Methane gas hydrate related bottom-simulating reflectors(BSRs)are imaged based on the in-line and cross-line multi-channel seismic(MCS)data from the Andaman Forearc Basin.The depth of the BSR depends on pressure and t...Methane gas hydrate related bottom-simulating reflectors(BSRs)are imaged based on the in-line and cross-line multi-channel seismic(MCS)data from the Andaman Forearc Basin.The depth of the BSR depends on pressure and temperature and pore water salinity.With these assumptions,the BSR depth can be used to estimate the geothermal gradient(GTG)based on the availability of in-situ temperature measurements.This calculation is done assuming a 1D conductive model based on available in-situ temperature measurement at site NGHP-01-17 in the study area.However,in the presence of seafloor topography,the conductive temperature field in the subsurface is affected by lateral refraction of heat,which focuses heat in topographic lows and away from topographic highs.The 1D estimate of GTG in the Andaman Forearc Basin has been validated by drilling results from the NGHP-01 expedition.2D analytic modeling to estimate the effects of topography is performed earlier along selected seismic profiles in the study area.The study extended to estimate the effect of topography in 3D using a numerical model.The corrected GTG data allow us to determine GTG values free of topographic effect.The difference between the estimated GTG and values corrected for the 3D topographic effect varies up to~5℃/km.These conclude that the topographic correction is relatively small compared to other uncertainties in the 1D model and that apparent GTG determined with the 1D model captures the major features,although the correction is needed prior to interpreting subtle features of the derived GTG maps.展开更多
The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan an...The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan and the 2013 Lushan earthquakes. This study analysed underground temperature sequence data for four years at seven measuring points at different depths（maximum depth： 18.9 m） in the southeastern section of the XSHF zone. High-frequency atmospheric noise was removed from the temperature sequences to obtain relatively stable temperature fields and heat fluxes near the measurement points. Our measurements show that the surrounding bedrock at（the seven stations distributed in the fault zone） had heat flux values range from-41.0 to 206 m W/m^2, with a median value of 54.3 m W/m^2. The results indicate a low heat flux in the northern section of DaofuKangting and a relatively high heat flux in the southern section of Kangting, which is consistent with the temperature distributions of the hot springs near the fault. Furthermore, our results suggest that the heat transfer in this field results primarily from stable underground heat conduction. In addition, the underground hydrothermal activity is also an obvious factor controlling the geothermal gradient.展开更多
Information on geothermal gradient and heat flow within the subsurface is critical in the quest for geothermal energy exploration. In a bid to ascertain the thermal potential of Nigeria sector of the Chad Basin for en...Information on geothermal gradient and heat flow within the subsurface is critical in the quest for geothermal energy exploration. In a bid to ascertain the thermal potential of Nigeria sector of the Chad Basin for energy generation, subsurface temperature information from 19 oil wells, 24 water boreholes drilled to depths beyond 100 metres and atmospheric temperature from the Chad basin were utilized in calculating geothermal gradient of the area. Selected ditch cuttings from the wells were subjected to thermal conductivity test using Thermal Conductivity Scanner (TCS) at the Polish Geological Institute Laboratory in Warsaw. The terrestrial heat flow was calculated according to the Fourier’s law as a simple product of the geothermal gradient and the mean thermal conductivity. Results obtained indicated geothermal gradient range of 2.81<sup> °</sup>C/100 m to 5.88<sup> °</sup>C/100 m with an average of 3.71<sup> °</sup>C/100 m. The thermal conductivity values from the different representative samples range from 0.58 W/m*K to 4.207 W/m*K with an average of 1.626 W/m*K. The work presented a heat flow value ranging from 45 mW/m<sup>2</sup> to about 90 mW/m<sup>2</sup> in the Nigerian sector of the Chad Basin.展开更多
The heat budget of sedimentary basins is determined by heat transfer across the lithosphereasthenosphere boundary and lithospheric heat sources,such that the tectonic evolution of their host continental and oceanic li...The heat budget of sedimentary basins is determined by heat transfer across the lithosphereasthenosphere boundary and lithospheric heat sources,such that the tectonic evolution of their host continental and oceanic lithosphere ultimately impact the present-day heat flow and average geothermal gradients.Recent increase in availability of publicly-accessible geothermal gradient measurements across the world provides an opportunity to globally assess the dominant controls on the thermal regime of sedimentary basins.Thus,we compile a global dataset of152,000 unique data points with constrained bottomhole temperature measurements and assess the relationships between geothermal gradient and selected independent tectonic variables,including crustal and lithospheric thicknesses,crustal age,sediment thickness,and basin type.The results show that in both oceanic and continental settings,geothermal gradients exhibit a non-linear,systematic variation with the tectonic variables.We find that oceanic geothermal gradients decrease with increasing crustal age and lithospheric thickness.Geothermal gradients in the continents show no clear relationships with thermotectonic crustal age,but decrease with increasing crustal and lithospheric thicknesses.Gradients drop significantly at 1.5 km sediment-cover thickness,likely reflecting the effect of high sedimentation rates,but show a striking rise at>12 km thicknesses,potentially influenced by thinned lithosphere and thermal blanketing effects.The commonly-assumed‘normal’gradient of 25℃/km for continents is only valid for a narrow range(1.5–12.5 km)of sedimentary cover-thickness,and oceanic‘normal’gradient may be as high as 50–75℃/km for>20 Ma crustal age and>50 km-thick lithosphere.We show that,conditionally,crustal age may best predict average geothermal gradients in oceanic settings,and lithosphere thickness in continents.Further,we observe that tectonic basin types exhibit distinct ranges of gradients that reflect their prevalent tectonic and geodynamic origins.Despite the complexities of determining shallow-crustal thermal conductivities,the results provide insights that fingerprint distinct tectonic settings based on the broad distribution of their geothermal gradients.展开更多
The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gra...The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.展开更多
In the last few decades, addressing the global challenge of implementation of strategies for renewable energy and energy efficiency has become crucial.Morocco, since 2009, has made a steadfast commitment to sustainabi...In the last few decades, addressing the global challenge of implementation of strategies for renewable energy and energy efficiency has become crucial.Morocco, since 2009, has made a steadfast commitment to sustainability, with a particular focus on advancing the development of renewable energy resources. A comprehensive strategy has been formulated, centering on utilizing the country's energy potential to drive progress in this vital sector. Morocco is considered a country with abundant thermal water, indicating deep reservoirs with significant hydrothermal potential. Geothermal zones were selected based on the abundance of hot springs where water temperatures were high and geothermal gradients were significant. The abundance and importance of hot springs, combined with recent volcanism and ongoing non-tectonic activity linked to alpine orogeny, strongly suggest that these regions are promising reservoirs for geothermal energy. This great potential also extends to neighboring countries. In northeast and south Morocco, the temperature of thermal water ranges from 26 to 54℃. This study serves as an inclusive review of the geothermal potentialities in Morocco.展开更多
Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat sour...Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat source structures in Eburru area. Modelling was done using Oasis montaj geosoft software which is an iteration process where the gravity and magnetic anomalies were calculated and compared to the observed residual anomaly until there was a fit. The start model was constructed based on depths from Euler deconvolution and models constrained using stratigraphy data from the existing wells in the study area. <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Forward modelling of gravity and magnetic data revealed intrusions within the Earth’s subsurface with depth to the top of the sources ranging from </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">739 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> to </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">5811 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. The density of the sources ranges between </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.0 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> and </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.2 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> while their magnetic susceptibility was zero. This implies that intrusions from the mantle with a magnetic susceptibility of zero have temperatures exceeding the curie temperature of rocks. The density of the intrusions modelled was higher than 2.67 </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, the average crustal density, hence it explains the observed positive gravity anomaly. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The results also revealed that areas with high heat flux have shallow heat sources and if the heat sources are deep, then there must be a good heat transfer mechanism to the surface.</span></span></span></span>展开更多
The Baxian area in the Jizhong Depression,west of the Bohai Bay Basin,is rich in geothermal resources,where Xiong County was built as the first smokeless city in China and the Xiong-county Model has become the geother...The Baxian area in the Jizhong Depression,west of the Bohai Bay Basin,is rich in geothermal resources,where Xiong County was built as the first smokeless city in China and the Xiong-county Model has become the geothermal resources demonstration model in China.In this study,the present-day geothermal gradient and the horizontal distribution characteristics of the temperature and pressure at different depths in the Baxian area were studied based on massive measured temperature and pressure data of the boreholes,and then the relationship was also dis-cussed between the temperatureepressure field and the geothermal resources.The following findings were obtained.(1)The present-day geothermal gradient of the Baxian area is within the range of 21.8-73.5℃/km,averaging 33.5℃/km.(2)Its strata temperature increases as the depth increases.The horizontal variations of the geothermal gradient and strata temperature correspond to the basement relief very well.As the abnormally high temperature areas,the northern Niutuozhen Uplift,the Central Baxian Depression and the central East Langgu Depression possess huge geothermal resources and will be the most favorable exploration targets.(3)The formation pressure of the Baxian area is characterized by normal pressure and weak overpressure,and its horizontal distribution varies at different depths.The middleestrong overpressure generally developed at the depth of 4000 m in the southern Langgu Depression and southern Baxian Depression.This study is of important guiding significance for the exploration and development of geothermal resources in the Baxian area.展开更多
Extracting geothermal energy from the oil-producing fields is an experimental venture globally.The exploitation and utilization of geothermal energy can partly reduce the larger dependence on conventional non-renewabl...Extracting geothermal energy from the oil-producing fields is an experimental venture globally.The exploitation and utilization of geothermal energy can partly reduce the larger dependence on conventional non-renewable energy sources like oil,gas,coal,and other fossil fuels,and has a bright prospect.The Upper Assam Basin is a mature petroliferous basin of NE India,where there are several hundred low production,high water cut,or abandoned oil and gas wells that can be retrofitted as geothermal wells instead of drilling new ones.This will help bridge the gap of growing energy demand and limited supply in energy-deficient state like Assam.Situated away from the active plate boundaries and in lack of active volcanism,the Upper Assam Basin remains a low-to-medium enthalpy geothermal fluid regime.The deeper reservoir in this regard can,therefore,be the best candidate for the introspection of the potential geothermal energy reservoir reconnaissance.The selection of a deeper horizon considered in the present case has been the stratified reservoirs of the Lakadong-Therria(Lk-Th)Formation,Sylhet Group of the Lower Eocene age occurring at a variable depth of 3400 me 4600 m.The Lk-Th Formation possesses a fair-quality reservoir with lateral continuity and favourable petrophysical properties.In this study,representative gamma-ray(GR)and resistivity(R)logs were examined to work out lithology,and bed boundary demarcation,etc.The total Formation thickness varies from 97 to 157 m;the individual sand body thickness is up to 6 m.Other reservoir parameters,e.g.,porosity(φ=8-33%),water saturation(S_(w)=4.57-95.15%),geothermal gradient(2.71℃/100m to 3.92 C/100 m at 4300 m and 3608 m)respectively,and theoretical estimate of high heat flux in the range 70e100 mW/m^(2)/s,are the necessary yard-stick to measure the subsurface geothermal reserves.Efficient energy extraction will have the potential in facilitating energy utilization for industrial purposes,especially in tea processing units present nearby oilfields and also for power generation by the binary mechanism.展开更多
The aim of this study is to estimate the variations in curie point depth, geothermal gradient and heat flux from the frequency analysis of magnetic data in order to evaluate the geothermal potential of the Kaladi loca...The aim of this study is to estimate the variations in curie point depth, geothermal gradient and heat flux from the frequency analysis of magnetic data in order to evaluate the geothermal potential of the Kaladi locality and its surroundings. For this purpose, the magnetic field map was first reduced to equator (RTE). The centroid method was used to divide the RTE grid into a set of 40 blocks. The spectral analysis applied to each block allowed determining the depth to top (Z<sub>t</sub>), center (Z<sub>0</sub>) and bottom (Z<sub>b</sub><sub> </sub>also called curie point depth or CPD) of the magnetic sources. Knowing the different CPD, the geothermal gradient associated with each block was calculated. The heat flow was then calculated from the geothermal gradient associated with the anomaly block considered. From the set of values obtained for each block, maps of geothermal gradient and heat flow variations were established. Analysis of these maps shows that the sectors that could be favourable for geothermal exploration are the north of Kaladi and the Goro-Bembara corridor, because they show variations in the geothermal gradient and heat flow between 0.4 and 0.8℃/m and between 1.2 and 2 mW/m<sup>2</sup> respectively. In addition, the superposition of the different hot springs highlighted in previous studies with areas of high geothermal gradient and heat flow values supports this analysis. The proposed models can be used as background documents for any geothermal exploration project in the study area.展开更多
With the depletion of coal resources due to excessive exploitation and the increasing adjustment of the national energy structure, in response to the call of national policy, some mines are forced to close, and the re...With the depletion of coal resources due to excessive exploitation and the increasing adjustment of the national energy structure, in response to the call of national policy, some mines are forced to close, and the reuse of abandoned mine resources plays an important role in the sustainable development of mining industry. This paper analyzes the general situation of abandoned mines in Huainan and Huaibei, elaborates the research methods of geothermal temperature and calculation methods of geothermal reserves in abandoned mines, analyzes and studies the utilization prospect of geothermal resources in abandoned mines in Huainan and Huaibei, and draws the following conclusions: the temperature of geothermal resources in abandoned mines in Huainan and Huaibei is 25℃- 60℃, which belongs to the moderate-hot water and warm water resources in low-temperature geothermal resources, and can be used for geothermal heating, industrial geothermal and entertainment industries. Based on the previous experience in geothermal resource utilization mode, this paper provides theoretical and technical support for the demonstration project of resource utilization and development of abandoned mines in the Huainan and Huaibei mining areas.展开更多
