Hydrogeophysical and Structural Investigations Using VES: A Case Study of Dosso Region in the Southwestern Part of the Meso-Cenozoic Iullemmeden Basin (Southwestern Niger)

A regional study connecting geolelectrical surveys with geology and hydrogeology was carried out in the western part of the Iullemmeden basin, precisely in the Dosso region in Niger. One hundred and four (104) vertical electrical sounds have been realized, among them nineteen representative were thus be used as parametric surveys. The local resistivity values of the geological formations of Quaternary range from 100 Ω⋅m to 1000 Ω⋅m (sands and lateritic sandstones). The Oligo-Miocene formation of the Continental terminal (Ct) shows resistivity values ranging from 1 to 5 Ω⋅m (brackish groundwaters) to 1500 Ω⋅m (clay sandstones) while the Upper Cretaceous formation of the Continental “hamadien” (Ch) indicates values ranging from 20 Ω⋅m (sandy clay) to 5000 Ω⋅m (clayey sandstones). The geological formations of Paleocene have values from 2 Ω⋅m (marls) to 60 Ω⋅m (calcareous marl), while the Precambrian basement exhibits values of granite around 300 Ω⋅m to 60,000 Ω⋅m. The update of the structural settings reveals many faults in the study area which explain both the shape of the basin and the geometry of the aquifers. Tectonics is also consistent with the hydraulic characteristics of aquifers. In addition, brackish groundwaters were identified as perched aquifer groundwaters in different depths in Dosso region. They probably come from the marine brines during the regression of the Paleocene Sea.

Geothermal Regime of Meso-Cenozoic Basins and Their Tectonic Background in East China

? This paper presents a brief analysis of the geothermal fields of Meso-Cenozoic basins and their evolution in East China by means of heat flow, geotemperature gradient, vitrinite reflectence and its gradient in the basins, and reveals a basic framework of the geothermal regime of the basins. The geothermal regime of Meso-Cenozioc basins in East China is mainly dominated by tectonic conditions. The important factor determining the geothermal state of basins is the thickness of lithosphere—burial depth of asthenospheric top, which is related to geodynamic type of basins. Basins in the western zone, represented by Sichuan and Ordos, belong to the flexure basins on the basement of continental block, with thick lithosphere, generally 120-150 km. All basins in this zone fall into middle heat basin type in the light of their lower ancient and present geotemperature gradient. While the middle zone is represented by Songliao and Bohaiwan basins, the continental margin zone is represented by East China Sea shelf basin and northern continental shelf basins of South China Sea. They belong to the extensional basins with thinning lithosphere, the smallest burial depth of paleoasthenospheric top, being 55-60 km. Therefore they should belong to heat basin type. The geothermal state of the basins is correlated positively with extension degree in the majority of basins controlled by dynamic mechanism of extension and transtension.

Influence of lithospheric thickness distribution on oil and gas basins,China seas and adjacent areas

The distribution of oil and gas resources is intricately connected to the underlying structure of the lithosphere.Therefore,investigating the characteristics of lithospheric thickness and its correlation with oil and gas basins is highly important.This research utilizes recently enhanced geological–geophysical data,including topographic,geoid,rock layer thickness,variable rock layer density,and interface depth data.Employing the principles of lithospheric isostasy and heat conduction,we compute the laterally varying lithospheric thickness in the China seas and adjacent areas.From these results,two pivotal parameters for different types of oil and gas basins were statistically analyzed:the minimum lithospheric thickness and the relative fluctuation in lithospheric thickness.A semiquantitative analysis was used to explore the connection between these parameters and the hydrocarbon abundance within the oil and gas basins.This study unveils distinct variations in lithospheric thickness among basins,with oil and gas rich basins exhibiting a thicker lithosphere in the superimposed basins of central China and a thinner lithosphere in the rift basins of eastern China.Notably,the relative fluctuations in lithospheric thickness in basins demonstrate significant disparities:basins rich in oil and gas often exhibit greater thickness fluctuations.Additionally,in the offshore basins of China,a conspicuous negative linear correlation is observed between the minimum lithospheric thickness and the relative fluctuation in lithospheric thickness.This study posits that deep-seated thermal upwelling results in lithospheric undulations and extensional thinning in oil and gas basins.Concurrently,sustained deep-seated heat influences sedimentary materials in basins,creating favorable conditions for oil and gas generation.The insights derived from this study contribute to a quantitative understanding of the intricate relationships between deep lithospheric structures and oil and gas basins.These findings provide valuable guidance for future oil and gas exploration in the studied areas.

