Cardiac rehabilitation helps improve the prognosis and quality of life for patients with heart disease. To show its interest in the African context, in the management of heart disease, a prospective study was carried ...Cardiac rehabilitation helps improve the prognosis and quality of life for patients with heart disease. To show its interest in the African context, in the management of heart disease, a prospective study was carried out. Its objective was to evaluate the effects of physical rehabilitation on cardiac function. Methods: Patients were evaluated at the beginning and at the end of cardiovascular rehabilitation by cardiovascular, biological, and echocardiographic parameters including the size of the heart chambers, the kinetics of the walls, and the systolic function of the ventricles. Results: The study involved 12 patients, 67% of whom were men. After cardiac rehabilitation, the mean hemodynamic constants had not been significantly modified. However, a significant decrease in Total-Cholesterol, LDL-Cholesterol and triglyceride levels was noted. Mean fasting blood sugar decreased from 1.25 ± 0.48 g/L to 0.92 ± 0.18 g/L and glycated hemoglobin from 7.72% ± 0.01% to 6.45% ± 0.008%. The echocardiographic parameters studied showed an improvement in the dilation of the heart chambers in 8.33% of the patients, the normalization of the ejection fraction of the left ventricle in 16% patients, the improvement of the kinetic disorders in 16% of patients and recovery of right ventricular systolic function in all patients. Conclusion: Cardiac rehabilitation as a secondary preventive measure for cardiovascular disease has contributed significantly to improving the clinico-biological parameters of the disease.展开更多
Interlayer is an important factor affecting the distribution of remaining oil.Accurate identification of interlayer distribution is of great significance in guiding oilfield production and development.However,the trad...Interlayer is an important factor affecting the distribution of remaining oil.Accurate identification of interlayer distribution is of great significance in guiding oilfield production and development.However,the traditional method of identifying interlayers has some limitations:(1)Due to the existence of overlaps in the cross plot for different categories of interlayers,it is difficult to establish a determined model to classify the type of interlayer;(2)Traditional identification methods only use two or three logging curves to identify the types of interlayers,making it difficult to fully utilize the information of the logging curves,the recognition accuracy will be greatly reduced;(3)For a large number of complex logging data,interlayer identification is time-consuming and laborintensive.Based on the existing well area data such as logging data and core data,this paper uses machine learning method to quantitatively identify the interlayers in the single well layer of CIII sandstone group in the M oilfield.Through the comparison of various classifiers,it is found that the decision tree method has the best applicability and the highest accuracy in the study area.Based on single well identification of interlayers,the continuity of well interval interlayers in the study area is analyzed according to the horizontal well.Finally,the influence of the continuity of interlayers on the distribution of remaining oil is verified by the spatial distribution characteristics of interlayers combined with the production situation of the M oilfield.展开更多
Benthic bivalves,the most widely distributed mollusks since the Mesozoic era,often inhabited environments where their fossilized remains are found adjacent to or intermingled with organic-rich shale.Recent Jurassic sh...Benthic bivalves,the most widely distributed mollusks since the Mesozoic era,often inhabited environments where their fossilized remains are found adjacent to or intermingled with organic-rich shale.Recent Jurassic shale oil exploration in the Sichuan Basin has revealed that bioclastic layers,composed of abundant fossil bivalves and closely associated with shales and,exhibit significant hydrocarbon potentials.However,the microscopic structures of these bivalve fossils and their role in hydrocarbon storage and migration remain poorly understood.In this study,we characterized the microporosity of bivalve shells within the Middle-Lower Jurassic bioclastic shale in the northeastern Sichuan Basin using a combination of 2D imaging(thin section,SEM),3D reconstruction(FIB-SEM),and permeability simulation.The micropores within the shell fossils range from 100 to 1000 nm in radius and are uniformly distributed in a grid-like pattern within the shell interior,where they host liquid hydrocarbons.The bioclastic carbonate layers exhibit an overall porosity of approximately 0.8%.Comparative analysis with extant bivalve shells suggests that these micropores represent residual pores from the nacreous brick wall structure.Due to the regular orientation of the shells and their microporous nacres,permeability coefficients along the long bivalve fossil axes are three to five times higher than those along the short axes.These residual micropores within the bioclastic fossil shells have a positive influence on both the storage and migration of shale oil and gas,making bioclastic fossil-bearing shalespromising sweet spots for shale oil and gas exploration in similar sedimentary environments.展开更多
Low exploration activity fields（e.g.,deep formation,deep water,and new exploration areas） are of great importance for petroleum exploration.The prediction of source rocks is critical to the preliminary evaluation of...Low exploration activity fields（e.g.,deep formation,deep water,and new exploration areas） are of great importance for petroleum exploration.The prediction of source rocks is critical to the preliminary evaluation of low exploration activity fields,which will determine the early strategic electoral district and decision of exploration activity.The northeast depression is a new exploration area at the South Yellow Sea basin at present.Based on lots of seismic data in the study area and a few of well data in adjacent homologous depression,the early evaluation of source rock in the northeast depression was finished by comprehensively using the techniques of geological analogy,geophysical inversion and basin modeling,and an integrated methodology about preliminary evaluation of source rocks to low exploration activity fields is also presented.The methodology consists of three aspects：（1） prediction of the main formation of major source rocks,based on analogy analysis of seismic reflection characteristics and quality of source rocks in adjacent homologous depression;（2） method of seismic attribution to determine the thickness of source rocks;and（3） prediction of vitrinite reflectance,based on basin modeling technique to determine the maturation of source rocks.The results suggest that the source rock of the Taizhou（泰州） Formation is the most important interval for hydrocarbon generationin the northeast depression,which is characterized as high TOC,fine OM type,huge thickness,and high maturity.The western subdepression is the most important hydrocarbon kitchen in the northeast depression.展开更多
The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore...The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.展开更多
