Evaluation Of Resource Potential Research Articles

A simple and effective evaluation method for lacustrine shale oil based on mass balance calculation of Rock-Eval data

Because the profit from the development of unconventional resources can be small, success usually depends on the quick identification of favorable areas. It is therefore very important to identify a rapid and robust resource potential evaluation method. However, it is challenging to evaluate shale oil content, especially the recoverable oil part. We explore a new evaluation index (SE) by using Rock-Eval data and mass balance. When SE ˃ 0, the shale interval has already expelled a certain amount of hydrocarbons, so it has poor shale oil potential. When SE is near 0, almost all the generated hydrocarbons are trapped in the shale itself, and simultaneously, no externally migrated hydrocarbons enter the shale. In the case of an SE near 0, the shale oil potential may depend on whether it is organic-rich; however, this type of shale tends to be compact and does not develop fractures. When SE ˂ 0, externally migrated hydrocarbons entered the shale interval, which usually indicates good shale oil potential. The more negative the SE is, the greater the shale oil potential. One of the advantages of this index is that it takes into account not only the residual oil content but also the conditions of hydrocarbon expulsion and migration. Moreover, this method is economical and convenient and is based on commonly available Rock-Eval data.

Экономическая оценка минерально-сырьевого потенциала арк­тических территорий Республики Коми

The Arctic zone of the Timan-North Ural Region, to which the Komi Republic belongs, has a rich resource potential that is underdeveloped and ecologically vulnerable. The article presents the results of the economic evaluation of mineral resource potential of the Region Arctic zone, which show its high potential cost and an insignificant share of resources involved in industrial development. The authors base the assessment on their methodology, which includes the identification of the most economically promising mineral objects, an estimation of the gross value of resources, an evaluation of deposits via the net present value method with determination of the budget efficiency of the projects. The authors consider environmental risks by calculating the value of environmental services and analyzing their consumption and benefits. They calculate the cost of the mineral resource potential, taking into account the factor of ecosystem services, on the example of the Nechensky lignite deposit assessment. They outline that the assessment of the mineral potential of the region due to be based on the most significant objects, take into account types of raw materials, the size of deposits and technological features of development, and include the analysis of economic and geographical factors when choosing objects. The key indicator is the net present value of reserves taking into account the estimated resources of the prospection phases. The calculation of ecosystem services should also be included into the overall assessment of the raw material potential.

Focus on research advances in the natural gas hydrate resource evaluation: Introduction to papers in the special section of Evaluation of Natural Gas Hydrate Resource Potential in the South China Sea

Focus on research advances in the natural gas hydrate resource evaluation: Introduction to papers in the special section of Evaluation of Natural Gas Hydrate Resource Potential in the South China Sea

An approach to differentiation and evaluation of mineral resource potential in coal mining

A mining company is a complex probabilistic system which functions in-between the geological and market environments. These environments are the carriers of various uncertainties which have influence on the business success. The authors discuss the background of differentiation of the mineral resource potential in terms of a coal field as transformation of a natural possibility to the manmade reality. It is distinguished between the limit, achievable and investment potentials. This type design takes into account the stages of geological exploration, study of coal properties and actual mining of the subsoil use object. The static, ergodic and non-ergodic categories of uncertainty are discussed.

Research progress and challenges of natural gas hydrate resource evaluation in the South China Sea

As an efficient clean energy, natural gas hydrate (NGH) has become a hot topic in recent researches. Since 1990s, China has made great achievements and progress in NGH exploration in the South China Sea (SCS), including determination of the favorable distribution areas and favorable strata thickness, identification of the dual source for accumulation, evaluation of the prospective gas contents, verification of the widespread existence, and confirmation of the technical recoverability of NGH resources. However, there are three major challenges in the NGH studies. First, all the 24 national key and major projects in the SCS focused on trial production engineering and geological engineering in the past 20 years, while 8 of the 10 international NGH research projects focused on resource potential. Second, resource evaluation methods are outdated and some parameter selection are subjective. Third, the existing resource evaluation results are low-level with a great uncertainty, and cannot be used to guide NGH exploration and production or strategic research. To improve the evaluation of NGH resources in the SCS, future researches should focus on four aspects: (1) improve the research on the criterion of the objective existence of NGH and the method of prediction and evaluation; (2) apply new theories and methods from the global NGH research; (3) boost the research on the difference and correlation of the conditions of hydrocarbon migration and accumulation in different basins; (4) innovate the theory and method of NGH resource potential evaluation.

