Hydrocarbon Source Rock Evaluation Research Articles

Hydrocarbon Source Rock Evaluation of the Lucaogou Shale in the Periphery of Bogeda Mountain (SE Junggar Basin, China) and Its Implications for Shale Oil Exploration: Insights from Organic Geochemistry, Petrology, and Kinetics Pyrolysis

Since the discovery of the vast Jimusaer shale oilfield in the southeastern Junggar Basin in 2012, there has been considerable interest in neighboring areas around Bogeda Mountain that have shale oil potential. The primary productive interval in the basin, the Middle Permian Lucaogou Formation (P2l), is well-developed in the areas of Qitai, Mulei, Shiqiantan, Chaiwopu, and Miquan. In this study, we conducted an assessment of the hydrocarbon generation potential of the P2l in these five areas and compared it with that of the P2l in the Jimusaer oilfield, which were determined by GC-MS, total organic carbon (TOC) and vitrinite reflectance (Ro) measurements, Rock-Eval pyrolysis, and organic petrology to investigate the type, origin, thermal maturity, hydrocarbon potential, and oil/gas proneness of organic matter in the P2l. Additionally, we applied open-system pyrolysis of hydrocarbon generation kinetics to explore differences in hydrocarbon generation and expulsion across various P2l mudstone/shale in the southeastern Junggar Basin. The findings of this study revealed that the P2l shale in Qitai and Miquan areas contains more abundant and lower thermally mature organic matter (early mature–mature stage), characterized by primarily Type II1–I kerogen, similar to that found in the P2l shale of the Jimusaer oilfield. Conversely, the P2l shale in Mulei, Shiqiantan, and Chaiwopu contains less abundant and more thermally mature organic matter (mainly mature–highly mature stage), dominated by Type II2–III kerogen. Consequently, shale in these areas is considerably less desirable for oil exploration compared to the Jimusaer shale. The semi-deep to deep lake facies in Miquan and Qitai exhibit the most promising exploration potential. This study can serve as a guide for shale oil exploration in the southeastern Junggar Basin.

Deep learning integrated approach for hydrocarbon source rock evaluation and geochemical indicators prediction in the Jurassic - Paleogene of the Mandawa basin, SE Tanzania

The world's energy demands are growing at an unprecedented rate, and the exploration of new hydrocarbon sources is more important than ever. Therefore, the objective of this study was first to quantitatively analyze hydrocarbon source rock potentiality of the Triassic-Jurassic of Mandawa Basin based on the generalized group method of data handling neural network (g-GMDH), Machine learning, and Geochemical using well logs data. Then a novel g-GMDH was presented to predict a continuous geochemical log profile of TOC, Tmax, S1, and S2. It was observed that the basin's hydrocarbon source rocks are classified as fair to very good source rocks with TOC contents ranging from 0.5 to 8.7 wt%. The source rocks contain mixed kerogen type II and III, which are oil and gas-prone, ranging from immature to mature source rocks. The results of the predictive models indicated that the g-GMDH model trained better whilst generalizing well throughout the testing data than both GPR and SVM models. Specifically, the g-GMDH when tested on unseen data had the least value of MSE = 0.18, 2.35, 0.08, and 61.74 for TOC, Tmax, S1, and S2 respectively, and MAE = 0.45, 1.37, 0.17 and 11.55 for TOC, Tmax, S1 and S2 respectively. The g-GMDH model was further applied to assess the source rock and predict the geochemical information in the East Lika well, which lacks core data. The proposed model can offer rapid and real-time values of geochemical indicators and are independent of laboratory-dependent parameters therefore, can be adopted as an improved technique for evaluating source rocks in frontier basins.

Organic facies and hydrocarbon source rock potentiality of the Neogene succession in the Central South Mediterranean, offshore Nile Delta Basin, Egypt

Neogene succession in the offshore Nile Delta region is essential to the hydrocarbon petroleum system. Up to date, little is known about the nature and distribution of organic matter and its potential to generate hydrocarbon. This potential is tested through extensive palynofacies and organic geochemical analyses in a new approach in this region. Based on the palynofacies analysis, the samples from NDOB-1 and Baltim-1wells are discriminated into four types using the statistical application of cluster and principal component analyses. These four types are distal-High Oxic type A, proximal-suboxic type B, proximal-dysoxic type C, and distal-oxic type D. In addition, the analysis leads to identifying the proximal-distal and oxygen depletion trends based on the values of the principal component analysis (axis 1). This palynofacies analysis is used as an environmental framework for hydrocarbon source rock evaluation. This evaluation is integrated with the organic geochemical parameters by pyrolysis (Rock-Eval and gas chromatography) and spectroscopic (Fourier Transform Infrared) methods. This study reveals that the dominant kerogen types are IV (inert) and III (gas-prone) which are remarked by the opaque and brown translucent phytoclasts palynofacies types A and D, respectively. Kerogen type II is presented in a minor abundance in palynofacies types B and C that are distinguished with AOM. However, kerogen type II organic matter is much diluted with kerogen type IV and III, leading to poor to fair organic geochemical quality (S2 and hydrogen index). Both wells' maturity levels are detected within the Kafr El Shiekh Formation. Nevertheless, the poor hydrocarbon source rock quality becomes important if considered with the volume and thickness of the Neogene sediment, as indicated by the source potential index that has a cumulative value of 2.5 t HC/m2 in NDOB-1 well and 2.8 t HC/m2in Baltim-1 well. These values are comparable to some of the prolific hydrocarbon fields in other places.

