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Kerogen Maturity based on Vitrinite Reflectance
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Organic matter quantity, quality and maturity studies was carried out on the Paleocene Ewekoro Formation to assess its source rock potentiality using organic geochemical and petrographic techniques. Organic richness assessment based on Total Organic Carbon content (TOC), Genetic Potential, Soluble Organic Matter (SOM), hydrocarbons generated before...
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... O values range from 0.13-0.25 %, (Av. 0.20)-they are thermally immature and a plot of Hydrogen Index (HI) against Vitrinite Reflectance ( Figure 6) also shows that the samples are immature. Also, figures 7 and 8 shows that the kerogen are immature and has low level of convertibility to hydrocarbons. ...
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... Assuming a recovery coefficient of 3.0, the TOC o of these Lower Cambrian shales reach 22%. In addition, the plot of S 1 versus TOC content reflects that all of the studied shales from the Lower Cambrian are characterized by autochthonous hydrocarbons (Figure 2(a)) [50,51]. Pyrolysis parameters, such as T max versus hydrogen indices (HI), are often used to indicate kerogen types. ...
In this study, we conducted systematic analysis of total organic carbon (TOC) content, lipid biomarkers, carbon isotopes of kerogen (δ13Ckerogen), and mineral composition in Niu-ti-tang (Є1n) and Pa-lang (Є1p) shales from Guizhou Province in order to provide a better understanding of the organic sources and marine environmental condition during deposition of the Lower Cambrian shales of South China. The results show that a broad variety of lipid biomarkers, such as n-alkanes, pristane, phytane, terpanes, hopanes, and steranes, are in these shales, which suggests a significant contribution of various paleobios with bacterial microorganisms and algae thriving under a low-salinity and stable anoxic environment. The negative δ13Ckerogen value (minimum −36.4‰) and occurrence of pyrite (1–7.5%) and carbonates (2.4–57.3%) indicate that bacterial sulfate reduction prevailed under anoxic conditions during deposition of the Lower Cambrian shales. Moreover, the difference in mineral and δ13Ckerogen composition between Є1n and Є1p shales might imply significant changes in primary production and paleoocean environments due to sea-level rise, as shown by the higher average TOC content in Є1p shales (2.52%) compared to that in Є1n shales (1.79%). The covariances of TOC content and mineral and δ13Ckerogen composition suggest that the Є1p shales might have been deposited under a higher sea level associated with high primary productivity, compared to Є1n shales. Thus, high primary productivity driven by sea-level rise is suggested to be the main controlling factor on organic matter enrichment in Є1p shales under stable anoxic conditions.
... Type of kerogen identification by HI vs OI plot in Van Krevelan diagram (after El Kammar, 2015). Furthermore, the cross plots of S 2 versus TOC values are also indicated that the outcrop samples from Takream Formations run into kerogen type IV ( Fig.6; Katz, 1994;Madukwe, 2014). S 2 vs TOC of the Rock-Eval data, indicate kerogen type IV (Katz, 1994;Madukwe, 2014). ...
... Furthermore, the cross plots of S 2 versus TOC values are also indicated that the outcrop samples from Takream Formations run into kerogen type IV ( Fig.6; Katz, 1994;Madukwe, 2014). S 2 vs TOC of the Rock-Eval data, indicate kerogen type IV (Katz, 1994;Madukwe, 2014). ...
Study organic matter quality in the Battambang province, onshore Cambodia is essential for the petroleum source rock. This paper aims to characterize the mineral compositions, TOC, kerogen types, and genetic potential in limestone and calcareous shale using petrographic thin section, TOC, and Rock-Eval Pyrolysis analyses, respectively. Eight outcrop samples were selected for analysis. The results demonstrated that the limestone and calcareous shale samples compose of carbonate mud and less amount of calcite mineral, and other organic matter. Furthermore, TOC values of limestone samples range from 0.03 wt% to 0.4 wt%, averaging = 0.13 wt%, indicated as poorly source rock. By the way, calcareous shale samples have TOC values range from 0.35 wt% to 1.43 wt%, suggested as poorly to good source rock. Moreover, the cross-plot of HI vs OI of limestone and calcareous shale samples indicated the kerogen type IV, an inert type of the organic matter and incapable of generating petroleum. The genetic potential values of those outcrop samples are very low, which range from 0 mgHC/ grock to 0.04 mgHC/ grock, indicate very poor hydrocarbon generation potential. Therefore, those source rocks contained mainly dead organic carbon with no hydrocarbon generation potential.
... It determines the types of organic matter in the rock. Likewise, it is used to determine maturity (Madukwe, 2014;El-Nady et al., 2015), and it has been observed that all samples of Ain Zalah well (Sargelu) are within the maturity range (oil window) while the samples of wells Baiji and Kand fall within the immature zone and graded to the mature zone. In the formation of Kurrachine in the Baiji well two samples fall within the maturity zone and two samples within the immature zone, while in K and Well, three samples within the immature zone and only one sample within the maturity zone. ...