Astronomical influence of the development of Paleogene thin coal seam groups in offshore Lacustrine basins:A case study of the ZhuⅠDepression's Enping Formation located in the northern South China Sea

The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stability,scattered vertical distribution,and a wide distribution range.This study selected the Enping Formation of the ZhuⅠDepression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups.An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region.A floating astronomical time scale of the Enping Formation was established,and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±.In addition,the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors.The formation process of coal seams was determined to have been affected by high seasonal contrast,precipitation,and insolation.During the periods with high values of short eccentricity,the seasonal contrasts tended to be high.During those periods,fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region,resulting in the development of thin coal seams.It was also found that the periods with low precession were the most conducive to coal seam development.On that basis,combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups,this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins.The patterns of the Paleogene astronomical periods and paleoclimate evolution,along with the control factors which impacted the development of thin coal seam groups in offshore lacustrine basins,were revealed.

Characteristics and main controlling factors of helium resources in the main petroliferous basins of the North China Craton

At present, the main controlling factors of helium accumulation is one of the key scientific problems restricting the exploration and development of helium reservoir. In this paper, based on the calculation results of He generation rate and the geochemical characteristics of the produced gas, both the similarities and differences between natural gas and He resources in the Bohai Bay, Ordos and the surrounding Songliao Basin are compared and analyzed, discussing the main controlling factors of helium resources in the three main petroliferous basins of the North China Craton. It is found that the three basins of Bohai Bay, Ordos and Songliao have similar characteristics of source rocks, reservoirs and cap rocks, that's why their methane resource characteristics are essentially the same. The calculated ~4He generation per cubic metamorphic crystalline basement in the three basins is roughly equivalent, which is consistent with the measured He resources, and it is believed that the ~4He of radiogenic from the crust is the main factor controlling the overall He accumulation in the three basins;there is almost no contribution of the mantle-derived CH_4, which suggests that the transport and uplift of mantle-derived ~3He carried by the present-day magmatic activities along the deep-large faults is not the main reason for the mantle-derived ~3He mixing in the basins. Combined with the results of regional volcanic and geophysical studies,it is concluded that under the background of the destruction of North China Craton, magma intrusion carried a large amount of mantle-derived material and formed basic volcanic rocks in the Bohai Bay Basin and Songliao Basin, which replenished mantle-derived ~3He for the interior of the basins, and that strong seismic activities in and around the basins also promoted the upward migration of mantle source ~3He. This study suggests that the tectonic zone with dense volcanic rocks in the Cenozoic era and a high incidence of historical strong earthquakes history may be a potential area for helium resource exploration.

Meso-Cenozoic Evolution of the Tanlu Fault and Formation of Sedimentary Basins

Abstract: There are a group of large and medium-scale Meso-Cenozoic petroliferous basins along both sides of the Tanlu fault or within the fault zone, e.g., the Songliao basin, the Bohai Bay basin and the Subei-Yellow Sea basin. As shown by studies of the structural types, sedimentary formations, volcanic activities, tectonic evolution as well as the time-space relationship between the Tanlu fault zone and the basins, the formation and distribution of the basins are controlled by the movement of the Tanlu fault. This paper presents an analysis of the tectono-geometric, kinematic and geodynamic features of the basins on the basis of integrated geological-geophysical data, and an exploration into the internal relations between the fault and the basins as well as the formation mechanism and geodynamic processes of the basins.

Stratigraphic Succession,Source-Rock Distribution and Paleoclimatic Zone in Meso-Cenozoic Basins,Eastern China

?The unequal spacetime distribution of the source rocks resulted from the mutual superimposition of the biota evolution, basin type, and paleoclimatic change. The basin type is the most important in controlling the distribution of source rocks. The effect of the paleoclimate on the source rocks varied with different basins. In the rift basin, the source rocks were accumulated in the humid, semihumid and semiarid climates; however, in the flexural basin, only in the humid and semihumid climates. The biota features may control, to a great extent, the distribution pattern and the sourcerock quality. The abundance of the terrestrial flora and lacustrine phytoplankton was essential for the generation of the Meso-Cenozoic source rocks on a large scale.