Sedimentary environments and mechanism of organic matter enrichment of dark shales with low TOC in the Mesoproterozoic Cuizhuang Formation of the Ordos Basin: Evidence from petrology, organic geochemistry, and major and trace elements

Proterozoic strata have become a new target for hydrocarbon exploration worldwide. They exhibit the potential to become a resource replacement target. To provide a reference for hydrocarbon source rock evaluation, the sedimentary environment and mechanism of organic matter enrichment of dark shales in the Mesoproterozoic Cuizhuang Fm. were investigated for the first time by combining organic and inorganic research concepts. Although the total organic carbon (TOC) content in the Cuizhuang Fm. is relatively low (mean value of 0.59%), it still can be considered as a potential source rock. Thin-section observations, main and trace element contents, and biomarker compounds revealed the following: (1) the Cuizhuang Fm. was deposited in a neritic shelf sedimentary environment at a passive continental margin, and the climate was warm and humid. The hydrocarbon-generating organisms mainly comprised prokaryotes such as cyanobacteria and other bacteria. All these characteristics meet the conditions of source rock formation. (2) The low oxygen level, felsic source provenance, and absence of submarine hydrothermal activity led to low productivity, and the low productivity and low-grade hydrocarbon-generating organisms led to low TOC content in the Cuizhuang Fm. (3) The enrichment of V in the Cuizhuang Fm. is apparent, but does not reach the hyper-enrichment threshold of 500 ppm associated with euxinic conditions, revealing anoxic ferruginous conditions. Moreover, the V content is positively correlated with TOC content, indicating that organic matter enrichment was mainly controlled by the redox conditions of the bottom water. Therefore, the sedimentary areas with high productivity were related to basic source provenance and submarine hydrothermal activity, and anoxic bottom water may have promoted the development of better source rocks. This findings may represent the main direction for identifying effective source rocks in subsequent work.

Hydrocarbon source rock evaluation and quantification of organic richness from correlation of well logs and geochemical data: A case study from the sembar formation, Southern Indus Basin, Pakistan

Sembar Formation of Cretaceous encountered in Khajari-01 and Miran-01 wells, which are located in the Southern Indus Basin (SIB), Pakistan. Total organic carbon (TOC) content is generally measured by traditional methods such as the evaluation of side wall cores and formation cuttings in a geochemical lab. Data obtained from these experimental techniques are not continuous and also a time-consuming process. A solution to this problem is high resolution and continuous information obtained from well logs. Different methods were used to estimate TOC through well logs. Among those methods, four methods have been chosen to estimate TOC in the current research, i.e., Density Log, Spectral Gamma-Ray Log, ΔlogR, and Multivariate Fitting methods. The TOC estimated values have been correlated with well cuttings TOC values to optimize a method for TOC estimation through well logs. Fourteen well cutting samples of Sembar Formation from Khajari-01 well and seven samples from Miran-01 well have been selected for measurements of geochemical parameters. These parameters were used for source rock evaluation of the formation to determine the quality, quantity, and maturity of the Sembar Formation. Modified van-Krevlen diagram of Hydrogen Index (HI) versus Oxygen Index (OI) and Langford diagram of S2 versus TOC indicates that Sembar Formation in Khajari-01 well contain kerogen type-III (gas prone) compare to Miran-01 well that contains kerogen type-IV which makes it non-productive. The organic richness results indicate that TOC in Khajari-01 well is poor to very good while in Miran-01 a fair to good generation potential exist. Maturity indicators i.e., Pyrolysis Temperature (Tmax) and Production Index (PI) values show an immature to early mature zone for Khajari-01 well and over-mature zone in Miran-01 within the Sembar Formation. Density Log, Spectral Gamma-Ray Log, and Multivariate Fitting methods have poor coefficient of determination (R2) values between the estimated TOC (from well logs) with well cuttings tested samples TOC values. It has been inferred from data obtained using ΔlogR method that it has good R2 value between well logs estimated TOC and actual laboratory measured TOC in both wells which is optimized for future study in Southern Indus Basin, Pakistan.