A total of 56 cuttings samples of Sargelu and Kurrachine formations from different wells (Ain Zalah, Baiji, and Jabal Kand) in northern Iraq have been investigated in this study. Both the Sargelu and Kurrachine formations were examined using Rock-Eval pyrolysis to assess the richness of organic matter and thermal maturity level. The Sargelu Formation Have Total Organic Carbon wt.% ranged from 0.22–2.52 wt.%, average 1.26 wt.% in Ain Zalah Well, and between 0.57–8.90 wt.%, average 2.95 wt.% in Baiji Well, and between 0.81–11.80 wt.%, average 5.01wt.% in for Kand Well. It is considered a potential source rock based on total organic carbon content. total organic carbon wt. % in Ain Zalah and Kand in the Kurrachine Formation is considered poor source rock with a total organic carbon content of 0.17, 0.39 wt. %, respectively, while in Baiji Well is considered moderate source rock with total organic carbon content 0.53 wt. %. The Rock-Eval data are not always sufficient to define the kind of organic matter through the use of the van Krevelen diagram because HI and OI are affected by both matrix mineralogy and the kerogen mixture. For accurate assessments of the source rocks, gas chromatography has been relied on, which provides a direct indication of the kerogen type as well as the type of hydrocarbons that kerogen can generate during maturity. Gas chromatography analysis indicates that all selected samples contained type II kerogen. The highest value of the TAS/ (MAS+TAS) ratio was found in Ain Zalah samples (Sargelu Formation), and this result indicates the occurrence of an aromatization process with increasing thermal maturation.
... Shale formations are generally defined as low permeable sedimentary rocks consisting of different clays with other minerals . The quality of hydrocarbons present in shale formation is estimated by kerogen and amount of total organic carbon (TOC) (You et al., 2019;Donadelli et al., 2019;Madukwe, 2014;Pan et al., 2020). Their permeability and porosity capacity depends on the type of clay, clay composition and minerals present. ...
Wellbore stability is essential to be maintained during drilling operation. It is on target due to many issues among them shale hydration is most critical problem using water-based drilling fluids especially. The reactive clay minerals of shale have greater affinity towards water and show swelling when interact with water and make wellbore conditions unstable. Different inhibitors have been utilized to inhibit water invasion. Among them, polymers proved to be efficient and biodegradable. In this paper, responsible clay minerals for hydration and their reactivity towards water is explained. The parametric mechanism of hydration and inhibition are thoroughly reviewed. In this review paper, the inhibition performance parameters of polymers are presented. Polymers utilized in WBDF are critically reviewed with respect to their inhibition ability based on the performance parameters like electrostatic interaction, hydrogen bonding with clay minerals, thermal stability, and their effect on drilling fluid rheology. Different researchers have explained some of the parameters. But they are found to be insufficient to explain all the important parameters. There are other parameters to investigate the polymer’s performance that are required to be explained for an efficient inhibition. These parameters are electronegativity difference in the active site of polymer, hydrophobicity, concentration, and agglomeration. These parameters are also important to discuss because they affect polymer’s performance and drilling fluid’s rheological properties. Nanoparticles have been used for inhibition with polymers and their effectiveness to plug nanopores is also reviewed. Some of the polymers were found to be unstable and contaminating nanoparticles. The reason behind this problem have also been explained parametrically here. The limitations of utilized polymers have been discussed in this paper w.r.t. performance parameters. Polymer performance and characterization results are presented and evaluated w.r.t. to performance parameters. Future perspective for a better inhibition performance is the utilization of a polymer with improved performance parameters.
The evaluation of shale source rocks is one of the most basic and important processes during shale gas exploration to estimate the hydrocarbon genetic potential, especially for shale source rocks at high-over maturity. This study focuses on the geochemistry of Niutitang shale at high-over maturity to identify the practicability of organic matter abundance calculation. Ninety-eight Niutitang shale samples from outcrops in the Micangshan-Hannan Uplift were selected and tested. The geochemical characteristics of the Niutitang shale source rocks including the total organic carbon (TOC), pyrolysis data, thermal maturity, kerogen types and clay mineral composition, were investigated using tests of C/N elemental analysis, Rock-Eval, bitumen reflectance (R b ), organic carbon isotope (δ ¹³ C org )and X-ray diffraction (XRD). Then, the formulas for calculating the coefficient of original TOC (Kc)and original genetic potential S 1 +S 2 (Ks)were deduced using the pyrolysis data and the results before and after calculation were analyzed. The result of the present work imply that it is necessary and reasonable to calculate the original abundance of organic matter in marine shale source rocks at high-over maturity and that a TOC of at least 1.0% may be appropriate to predict favorable zones of marine shale at high-over maturity in China.