Influence of the Moho surface distribution on the oil and gas basins in China seas and adjacent areas

Owing to the strategic significance of national oil and gas resources,their exploration and production must be prioritized in China.Oil and gas resources are closely related to deep crustal structures,and Moho characteristics influence oil and gas distribution.Therefore,it is important to study the relationship between the variation of the Moho surface depth undulation and hydrocarbon basins for the future prediction of their locations.The Moho depth in the study area can be inverted using the Moho depth control information,the Moho gravity anomaly,and the variable density distribution calculated by the infinite plate.Based on these results,the influences of Moho characteristics on petroleum basins were studied.We found that the Moho surface depth undulation deviation and crustal thickness undulation deviation in the hydrocarbon-rich basins are large,and the horizontal gradient deviation of the Moho surface shows a positive linear relationship with oil and gas resources in the basin.The oil-bearing mechanism of the Moho basin is further discussed herein.The Moho uplift area and the slope zone correspond to the distribution of oil and gas fields.The tensile stress produced by the Moho uplift can form tensile fractures or cause tensile fractures on the surface,further developing into a fault or depression basin that receives deposits.The organic matter can become oil and natural gas under suitable chemical and structural conditions.Under the action of groundwater or other dynamic forces,oil and natural gas are gradually transported to the uplift or the buried hill in the depression zone,and oil and gas fields are formed under the condition of good caprock.The research results can provide new insights into the relationship between deep structures and oil and gas basins as well as assist in the strategic planning of oil and gas exploration activities.

Machine learning-based automatic construction of earthquake catalog for reservoir areas in multiple river basins of Guizhou province,China

Large reservoirs have the risk of reservoir induced seismicity.Accurately detecting and locating microseismic events are crucial when studying reservoir earthquakes.Automatic earthquake monitoring in reservoir areas is one of the effective measures for earthquake disaster prevention and mitigation.In this study,we first applied the automatic location workflow(named LOCFLOW)to process 14-day continuous waveform data from several reservoir areas in different river basins of Guizhou province.Compared with the manual seismic catalog,the recall rate of seismic event detection using the workflow was 83.9%.Of the detected earthquakes,88.9%had an onset time difference below 1 s,81.8%has a deviation in epicenter location within 5 km,and 77.8%had a focal depth difference of less than 5 km,indicating that the workflow has good generalization capacity in reservoir areas.We further applied the workflow to retrospectively process continuous waveform data recorded from 2020 to the first half of 2021 in reservoir areas in multiple river basins of western Guizhou province and identified five times the number of seismic events obtained through manual processing.Compared with manual processing of seismic catalog,the completeness magnitude had decreased from 1.3 to 0.8,and a b-value of 1.25 was calculated for seismicity in western Guizhou province,consistent with the b-values obtained for the reservoir area in previous studies.Our results show that seismicity levels were relatively low around large reservoirs that were impounded over 15 years ago,and there is no significant correlation between the seismicity in these areas and reservoir impoundment.Seismicity patterns were notably different around two large reservoirs that were only impounded about 12 years ago,which may be explained by differences in reservoir storage capacity,the geologic and tectonic settings,hydrogeological characteristics,and active fault the reservoir areas.Prominent seismicity persisted around two large reservoirs that have been impounded for less than 10 years.These events were clustered and had relatively shallow focal depths.The impoundment of the Jiayan Reservoir had not officially begun during this study period,but earthquake location results suggested a high seismicity level in this reservoir area.Therefore,any seismicity in this reservoir area after the official impoundment deserves special attention.

Study on the distribution characteristics of faults and their control over petroliferous basins in the China seas and its adjacent areas

As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In this work,we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly,the fusion results of gravity and magnetic anomalies,and the residual Bouguer gravity anomaly.The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly.The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW,followed by EW,and near-SN.Among them,the lengths of most ultra-crustal faults are in the range of 1000–3000 km,and their apparent depths lie between 10 km and 40 km.The lengths of crustal faults lie between 300 km and 1000 km,and their apparent depths are between 0 km and 20 km.According to the plane positions and apparent depths of the faults,we put forward the concept of fault influence factor for the first time.Based on this factor,the key areas for oil and gas exploration were found as follows:the east of South North China Basin in the intracontinental rift basins;the southeast region of East China Sea Shelf Basin,the Taixinan and Qiongdongnan basins in the continental margin rift basins;Zhongjiannan Basin in the strike-slip pull-apart basins;the Liyue,Beikang,and the Nanweixi basins in the rifted continental basins.This work provides valuable insights into oil and gas exploration,mineral resource exploration,and deep geological structure research in the China seas and its adjacent areas.