The managing of information and data between researching groups is critical to the success of any exploration or development project. Poor communication and data sharing between technological departments can result in...The managing of information and data between researching groups is critical to the success of any exploration or development project. Poor communication and data sharing between technological departments can result in incomplete interpretations or inaccurate drilling decisions making. According to the statistic results, the time cost in retrieving and collecting data will occupy more than 70 % percent of the total working time of technicians during the petroleum geological researching. This paper is a summary of the characteristics and the development of the Data & Graphic management system for oil & gas exploration.After that the system's application in oil & gas exploration and researching, which has improved the quality and accurateness of mapping has been summarized in detail. The application of the system mentioned above has proved to be very successful in Daqing oilfield.展开更多
The Middle Permian system in the Sichuan Basin represents favorable conditions for the formation of natural gas reservoirs.However,only fracture-vuggy limestone gas reservoirs were discovered in early exploration,whos...The Middle Permian system in the Sichuan Basin represents favorable conditions for the formation of natural gas reservoirs.However,only fracture-vuggy limestone gas reservoirs were discovered in early exploration,whose scales and results were limited.In 2014,a high-yield industrial gas flow was produced there in Well Shuangtan 1,the major risk-exploration well,which means a great breakthrough in natural gas exploration in the Middle Permian system,Sichuan Basin.This plays a strategically important and guiding role in oil and gas exploration in ultra-deep marine formations.This paper illustrates the deployment background of Well Shuangtan 1,major exploration achievements and its significance in the gas exploration in the Middle Permian system,Sichuan Basin.Moreover,exploration potential and subsequent exploration targets of Middle Permian are analyzed in terms of its hydrocarbon source conditions,sedimentary characteristics,reservoir characteristics and areal extension,resources and favorable exploration zones.It is concluded that the Middle Permian system in the Sichuan Basin is a continent-connected carbonate platform with carbonate deposits being dominant.There are three types of reservoirs,including pore dolomite,karst fracture-vuggy,and fracture,which present considerable natural gas resources and huge exploration potential.Favorable exploration zones classification of Middle Permian in the Sichuan Basin indicates that the most favorable exploration zones are mainly distributed in the central-western Sichuan Basin.In particular,the northwestern Sichuan Basin is the most favorable exploration area which is characterized by the most excellent hydrocarbon source conditions,developed dolomite reservoirs and zonal distribution of structures.展开更多
3D seismic data recently acquired from the Ordos Basin shows three sets of regularly distributed fault systems,which overrides previous understanding that no faults were developed in this basin.Seismic interpretation ...3D seismic data recently acquired from the Ordos Basin shows three sets of regularly distributed fault systems,which overrides previous understanding that no faults were developed in this basin.Seismic interpretation suggests that the faults in the southwestern Ordos Basin have three basic characteristics,namely extreme micro-scale,distinct vertical stratification,and regularity of planar distribution.These NS-,NW-,and NE-trending fault systems developed in the Meso-Neoproterozoic e Lower Ordovician strata.Of these,the NS-trending fault system mainly consists of consequent and antithetic faults which show clear syndepositional deformation.The fault systems in the Carboniferous e Middle-Lower Triassic strata are not clear on seismic reflection profiles.The NW-and NE-trending fault systems are developed in the Upper Triassic e Middle Jurassic strata.Of these,the NW-trending fault system appears as a negative flower structure in sectional view and in an en echelon pattern in plan-view;they show transtensional deformation.A NE-trending fault system that developed in the Lower Cretaceous e Cenozoic strata shows a Y-shaped structural style and tension-shear properties.A comprehensive analysis of the regional stress fields at different geologic times is essential to determine the development,distribution direction,and intensity of the activity of fault systems in the Ordos Basin.Current exploration suggests three aspects in which the faults within the Ordos Basin are crucial to oil and gas accumulation.Firstly,these faults serve as vertical barriers that cause the formation of two sets of relatively independent petroleum systems in the Paleozoic and Mesozoic strata respectively;this is the basis for the‘upper oil and lower gas’distribution pattern.Secondly,the vertical communication of these faults is favorable for oil and gas migration,thus contributing to the typical characteristics of multiple oil and gas fields within the basin,i.e.oil and gas reservoirs with multiple superimposed strata.Finally,these faults and their associated fractures improve the permeability of Mesozoic tight reservoirs,providing favorable conditions for oil enrichment in areas around the fault systems.展开更多
The transientflow testing of ultra-deepwater gas wells is greatly impacted by the low temperatures of seawater encountered over extended distances.This leads to a redistribution of temperature within the wellbore,whic...The transientflow testing of ultra-deepwater gas wells is greatly impacted by the low temperatures of seawater encountered over extended distances.This leads to a redistribution of temperature within the wellbore,which in turn influences theflow behavior.To accurately predict such a temperature distribution,in this study a comprehensive model of theflowing temperature and pressurefields is developed.This model is based on principles offluid mechanics,heat transfer,mass conservation,and energy conservation and relies on the Runge-Kutta method for accurate integration in time of the resulting equations.The analysis includes the examination of the influence of various factors,such as gasflow production rate,thermal diffusivity of the formation,and thermal diffusivity of seawater,on the temperature and pressure profiles of the wellbore.The keyfindings can be summarized as follows:1.Higher production rates during testing lead to increasedflowing temperatures and decreased pressures within the wellbore.However,in the presence of a seawater thermocline,a crossover inflowing temperature is observed.2.An increase in wellbore pressure is associated with larger pipe diameters.3.Greater thermal diffusivity of the formation results in more rapid heat transfer from the wellbore to the formation,which causes lowerflowing temperatures within the wellbore.4.In an isothermal layer,higher thermal diffusivity of seawater leads to increased wellboreflowing temperatures.Conversely,in thermocline and mixed layer segments,lower temperatures are noted.5.Production test data from a representative deep-water gas well in the South China Sea,used to calculate the bottom-seafloor-wellhead temperature and pressurefields across three operating modes,indicate that the average error in temperature prediction is 2.18%,while the average error in pressure prediction is 5.26%,thereby confirming the reliability of the theoretical model.展开更多