Geothermal exploration and development in North Africa have advanced significantly,driven by the region's rich geothermal resources and rising energy demand.The countries of Mauritania,Morocco,Algeria,Tunisia,Liby...Geothermal exploration and development in North Africa have advanced significantly,driven by the region's rich geothermal resources and rising energy demand.The countries of Mauritania,Morocco,Algeria,Tunisia,Libya,and Egypt are located near tectonic plate boundaries(African and Eurasian plates),giving them substantial geothermal potential.Various exploration activities,including geological surveys and geophysical studies,have been conducted to assess geothermal reservoirs and identify suitable development sites.This article reviews the progress made in geothermal exploration across the region,highlighting the key activities undertaken to evaluate geothermal resources.It also explores how government policies have played a critical role either in fostering or in freezing geothermal development.The different conducted assessments such as analyzing geological structures,hydrothermal systems,and subsurface temperatures lead to identify suitable sites for geothermal development and improve the understanding of subsurface conditions and ongoing projects.Today,some countries in North Africa are positioning themselves to become important players in the global geothermal energy landscape,and with continued investment and concerted efforts,the region has the potential to emerge as a prominent player in the global geothermal energy landscape.展开更多
Based on the analysis of sea-bottom temperature and geothermal gradient, andby means of the phase boundary curve of gas hydrate and the sea-bottom temperature versus waterdepth curve in the South China Sea, this paper...Based on the analysis of sea-bottom temperature and geothermal gradient, andby means of the phase boundary curve of gas hydrate and the sea-bottom temperature versus waterdepth curve in the South China Sea, this paper studies the temperature and pressure conditions forgas hydrate to keep stable. In a marine environment, methane hydrate keeps stable at water depthsgreater than 550 min the South China Sea. Further, the thickness of the gas hydrate stability zonein the South China Sea was calculated by using the phase boundary curve and temperature-depthequations. The result shows that gas hydrate have a better perspective in the southeast of theDongsha Islands. the northeast of the Xisha Islands and the north of the Nansha Islands for thickerstability zones.展开更多
Due to its large heat transfer area and stable thermal performance,the middledeep coaxial borehole heat exchanger(CBHE)has become one of the emerging technologies to extract geothermal energy.In this paper,a numerical...Due to its large heat transfer area and stable thermal performance,the middledeep coaxial borehole heat exchanger(CBHE)has become one of the emerging technologies to extract geothermal energy.In this paper,a numerical modeling on a three-dimensional unsteady heat transfer model of a CBHE was conducted by using software FEFLOW,in which the model simulation was compared with the other studies and was validated with experimental data.On this basis,a further simulation was done in respect of assessing the influencing factors of thermal extraction performance and thermal influence radius of the CBHE.The results show that the outlet temperature of the heat exchanger decreases rapidly at the initial stage,and then tended to be stable;and the thermal influence radius increases with the increase of borehole depth.The heat extraction rate of the borehole increases linearly with the geothermal gradient.Rock heat capacity has limited impact on the heat extraction rate,but has a great influence on the thermal influence radius of the CBHE.When there is groundwater flow in the reservoir,the increase of groundwater velocity will result in the rise of both outlet temperature and heat extraction rate.The heat affected zone extends along with the groundwater flow direction;and its influence radius is increasing along with flow velocity.In addition,the material of the inner pipe has a significant effect on the heat loss in the pipe,so it is recommended that the material with low thermal conductivity should be used if possible.展开更多
The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and...The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and paleo heat flow,geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins.The average heat flow of the Tarim and Sichuan basins are 42.5±7.6 mW/m^(2)and 53.8±7.6 mW/m^(2),respectively,reflecting the characteristics of’cold’and’warm’basins.The geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Tarim Basin are 21.6±2.9℃/km,20.5±2.8℃/km and 19.6±2.8℃/km,respectively,while the geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Sichuan Basin are 21.9±2.3℃/km,22.1±2.5℃/km and23.3±2.4℃/km respectively.The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate.The formation temperatures at depths of 6,000 m,7,000 m,8,000 m,9,000 m and 10,000 m in the Tarim Basin are 80℃-190℃,90℃-220℃,100℃-230℃,110℃-240℃and 120℃-250℃,respectively,while the formation temperatures at depths of 6,000 m,7,000 m,8,000 m and 9,000 m in the Sichuan Basin are 120℃-200℃,140℃-210℃,160℃-260℃and 180℃-280℃,respectively.The horizontal distribution pattern of the ultra-deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief,fault activity and hydrothermal upwelling.The thermal modeling revealed that the paleo-heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak,while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian,rapidly rising at the end of the early Permian and declining since the late Permian.The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin,which results in differential oil and gas generation and conservation in the ultra-deep ancient strata.This study not only promotes theoretical development in the exploration of ultra-deep geothermal fields,but also plays an important role in determining the maturation phase of the ultra-deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.展开更多
The rock forming temperatures and pressures represent the p T points of the local regions in the lithosphere at a certain age, providing some important information on rock formation. Based on the preliminary sta...The rock forming temperatures and pressures represent the p T points of the local regions in the lithosphere at a certain age, providing some important information on rock formation. Based on the preliminary statistics on the temperatures and pressures for the formation of eclogites, granulites and peridotites in China, the variant ranges are given, in this paper, of temperatures, pressures and linear geothermal gradients of eclogites, granulites and peridotites. In addition, since the eclogite is different from granulite and peridotite in the p T diagram, these three rocks can be classified into two groups: the first group includes eclogites and the second group granulites and peridotites. Then, the p T correlation functions of these two groups of rocks are provided. Finally, the two groups of rocks have different geothermal gradients at the same pressure gradient or have different pressure gradients at the same geothermal gradient. The temperatures and pressures for the formation of the rocks can be calculated from the mineral chemical compositions, but the depths ( H ) for the rock formation can be calculated only under the hypotheses of given p H (or T H ) correlation functions. The explanations for the ultrahigh pressure metamorphism vary obviously with different hypotheses.展开更多