Characteristics of Meso-Cenozoic Igneous Complexes in the South Yellow Sea Basin,Lower Yangtze Craton of Eastern China and the Tectonic Setting

The South Yellow Sea Basin is partially surrounded by the East Asian continental Meso- Cenozoic widespread igneous rocks belt. Magnetic anomaly and multi-channel seismic data both reveal the prevalent occurrence of igneous rocks. We preliminarily defined the coupling relation between magnetic anomalies and igneous rock bodies. Some igneous complexes were also recognized by using multi-channel seismic and drilling data. We identified various intrusive and extrusive igneous rock bodies, such as stocks, sills, dikes, laccoliths and volcanic edifice relics through seismic facies analysis. We also forecasted the distribution characteristics of igneous complexes. More than fifty hypabyssal intrusions and volcanic relics were delineated based on the interpretation of magnetic anomaly and dense intersecting multi-channel seismic data. It is an important supplement to regional geology and basin evolution research. Spatial matching relations between igneous rock belts and fractures document that extensional N-E and N-NE-trending deep fractures may be effective pathways for magma intrusion. These fractures formed under the influence of regional extension during the Meso- Cenozoic after the Indosinian movement. Isotopic ages and crosscutting relations between igneous rock bodies and the surrounding bedded sedimentary strata both indicate that igneous activities might have initiated during the Late Jurassic, peaked in the Early Cretaceous, gradually weakened in the Late Cretaceous, and continued until the Miocene. Combined with previous studies, it is considered that the Meso-Cenozoic igneous activities, especially the intensive igneous activity of the Early Cretaceous, are closely associated with the subduction of the Paleo-Pacific Plate.

Meso-Cenozoic lithospheric thermal structure in the Bohai Bay Basin,eastern North China Craton

The Bohai Bay Basin is a region where part of the North China Craton has been thinned and destroyed. It has experienced two periods of crustal thinning that occurred during the Cretaceous and Paleogene, but investigations of its Mesozoic and Cenozoic lithospheric thermal structure are limited. Therefore, in this study,the distributions of mantle heat flow, crustal heat flow, and Moho temperatures during the Meso-Cenozoic are calculated based on analyses of the thermal history of the Bohai Bay Basin. The results indicate that the ratio of mantle heat flow to surface heat flow peaked during the late stages of the early Cretaceous and during the middle to late Paleogene. The corresponding mantle heat flow was more than 65% of the surface heat flow. Moho temperatures reached three peaks: 900-1100℃ in the late stages of the early Cretaceous;820-900℃ in the middle to late Paleogene; and(in the Linqing Depression, Cangxian Uplift, and Jizhong Depression) 770-810℃ during the early Neogene. These results reveal that the Bohai Bay Basin experienced significant geological change during the Cretaceous, including the transformation of lithospheric thermal structure from "cold mantle and hot crust" before the Cretaceous to "hot mantle and cold crust" after the Cretaceous. The results also indicate that the basin experienced two large-scale rifting events.Therefore, this work may provide the thermal parameters for further investigations of the geodynamic evolution of eastern China.

Formation of the Zengmu and Beikang Basins,and West Baram Line in the southwestern South China Sea margin

The Zengmu and Beikang basins,separated by the West Baram Line(WBL)in the southwestern South China Sea margin,display distinct geological and geophysical features.However,the nature of the basins and the WBL are debated.Here we explore this issue by conducting the stratigraphic and structural interpretation,faults and subsidence analysis,and lithospheric finite extension modelling using seismic data.Results show that the WBL is a trans-extensional fault zone comprising normal faults and flower structures mainly active in the Late Eocene to Early Miocene.The Zengmu Basin,to the southwest of the WBL,shows an overall synformal geometry,thick folded strata in the Late Eocene to Late Miocene(40.4-5.2 Ma),and pretty small normal faults at the basin edge,which imply that the Zengmu Basin is a foreland basin under the Luconia and Borneo collision in the Sarawak since the Eocene.Furthermore,the basin exhibits two stages of subsidence(fast in 40.4-30 Ma and slow in 30-0 Ma);but the amount of observed subsidence and heat flow are both greater than that predicted by crustal thinning.The Beikang Basin,to the NE of the WBL,consists of the syn-rift faulted sub-basins(45-16.4 Ma)and the post-rift less deformed sequences(16.4-0 Ma).The heat flow(~60 mW/m2)is also consistent with that predicted based on crustal thinning,inferring that it is a rifted basin.However,the basin shows three stages of subsidence(fast in 45-30 Ma,uplift in 30-16.4 Ma,and fast in 16.4-0 Ma).In the uplift stage,the strata were partly folded in the Late Oligocene and partly eroded in the Early Miocene,which is probably caused by the flexural bulging in response to the paleo-South China Sea subduction and the subsequent Dangerous Grounds and Borneo collision in the Sabah to the east of the WBL.