Quantitative prediction of reservoir properties(e.g., gas saturation, porosity, and shale content) of tight reservoirs is of great significance for resource evaluation and well placements. However, the complex pore st...Quantitative prediction of reservoir properties(e.g., gas saturation, porosity, and shale content) of tight reservoirs is of great significance for resource evaluation and well placements. However, the complex pore structures, poor pore connectivity, and uneven fluid distribution of tight sandstone reservoirs make the correlation between reservoir parameters and elastic properties more complicated and thus pose a major challenge in seismic reservoir characterization. We have developed a partially connected double porosity model to calculate elastic properties by considering the pore structure and connectivity, and to analyze these factors' influences on the elastic behaviors of tight sandstone reservoirs. The modeling results suggest that the bulk modulus is likely to be affected by the pore connectivity coefficient, while the shear modulus is sensitive to the volumetric fraction of stiff pores. By comparing the model predictions with the acoustic measurements of the dry and saturated quartz sandstone samples, the volumetric fraction of stiff pores and the pore connectivity coefficient can be determined. Based on the calibrated model, we have constructed a 3D rock physics template that accounts for the reservoir properties' impacts on the P-wave impedance, S-wave impedance, and density. The template combined with Bayesian inverse theory is used to quantify gas saturation, porosity, clay content, and their corresponding uncertainties from elastic parameters. The application of well-log and seismic data demonstrates that our 3D rock physics template-based probabilistic inversion approach performs well in predicting the spatial distribution of high-quality tight sandstone reservoirs in southwestern China.展开更多
The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three...The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three environments of focused fluid flow： gas chimneys, mud diapirs and active faults have been identified. Widespread gas chimneys that act as important conduits for fluid flow are located below bottom simulating reflections and above basal uplifts. The occurrence and evolution of gas chimneys can be divided into a violent eruptive stage and a quiet seepage stage. For most gas chimneys, the strong eruptions are deduced to have happened during the Dongsha Movement in the latest Miocene, which are observed below Pliocene strata and few active faults develop above the top of the Miocene. The formation pressures of the Baiyun Sag currently are considered to be normal, based on these terms： 1） Borehole pressure tests with pressure coefficients of 1.043-l.047; 2） The distribution of gas chimneys is limited to strata older than the Pliocene; 3） Disseminated methane hydrates, rather than fractured hydrates, are found in the hydrate samples; 4） The gas hydrate is mainly charged with biogenic gas rather than thermogenic gas based on the chemical tests from gas hydrates cores. However, periods of quiet focused fluid flow also enable the establishment of good conduits for the migration of abundant biogenic gas and lesser volumes ofthermogenic gas. A geological model goveming fluid flow has been proposed to interpret the release of overpressure, the migration of fluids and the formation of gas hydrates, in an integrated manner. This model suggests that gas chimneys positioned above basal uplifts were caused by the Dongsha Movement at about 5.5 Ma. Biogenic gas occupies the strata above the base of the middle Miocene and migrates slowly into the gas chimney columns. Some of the biogenic gas and small volumes ofthermogenic gas eventually contribute to the formation of the gas hydrates.展开更多
Pore pressure is an essential parameter for establishing reservoir conditions,geological interpretation and drilling programs.Pore pressure prediction depends on information from various geophysical logs,seismic,and d...Pore pressure is an essential parameter for establishing reservoir conditions,geological interpretation and drilling programs.Pore pressure prediction depends on information from various geophysical logs,seismic,and direct down-hole pressure measurements.However,a level of uncertainty accompanies the prediction of pore pressure because insufficient information is usually recorded in many wells.Applying machine learning(ML)algorithms can decrease the level of uncertainty of pore pressure prediction uncertainty in cases where available information is limited.In this research,several ML techniques are applied to predict pore pressure through the over-pressured Eocene reservoir section penetrated by four wells in the Mangahewa gas field,New Zealand.Their predictions substantially outperform,in terms of prediction performance,those generated using a multiple linear regression(MLR)model.The geophysical logs used as input variables are sonic,temperature and density logs,and some direct pore pressure measurements were available at the reservoir level to calibrate the predictions.A total of 25,935 data records involving six well-log input variables were evaluated across the four wells.All ML methods achieved credible levels of pore pressure prediction performance.The most accurate models for predicting pore pressure in individual wells on a supervised basis are decision tree(DT),adaboost(ADA),random forest(RF)and transparent open box(TOB).The DT achieved root mean square error(RMSE)ranging from 0.25 psi to 14.71 psi for the four wells.The trained models were less accurate when deployed on a semi-supervised basis to predict pore pressure in the other wellbores.For two wells(Mangahewa-03 and Mangahewa-06),semi-supervised prediction achieved acceptable prediction performance of RMSE of 130—140 psi;while for the other wells,semi-supervised prediction performance was reduced to RMSE>300 psi.The results suggest that these models can be used to predict pore pressure in nearby locations,i.e.similar geology at corresponding depths within a field,but they become less reliable as the step-out distance increases and geological conditions change significantly.In comparison to other approaches to predict pore pressures,this study has identified that application of several ML algorithms involving a large number of data records can lead to more accurate prediction results.展开更多
We investigate the growth of the northern Tibetan Plateau and associated climate change by applying oxygen and carbon isotopic compositions in Cenozoic strata in the southwestern Qaidam basin. The X-ray diffraction an...We investigate the growth of the northern Tibetan Plateau and associated climate change by applying oxygen and carbon isotopic compositions in Cenozoic strata in the southwestern Qaidam basin. The X-ray diffraction and isotopic studies reveal that the carbonate minerals are mainly authigenic and they do not preserve any evidence for detrital carbonate and diagenesis. The isotope data show large fluctuations in the δ^(18)O and δ^(13)C values in the middle-late Eocene, indicating relatively warm and seasonal dry climate.The positive correlation of the δ^(18)O and δ^(13)C values in the Oligocene and the positive shift of the δ^(13)C values from the Eocene to Oligocene suggest that the climate changed to arid in the Oligocene. However,the δ^(18) values show negative shift, which is closely related to the global cooling event. During the Miocene, the δ^(13)C values vary between-2‰ and-4‰, whereas the δ^(18)O values show continuous negative shift. The mean δ^(18) values decrease from-8.5‰, in the early Miocene to-10.0‰, in the late Miocene. The stable isotope-based paleoaltimetry results suggest that the elevation of the southwestern Qaidam basin was approximately 1500 m in the middle-late Eocene and Oligocene. Subsequently, during Miocene the crustal uplift process started and the elevation reached approximately 2000 m in the early Miocene and 2500 m in the late Miocene, which suggests large-scale growth of the northern Tibet Plateau during the Miocene.展开更多
Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits,with the exception of Carlin-type deposits and rare intrusion-related gold systems,there has been continuing debate...Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits,with the exception of Carlin-type deposits and rare intrusion-related gold systems,there has been continuing debate on their genesis.Early syngenetic models and hydrothermal models dominated by meteoric fluids are now clearly unacceptable.Magmatic-hydrothermal models fail to explain the genesis of orogenic gold deposits because of the lack of consistent spatially- associated granitic intrusions and inconsistent temporal relationships.The most plausible,and widely accepted,models involve metamorphic fluids,but the source of these fluids is hotly debated.Sources within deeper segments of the supracrustal successions hosting the deposits,the underlying continental crust,and subducted oceanic lithosphere and its overlying sediment wedge all have their proponents.The orogenic gold deposits of the giant Jiaodong gold province of China,in the delaminated North China Craton,contain ca.120 Ma gold deposits in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization.The only realistic source of fluid and gold is a subducted oceanic slab with its overlying sulfide-rich sedimentary package,or the associated mantle wedge.This could be viewed as an exception to a general metamorphic model where orogenic gold has been derived during greenschist- to amphibolite-facies metamorphism of supracrustal rocks：basaltic rocks in the Precambrian and sedimentary rocks in the Phanerozoic.Alternatively,if a holistic view is taken,Jiaodong can be considered the key orogenic gold province for a unified model in which gold is derived from late-orogenic metamorphic devolatilization of stalled subduction slabs and oceanic sediments throughout Earth history.The latter model satisfies all geological,geochronological,isotopic and geochemical constraints but the precise mechanisms of auriferous fluid release,like many other subduction-related processes,are model-driven and remain uncertain.展开更多
The purpose of this study was to determine the displacement and dynamic distribution characteristics of the remaining oil in the two development stages of water flooding and subsequent alkaline surfactant polymer(ASP)...The purpose of this study was to determine the displacement and dynamic distribution characteristics of the remaining oil in the two development stages of water flooding and subsequent alkaline surfactant polymer(ASP) flooding. The well pattern types in the water and ASP flooding stages are a longdistance determinant well pattern and short-distance five-point well pattern, respectively. The type A displacement characteristic curve can be obtained using the production data, and the slope of the straight-line section of the curve can reflect the displacement strength of the oil displacement agent. A numerical simulation was carried out based on the geological model. The results revealed that the injected water advances steadily with a large-distance determinant water-flooding well pattern. The single-well water production rate increases monotonically during water flooding. There is a significant positive correlation between the cumulative water-oil ratio and the formation parameter. Differential seepage between the oil and water phases is the main factor causing residual oil formation after water flooding, while the residual oil is still relatively concentrated. The effect of the chemical oildisplacement agent on improving the oil-water two-phase seepage flow has distinct stages during ASP flooding. The remaining oil production is extremely sporadic after ASP flooding.展开更多
Neotectonic movement refers to the tectonic movement that has happened since the Cenozoic, which is the latest movement. It has the most important influence on the basins in west China, especially on the hydrocarbon a...Neotectonic movement refers to the tectonic movement that has happened since the Cenozoic, which is the latest movement. It has the most important influence on the basins in west China, especially on the hydrocarbon accumulation in the western foreland basins. We determined the time of neotectonic movement in the Kuqa Foreland Basin, which began from the Neogene, and analyzed the patterns of movement, which were continuous and fast subsidence in the vertical direction and intense lateral compression. The structure styles are that the faulting is weakened and the folding is strengthened gradually from north to south. We studied the control of neotectonic movement on the hydrocarbon accumulation process and model in the Kuqa Foreland Basin with basin simulation technique. The largest subsidence rate of the Kuqa Foreland Basin reached 1,200 m/Ma during the neotectonic movement, leading to rapid maturing of source rock within 5 Ma and a large quantity of hydrocarbon being generated and expelled. The thick neotectonic strata can form high quality reservoirs with the proved gas and oil reserves accounting for 5% and 27% of the total reserves, respectively. 86% of the structural traps were formed in the neotectonic movement period. The faults formed during the neotectonic movement serve as important migration pathways and they exist in the region where the hydrocarbon reservoirs are distributed. Abnormally high pressure caused by the intense lateral compression, thick neotectonic strata deposition and rapid hydrocarbon generation provide driving force for hydrocarbon migration. The accumulation elements match each other well over a short period, leading to many large gas fields formed later in the Kuqa Foreland Basin.展开更多
The resistivity experimental measurements of core samples drilled from low permeability reservoirs of Ordos Basin, Northwest China, illustrate that the cementation factors are not agminate, but vary from 1.335 to 1.74...The resistivity experimental measurements of core samples drilled from low permeability reservoirs of Ordos Basin, Northwest China, illustrate that the cementation factors are not agminate, but vary from 1.335 to 1.749. This leads to a challenge for the estimation of water and hydrocarbon sa- turation. Based on the analysis of Purcell equation and assumption that rock resistivity is determined by the parallel connection of numerous capillary resistances, a theoretical expression of cementation factor in terms of porosity and permeability is established. Then, cementation factor can be calculated if the parameters of porosity and permeability are determined. In the field application, porosity can be easily obtained by conventional logs. However, it is a tough challenge to estimate permeability due to the strong heterogeneity of low permeability reservoirs. Thus, the Schlumberger Doll Research （SDR） model derived from NMR logs has been proposed to estimate permeability. Based on the analysis of the theoretical expressions of cementation factor and SDR model, a novel cementation factor prediction model, which is relevant to porosity and logarithmic mean of NMR T2 spectrum （T21m）, is derived. The advantage of this model is that all the input information can be acquired from NMR logs accurately. In order to confirm the credibility of the novel model, the resistivity and corresponding laboratory NMR measurements of 27 core samples are conducted. The credibility of the model is confirmed by compar- ing the predicted cementation factors with the core analyzed results. The absolute errors for all core samples are lower than 0.071. Once this model is extended to field application, the accuracy of water and hydrocarbon saturation estimation will be significantly improved.展开更多