Quantitative characterization of various oil contents and spatial distribution in lacustrine shales: Insight from petroleum compositional characteristics derived from programed pyrolysis

The strong heterogeneity of lacustrine shale oil occurrences and the lack of proper parameters representing the shale oil content are impediments to assessing shale oil reserves. The shale oil content was characterized in the study using petroleum compositional characteristics determined by loss light hydrocarbon restoration and chemical kinetics decomposition and reconstruction of hydrocarbon groups; the shale oil spatial occurrence of the Second Mbr of the Funing Fm in Haian Sag, Subei Basin was determined using logging prediction and measured data; and finally, the controlling factors of shale oil content were discussed. Organic matter abundance, thermal maturity, and lithofacies have the primary impact on shale oil content. Shale oil enrichment intervals are distributed in an adjacent part of the maximum flood surface in the third-order sequence and some ascending semi-cycles in the fourth-order sequences in the deep sag area. This work has implications for exploration target optimization and resource potential evaluation of shale oil.

Survey on Geothermal Resources in Zhangjiakou Area

The Zhangjiakou area is rich in geothermal resources, and many counties in the region have discovered low-temperature geothermal. Structurally, Huailai County, Zhangjiakou City is located at the intersection of Zhangjiakou-Penglai Fault Zone and Shanxi Fault Basin (or Fenwei Seismic Tectonic Zone), namely the Yanqing-Huailai Basin (Yanhuai Basin). A large amount of geothermal resource investigation and research works has preliminarily defined that the area has good geothermal resource accumulation conditions. From 2019 to 2020, the China Geological Survey has organized several investigation and research in the area for in-depth geothermal resource. As one method of the survey results verification, a parameter well for geothermal resource survey was deployed as ZK02 and completed at 3000m depth. The ZK02 well was completed at a depth of 3006.9m, drilling through the Quaternary, Neogene, and Jixian strata, and entered the Archean gneiss strata. The well successfully explored high-quality artesian heat storage in the Jixian strata, obtained deep geothermal geological data and physical data, revealed the regional stratigraphic sequence and geological structure characteristics, and provided a scientific basis for regional geothermal resource potential evaluation. Based on the engineering practice of ZK02 well, this paper systematically summarizes drilling technology and experience from well structure to drilling equipment, construction technology and key technology, analyses the complex conditions and countermeasures downhole, and provide reference for the follow-up regional geothermal resources investigation, research and development and.

Petroleum resource potential evaluation using insights based on hydrocarbon generation, expulsion, and retention capabilities—A case study targeting the Paleogene Es1 formation, Qikou Sag

The Shahejie Formation of the Bohai Bay Basin has been set as a favorable shale oil area for exploration in currently practice. However, the process was impeded by the obscurity of favorable exploration area in the shale play and resource evaluation targeted at the main research area, the Qikou Sag. In particular, there is a need for a systematic assessment of the various types of resources present. The study presented herein emphasizes on quantifying source rock generation, expulsion, and retention hydrocarbon characteristics using the advanced hydrocarbon-generation potential model (HGPM) in the first member of the Paleogene Shahejie Formation (Es 1 ) of the Qikou Sag. Geological and geochemical features reveal that the Es 1 source rocks are of relatively high quality with a 1200-m maximum thickness and abundant organic matter (total organic carbon (TOC) content of 2.27% on average; type I kerogen dominated; mature stage). The type of organic matter was reassessed using the progressive and reasonable dimensionless TOC and S 2 variables. The HGPM demonstrated that the expulsion threshold was R o = 0.50% and the maximum generation hydrocarbon potential ( Q g ), expulsion hydrocarbon potential ( Q e ), and retention potential ( Q r ) were 746.99, 231.57, and 515.42 mg HC/g TOC, respectively. The hydrocarbon generation (I g ), expulsion (I e ), retention (I r ), and effective retention intensity (I re ) all centered in the Qikou main depression at 450 × 10 4 , 200 × 10 4 , 300 × 10 4 , and 230 × 10 4 t/km 2 , respectively. The predicted resource potential can be finally queued as follows: retention shale resources with 22.90 × 10 8 t oil equivalent, including movable shale oil and gas of 12.21 × 10 8 t, and conventional and tight oil or gas resources with 9.62 × 10 8 t oil equivalent. The most favorable exploration areas are mainly distributed in the Qikou main depression and Qibei Subsag. Quantitative and detailed evaluation provides a reasonable prediction of exploration targets and prospects and further mitigates risks and losses incurred during shale-exploration successions. • Advanced hydrocarbon generation potential model is used in the Qikou Sag, NE China. • Potential resources and favorable targes of study area are presented. • Redetermination on organic matter type and redescription on HC generation process. • Unconventional oil and gas occupy a desirable resource scale. • The resources comparisons between Qikou Sag and the adjacent Nanpu Sag.