Fossil Equidae in the Linxia Basin with Biostratigraphic and Paleozoogeographic Significance

The Linxia Basin is characterized by an abundance of Cenozoic sediments,that contain exceptionally rich fossil resources.Equids are abundant in the Linxia Basin,the fossil record of equids in this region including 16 species that represent 10 genera.In comparison to other classic late Cenozoic areas in China,the Linxia Basin stands out,because the fauna and chronological data accompanying Linxia equids render them remarkably useful for biostratigraphy.The anchitheriines in the region,such as Anchitherium and Sinohippus,represent early equids that appeared in the late stages of the middle and late Miocene,respectively.Among the equines,most species of Chinese hipparions have been identified in the Linxia Basin and some species of the genera Hipparion and Hippotherium have FAD records for China.Furthermore,Equus eisenmannae is one of the earliest known species of Equus in the Old World and is well-represented at the Longdan locality.Some species with precise geohistorical distributions can serve as standards for high-resolution chronological units within this framework.Located at the eastern margin of the Tibetan Plateau and subject to considerable uplift,the Linxia Basin has served as a biogeographic transition area for equids throughout the late Cenozoic.

Geochemistry and origins of hydrogen-containing natural gases in deep Songliao Basin,China:Insights from continental scientific drilling

The different reservoirs in deep Songliao Basin have non-homogeneous lithologies and include multiple layers with a high content of hydrogen gas.The gas composition and stable isotope characteristics vary significantly,but the origin analysis of different gas types has previously been weak.Based on the geochemical parameters of gas samples from different depths and the analysis of geological settings,this research covers the diverse origins of natural gas in different strata.The gas components are mainly methane with a small amount of C_(2+),and non-hydrocarbon gases,including nitrogen(N_(2)),hydrogen(H_(2)),carbon dioxide(CO_(2)),and helium(He).At greater depth,the carbon isotope of methane becomes heavier,and the hydrogen isotope points to a lacustrine sedimentary environment.With increasing depth,the origins of N_(2)and CO_(2)change gradually from a mixture of organic and inorganic to inorganic.The origins of hydrogen gas are complex and include organic sources,water radiolysis,water-rock(Fe^(2+)-containing minerals)reactions,and mantle-derived.The shales of Denglouku and Shahezi Formations,as source rocks,provide the premise for generation and occurrence of organic gas.Furthermore,the deep faults and fluid activities in Basement Formation control the generation and migration of mantle-derived gas.The discovery of a high content of H_(2)in study area not only reveals the organic and inorganic association of natural-gas generation,but also provides a scientific basis for the exploration of deep hydrogen-rich gas.

Geochemical characteristics and exploration significance of ultra-deep Sinian oil and gas from Well Tashen 5,Tarim Basin,NW China