The Triassic Lower Karamay Formation（T2k1） is one of the main oil-bearing stratigraphic units in the northwestern margin of Junggar Basin（NW Junggar）, China. Based on an integrated investigation of outcrops, well ...The Triassic Lower Karamay Formation（T2k1） is one of the main oil-bearing stratigraphic units in the northwestern margin of Junggar Basin（NW Junggar）, China. Based on an integrated investigation of outcrops, well logs and seismic data of NW Junggar, the Lower Karamay Formation is subdivided into 2 sets, 6 beds and 13 layers. Also, it is considered that the alluvial fan, the braided river, the meandering river and the shore-shallow lacustrine were developed during the early period of Middle Triassic in Karamay districts Ⅰ, Ⅲ. The Lower Karamay Formation deposits the following 9 sedimentary subfacies： the lower fan, the middle fan, the upper fan, the braided channel, the overflow bank, the river flood of braided river, the meandering channel, the river flood of meandering river, the shore-shallow lacustrine. Seventeen microfacies such as the braided stream channel, the alluvial sand floodplain, the alluvial glutenite floodplain, the water channel, the channel bar etc. have been identified in subfacies as well. The thickness of strata is firstly up-thinning and then thickening upward to the top, it is a process from large-scale lacustrine transgression to partly lacustrine regression. Furthermore, the microfacies planar distributing law proves that the remaining oil may enrich along the margin of microfacies because of the planar microfacies changes. Therefore, this research is beneficial for searching remaining oil in NW Junggar and providing information to the project ＂The Secondary Exploration＂ of PetroChina.展开更多
In 2022,the risk exploration well Chongtan1(CT1)in the Sichuan Basin revealed commercial oil and gas flow during test in a new zone–the marl of the second submember of the third member of Leikoupo Formation(Lei-32)of...In 2022,the risk exploration well Chongtan1(CT1)in the Sichuan Basin revealed commercial oil and gas flow during test in a new zone–the marl of the second submember of the third member of Leikoupo Formation(Lei-32)of Middle Triassic,recording a significant discovery.However,the hydrocarbon accumulation in marl remains unclear,which restricts the selection and deployment of exploration area.Focusing on Well CT1,the hydrocarbon accumulation characteristics of Lei-32 marl are analyzed to clarify the potential zones for exploration.The following findings are obtained.First,according to the geochemical analysis of petroleum and source rocks,oil and gas in the Lei-32 marl of Well CT1 are originated from the same marl.The marl acts as both source rock and reservoir rock.Second,the Lei-32 marl in central Sichuan Basin is of lagoonal facies,with a thickness of 40–130 m,an area of about 40000 km^(2),a hydrocarbon generation intensity of(4–12)×10^(8) m^(3)/km^(2),and an estimated quantity of generated hydrocarbons of 25×10^(12) m^(3).Third,the lagoonal marl reservoirs are widely distributed in central Sichuan Basin.Typically,in Xichong–Yilong,Ziyang–Jianyang and Moxi South,the reservoirs are 20–60 m thick and cover an area of 7500 km^(2).Fourth,hydrocarbons in the lagoonal marl are generated and stored in the Lei-32 marl,which means that marl serves as both source rock and reservoir rock.They represent a new type of unconventional resource,which is worthy of exploring.Fifth,based on the interpretation of 2D and 3D seismic data from central Sichuan Basin,Xichong and Suining are defined as favorable prospects with estimated resources of(2000–3000)×10^(8) m^(3).展开更多
Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inc...Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inclined and even vertical sections of gas wells.To grasp the flow law of slug flow and guide engineering practice,the flow law of slug flow at various inclination angles(30°~90°)is studied by means of the combination of laboratory experiments(including high frequency pressure data acquisition system)and finite element numerical simulation.The results reveal that because of the delay of pressure variation at the corresponding position of pipeline resulting from gas expansion,the highest point of pressure change curve corresponds not to the highest point of liquid holdup curve(pressure change lags behind 0.125 s of liquid holdup change).Thus,the delay of pressure should be highlighted in predicting slug flow using pressure parameter change;otherwise the accuracy of prediction will be affected when slug flow occurs.It is generally known that liquid holdup and pressure drop are the major factors affecting the pressure variation and stable operation of pipelines.Accordingly,the results of finite element numerical simulation and Beggs-Brill model calculation are compared with those of laboratory experiments.The numerical simulation method is applicable to predicting the pressure drop of the pipeline,while the Beggs-Brill model is more suitable for predicting the liquid holdup variation of the pipeline.The research conclusion helps reveal the slug flow law,and it is of a scientific guiding implication to the prediction method of flow parameters under slug flow pattern in the process of gas well exploitation.展开更多
文摘Cardiac rehabilitation helps improve the prognosis and quality of life for patients with heart disease. To show its interest in the African context, in the management of heart disease, a prospective study was carried out. Its objective was to evaluate the effects of physical rehabilitation on cardiac function. Methods: Patients were evaluated at the beginning and at the end of cardiovascular rehabilitation by cardiovascular, biological, and echocardiographic parameters including the size of the heart chambers, the kinetics of the walls, and the systolic function of the ventricles. Results: The study involved 12 patients, 67% of whom were men. After cardiac rehabilitation, the mean hemodynamic constants had not been significantly modified. However, a significant decrease in Total-Cholesterol, LDL-Cholesterol and triglyceride levels was noted. Mean fasting blood sugar decreased from 1.25 ± 0.48 g/L to 0.92 ± 0.18 g/L and glycated hemoglobin from 7.72% ± 0.01% to 6.45% ± 0.008%. The echocardiographic parameters studied showed an improvement in the dilation of the heart chambers in 8.33% of the patients, the normalization of the ejection fraction of the left ventricle in 16% patients, the improvement of the kinetic disorders in 16% of patients and recovery of right ventricular systolic function in all patients. Conclusion: Cardiac rehabilitation as a secondary preventive measure for cardiovascular disease has contributed significantly to improving the clinico-biological parameters of the disease.
基金supported by the Natural Science Basic Research Program of Shaanxi(2024JC-YBMS-202).
文摘Interlayer is an important factor affecting the distribution of remaining oil.Accurate identification of interlayer distribution is of great significance in guiding oilfield production and development.However,the traditional method of identifying interlayers has some limitations:(1)Due to the existence of overlaps in the cross plot for different categories of interlayers,it is difficult to establish a determined model to classify the type of interlayer;(2)Traditional identification methods only use two or three logging curves to identify the types of interlayers,making it difficult to fully utilize the information of the logging curves,the recognition accuracy will be greatly reduced;(3)For a large number of complex logging data,interlayer identification is time-consuming and laborintensive.Based on the existing well area data such as logging data and core data,this paper uses machine learning method to quantitatively identify the interlayers in the single well layer of CIII sandstone group in the M oilfield.Through the comparison of various classifiers,it is found that the decision tree method has the best applicability and the highest accuracy in the study area.Based on single well identification of interlayers,the continuity of well interval interlayers in the study area is analyzed according to the horizontal well.Finally,the influence of the continuity of interlayers on the distribution of remaining oil is verified by the spatial distribution characteristics of interlayers combined with the production situation of the M oilfield.
