin; Kozakhurian sediments, Kaliakra canyon of the western Black Sea) has been studied previously. The comparison shows that diatomaceous rocks deposited in similar depositional settings may hold largely varying petroleum potential and that the petroleum potential is mainly controlled by local factors. For example, both the Kozakhurian sediments and the Limberg Member accumulated in upwelling environments but differ greatly in source rock potential. Moreover, the petroleum potential of the Szurdokpüspöki diatomite, the Chert Member and the Groisenbach Member differs greatly, although all units are deposited in silled basins.

Organic facies and palynology from the middle to late Devonian of the Pimenteiras Formation, Parnaíba Basin, Brazil

A detailed study of organic facies and palynological assemblages was carried out on 11 samples of potential hydrocarbon source rocks of the Pimenteiras Formation, an outcropping at the western edge of the Parnaíba Basin, Brazil. The main objectives are to characterize the depositional paleoenvironment and hydrocarbon source potential. The selection of this outcrop occurred in the function of its preservation and accessibility, and the samples collection observed 1 m of vertical spacing. Generally, the organic matter and the palynomorphs showed a good state of preservation and fluorescence. The most notable spores and acritarchs and phycomates species were discussed in light of international biozones, and the chronostratigraphic range defined as Late Eifelian - Latest Frasnian in age. TOC results show ranges from 0.40 to 2.91%, with most samples showing greater than 1%, thereby holding a high potential generation. The S1 values were virtually null, and the S2 peak ranged from 0.9 to 5.33 mg/g. The kerogen 435 °C, and the ICE between 4.0 and 4.5 demonstrating the material immaturity. For the palynofacies associations definition, only 10 out of the 25 total quantified of subgroups of kerogen categories were considered in the counting of 300 particles. A dendrogram constructed based on these results through cluster analysis, revealed four palynofacies, as follows: I constituted mainly by palynomorphs (acritarchs, prasinophytes and sporomorphs); II – Dominance of Translucent organic matter (cuticles, epidermal tissue and translucent phytoclasts with and without structure); III - Dominance of Opaque/non-fluorescent (opaque phytoclasts and non-fluorescent AOM) and IV - Dominance of AOM fluorescent (amorphous organic matter with fluorescence). The palynomorphs are the most abundant constituents of all studied kerogen. Quantitative analysis based on the distribution of palynomorphs groups throughout the section indicates the dominance of sporomorphs in the palynological assemblages from the Middle Devonian aged samples. On the other hand, occurred the predominance of microplankton elements in the Late Devonian aged samples. Thus, the depositional paleoenvironment was established as a distal oxic mud-dominated shelf with the deltaic influence of the Late Eifelian to Late Givetian, and there is a tendency distal (dysoxic-anoxic ‘shelf’) from the Frasnian, which indicates the maximum flooding surface.

Hydrocarbon Source and Reservoir Rock Potential of the Paleocene Hangu Formation in the Himalayan Foreland Basin, North West Pakistan: Insight from Geochemical and Diagenetic Study

The detail study of the Paleocene Hangu Formation consisting of sandstone, carbonaceous shale, coal, and laterite has been carried out for its source and reservoir rock potential in the Salt Range, Surghar Range, and Attock-Cherat Ranges. The TOC values of the shales range from 0.33-11.19 (2.97 wt. %) and are characterized as good to very good quality source rock except the samples from Attock-Cherat Ranges. Similarly, the free (S1) and cracked hydrocarbons (S2) amount are very small suggesting Hangu Formation as a poor source rock for free and cracked hydrocarbons except the samples from the Lumshiwal Nala. The generative potential, type of kerogen and thermal maturity calculated on the basis of TOC, S1, S2, HI, PI and Tmax all characterized Hangu Formation as fair to excellent gas or oil source, type III and mixed type III/II kerogen and immature source rock. The Hangu Formation sandstone is brownish to yellowish brown, fine to coarse grained, medium to thick bedded and massive in places. The major diagenetic changes observed in a sandstone of the Hangu Formation are; compaction, cementation, replacement and grain fracturing. The effect of mechanical compaction is more evident than that of chemical compaction. Grain contact ranges from pointed to long through sutured. The type of cement present includes silica-cement, calcite-cement, dolomite-cement, and iron-oxide cement. Silica-cement is present as both overgrowth and pore-filling cement. Clay rim is present around few grains. The process of early calcite cementation, mechanical compaction, silica, and iron oxide cementation destroys the reservoir properties of the Hangu Formation sandstone. There is no visible porosity observed except the dissolution of few grains at their margins. However, during the process of uplifting such porosity usually filled by the iron- oxide cementation. Hence, Hangu Formation is an immature source rock with a poor reservoir potential.&#x0D;

Organo-petrographic and geochemical characteristics of Gurha lignite deposits, Rajasthan, India: Insights into the palaeovegetation, palaeoenvironment and hydrocarbon source rock potential