There is a long-standing discrepancy for numerous North American Cordillera metamorphic core complexes between geobarometric pressures recorded in the exhumed rocks and their apparent burial depths based on palinspast...There is a long-standing discrepancy for numerous North American Cordillera metamorphic core complexes between geobarometric pressures recorded in the exhumed rocks and their apparent burial depths based on palinspastic reconstructions from geologic field data.In particular,metamorphic core complexes in eastern Nevada are comprised of well-documented~12-15 km thick Neoproterozoic-Paleozoic stratigraphy of Laurentia’s western passive margin,which allows for critical characterization of field relationships.In this contribution we focus on the Ruby Mountain-East Humboldt Range-Wood Hills-Pequop Mountains(REWP)metamorphic core complex of northeast Nevada to explore reported peak pressure estimates versus geologic field relationships that appear to prohibit deep burial.Relatively high pressure estimates of 6-8 kbar(23-30 km depth,if lithostatic)from the lower section of the Neoproterozoic-Paleozoic passive margin sequence require burial and or repetition of the passive margin sequence by 2-3×stratigraphic depths.Our observations from the least migmatized and/or mylonitized parts of this complex,including field observations,a transect of peak-temperature(T_(p))estimates,and critical evaluation of proposed thickening/burial mechanisms cannot account for such deep burial.From Neoproterozoic-Cambrian(€)rocks part of a continuous stratigraphic section that transitions~8 km upsection to unmetamorphosed Permian strata that were not buried,we obtained new quartz-in-garnet barometry via Raman analysis that suggest pressures of~7 kbar(~26 km).A T_(p)traverse starting at the same basal€rocks reveals a smooth but hot geothermal gradient of≥40℃/km that is inconsistent with deep burial.This observation is clearly at odds with thermal gradients implied by high P-T estimates that are all≤25℃/km.Remarkably similar discrepancies between pressure estimates and field observations have been discussed for the northern Snake Range metamorphic core complex,~200 km to the southeast.We argue that a possible reconciliation of longestablished field observations versus pressures estimated from a variety of barometry techniques is that the rocks experienced non-lithostatic tectonic overpressure.We illustrate how proposed mechanisms to structurally bury the rocks,as have been invoked to justify published high pressure estimates,are entirely atypical of the Cordillera hinterland and unlike structures interpreted from other analogous orogenic plateau hinterlands.Proposed overpressure mechanisms are relevant in the REWP,including impacts from deviatoric/differential stress considerations,tectonic mode switching,and the autoclave effect driven by dehydration melting.Simple mechanical arguments demonstrate how this overpressure could have been achieved.This study highlights that detailed field and structural restorations of the least strained rocks in an orogen are critical to evaluate the tectonic history of more deformed rocks.展开更多
Deep and ultra-deep layers in the petroliferous basins of China are characterized by large temperature difference and complicated thermal evolution history.The control effects of temperature and thermal evolution hist...Deep and ultra-deep layers in the petroliferous basins of China are characterized by large temperature difference and complicated thermal evolution history.The control effects of temperature and thermal evolution history on the differences of hydrocarbon phase states and the hydrocarbon generation history in deep and ultra-deep layers are researched less and unsystematically.To deal with this situation,based on a large number of temperature and pressure data of deeplayers and combined with the complicated historical situation of deep layer evolution in the oil and gas basins of China,the effects of temperature,heating time and pressure on the hydrocarbon formation temperature and phase state were analyzed,and the types of temperature and pressure relationships were classified.Finally,based on the classification of thermal evolution history of deep and ultra-deep layers,We discussed the control effects of basin thermal evolution history on the hydrocarbon generation and phase state,and the following research results were obtained.First,the hydrocarbon phase states of deep layers in different basins and regions are greatly different,and they are mainly affected by temperature,heating time,heating rate,pressure,source rock types and other factors.And temperature is the most important factor controlling hydrocarbon generation and phase state distribution.Second,under the conditions of rapid temperature increasing and short heating time,there still maybe oil reservoirs and condensate gas reservoirs in deep and ultra-deep layersin thecase ofhigh temperature.Third,overpressureinhibitshydrocarbon generationand pyrolysis.Fourth,thereis a closerelationship betweentemperature and formation pressure of deeplayers,whichcan be divided into three types,i.e.,lowemedium temperature and high pressure type,high temperature and high pressure type,and medium temperature and lowemedium pressure type.Fifth,the thermal evolution history of deep and ultra-deep layers can be divided into four types,namely the late rapid subsidence,heating and low geothermal gradient type,the late rapid subsidence,heating and high geothermal gradient type,the middleelate rapid heating and late uplifting and cooling type,and the early great subsidence and rapid heating and middleelate great uplift erosion and cooling type.In conclusion,deep and ultra-deep layers in the basins with different types of thermal history are different in hydrocarbon phase states,accumulation stages and prospects.展开更多
This study documents the discovery of mound morphologies containing gas hydrate and methane-derived authigenic carbonate(MDAC)in the southwestern slope of the Chukchi Plateau,during the IBRV Araon expeditions in 2016 ...This study documents the discovery of mound morphologies containing gas hydrate and methane-derived authigenic carbonate(MDAC)in the southwestern slope of the Chukchi Plateau,during the IBRV Araon expeditions in 2016 and 2018.A multibeam bathymetric surveying was the basis for a new and detailed rendering around the mounds.Sub-bottom profiles and site-targeted gravity cores were also collected across these mounds which were located at water depths between 780 m and 580 m.Mounds are characterized by a circular plan shape of hundreds of meters in width and tens of meters in height.Below the mounds,gas accumulation in the sediment produces acoustic blanking in seismic data.MDACs are identified along the core collected from the top of a mound structure,indicating past methane oxidation processes.Gas hydrate has also been observed at the bottom of the core.Reverse geothermal gradients of the mound support the idea of active presentday seepage.We argue that the prolonged seepage activity of methane-rich fluid,possibly related to the formation of the rifted North Chukchi Basin,has led to the formation of the gas hydrate mounds,named hereafter the Araon Mounds,in the vicinity of the basin margin.展开更多
Heat flow was measured on the Lomonosov Ridge during the 5th Chinese National Arctic Expedition in 2012. To derive the time-temperature curve, resistivity data were transformed to temperature by the resistivity- tempe...Heat flow was measured on the Lomonosov Ridge during the 5th Chinese National Arctic Expedition in 2012. To derive the time-temperature curve, resistivity data were transformed to temperature by the resistivity- temperature program. Direct reading and linear regression methods were used to calculate the equilibrium temperature, which were regressed against the depth of the probes in sediment to derive the geothermal gradient. Then, heat flow was calculated as the product of geothermal gradient and thermal conductivity of sediments. The heat flow values on the basis of the two methods were similar （i.e., 67.27 mW/m2 and 63.99 mW/m2, respectively）. The results are consistent with the measurements carried out at adjacent sites. The age of the Lomonosov Ridge predicted by the heat flow-age model was 62 Ma, which is in accordance with the inference that the ridge was separated from Eurasia at about 60 Ma.展开更多
文摘Methane gas hydrate related bottom-simulating reflectors(BSRs)are imaged based on the in-line and cross-line multi-channel seismic(MCS)data from the Andaman Forearc Basin.The depth of the BSR depends on pressure and temperature and pore water salinity.With these assumptions,the BSR depth can be used to estimate the geothermal gradient(GTG)based on the availability of in-situ temperature measurements.This calculation is done assuming a 1D conductive model based on available in-situ temperature measurement at site NGHP-01-17 in the study area.However,in the presence of seafloor topography,the conductive temperature field in the subsurface is affected by lateral refraction of heat,which focuses heat in topographic lows and away from topographic highs.The 1D estimate of GTG in the Andaman Forearc Basin has been validated by drilling results from the NGHP-01 expedition.2D analytic modeling to estimate the effects of topography is performed earlier along selected seismic profiles in the study area.The study extended to estimate the effect of topography in 3D using a numerical model.The corrected GTG data allow us to determine GTG values free of topographic effect.The difference between the estimated GTG and values corrected for the 3D topographic effect varies up to~5℃/km.These conclude that the topographic correction is relatively small compared to other uncertainties in the 1D model and that apparent GTG determined with the 1D model captures the major features,although the correction is needed prior to interpreting subtle features of the derived GTG maps.