Molecular Organic Geochemical Characteristics and Coal Gas Potential Evaluation of Mesozoic Coal Seams in the Western Great Khingan Mountains

AbstractCoal‐bearing strata are widespread in the western Great Khingan Mountains. Abundant coal resources have been found in the Jurassic Alatanheli Groups, the Cretaceous Bayanhua Groups, the Damoguaihe Formation and the Yimin Formation. The organic geochemical characteristics were analyzed in combination with hydrocarbon source rock evaluation and molecular organic geochemistry experiments, and the coal gas potential of coal seams was evaluated. The source rock evaluation results indicated that the Mesozoic coal samples have the characteristics of high organic matter abundance (TOC>30%), low maturity (Ro values of approximately 0.6%), and type III composition. The hydrocarbon generation potentials of the Alatanheli Groups and Bayanhua Groups are high, while the generation potentials of the Damoguaihe Formation and the Yimin Formation are low. The results of geochemistry show that the depositional environment of the coal seam was a lacustrine, oxidizing environment with a low salinity, and the source of the organic matter was mainly higher plants. Affected by weak degradation, the coal seams mainly formed low‐maturity gas of thermal catalytic origin. The Cretaceous coal seams contain a large amount of phytoplankton groups deposited in a low‐stability environment affected by a transgression event, and the potential range varied widely. For the Jurassic coal seams, the depositional environment was more stable, and the coal seams feature a higher coal‐forming gas potential.

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

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.

A new method of reconstruction of original total organic carbon for sediments in salt water lakes-A case study on modern sediments in Buha River estuary, Lake Qinghai

烃源岩中原始有机碳（TOC）总量的恢复是烃源岩评价的重点和难点，以青海湖西北部的布哈河口区沉积物为研究对象，探讨一种全新的利用沉积物中硼元素含量对原始TOC含量进行恢复的方法.布哈河口区沉积物主要为泥、粉砂、细砂及其过渡类型，黏土矿物含量总体较低，沉积物中干酪根类型主要为Ⅱ₁和Ⅱ₂型，有机质大部分来自陆源生物，少量来自水生生物.布哈河口区沉积物中TOC含量介于0.02%~4.29%之间，其中半深湖及前三角洲环境TOC含量总体较高.有机质对部分微量元素有明显的富集作用，沉积物中TOC含量与硼、钪、钴、镍、锌、镓、铷、铯、铅及铀等微量元素存在明显相关性.有机质对微量元素的富集能力和强度受沉积物和水体接触时间控制，因此微量元素与TOC含量的相关性在不同沉积环境存在明显差异：在河流、三角洲平原、前三角洲、浅湖及半深湖沉积区较高，而在滨湖区较低.硼元素对TOC含量变化的反映最灵敏，即便是在间歇暴露的滨湖沉积中硼含量与TOC含量呈明显的正相关性，因此硼可以作为反映烃源岩原始TOC含量的有效指标.根据布哈河口区沉积物中硼含量与TOC含量之间极好的线性相关性，建立了利用烃源岩中的硼含量对原始TOC含量进行定量计算的公式，该公式主要适用于陆相微咸水、半咸水及咸水环境泥质岩类原始TOC总量的恢复.;Reconstruction of original total organic carbon (TOC) in source rocks is the key and difficult point of hydrocarbon source rock evaluation. The paper focuses on the sediments of Buha River estuary in the northwest of Lake Qinghai, and a new method of original TOC reconstruction via born element in sediments was discussed. The sediments of Buha River estuary sediments are mainly made of mud, silt, fine sand and transitional type composition. The sediments are generally have low clay mineral content. The main types of kerogen in the sediments were Ⅱ₁ and Ⅱ₂, and most of organic matter come from terrigenous organisms while a small quantity of organic matter come from aquatic organisms. TOC in Buha River estuary sediments is in the range of 0.02% to 4.29%. TOC in the sediments of semi-deep lake and prodelta is usually higher than that in other environmental sediments. Organic matter has a significant effect on the enrichment of some trace elements. There is a significant positive correlation between the trace element concentration and TOC content in the sediments, the trace elements include boron, cobalt, nickel, zinc, gallium, rubidium, cesium, lead and uranium. The enrichment ability and intensity of organic matter to trace elements are controlled by the contact time of sediment and water, and so the correlation between trace element and TOC has obvious difference in different sedimentary environment. TOC is higher in sediments of fluvial, delta plain, prodelta, shallow lake and semi-deep lake environment, while it is lower in sediments of lakeshore environment. Boron was the most sensitive to the variation of organic carbon content, and the content of boron in the sediments of intermittent exposure environment like lakeshore is also showed a significant positive correlation with TOC. Boron is an effective index that can reflect original organic carbon content of the hydrocarbon source rocks. According to the excellent linear relationship between the boron concentration and TOC in the sediments of Buha River estuary, a formula for the quantitative calculation of the original organic carbon content via the content of boron in the source rock was established. The formula is suitable for the reconstruction of the original total organic carbon in the terrestrial brackish water and salt water of environment.