基金supported by the National Natural Science Foundation of China(No.42173030)the Open Project from the Key Laboratory of Shale Gas Exploration,Ministry of Natural Resources(KLSGE-202406).
文摘Benthic bivalves,the most widely distributed mollusks since the Mesozoic era,often inhabited environments where their fossilized remains are found adjacent to or intermingled with organic-rich shale.Recent Jurassic shale oil exploration in the Sichuan Basin has revealed that bioclastic layers,composed of abundant fossil bivalves and closely associated with shales and,exhibit significant hydrocarbon potentials.However,the microscopic structures of these bivalve fossils and their role in hydrocarbon storage and migration remain poorly understood.In this study,we characterized the microporosity of bivalve shells within the Middle-Lower Jurassic bioclastic shale in the northeastern Sichuan Basin using a combination of 2D imaging(thin section,SEM),3D reconstruction(FIB-SEM),and permeability simulation.The micropores within the shell fossils range from 100 to 1000 nm in radius and are uniformly distributed in a grid-like pattern within the shell interior,where they host liquid hydrocarbons.The bioclastic carbonate layers exhibit an overall porosity of approximately 0.8%.Comparative analysis with extant bivalve shells suggests that these micropores represent residual pores from the nacreous brick wall structure.Due to the regular orientation of the shells and their microporous nacres,permeability coefficients along the long bivalve fossil axes are three to five times higher than those along the short axes.These residual micropores within the bioclastic fossil shells have a positive influence on both the storage and migration of shale oil and gas,making bioclastic fossil-bearing shalespromising sweet spots for shale oil and gas exploration in similar sedimentary environments.
基金supported by the National Natural Science Foundation of China (No. 40172051)the CNOOC Project (No. CT/07-EXP-004)
文摘Low exploration activity fields（e.g.,deep formation,deep water,and new exploration areas） are of great importance for petroleum exploration.The prediction of source rocks is critical to the preliminary evaluation of low exploration activity fields,which will determine the early strategic electoral district and decision of exploration activity.The northeast depression is a new exploration area at the South Yellow Sea basin at present.Based on lots of seismic data in the study area and a few of well data in adjacent homologous depression,the early evaluation of source rock in the northeast depression was finished by comprehensively using the techniques of geological analogy,geophysical inversion and basin modeling,and an integrated methodology about preliminary evaluation of source rocks to low exploration activity fields is also presented.The methodology consists of three aspects：（1） prediction of the main formation of major source rocks,based on analogy analysis of seismic reflection characteristics and quality of source rocks in adjacent homologous depression;（2） method of seismic attribution to determine the thickness of source rocks;and（3） prediction of vitrinite reflectance,based on basin modeling technique to determine the maturation of source rocks.The results suggest that the source rock of the Taizhou（泰州） Formation is the most important interval for hydrocarbon generationin the northeast depression,which is characterized as high TOC,fine OM type,huge thickness,and high maturity.The western subdepression is the most important hydrocarbon kitchen in the northeast depression.
基金Major Project of National Science and Technology(No.2011ZX05004-005)Major Project of Exploration of PetroChina“Hydrocarbon Evaluation of Leshan-Longnüsi Palaeohigh in Sichuan Basin and Research on Exploration Support Technologies”(No.2012ZD01-03-01)。
文摘The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.
文摘The managing of information and data between researching groups is critical to the success of any exploration or development project. Poor communication and data sharing between technological departments can result in incomplete interpretations or inaccurate drilling decisions making. According to the statistic results, the time cost in retrieving and collecting data will occupy more than 70 % percent of the total working time of technicians during the petroleum geological researching. This paper is a summary of the characteristics and the development of the Data & Graphic management system for oil & gas exploration.After that the system's application in oil & gas exploration and researching, which has improved the quality and accurateness of mapping has been summarized in detail. The application of the system mentioned above has proved to be very successful in Daqing oilfield.
文摘The Middle Permian system in the Sichuan Basin represents favorable conditions for the formation of natural gas reservoirs.However,only fracture-vuggy limestone gas reservoirs were discovered in early exploration,whose scales and results were limited.In 2014,a high-yield industrial gas flow was produced there in Well Shuangtan 1,the major risk-exploration well,which means a great breakthrough in natural gas exploration in the Middle Permian system,Sichuan Basin.This plays a strategically important and guiding role in oil and gas exploration in ultra-deep marine formations.This paper illustrates the deployment background of Well Shuangtan 1,major exploration achievements and its significance in the gas exploration in the Middle Permian system,Sichuan Basin.Moreover,exploration potential and subsequent exploration targets of Middle Permian are analyzed in terms of its hydrocarbon source conditions,sedimentary characteristics,reservoir characteristics and areal extension,resources and favorable exploration zones.It is concluded that the Middle Permian system in the Sichuan Basin is a continent-connected carbonate platform with carbonate deposits being dominant.There are three types of reservoirs,including pore dolomite,karst fracture-vuggy,and fracture,which present considerable natural gas resources and huge exploration potential.Favorable exploration zones classification of Middle Permian in the Sichuan Basin indicates that the most favorable exploration zones are mainly distributed in the central-western Sichuan Basin.In particular,the northwestern Sichuan Basin is the most favorable exploration area which is characterized by the most excellent hydrocarbon source conditions,developed dolomite reservoirs and zonal distribution of structures.
基金project entitled Seismic Identification and Accumulation Control of Strike-Slip Faults in Superimposed Basins inWest-central Part of China initiated by the Bureau of Geophysical Prospecting,CNPC(No.:03-02-2022).