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No.4147408641174084)+2 种基金the CAS/CAFEA international partnership program for creative research teams (KZZD-EW-TZ-19)funded by the Special Fund for Seismic Scientific Research (200808011,2004DIB3J1290)the State Key Laboratory of Earthquake Dynamics,Institute of Geology (LED2009A07)
文摘The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan and the 2013 Lushan earthquakes. This study analysed underground temperature sequence data for four years at seven measuring points at different depths（maximum depth： 18.9 m） in the southeastern section of the XSHF zone. High-frequency atmospheric noise was removed from the temperature sequences to obtain relatively stable temperature fields and heat fluxes near the measurement points. Our measurements show that the surrounding bedrock at（the seven stations distributed in the fault zone） had heat flux values range from-41.0 to 206 m W/m^2, with a median value of 54.3 m W/m^2. The results indicate a low heat flux in the northern section of DaofuKangting and a relatively high heat flux in the southern section of Kangting, which is consistent with the temperature distributions of the hot springs near the fault. Furthermore, our results suggest that the heat transfer in this field results primarily from stable underground heat conduction. In addition, the underground hydrothermal activity is also an obvious factor controlling the geothermal gradient.
文摘Information on geothermal gradient and heat flow within the subsurface is critical in the quest for geothermal energy exploration. In a bid to ascertain the thermal potential of Nigeria sector of the Chad Basin for energy generation, subsurface temperature information from 19 oil wells, 24 water boreholes drilled to depths beyond 100 metres and atmospheric temperature from the Chad basin were utilized in calculating geothermal gradient of the area. Selected ditch cuttings from the wells were subjected to thermal conductivity test using Thermal Conductivity Scanner (TCS) at the Polish Geological Institute Laboratory in Warsaw. The terrestrial heat flow was calculated according to the Fourier’s law as a simple product of the geothermal gradient and the mean thermal conductivity. Results obtained indicated geothermal gradient range of 2.81<sup> °</sup>C/100 m to 5.88<sup> °</sup>C/100 m with an average of 3.71<sup> °</sup>C/100 m. The thermal conductivity values from the different representative samples range from 0.58 W/m*K to 4.207 W/m*K with an average of 1.626 W/m*K. The work presented a heat flow value ranging from 45 mW/m<sup>2</sup> to about 90 mW/m<sup>2</sup> in the Nigerian sector of the Chad Basin.
文摘The heat budget of sedimentary basins is determined by heat transfer across the lithosphereasthenosphere boundary and lithospheric heat sources,such that the tectonic evolution of their host continental and oceanic lithosphere ultimately impact the present-day heat flow and average geothermal gradients.Recent increase in availability of publicly-accessible geothermal gradient measurements across the world provides an opportunity to globally assess the dominant controls on the thermal regime of sedimentary basins.Thus,we compile a global dataset of152,000 unique data points with constrained bottomhole temperature measurements and assess the relationships between geothermal gradient and selected independent tectonic variables,including crustal and lithospheric thicknesses,crustal age,sediment thickness,and basin type.The results show that in both oceanic and continental settings,geothermal gradients exhibit a non-linear,systematic variation with the tectonic variables.We find that oceanic geothermal gradients decrease with increasing crustal age and lithospheric thickness.Geothermal gradients in the continents show no clear relationships with thermotectonic crustal age,but decrease with increasing crustal and lithospheric thicknesses.Gradients drop significantly at 1.5 km sediment-cover thickness,likely reflecting the effect of high sedimentation rates,but show a striking rise at>12 km thicknesses,potentially influenced by thinned lithosphere and thermal blanketing effects.The commonly-assumed‘normal’gradient of 25℃/km for continents is only valid for a narrow range(1.5–12.5 km)of sedimentary cover-thickness,and oceanic‘normal’gradient may be as high as 50–75℃/km for>20 Ma crustal age and>50 km-thick lithosphere.We show that,conditionally,crustal age may best predict average geothermal gradients in oceanic settings,and lithosphere thickness in continents.Further,we observe that tectonic basin types exhibit distinct ranges of gradients that reflect their prevalent tectonic and geodynamic origins.Despite the complexities of determining shallow-crustal thermal conductivities,the results provide insights that fingerprint distinct tectonic settings based on the broad distribution of their geothermal gradients.
基金the Scientific Project of Ministry of Land and Resource of Chinathe National Natural Science Foundation of Chinathe Doctoral Station Foundation of Ministry of Education of China
文摘The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.
文摘In the last few decades, addressing the global challenge of implementation of strategies for renewable energy and energy efficiency has become crucial.Morocco, since 2009, has made a steadfast commitment to sustainability, with a particular focus on advancing the development of renewable energy resources. A comprehensive strategy has been formulated, centering on utilizing the country's energy potential to drive progress in this vital sector. Morocco is considered a country with abundant thermal water, indicating deep reservoirs with significant hydrothermal potential. Geothermal zones were selected based on the abundance of hot springs where water temperatures were high and geothermal gradients were significant. The abundance and importance of hot springs, combined with recent volcanism and ongoing non-tectonic activity linked to alpine orogeny, strongly suggest that these regions are promising reservoirs for geothermal energy. This great potential also extends to neighboring countries. In northeast and south Morocco, the temperature of thermal water ranges from 26 to 54℃. This study serves as an inclusive review of the geothermal potentialities in Morocco.