Hydrocarbon source rock evaluation of the Lower Cretaceous system in the Baibei Depression, Erlian Basin

The K1s, K1d, K1t, and K1a Formations are potential source rock intervals for hydrocarbon formation, all of which are part of the Lower Cretaceous system in the Baibei Depression in the Erlian Basin in China. However, no well has found oil flow because the hydrocarbon-generating potential of the source rocks has not been comprehensively evaluated. Based on organic geochemical and petrological analyses, all the source rocks possess highly variable total organic carbon and S1 + S2 contents. Total organic carbon and S1 + S2 contents indicate that the K1a2 Formation through the K1d1 Formation are source rocks that have fair to good generative potential and the K1d2 Formation through the K1s Formation are source rocks that have good to very good generative potential. The organic matter in the K1a2 Formation is dominated by Type I and II kerogen; thus, it is considered to be oil prone based on H/C versus O/C plots. Most of the analyzed samples were deposited in reducing environments and sourced from marine algae; thus, they are oil prone. However, only two source rock intervals were thermally mature with vitrinite reflectance values in the required range. Hydrocarbon-generating histories show that the K1t and K1a2 intervals began to generate hydrocarbons during the depositional period of the K1d2 and K1d3 Formations, respectively, and stopped generating hydrocarbons at the end of the depositional period of the late Cretaceous. Therefore, the main stage of hydrocarbon migration and accumulation was between the depositional period of the K1d2 and K1s Formations, and the critical moment was the depositional period of the late K1s Formation. The generation conversion efficiency reached approximately 55% in the K1a2 Formation and 18% in the K1t Formation at the end of the Cretaceous sedimentary stage. In general, the effective oil traps are those reservoirs that are near the active source rock in the generating sags in the Baibei Depression.

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.

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.

Hydrocarbon Source-Rock Evaluation of Desmoinesian (Middle Pennsylvanian) Coals from Part of the Western Region of the Interior Coal Province, U.S.A.

Hydrocarbon Source-Rock Evaluation of Desmoinesian (Middle Pennsylvanian) Coals from Part of the Western Region of the Interior Coal Province, U.S.A.

Hydrocarbon Source Rock Evaluation of Middle Proterozoic Solor Church Formation, North American Mid-Continent Rift System, Rice County, Minnesota

Hydrocarbon source rock evaluation of the Middle Proterozoic Solor Church Formation (Keweenawan Supergroup) as sampled in the Lonsdale 65-1 well, Rice County, Minnesota, shows that: (1) the rocks are organic matter lean (24 of 25 samples have less than 0.8% organic carbon); (2) the organic matter is thermally post-mature, probably near the transition between the wet gas phase of catagenesis and metagenesis (dry gas zone); and (3) the rocks have minimal potential for producing additional hydrocarbons (genetic potential < 0.30 mg HC/g rock). Although no direct evidence exists from which to determine maximum burial depths, the observed thermal maturity of the organic matter requires significantly greater burial depths, a higher geothermal gradient, or both. It is likely, t least on the Saint Croix horst, that thermal maturation of the organic matter in the Solor Church took place relatively early, and that any hydrocarbons generated during this early phase were probably lost prior to deposition of the overlying Middle Proterozoic Fond du Lac Formation (Keweenawan Supergroup).

Regional Hydrocarbon Source-Rock Evaluation of Atlantic Coastal Plain Adjacent to Georgia Embayment: ABSTRACT

In January 1978, GeoChem Laboratories completed a regional hydrocarbon source-rock study involving 13 wells in the Atlantic coastal plain adjacent to the GE-1 COST well. The purpose of this study was to characterize the geochemical zones within the stratigraphic section of the individual wells, to establish their onshore hydrocarbon generating potential, and to assist in the evaluation of the Georgia embayment by projection of the geochemical data into the offshore region. Although the analyses were performed on the Tertiary through Lower Cretaceous sediments, only the Upper Cretaceous section exhibited source-generating potential. Evaluation of the sediments as to total organic content (richness), organic-matter type (prone to be gas-, condensate-, or oil-productive), and state of thermal maturity, showed that both the Selma Group of the Upper Cretaceous (Navarro, Taylor, and Austin Formations) and the Tuscaloosa exhibit good to very good source-generating potential. This favorable potential appears to extend into the offshore region to the northern part of the blocks involved in OCS Sale 43, held in March 1978. Unfortunately, the Upper Cretaceous appears End_Page 425------------------------------ to be geothermally immature in both the onshore and offshore region and neither the Selma Group nor the Tuscaloosa is considered capable of generating producible quantities of either liquid or gaseous hydrocarbons within these areas. End_of_Article - Last_Page 426------------