文摘3D seismic data recently acquired from the Ordos Basin shows three sets of regularly distributed fault systems,which overrides previous understanding that no faults were developed in this basin.Seismic interpretation suggests that the faults in the southwestern Ordos Basin have three basic characteristics,namely extreme micro-scale,distinct vertical stratification,and regularity of planar distribution.These NS-,NW-,and NE-trending fault systems developed in the Meso-Neoproterozoic e Lower Ordovician strata.Of these,the NS-trending fault system mainly consists of consequent and antithetic faults which show clear syndepositional deformation.The fault systems in the Carboniferous e Middle-Lower Triassic strata are not clear on seismic reflection profiles.The NW-and NE-trending fault systems are developed in the Upper Triassic e Middle Jurassic strata.Of these,the NW-trending fault system appears as a negative flower structure in sectional view and in an en echelon pattern in plan-view;they show transtensional deformation.A NE-trending fault system that developed in the Lower Cretaceous e Cenozoic strata shows a Y-shaped structural style and tension-shear properties.A comprehensive analysis of the regional stress fields at different geologic times is essential to determine the development,distribution direction,and intensity of the activity of fault systems in the Ordos Basin.Current exploration suggests three aspects in which the faults within the Ordos Basin are crucial to oil and gas accumulation.Firstly,these faults serve as vertical barriers that cause the formation of two sets of relatively independent petroleum systems in the Paleozoic and Mesozoic strata respectively;this is the basis for the‘upper oil and lower gas’distribution pattern.Secondly,the vertical communication of these faults is favorable for oil and gas migration,thus contributing to the typical characteristics of multiple oil and gas fields within the basin,i.e.oil and gas reservoirs with multiple superimposed strata.Finally,these faults and their associated fractures improve the permeability of Mesozoic tight reservoirs,providing favorable conditions for oil enrichment in areas around the fault systems.
文摘The transientflow testing of ultra-deepwater gas wells is greatly impacted by the low temperatures of seawater encountered over extended distances.This leads to a redistribution of temperature within the wellbore,which in turn influences theflow behavior.To accurately predict such a temperature distribution,in this study a comprehensive model of theflowing temperature and pressurefields is developed.This model is based on principles offluid mechanics,heat transfer,mass conservation,and energy conservation and relies on the Runge-Kutta method for accurate integration in time of the resulting equations.The analysis includes the examination of the influence of various factors,such as gasflow production rate,thermal diffusivity of the formation,and thermal diffusivity of seawater,on the temperature and pressure profiles of the wellbore.The keyfindings can be summarized as follows:1.Higher production rates during testing lead to increasedflowing temperatures and decreased pressures within the wellbore.However,in the presence of a seawater thermocline,a crossover inflowing temperature is observed.2.An increase in wellbore pressure is associated with larger pipe diameters.3.Greater thermal diffusivity of the formation results in more rapid heat transfer from the wellbore to the formation,which causes lowerflowing temperatures within the wellbore.4.In an isothermal layer,higher thermal diffusivity of seawater leads to increased wellboreflowing temperatures.Conversely,in thermocline and mixed layer segments,lower temperatures are noted.5.Production test data from a representative deep-water gas well in the South China Sea,used to calculate the bottom-seafloor-wellhead temperature and pressurefields across three operating modes,indicate that the average error in temperature prediction is 2.18%,while the average error in pressure prediction is 5.26%,thereby confirming the reliability of the theoretical model.
基金supported by the National Natural Science Foundation of China (42104121)the Scientific Research and Technology Development Project of the CNPC (2021DJ0606)。
文摘Quantitative prediction of reservoir properties(e.g., gas saturation, porosity, and shale content) of tight reservoirs is of great significance for resource evaluation and well placements. However, the complex pore structures, poor pore connectivity, and uneven fluid distribution of tight sandstone reservoirs make the correlation between reservoir parameters and elastic properties more complicated and thus pose a major challenge in seismic reservoir characterization. We have developed a partially connected double porosity model to calculate elastic properties by considering the pore structure and connectivity, and to analyze these factors' influences on the elastic behaviors of tight sandstone reservoirs. The modeling results suggest that the bulk modulus is likely to be affected by the pore connectivity coefficient, while the shear modulus is sensitive to the volumetric fraction of stiff pores. By comparing the model predictions with the acoustic measurements of the dry and saturated quartz sandstone samples, the volumetric fraction of stiff pores and the pore connectivity coefficient can be determined. Based on the calibrated model, we have constructed a 3D rock physics template that accounts for the reservoir properties' impacts on the P-wave impedance, S-wave impedance, and density. The template combined with Bayesian inverse theory is used to quantify gas saturation, porosity, clay content, and their corresponding uncertainties from elastic parameters. The application of well-log and seismic data demonstrates that our 3D rock physics template-based probabilistic inversion approach performs well in predicting the spatial distribution of high-quality tight sandstone reservoirs in southwestern China.
基金Supported by the National Natural Science Foundation of China (Nos.40930845 and 41006031)the International Science & Technology Cooperation Program of China (No. 2010DFA21740)the National Science and Technology Major Project (No. 2011ZX05026-004-06)
文摘The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three environments of focused fluid flow： gas chimneys, mud diapirs and active faults have been identified. Widespread gas chimneys that act as important conduits for fluid flow are located below bottom simulating reflections and above basal uplifts. The occurrence and evolution of gas chimneys can be divided into a violent eruptive stage and a quiet seepage stage. For most gas chimneys, the strong eruptions are deduced to have happened during the Dongsha Movement in the latest Miocene, which are observed below Pliocene strata and few active faults develop above the top of the Miocene. The formation pressures of the Baiyun Sag currently are considered to be normal, based on these terms： 1） Borehole pressure tests with pressure coefficients of 1.043-l.047; 2） The distribution of gas chimneys is limited to strata older than the Pliocene; 3） Disseminated methane hydrates, rather than fractured hydrates, are found in the hydrate samples; 4） The gas hydrate is mainly charged with biogenic gas rather than thermogenic gas based on the chemical tests from gas hydrates cores. However, periods of quiet focused fluid flow also enable the establishment of good conduits for the migration of abundant biogenic gas and lesser volumes ofthermogenic gas. A geological model goveming fluid flow has been proposed to interpret the release of overpressure, the migration of fluids and the formation of gas hydrates, in an integrated manner. This model suggests that gas chimneys positioned above basal uplifts were caused by the Dongsha Movement at about 5.5 Ma. Biogenic gas occupies the strata above the base of the middle Miocene and migrates slowly into the gas chimney columns. Some of the biogenic gas and small volumes ofthermogenic gas eventually contribute to the formation of the gas hydrates.