文摘Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat source structures in Eburru area. Modelling was done using Oasis montaj geosoft software which is an iteration process where the gravity and magnetic anomalies were calculated and compared to the observed residual anomaly until there was a fit. The start model was constructed based on depths from Euler deconvolution and models constrained using stratigraphy data from the existing wells in the study area. <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Forward modelling of gravity and magnetic data revealed intrusions within the Earth’s subsurface with depth to the top of the sources ranging from </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">739 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> to </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">5811 m</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. The density of the sources ranges between </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.0 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> and </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">3.2 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> while their magnetic susceptibility was zero. This implies that intrusions from the mantle with a magnetic susceptibility of zero have temperatures exceeding the curie temperature of rocks. The density of the intrusions modelled was higher than 2.67 </span></span></span></span><span><span><span><span style="font-family:""><span style="font-family:Verdana;">g/cm</span><sup><span style="font-family:Verdana;">3</span></sup></span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">, the average crustal density, hence it explains the observed positive gravity anomaly. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The results also revealed that areas with high heat flux have shallow heat sources and if the heat sources are deep, then there must be a good heat transfer mechanism to the surface.</span></span></span></span>
基金Project supported by PetroChina's Major Science and Technology Project(No.2014E-35,2017E-15)School-Enterprise Cooperation Project of PetroChina Huabei Oilfield Company(No.HBYT-YJY-2015-JS-222).
文摘The Baxian area in the Jizhong Depression,west of the Bohai Bay Basin,is rich in geothermal resources,where Xiong County was built as the first smokeless city in China and the Xiong-county Model has become the geothermal resources demonstration model in China.In this study,the present-day geothermal gradient and the horizontal distribution characteristics of the temperature and pressure at different depths in the Baxian area were studied based on massive measured temperature and pressure data of the boreholes,and then the relationship was also dis-cussed between the temperatureepressure field and the geothermal resources.The following findings were obtained.(1)The present-day geothermal gradient of the Baxian area is within the range of 21.8-73.5℃/km,averaging 33.5℃/km.(2)Its strata temperature increases as the depth increases.The horizontal variations of the geothermal gradient and strata temperature correspond to the basement relief very well.As the abnormally high temperature areas,the northern Niutuozhen Uplift,the Central Baxian Depression and the central East Langgu Depression possess huge geothermal resources and will be the most favorable exploration targets.(3)The formation pressure of the Baxian area is characterized by normal pressure and weak overpressure,and its horizontal distribution varies at different depths.The middleestrong overpressure generally developed at the depth of 4000 m in the southern Langgu Depression and southern Baxian Depression.This study is of important guiding significance for the exploration and development of geothermal resources in the Baxian area.
文摘Extracting geothermal energy from the oil-producing fields is an experimental venture globally.The exploitation and utilization of geothermal energy can partly reduce the larger dependence on conventional non-renewable energy sources like oil,gas,coal,and other fossil fuels,and has a bright prospect.The Upper Assam Basin is a mature petroliferous basin of NE India,where there are several hundred low production,high water cut,or abandoned oil and gas wells that can be retrofitted as geothermal wells instead of drilling new ones.This will help bridge the gap of growing energy demand and limited supply in energy-deficient state like Assam.Situated away from the active plate boundaries and in lack of active volcanism,the Upper Assam Basin remains a low-to-medium enthalpy geothermal fluid regime.The deeper reservoir in this regard can,therefore,be the best candidate for the introspection of the potential geothermal energy reservoir reconnaissance.The selection of a deeper horizon considered in the present case has been the stratified reservoirs of the Lakadong-Therria(Lk-Th)Formation,Sylhet Group of the Lower Eocene age occurring at a variable depth of 3400 me 4600 m.The Lk-Th Formation possesses a fair-quality reservoir with lateral continuity and favourable petrophysical properties.In this study,representative gamma-ray(GR)and resistivity(R)logs were examined to work out lithology,and bed boundary demarcation,etc.The total Formation thickness varies from 97 to 157 m;the individual sand body thickness is up to 6 m.Other reservoir parameters,e.g.,porosity(φ=8-33%),water saturation(S_(w)=4.57-95.15%),geothermal gradient(2.71℃/100m to 3.92 C/100 m at 4300 m and 3608 m)respectively,and theoretical estimate of high heat flux in the range 70e100 mW/m^(2)/s,are the necessary yard-stick to measure the subsurface geothermal reserves.Efficient energy extraction will have the potential in facilitating energy utilization for industrial purposes,especially in tea processing units present nearby oilfields and also for power generation by the binary mechanism.
文摘The aim of this study is to estimate the variations in curie point depth, geothermal gradient and heat flux from the frequency analysis of magnetic data in order to evaluate the geothermal potential of the Kaladi locality and its surroundings. For this purpose, the magnetic field map was first reduced to equator (RTE). The centroid method was used to divide the RTE grid into a set of 40 blocks. The spectral analysis applied to each block allowed determining the depth to top (Z<sub>t</sub>), center (Z<sub>0</sub>) and bottom (Z<sub>b</sub><sub> </sub>also called curie point depth or CPD) of the magnetic sources. Knowing the different CPD, the geothermal gradient associated with each block was calculated. The heat flow was then calculated from the geothermal gradient associated with the anomaly block considered. From the set of values obtained for each block, maps of geothermal gradient and heat flow variations were established. Analysis of these maps shows that the sectors that could be favourable for geothermal exploration are the north of Kaladi and the Goro-Bembara corridor, because they show variations in the geothermal gradient and heat flow between 0.4 and 0.8℃/m and between 1.2 and 2 mW/m<sup>2</sup> respectively. In addition, the superposition of the different hot springs highlighted in previous studies with areas of high geothermal gradient and heat flow values supports this analysis. The proposed models can be used as background documents for any geothermal exploration project in the study area.
文摘With the depletion of coal resources due to excessive exploitation and the increasing adjustment of the national energy structure, in response to the call of national policy, some mines are forced to close, and the reuse of abandoned mine resources plays an important role in the sustainable development of mining industry. This paper analyzes the general situation of abandoned mines in Huainan and Huaibei, elaborates the research methods of geothermal temperature and calculation methods of geothermal reserves in abandoned mines, analyzes and studies the utilization prospect of geothermal resources in abandoned mines in Huainan and Huaibei, and draws the following conclusions: the temperature of geothermal resources in abandoned mines in Huainan and Huaibei is 25℃- 60℃, which belongs to the moderate-hot water and warm water resources in low-temperature geothermal resources, and can be used for geothermal heating, industrial geothermal and entertainment industries. Based on the previous experience in geothermal resource utilization mode, this paper provides theoretical and technical support for the demonstration project of resource utilization and development of abandoned mines in the Huainan and Huaibei mining areas.