The Well Tashen 5(TS5),drilled and completed at a vertical depth of 9017 m in the Tabei Uplift of the Tarim Basin,NW China,is the deepest well in Asia.It has been producing both oil and gas from the Sinian at a depth of 8780e8840 m,also the deepest in Asia in terms of oil discovery.In this paper,the geochemical characteristics of Sinian oil and gas from the well were investigated and compared with those of Cambrian oil and gas discovered in the same basin.The oil samples,with Pr/Ph ratio of 0.78 and a whole oil carbon isotopic value of31.6‰,have geochemical characteristics similar to those of Ordovician oils from the No.1 fault in the North Shuntuoguole area(also named Shunbei area)and the Middle Cambrian oil from wells Zhongshen 1(ZS1)and Zhongshen 5(ZS5)of Tazhong Uplift.The maturity of light hydrocarbons,diamondoids and aromatic fractions all suggest an approximate maturity of 1.5%e1.7%Ro for the samples.The(4-+3-)methyldiamantane concentration of the samples is 113.5 mg/g,indicating intense cracking with a cracking degree of about 80%,which is consistent with the high bottom hole temperature(179℃).The Sinian gas samples are dry with a dryness coefficient of 0.97.The gas is a mixture of kerogen-cracking gas and oil-cracking gas and has Ro values ranging between 1.5%and 1.7%,and methane carbon isotopic values of41.6‰.Based on the equivalent vitrinite reflectance(R_(eqv)=1.51%e1.61%)and the thermal evolution of source rocks from the Cambrian Yu'ertusi Formation of the same well,it is proposed that the Sinian oil and gas be mainly sourced from the Cambrian Yu'ertusi Formation during the Himalayan period but probably also be joined by hydrocarbon of higher maturity that migrated from other source rocks in deeper formations.The discovery of Sinian oil and gas from Well TS5 suggests that the ancient ultra-deep strata in the northern Tarim Basin have the potential for finding volatile oil or condensate reservoirs.

Geochemical fingerprints and hydrocarbon potential of Paleocene mudrocks in the Tano Basin, Ghana: insights from biomarkers and stable carbon isotopes

The Paleocene mudrocks in Ghana’s Tano Basin have received limited attention despite ongoing efforts to explore hydrocarbon resources.A thorough geochemical analysis is imperative to assess these mudrocks’petroleum generation potential and formulate effective exploration strategies.In this study,a comprehensive geochemical analysis was carried out on ten Paleocene rock cuttings extracted from TP-1,a discovery well within the Tano Basin.Various analytical techniques,including total organic carbon(TOC)analysis,Rock–Eval pyrolysis,gas chromatography-mass spectrometry,and isotope ratio-mass spectrometry,were employed to elucidate their hydrocar-bon potential and organic facies.Thefindings in this study were subsequently compared to existing geochemical data on Paleocene source rocks in the South Atlantic marginal basins.The results indicated that the Paleocene samples have TOC content ranging from 0.68 to 2.93 wt%.The prevalent kerogen types identified in these samples were Type Ⅱ and Type Ⅲ.Molecular and isotope data suggest that the organic matter found in the Paleocene mudrocks can be traced back to land plants and lower aquatic organisms.These mudrocks were deposited in a transi-tional environment withfluctuating water salinity,charac-terized by sub-oxic redox conditions.Maturity indices,both bulk and molecular,indicated a spectrum of maturity levels within the Paleocene mudrocks,spanning from immature to marginally mature,with increasing maturity observed with greater depth.In comparison,the organic composition and depositional environments of Paleocene source rocks in the Tano Basin closely resemble those found in the Niger Delta Basin,Douala,and Kribi-Campo Basins,the Kwanza Formation in Angola,and certain Brazilian marginal basins.However,it is worth noting that Paleocene source rocks in some of the basins,such as the Niger Delta and Brazilian marginal basins,exhibit rela-tively higher thermal maturity levels compared to those observed in the current Paleocene samples from the Tano Basin.In conclusion,the comprehensive geochemical analysis of Paleocene mudrocks within Ghana’s Tano Basin has unveiled their marginal hydrocarbon generation potential.The shared geochemical characteristics between the Paleocene mudrocks in the Tano Basin and those in the nearby South Atlantic marginal basins offer valuable insights into source rock quality,which is crucial for shaping future strategies in petroleum exploration in this region.

Effect of tectonic-climatic controllers on the transition of Endorheic to Exorheic Basins in the Zagros mountain range

Endorheic basins(ENBs) are inland drainage basins allowing no outflow to oceans.These basins in the active mountain chains of the convergence zones are under the influence of compressional tectonic activity and climate condition.The Zagros Mountains of Iran is one of the youngest convergence zones in which continental-continental collision has occurred.In this paper we hypothesize the formation of ENBs among the Zagros range after the epeirogenic stage in the Late Paleogene-Early Neogene.Due to tectonic activity and Quaternary climatic conditions,the ENBs pass the transition stage to exorheic,and still,some tectonic depressions are not linked to the evolutionary process of exorheic drainage of Zagros.The geometry of the drainage network of Kul and Mond basins in Fars arch shows that 67% of their water gaps are located along the thrusts and transverse basement faults in the east and west of the Fars arch.Geometrically,the Kul and Mond basins form triangles with their sides matching with the edges of the Arabian Plate where the major inherited faults of Arabian plate controls the shape of the Zagros basin and a low strain zone along the Razak fault with lower salt tectonic activity,where the wind gaps are created.The ENBs are located in the rainshadow slopes,but the Kul and Mond basins are located in the upwind slopes of rain waves.This factor and the heavy rains of the basin lead to increase of the erosion potential,destruction of depressions,and floods and consequently,the funnel-shaped gaps have a significant impact on the flood flow.