Conventional and Unconventional Hydrocarbon Resource Potential Evaluation of Source Rocks and Reservoirs: A Case Study of the Upper Xiaganchaigou Formation, Western Qaidam Basin, Northwest China

Conventional and Unconventional Hydrocarbon Resource Potential Evaluation of Source Rocks and Reservoirs: A Case Study of the Upper Xiaganchaigou Formation, Western Qaidam Basin, Northwest China

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

Shale oil is a vital alternative energy source for oil and gas and has recently received an extensive attention. Characterization of the shale oil content provides an important guiding significance for resource potential evaluation, sweet spot prediction, and development of shale oil. In this paper, the mechanism, evaluation and influencing factors of oil retention in shales are reviewed. Oil is retained in shales through adsorption and swelling of kerogen, adsorption onto minerals and storage in shale pores. Quite a few methods are developed for oil content evaluation, such as three-dimensional fluorescence quantitation, two-dimensional nuclear magnetic resonance (2D NMR), solvent extraction, pyrolysis, multiple extraction-multiple pyrolysis-multiple chromatography, logging calculation, statistical regression, pyrolysis simulation experiment, and mass balance calculation. However, the limitations of these methods represent a challenge in practical applications. On this basis, the influencing factors of the oil retention are summarized from the microscale to the macroscale. The oil retention capacity is comprehensively controlled by organic matter abundance, type and maturity, mineral composition and diagenesis, oil storage space, shale thickness, and preservation conditions. Finally, oil mobility evaluation methods are introduced, mainly including the multitemperature pyrolysis, 2D NMR, and adsorption-swelling experiment, and the influencing factors of movable shale oil are briefly discussed. The aim of this paper is to deepen the understanding of shale oil evaluation and provide a basis for further research.

Jurassic Terrestrial Shale Gas Potential of the Northern Kashi Sag in the Tarim Basin, Northwestern China

Evaluation of terrestrial shale gas resource potential is a hot issue in unconventional oil and gas exploration. Organic-rich shales are widely developed in the Jurassic strata of Tarim Basin, but their shale gas potential has not been described well. In the study, the Lower-Middle Jurassic fine-grained sedimentary rocks (Kangsu and Yangye Formations) in northern Kashi Sag, northwestern Tarim Basin, were taken as the study object. The comprehensive studies include petrology, mineralogy, organic geochemistry, and physical properties, which were used to characterize the organic matter and reservoir characteristics. Results show that the Jurassic terrestrial shale in the northern Kashi Sag was mainly deposited in lakes, rivers, and deltas. The thickness of black lacustrine shale developed in the Early-Middle Jurassic in the study area is generally over 100 m. The total organic carbon (TOC) content is rich, averaging 2.77%. The vitrinite reflectance ( R o ) values indicate that the Lower Jurassic shale organic matter is in the early mature–mature stage, while the Middle Jurassic is in the mature stage. Besides, organic matter is primarily II and III in kerogen types. The whole shale contains a large number of clay minerals, especially illite. The average brittle minerals such as quartz and feldspar are 28.67%, and the average brittleness index is 38.63%. Nanoscale pores containing intergranular pores, dissolution pores, and organic pores, coupled with microcracks, are well developed in Jurassic shale. The sample’s average pore volume is 0.017 cm3/g, and the specific surface area is 9.36 m2/g. Mesoporous contribute the most to pore volume, while the number of microporous is the largest. Both of them provide most of the surface area for the shale. Combined with regional geologic settings, we propose that the Jurassic terrestrial shale has good-excellent shale gas exploration potential and development prospects.