文摘Geothermal exploration and development in North Africa have advanced significantly,driven by the region's rich geothermal resources and rising energy demand.The countries of Mauritania,Morocco,Algeria,Tunisia,Libya,and Egypt are located near tectonic plate boundaries(African and Eurasian plates),giving them substantial geothermal potential.Various exploration activities,including geological surveys and geophysical studies,have been conducted to assess geothermal reservoirs and identify suitable development sites.This article reviews the progress made in geothermal exploration across the region,highlighting the key activities undertaken to evaluate geothermal resources.It also explores how government policies have played a critical role either in fostering or in freezing geothermal development.The different conducted assessments such as analyzing geological structures,hydrothermal systems,and subsurface temperatures lead to identify suitable sites for geothermal development and improve the understanding of subsurface conditions and ongoing projects.Today,some countries in North Africa are positioning themselves to become important players in the global geothermal energy landscape,and with continued investment and concerted efforts,the region has the potential to emerge as a prominent player in the global geothermal energy landscape.
文摘Based on the analysis of sea-bottom temperature and geothermal gradient, andby means of the phase boundary curve of gas hydrate and the sea-bottom temperature versus waterdepth curve in the South China Sea, this paper studies the temperature and pressure conditions forgas hydrate to keep stable. In a marine environment, methane hydrate keeps stable at water depthsgreater than 550 min the South China Sea. Further, the thickness of the gas hydrate stability zonein the South China Sea was calculated by using the phase boundary curve and temperature-depthequations. The result shows that gas hydrate have a better perspective in the southeast of theDongsha Islands. the northeast of the Xisha Islands and the north of the Nansha Islands for thickerstability zones.
基金This study was supported by China Geological Survey Program(No.DD20160190 and DD20190128)Natural Science Foundation of Hebei Province(No.E2020202065).
文摘Due to its large heat transfer area and stable thermal performance,the middledeep coaxial borehole heat exchanger(CBHE)has become one of the emerging technologies to extract geothermal energy.In this paper,a numerical modeling on a three-dimensional unsteady heat transfer model of a CBHE was conducted by using software FEFLOW,in which the model simulation was compared with the other studies and was validated with experimental data.On this basis,a further simulation was done in respect of assessing the influencing factors of thermal extraction performance and thermal influence radius of the CBHE.The results show that the outlet temperature of the heat exchanger decreases rapidly at the initial stage,and then tended to be stable;and the thermal influence radius increases with the increase of borehole depth.The heat extraction rate of the borehole increases linearly with the geothermal gradient.Rock heat capacity has limited impact on the heat extraction rate,but has a great influence on the thermal influence radius of the CBHE.When there is groundwater flow in the reservoir,the increase of groundwater velocity will result in the rise of both outlet temperature and heat extraction rate.The heat affected zone extends along with the groundwater flow direction;and its influence radius is increasing along with flow velocity.In addition,the material of the inner pipe has a significant effect on the heat loss in the pipe,so it is recommended that the material with low thermal conductivity should be used if possible.
基金supported by the National Key Researchand Development Program of China(No.2017YFC0603102)the National Natural ScienceFoundation of China(No.U19B6003 and 41972125)。
文摘The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and paleo heat flow,geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins.The average heat flow of the Tarim and Sichuan basins are 42.5±7.6 mW/m^(2)and 53.8±7.6 mW/m^(2),respectively,reflecting the characteristics of’cold’and’warm’basins.The geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Tarim Basin are 21.6±2.9℃/km,20.5±2.8℃/km and 19.6±2.8℃/km,respectively,while the geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Sichuan Basin are 21.9±2.3℃/km,22.1±2.5℃/km and23.3±2.4℃/km respectively.The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate.The formation temperatures at depths of 6,000 m,7,000 m,8,000 m,9,000 m and 10,000 m in the Tarim Basin are 80℃-190℃,90℃-220℃,100℃-230℃,110℃-240℃and 120℃-250℃,respectively,while the formation temperatures at depths of 6,000 m,7,000 m,8,000 m and 9,000 m in the Sichuan Basin are 120℃-200℃,140℃-210℃,160℃-260℃and 180℃-280℃,respectively.The horizontal distribution pattern of the ultra-deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief,fault activity and hydrothermal upwelling.The thermal modeling revealed that the paleo-heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak,while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian,rapidly rising at the end of the early Permian and declining since the late Permian.The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin,which results in differential oil and gas generation and conservation in the ultra-deep ancient strata.This study not only promotes theoretical development in the exploration of ultra-deep geothermal fields,but also plays an important role in determining the maturation phase of the ultra-deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.
文摘The rock forming temperatures and pressures represent the p T points of the local regions in the lithosphere at a certain age, providing some important information on rock formation. Based on the preliminary statistics on the temperatures and pressures for the formation of eclogites, granulites and peridotites in China, the variant ranges are given, in this paper, of temperatures, pressures and linear geothermal gradients of eclogites, granulites and peridotites. In addition, since the eclogite is different from granulite and peridotite in the p T diagram, these three rocks can be classified into two groups: the first group includes eclogites and the second group granulites and peridotites. Then, the p T correlation functions of these two groups of rocks are provided. Finally, the two groups of rocks have different geothermal gradients at the same pressure gradient or have different pressure gradients at the same geothermal gradient. The temperatures and pressures for the formation of the rocks can be calculated from the mineral chemical compositions, but the depths ( H ) for the rock formation can be calculated only under the hypotheses of given p H (or T H ) correlation functions. The explanations for the ultrahigh pressure metamorphism vary obviously with different hypotheses.