Grading Evaluation and Ranking of CO_(2) Sequestration Capacity in Place(CSCIP) in China’s Major Oil Basins:Theoretical,Effective,Practical and CCUS-EOR

Because it is necessary to focus on differences in regional oil reservoirs and determine the priority of the CCUSEOR(Carbon capture,utilization,and storage-enhanced oil recovery) deployment under China’s net-zero CO_(2) emission target,systematic and regional evaluations of CO_(2) sequestration capacity in major oil basins are needed considering the geofluid properties―carbon sequestration capacity in place(CSCIP)―where the ’in place’ indicates actual geological formation conditions underground,e.g.,formation temperature and pressure.Therefore,physical properties of geofluids at different depths with different geologic temperatures and pressure conditions are considered for the CO_(2) sequestration capacity evaluation in place,including shallow(800–2000 m),medium(2000–3500 m),deep(3500–4500 m) and ultra-deep(4500–8000 m) depth intervals.A modified evaluation model with four grading levels is proposed,combining the P-V-T equations of state(EOS) and evaluation equations of the Carbon Sequestration Leadership Forum(CSLF),including theoretical,effective,practical,and CCUS-EOR CSCIP,which is more consistent with geofluid physical properties underground,to make the grading evaluation and ranking of the CSCIP in China’s major oil basins.Then,the grading CSCIP of 29 major oil basins in China was evaluated based on the petroleum resources evaluation results of the Ministry of Natural Resources of China(MNRC) during China’s 13th Five-Year Plan period.According to the grading evaluation results,suggestions for China’s CCUS-EOR prospective regions are given as follows:shallow oil fields of the Songliao Basin in Northeast China,shallow–medium oil fields of the Bohai Bay Basin in East China,medium oil fields of the Zhungeer Basin in West China,and medium oil fields of the Ordos Basin in Central China;all are potential areas for the CCUS-EOR geological sequestration in China’s onshore oil basins.In addition,in China’s offshore oil basins,shallow–medium oil fields of the Bohai Sea and shallow oil fields of the Pearl River Mouth Basin have potential for CCUS-EOR geological sequestration.

Reservoir characteristics and controlling factor of tight sandstone in Shuixigou Group in Taibei depression,Turpan-Hami basin

The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to source rocks in the sag,where the Shuixigou Group with substantial oil and gas potential constitutes the primary focus for near-source exploration.Consequently,characterization of development and key controlling factors of reservoir space becomes a must for future exploration in the area.This study investigates the development traits,genesis,and controlling factors of the Xishanyao and Sangonghe formations in the Shengbei and Qiudong Sub-sags of the Taibei Sag with techniques such as cast thin-section observation,porosity and permeability tests,high-pressure mercury injection,and saturation fluid NMR analysis of reservoir rocks.The findings reveal that the Shuixigou Group in the Taibei Sag consists of lithic sandstone.Reservoirs in the group are mostly poor in terms of physical properties,with undeveloped primary pores dominated by intergranular dissolved pores as a result of a strong compaction.Comparative analysis of key controlling factors of the Sangonghe Formation reveals significant distinctions in sandstone particle size,sand body thickness,genesis and distribution,provenance location,and source rock type between the Qiudong area and Shengbei area.Vertically,the coal seams of the Xishanyao Formation exhibit heightened development with shallower burial depth and lower maturity compared to those of the Sangonghe Formation.Consequently,this environment fosters the formation of organic acids,which have a stronger dissolution effect on minerals to develop secondary dissolution pores,and ultimately resulting in better reservoir physical properties.Overall,the reservoirs within the Qiudong area of the Taibei Sag demonstrate superior characteristics compared to those in the Shengbei area.Furthermore,the reservoir physical properties of the Xishanyao Formation are better than those of the Sangonghe Formation.The research findings will provide valuable guidance for the exploration and development of lithological oil and gas reservoirs within the Taibei Sag.