Long-term characterization and resource potential evaluation of the digestate from food waste anaerobic digestion plants

The management of digestate from food waste (DFW) has become a big challenge for anaerobic digestion (AD) plants. It is crucial to understand the characteristics of DFW for its beneficial utilization. This study investigated the long-term characteristics of DFW from an industrial-scale AD plant in China for 16 months. The result showed that the characteristics of the DFW were relatively stable. The DFW contained considerable amounts of organic matter (23–40% of lignin and 12–26% of protein) and abundant nutrients (N, P, and K), with high concentrations of metals (e.g., 55.17 mg g−1 and 15.55 mg g−1 of Ca and Fe) and sulfur (1.40%) on a dry basis. Based on the results, pyrolysis and composting were evaluated as optional conversion ways of DFW. The pyrolysis temperature range of 500 °C to 600 °C was recommended for producing biochar. In this temperature range, the Brunauer-Emmett-Teller surface area of the produced biochar is over 120 m2 g−1. The composting offered the best potential for recovering the nutrients from DFW, but the high ammonia gas content (6970 ppm) should be paid attention to during composting.

Differences in source kitchens for lacustrine in-source and out-of-source hydrocarbon accumulations

Because of the differences of hydrocarbon accumulation between in-source and out-of-source oil pools, the demand for source kitchen is different. Based on the establishment of source-to-reservoir correlation in the known conventional accumulations, and the characteristics of shale oil source kitchens as well, this paper discusses the differences of source kitchens for the formation of both conventional and shale oils. The formation of conventional oil pools is a process of hydrocarbons enriching from disperse state under the action of buoyancy, which enables most of the oil pools to be formed outside the source kitchens. The source rock does not necessarily have high abundance of organic matter, but has to have high efficiency and enough amount of hydrocarbon expulsion. The TOC threshold of source rocks for conventional oil accumulations is 0.5%, with the best TOC window ranging from 1% to 3%. The oil pools formed inside the source kitchens, mainly shale oil, are the retention of oil and gas in the source rock and there is no large-scale hydrocarbon migration and enrichment process happened, which requires better quality and bigger scale of source rocks. The threshold of TOC for medium to high maturity of shale oil is 2%, with the best range falling in 3%–5%. Medium to low mature shale oil resource has a TOC threshold of 6%, and the higher the better in particular. The most favorable kerogen for both high and low-mature shale oils is oil-prone type of I–II1. Carrying out source rock quality and classification evaluation and looking for large-scale and high-quality source rock enrichment areas are a scientific issue that must be paid attention to when exploration activity changes from out-of-source regions to in-source kitchen areas. The purpose is to provide theoretical guidance for the upcoming shale oil enrichment area selection, economic discovery and objective evaluation of resource potential.

Origin of the Gas Hydrate and Free Gas in the Qilian Permafrost, Northwest China: Evidence from Molecular Composition and Carbon Isotopes

AbstractThe Qilian permafrost of the South Qilian Basin (SQB) has become a research focus since gas hydrates were discovered in 2009. Although many works from different perspectives have been conducted in this area, the origin of gas from gas hydrate is still controversial. Molecular composition and carbon isotope of 190 samples related to gas hydrates collected from 11 boreholes allowed exploration of genetic type, thermal maturity, biodegradation, as well as gas‐source correlation of alkane gases from gas hydrates and free gases. Results indicate that alkane gases biodegraded after the formation of natural gas. According to differences in carbon isotopes of methane and their congeners (CH4, C2H6, C3H8), the thermal maturity (vitrinite reflectance, VRo) of most alkane gases ranges from 0.6% to 1.5%, indicating a mature to high mature stage. The thermal maturity VRo of a small part of alkane gas (in boreholes DK5 and DK6) is higher than 1.3%, indicating a high mature stage. Alkane gases were mainly produced by secondary cracking, consisting of crude oil‐cracking gases and wet gases cracking to dry gases. Genetic types of alkane gases are primarily oil‐type gases generated from shales and mudstones in the upper Yaojie Formation of Jurassic, with less coal‐type gases originated from the mudstones in the Triassic Galedesi Formation and the lower Yaojie Formation of Jurassic. Carbon dioxides associated with alkanes from gas hydrates and free gases indicate the thermal decomposition and biodegradation of organic matter. The origins of natural gases from gas hydrates and free gases shed light on the evaluation of petroleum resource potential, deeply buried sediments, and petroleum resource exploration in the SQB.