基金supported by USGS STATEMAP(G16AC00186,G17AC00212,G18AC00198,G19AC00383)the Tectonics program of the National Science Foundation(EAR 1830139)startup funds at UNR。
文摘There is a long-standing discrepancy for numerous North American Cordillera metamorphic core complexes between geobarometric pressures recorded in the exhumed rocks and their apparent burial depths based on palinspastic reconstructions from geologic field data.In particular,metamorphic core complexes in eastern Nevada are comprised of well-documented~12-15 km thick Neoproterozoic-Paleozoic stratigraphy of Laurentia’s western passive margin,which allows for critical characterization of field relationships.In this contribution we focus on the Ruby Mountain-East Humboldt Range-Wood Hills-Pequop Mountains(REWP)metamorphic core complex of northeast Nevada to explore reported peak pressure estimates versus geologic field relationships that appear to prohibit deep burial.Relatively high pressure estimates of 6-8 kbar(23-30 km depth,if lithostatic)from the lower section of the Neoproterozoic-Paleozoic passive margin sequence require burial and or repetition of the passive margin sequence by 2-3×stratigraphic depths.Our observations from the least migmatized and/or mylonitized parts of this complex,including field observations,a transect of peak-temperature(T_(p))estimates,and critical evaluation of proposed thickening/burial mechanisms cannot account for such deep burial.From Neoproterozoic-Cambrian(€)rocks part of a continuous stratigraphic section that transitions~8 km upsection to unmetamorphosed Permian strata that were not buried,we obtained new quartz-in-garnet barometry via Raman analysis that suggest pressures of~7 kbar(~26 km).A T_(p)traverse starting at the same basal€rocks reveals a smooth but hot geothermal gradient of≥40℃/km that is inconsistent with deep burial.This observation is clearly at odds with thermal gradients implied by high P-T estimates that are all≤25℃/km.Remarkably similar discrepancies between pressure estimates and field observations have been discussed for the northern Snake Range metamorphic core complex,~200 km to the southeast.We argue that a possible reconciliation of longestablished field observations versus pressures estimated from a variety of barometry techniques is that the rocks experienced non-lithostatic tectonic overpressure.We illustrate how proposed mechanisms to structurally bury the rocks,as have been invoked to justify published high pressure estimates,are entirely atypical of the Cordillera hinterland and unlike structures interpreted from other analogous orogenic plateau hinterlands.Proposed overpressure mechanisms are relevant in the REWP,including impacts from deviatoric/differential stress considerations,tectonic mode switching,and the autoclave effect driven by dehydration melting.Simple mechanical arguments demonstrate how this overpressure could have been achieved.This study highlights that detailed field and structural restorations of the least strained rocks in an orogen are critical to evaluate the tectonic history of more deformed rocks.
基金supported by the National Key Rescarch and Development Program of China"Accumulation patem and exploration direction of ultra-deep and middle Ncoprotierozoic oil and gas"(No.2017YFC0603106)Key Project of Natural Science Foundation of China"Constraints of hate Mesoznic palcogoothermal fiekd on litho sphenic dynamic evolution andoil and gas occ urrence inOrdosand Qinshui sedimentary basins"(No.41630312)MajorNational Science and Technology Project of the 13th FYP"Structural evolution and preservation conditions of the southwest of Ordos Basin in the middle-upper Proterozoic and lower Palcozoic"(No.2017ZX05005-002-008).
文摘Deep and ultra-deep layers in the petroliferous basins of China are characterized by large temperature difference and complicated thermal evolution history.The control effects of temperature and thermal evolution history on the differences of hydrocarbon phase states and the hydrocarbon generation history in deep and ultra-deep layers are researched less and unsystematically.To deal with this situation,based on a large number of temperature and pressure data of deeplayers and combined with the complicated historical situation of deep layer evolution in the oil and gas basins of China,the effects of temperature,heating time and pressure on the hydrocarbon formation temperature and phase state were analyzed,and the types of temperature and pressure relationships were classified.Finally,based on the classification of thermal evolution history of deep and ultra-deep layers,We discussed the control effects of basin thermal evolution history on the hydrocarbon generation and phase state,and the following research results were obtained.First,the hydrocarbon phase states of deep layers in different basins and regions are greatly different,and they are mainly affected by temperature,heating time,heating rate,pressure,source rock types and other factors.And temperature is the most important factor controlling hydrocarbon generation and phase state distribution.Second,under the conditions of rapid temperature increasing and short heating time,there still maybe oil reservoirs and condensate gas reservoirs in deep and ultra-deep layersin thecase ofhigh temperature.Third,overpressureinhibitshydrocarbon generationand pyrolysis.Fourth,thereis a closerelationship betweentemperature and formation pressure of deeplayers,whichcan be divided into three types,i.e.,lowemedium temperature and high pressure type,high temperature and high pressure type,and medium temperature and lowemedium pressure type.Fifth,the thermal evolution history of deep and ultra-deep layers can be divided into four types,namely the late rapid subsidence,heating and low geothermal gradient type,the late rapid subsidence,heating and high geothermal gradient type,the middleelate rapid heating and late uplifting and cooling type,and the early great subsidence and rapid heating and middleelate great uplift erosion and cooling type.In conclusion,deep and ultra-deep layers in the basins with different types of thermal history are different in hydrocarbon phase states,accumulation stages and prospects.
基金supported by the KIMST Grant 20160247.Y.-G.Kim was also supported by the KMA Research and Development Program(KMI2018-02110)the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2019R1A6A1A03033167)the Young Researcher Program through the NRF grant funded by the Korea government(MSIT)(No.2020R1C1C1007495).
文摘This study documents the discovery of mound morphologies containing gas hydrate and methane-derived authigenic carbonate(MDAC)in the southwestern slope of the Chukchi Plateau,during the IBRV Araon expeditions in 2016 and 2018.A multibeam bathymetric surveying was the basis for a new and detailed rendering around the mounds.Sub-bottom profiles and site-targeted gravity cores were also collected across these mounds which were located at water depths between 780 m and 580 m.Mounds are characterized by a circular plan shape of hundreds of meters in width and tens of meters in height.Below the mounds,gas accumulation in the sediment produces acoustic blanking in seismic data.MDACs are identified along the core collected from the top of a mound structure,indicating past methane oxidation processes.Gas hydrate has also been observed at the bottom of the core.Reverse geothermal gradients of the mound support the idea of active presentday seepage.We argue that the prolonged seepage activity of methane-rich fluid,possibly related to the formation of the rifted North Chukchi Basin,has led to the formation of the gas hydrate mounds,named hereafter the Araon Mounds,in the vicinity of the basin margin.
基金Expedition and Assessment of Environment in the Polar Area under contract Nos CHINARE 2012-03-03 and 2013-04-03the Polar Strategic Research Foundation under contract No.20100210Public Science and Technology Research Funds Projects of Ocean under contract No.200905024-3
文摘Heat flow was measured on the Lomonosov Ridge during the 5th Chinese National Arctic Expedition in 2012. To derive the time-temperature curve, resistivity data were transformed to temperature by the resistivity- temperature program. Direct reading and linear regression methods were used to calculate the equilibrium temperature, which were regressed against the depth of the probes in sediment to derive the geothermal gradient. Then, heat flow was calculated as the product of geothermal gradient and thermal conductivity of sediments. The heat flow values on the basis of the two methods were similar （i.e., 67.27 mW/m2 and 63.99 mW/m2, respectively）. The results are consistent with the measurements carried out at adjacent sites. The age of the Lomonosov Ridge predicted by the heat flow-age model was 62 Ma, which is in accordance with the inference that the ridge was separated from Eurasia at about 60 Ma.