The sedimentary sequence containing lignite deposits in Gurha quarry of the Bikaner-Nagaur Basin (Rajasthan) has been investigated. The samples from lignite and allied shale horizons were evaluated for petrographical, palynological, palynofacies and organic geochemical inferences, to depict the source flora and to reconstruct the palaeodepositional conditions prevailed during the sedimentation. An assessment for the hydrocarbon generation potential of these deposits has also been made. The results revealed the dominance of huminite macerals and phytoclasts organic matter (OM) indicating the existence of forested vegetation in the vicinity of the depositional site. A relatively high terrigenous/aquatic ratio (TAR) and the carbon preference index (CPI) are also suggesting the contribution of higher plants in the peat formation. However, the n-alkane distributions, maximizing at n-C17 and n-C29, showed inputs from the algal communities along with the higher plant derived organic matters. Recovered palynomorphs of the families Onagraceae, Meliaceae, Arecaceae, Rhizophoraceae, Rubiaceae, Ctenolophonaceae, etc. together with oleanene and ursane types of triterpenoids suggest the contribution from angiosperms source vegetation. Interestingly, the presence of Araucareaceae and Podocarpaceae pollen grains shows the existence of gymnosperms vegetation. Further, the presence of tetracyclic diterpanes; demethylated ent-beyerane, sandaracopimarane, pimarane, and Kaurane type of compounds confirms the contribution of conifers. The variation in the values of the coefficient of non-equality (H: 0.68%–7.56%), the standard deviation (δ: 0.04%–0.16%) and the coefficient of variability (V: 16.10%–46.47%), also shows the heterogeneity in the source organic matter.The various petrographical indices, palynological entities, and geochemical parameters indicate that the peat-forming vegetation was accumulated under a mixed environment and fluctuating hydrological settings. The interpretation of palynofacies data on APP (Amorphous organic matter-Phytoclast-Palynomorphs) diagram suggests that the accumulation of organic matter occurred in a dysoxic-suboxic condition in a proximal (to land) setting with the shift to an anoxic condition in distal setting towards the termination of sedimentation. The huminite (ulminite) reflectance (Rr) values (av. 0.28%) showed a good relationship with average Tmax value (414 ​°C), suggesting the immaturity. The TOC content ranges of 13–59 ​wt.%, and HI values vary between 101 and 546 ​mg HC/g TOC in the studied samples. Collectively, the studied lignite and shale samples have the admixed kerogens (Type III–II) and exhibit the ability to generate the gaseous to oil hydrocarbons upon maturation.

Burial History, Thermal Maturation, and Source Rock Evaluation of Ngimbang Formation in East Java Basin

East Java Basin is the back-arc basin and it was the result of collision between the Indian Plate and Sunda Microplate. East Java Basin was formed in Early Tertiary subduction and it is related on the process in Java. In the exploration of Indonesian Basin over years, East Java is one of the successful hydrocarbon producers in Indonesia. In East Java Basin especially Rembang Zone, The Middle Eocene Ngimbang Formation is known as source rock materials. It consists of sandstone, siltstone, limestone, shale, and coal seams. The objective of this research is to determine the hydrocarbon source rock potential based on geochemical analyses and thermal maturation by making basin model. The main target source rock formation is Middle Eocene Ngimbang Formation. Log, seismic, and geochemical sample are the primary data in this research. These methods help the sense of exploring the new hydrocarbon potential. According to geochemical analyses, the source rock potential within TOC value in this area is good – very good. Fine sediments of Middle Eocene Ngimbang Formation tend to produce oil and gas originated from kerogen types II/III. Furthermore, the migration pathway started from south to north. Generation, migration, accumulation, and preservation occurred in Early Miocene.

Storm-induced concentration of sulfurized, marine-origin, organic matter as a possible mechanism in the formation of petroleum source-rock

Abstract Black shales, though laminated, are not systematically synonymous with quiet conditions of deposition. A number of papers report about black shales yielding sedimentary structures echoing relatively high hydrodynamic conditions. Here we examine two sedimentary sequences pertaining to the Late Jurassic Argiles de Châtillon Formation of the Boulonnais area (Northernmost France), each of them including a meter-thick black-shale horizon. The two laminated black shales contain sulfurized (i.e., organic S-rich) organic matter, reaching a maximum of 9%. However, some differences set the two black shales apart. The lower one was deposited under calm, suboxic to anoxic, bottom-water conditions (the « classic » way); the upper black shale was deposited under oxic, agitated bottom-water conditions, not compatible with stable sulfidic conditions required for organic-matter sulfurization. The upper black shale experienced hydrodynamically-induced concentration of sulfurized, recalcitrant organic matter of marine origin. The sulfurized organic matter could be preserved and quantitatively accumulated owing to its non-putrescible nature, leading to the formation of a potential hydrocarbon source rock. The association of pyrite inclusions with sulfurized organic matter probably modified the hydrodynamic behavior of organic particles. The storm-induced remobilization and concentration of sulfurized organic matter implies that the “sulfurization factory” operated in proximal, shallow environments such as estuaries, mud flats or mangrove environments. Such a model is in agreement with findings from modern coastal/shelf environments (notably mangroves) and fully transposable to many other sedimentary situations of any geological time period.