Enrichment Factors and Resource Potential Evaluation of Qingshankou Formation Lacustrine Shale Oil in the Southern Songliao Basin, NE China

China shale oil, which is preserved in lacustrine shale with strong heterogeneity and relatively low maturity, has been a research hotspot of unconventional resources. However, controlling factors of shale oil enrichment and resource potential evaluation restricted efficient exploration and development of lacustrine shale oil. On the basis of well logging data, TOC content, Rock-Eval pyrolysis values, thermal maturity, 100 oil saturation data, and pressure coefficient, the core observation, X-ray diffraction analysis, physical property analysis, scanning electron microscopy, CT scan, well logging interpretation, and volumetric genesis method depending on three-dimensional geological modeling were used to determine enrichment factors and evaluate the resource potential of Qingshankou Formation shale oil in the Southern Songliao Basin. Shale oil was mainly enriched in the semideep and deep lake shale of K2qn1, with the high capacity of hydrocarbon generation and favorable petrological and mineralogical characteristics, pore space characteristics, and physical properties in the low structural part of the Southern Songliao Basin. The three-dimensional geological resource model of Qingshankou Formation lacustrine shale oil was determined by the key parameters (Ro, TOC, and S 1 ) of shale oil in the favorable zone of the Southern Songliao Basin, northeast China. The geological resource of shale oil, which was calculated by two grid computing methods ( F 1 and F 2 ), was, respectively, 1.713 × 10 12 kg and 1.654 × 10 12 kg . The great shale oil resource indicates a promising future in the exploration and development of Qingshankou Formation shale oil of the Southern Songliao Basin.

Hydrocarbon source potential evaluation insight into source rocks—A case study of the first member of the Paleogene Shahejie Formation, Nanpu Sag, NE China

The features of source rock hydrocarbon generation, expulsion, and retention are essential factors in petroleum resource potential evaluation. In this study, the improved hydrocarbon generation potential evaluation method was used to quantify the characteristics of the source rocks of the first member of the Paleogene Shahejie Formation (Es1) in the Nanpu Sag, Bohai Bay Basin, NE China. Based on the geological and geochemical data for the source rocks, the favorable exploration areas were predicted and the resource potential was evaluated. Our results show that Es1 is a set of high-quality source rocks with desirable geological (maximum thickness > 600 m) and geochemical (average total organic carbon content of 1.44%; dominantly type II kerogen; mature stage) characteristics. The improved hydrocarbon generation potential model shows that the hydrocarbon expulsion threshold is located at Ro=1.0%. The maximum hydrocarbon generation potential (Qg), hydrocarbon expulsion potential (Qe), hydrocarbon retention potential (Qs), and efficient hydrocarbon retention potential (Qse) are 549.31, 162.20, 387.11, and 287.11 mg HC/g TOC, respectively. The maximum hydrocarbon generation, expulsion, retention, and effective retention intensities are 250×104, 70×104, 180×104, and 150×104 t/km2, respectively. These parameters reach the highest value in the Linque and Caofeidian Sub-sag. The resource potential of the retention shale oil, the movable shale oil, and the conventional and the tight petroleum resources are 1.99×108, 4.38×108, and 1.37×108 t oil equivalent, respectively. This study offers a fresh and plain but operable workflow for resource evaluation, which can be applied in other petroliferous basins with low degree of exploration.

Exploration domains and technological breakthrough directions of natural gas in SINOPEC exploratory areas, Sichuan Basin, China

Natural gas exploration in SINOPEC's exploratory areas in the Sichuan Basin has achieved rapid development. Since discovering the Xinchang gas field, natural gas exploration has expanded gradually, with both reserves and production growing fast. The deepening understanding of geological theory and crucial technology's progress is the main driving force for the natural gas industry's significant development. Considering the rich natural gas resources, various types of promising targets, exploration degree of 16% of conventional natural gas, and the initial stage of shale gas exploration, the HCZ model predicted natural gas exploration. Additionally, it indicated that the shale gas in the SINOPEC exploratory areas in the Sichuan Basin would consistently have rapid development with proven reserves increasing by (160–200) × 109m3/a. In the future, the development strategy is to vigorously develop shale gas, steadily promote marine conventional natural gas, and continually research continental tight sandstone gas. The following tasks need to be strengthened for efficient exploration of the three resource types: prediction of deep and ultra-deep reef-shoal reservoirs, weathered crust reservoirs, and technological breakthrough of efficient drilling and fracturing test of ultra-deep wells; the technological breakthrough of geological-logging-seismic integrated sweets pot prediction of tight sandstones and low-cost multi-layer fracturing of vertical wells; the technological breakthrough of increasing-yield and reducing-cost drilling, completion, and fracturing of deep marine shale gas; resources potential evaluation and adaptive exploration and development technologies preparation of continental and transitional shale gas.

Evaluation of wind resource potential using statistical analysis of probability density functions in New South Wales, Australia

ABSTRACT Wind energy is a vital part of Australia’s energy mix. The first step in a wind power project at a particular site is to assess the wind resource potential and feasibility for wind energy production. Research on wind potential and statistical analysis has been done throughout the world. Currently, recent potential wind studies are lacking, especially in New South Wales (NSW), Australia. This study highlighted the feasibility of wind potential at four sites in NSW, namely Ballina, Merriwa, Deniliquin, and the Bega region. The type of wind speed distribution function dramatically affects the output of the available wind energy and wind turbine performance at a particular site. Therefore, the accuracy of four probability density functions was evaluated, namely Rayleigh, Weibull, Gamma, and Lognormal distributions. The outcomes showed Weibull provided the most accurate distribution. The annual average scale and shape parameters of Weibull distribution varied between 2.935–5.042 m/s and 1.137–2.096, respectively. The maximum shape and scale factors were at Deniliquin, while the minimum shape and scale factors were at Bega area. Assessment of power density indicated that Deniliquin had a marginal wind speed resource, while Ballina, Bega, and Merriwa had poor wind resources.

Metallogeny of critical metals in the SouthwesternYangtze Block

The Yangtze Block is one of the major geological units in China. Numerous and diverse mineralization are extensively distributed in this block, making the Yangtze Block be one of the well-known providers of mineral-resources worldwide. In the southwestern Yangtze Block, since Proterozoic, the diverse mineralization involves magmatic, magmatic-hydrothermal, low-temperature hydrothermal and weathering-sedimentary processes were extensively developed, of which critical metal mineralization (e.g., In, Ge, Ga, Cd, Re, W, Sn, Li, Nb, REE, and PGE) is generally present as by-products in some basic or precious deposits or as independent deposits. Previous studies have revealed ten types of critical metal mineralization in the region, specifically including the REE-rich phosphorite, PGE-Re-rich black shales, carbonate clay-type Li-Ga-REE, basalt weathering-type Nb-Ga-Zr-REE, In-rich cassiterite sulfide, REE-rich IOCG, Tl-rich low-temperature hydrothermal, Ge-rich Pb-Zn, Cu-Ni-PGE sulfides and carbonatite-related REE deposits. In the past decade, numerous studies have advanced our understanding of the mineralization styles, timing and ore genesis of these types of critical-metal mineralization, and are summarized in this paper. It was indicated that the Cu-Ni-PGE sulfide deposits are genetically related to the late Permian E’meishan mantle plume, whereas the carbonatite-related REE deposits are Cenozoic in age and have formed during post-collision between the Indian and Asian continents. Moreover, the REE-rich IOCG deposits were newly identified, constituting a Proterozoic IOCG metallogenic province that was first documented in China, and enrichments of REEs were suggested to be related to the chemical attributes of the late Cu mineralizing fluids; the In-rich sulfide deposits, distributed in a small area of the SW Yangtze Block, were suggested to be genetically related to late Yanshanian granites; the low-temperature hydrothermal mineralization, characterized mainly by the Pb-Zn and Au-As-Sb-Hg-Tl deposits that define one of the two world-largest low-temperature metallogenic provinces, was mainly formed at the Indosinian and Yanshanian periods during which granitic activities are relatively weak; numerous marine-facies sedimentary rocks particularly including the black shales and carbonate rocks are associated with the development of multi-episodes of sedimentary and/or weathering-sedimentary deposits that are uniquely enriched in Li, Nb, Zr, Ga. Re, REE and PGE. We also proposed some issues that are important but currently poorly addressed, including aspects of the evaluation of REE resource potential and mechanisms of REE concentrations in IOCG deposits, and key factors controlling the extreme enrichment of Ge, Ga, Cd and Tl in the Mesozoic low-temperature metallogenic province, with focuses on the background values of these elements in the region. Moreover, available studies show that In is extremely enriched in four giant cassiterite-rich, granite-related sulfide deposits distributed in the border area of Yunnan and Guangxi, making this area a unique In metallogenic province in the world. However, it is currently not clear why In is enriched in cassiterite-rich sulfide deposits and why In is enriched in the sphalerite as a function of “indium window” effect, which should be constrained through a combined study involving crust-mantle circulation, crystallization fractionation of magma, geochemical behaviors of metals and mineralogy. We also proposed that the weathering-sedimentary deposits, such as the clay-type Li-Ga-REE and basalt weathering-type Nb-Ga-Zr-REE ones, are likely brand-new types with huge potential of critical metal resources, and emphasized that in addition to ore genesis studies, researches on the distributions of metals and potential utilization of resources should also be paid more attention. We also highlight that current prospecting techniques and methods that are mostly used for exploration of some common basic or precious deposits are likely not applicable for the exploration of critical metal deposits. As such, new techniques and methods involving the integration of prospecting information, predication and locating of ore bodies and evaluation of resources should also be developed for critical metal deposits.

A revised method for reconstructing the hydrocarbon generation and expulsion history and evaluating the hydrocarbon resource potential: Example from the first member of the Qingshankou Formation in the Northern Songliao Basin, Northeast China

Reconstructing the hydrocarbon generation and expulsion history of source rocks is an essential part of evaluating the hydrocarbon resource potential by genetic method. The hydrocarbon generation potential method is an efficient tool for quantifying the hydrocarbon generation and expulsion characteristics of source rock and evaluating the hydrocarbon resource potential based on Rock-Eval data. Although various revised versions of the method are publicly available, the following problems remain to be resolved: (a) the method is subjective; (b) implicit limitations are observed; and (c) rock mass loss is not considered, which may result in unacceptable errors. In this study, we propose a revised hydrocarbon generation potential method. Expressions for calculating the original rock mass (Go), original total organic carbon (TOCo), transformation ratio (TR), hydrocarbon expulsion ratio (ER) and hydrocarbon expulsion efficiency (f) were developed and incorporated into the hydrocarbon generation and expulsion history reconstruction and hydrocarbon resource potential evaluation, and these expressions combined conventional and unconventional resource evaluations systematically with objective and accurate results. The first member of the Qingshankou Formation (K2qn1) in the Northern Songliao Basin, Northeast China, was used as an example to demonstrate the application of the proposed method. The results have been compared with the unrevised method using the same Rock-Eval data sets and verified with previous reports to demonstrate its reliability. The results also indicate that the hydrocarbon generation threshold (HGT) and hydrocarbon expulsion threshold (HET) of K2qn1 are Ro = 0.4% and Ro = 0.6%, respectively. Three hydrocarbon generation and expulsion peak stages were identified: K2n (81–74 Ma), K2m (74–66 Ma), and N2t (66–0 Ma). The hydrocarbon generation and expulsion centers of K2qn1 are mainly the Qijia-Gulong Sag and Sanzhao Sag. The resource potentials of conventional oil, unconventional tight oil, and shale oil associated with K2qn1 source rocks in the Northern Songliao Basin are 8.15 × 108 t, 22.97 × 108 t, and 62.1 × 108 t, respectively.