文摘Pore pressure is an essential parameter for establishing reservoir conditions,geological interpretation and drilling programs.Pore pressure prediction depends on information from various geophysical logs,seismic,and direct down-hole pressure measurements.However,a level of uncertainty accompanies the prediction of pore pressure because insufficient information is usually recorded in many wells.Applying machine learning(ML)algorithms can decrease the level of uncertainty of pore pressure prediction uncertainty in cases where available information is limited.In this research,several ML techniques are applied to predict pore pressure through the over-pressured Eocene reservoir section penetrated by four wells in the Mangahewa gas field,New Zealand.Their predictions substantially outperform,in terms of prediction performance,those generated using a multiple linear regression(MLR)model.The geophysical logs used as input variables are sonic,temperature and density logs,and some direct pore pressure measurements were available at the reservoir level to calibrate the predictions.A total of 25,935 data records involving six well-log input variables were evaluated across the four wells.All ML methods achieved credible levels of pore pressure prediction performance.The most accurate models for predicting pore pressure in individual wells on a supervised basis are decision tree(DT),adaboost(ADA),random forest(RF)and transparent open box(TOB).The DT achieved root mean square error(RMSE)ranging from 0.25 psi to 14.71 psi for the four wells.The trained models were less accurate when deployed on a semi-supervised basis to predict pore pressure in the other wellbores.For two wells(Mangahewa-03 and Mangahewa-06),semi-supervised prediction achieved acceptable prediction performance of RMSE of 130—140 psi;while for the other wells,semi-supervised prediction performance was reduced to RMSE>300 psi.The results suggest that these models can be used to predict pore pressure in nearby locations,i.e.similar geology at corresponding depths within a field,but they become less reliable as the step-out distance increases and geological conditions change significantly.In comparison to other approaches to predict pore pressures,this study has identified that application of several ML algorithms involving a large number of data records can lead to more accurate prediction results.
基金supported by National Science and Technology Major Project (2011ZX05009-001)
文摘We investigate the growth of the northern Tibetan Plateau and associated climate change by applying oxygen and carbon isotopic compositions in Cenozoic strata in the southwestern Qaidam basin. The X-ray diffraction and isotopic studies reveal that the carbonate minerals are mainly authigenic and they do not preserve any evidence for detrital carbonate and diagenesis. The isotope data show large fluctuations in the δ^(18)O and δ^(13)C values in the middle-late Eocene, indicating relatively warm and seasonal dry climate.The positive correlation of the δ^(18)O and δ^(13)C values in the Oligocene and the positive shift of the δ^(13)C values from the Eocene to Oligocene suggest that the climate changed to arid in the Oligocene. However,the δ^(18) values show negative shift, which is closely related to the global cooling event. During the Miocene, the δ^(13)C values vary between-2‰ and-4‰, whereas the δ^(18)O values show continuous negative shift. The mean δ^(18) values decrease from-8.5‰, in the early Miocene to-10.0‰, in the late Miocene. The stable isotope-based paleoaltimetry results suggest that the elevation of the southwestern Qaidam basin was approximately 1500 m in the middle-late Eocene and Oligocene. Subsequently, during Miocene the crustal uplift process started and the elevation reached approximately 2000 m in the early Miocene and 2500 m in the late Miocene, which suggests large-scale growth of the northern Tibet Plateau during the Miocene.
文摘Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits,with the exception of Carlin-type deposits and rare intrusion-related gold systems,there has been continuing debate on their genesis.Early syngenetic models and hydrothermal models dominated by meteoric fluids are now clearly unacceptable.Magmatic-hydrothermal models fail to explain the genesis of orogenic gold deposits because of the lack of consistent spatially- associated granitic intrusions and inconsistent temporal relationships.The most plausible,and widely accepted,models involve metamorphic fluids,but the source of these fluids is hotly debated.Sources within deeper segments of the supracrustal successions hosting the deposits,the underlying continental crust,and subducted oceanic lithosphere and its overlying sediment wedge all have their proponents.The orogenic gold deposits of the giant Jiaodong gold province of China,in the delaminated North China Craton,contain ca.120 Ma gold deposits in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization.The only realistic source of fluid and gold is a subducted oceanic slab with its overlying sulfide-rich sedimentary package,or the associated mantle wedge.This could be viewed as an exception to a general metamorphic model where orogenic gold has been derived during greenschist- to amphibolite-facies metamorphism of supracrustal rocks：basaltic rocks in the Precambrian and sedimentary rocks in the Phanerozoic.Alternatively,if a holistic view is taken,Jiaodong can be considered the key orogenic gold province for a unified model in which gold is derived from late-orogenic metamorphic devolatilization of stalled subduction slabs and oceanic sediments throughout Earth history.The latter model satisfies all geological,geochronological,isotopic and geochemical constraints but the precise mechanisms of auriferous fluid release,like many other subduction-related processes,are model-driven and remain uncertain.
基金The authors would like to thank the National Science and Technology Major Project(2016ZX05054012)for funding.
文摘The purpose of this study was to determine the displacement and dynamic distribution characteristics of the remaining oil in the two development stages of water flooding and subsequent alkaline surfactant polymer(ASP) flooding. The well pattern types in the water and ASP flooding stages are a longdistance determinant well pattern and short-distance five-point well pattern, respectively. The type A displacement characteristic curve can be obtained using the production data, and the slope of the straight-line section of the curve can reflect the displacement strength of the oil displacement agent. A numerical simulation was carried out based on the geological model. The results revealed that the injected water advances steadily with a large-distance determinant water-flooding well pattern. The single-well water production rate increases monotonically during water flooding. There is a significant positive correlation between the cumulative water-oil ratio and the formation parameter. Differential seepage between the oil and water phases is the main factor causing residual oil formation after water flooding, while the residual oil is still relatively concentrated. The effect of the chemical oildisplacement agent on improving the oil-water two-phase seepage flow has distinct stages during ASP flooding. The remaining oil production is extremely sporadic after ASP flooding.
基金supported by the Foundation Project of State Key Laboratory of Petroleum Resources and Prospecting (PRPDX2008-05)the "973" National Key Basic Research Program (2006CB202308)
文摘Neotectonic movement refers to the tectonic movement that has happened since the Cenozoic, which is the latest movement. It has the most important influence on the basins in west China, especially on the hydrocarbon accumulation in the western foreland basins. We determined the time of neotectonic movement in the Kuqa Foreland Basin, which began from the Neogene, and analyzed the patterns of movement, which were continuous and fast subsidence in the vertical direction and intense lateral compression. The structure styles are that the faulting is weakened and the folding is strengthened gradually from north to south. We studied the control of neotectonic movement on the hydrocarbon accumulation process and model in the Kuqa Foreland Basin with basin simulation technique. The largest subsidence rate of the Kuqa Foreland Basin reached 1,200 m/Ma during the neotectonic movement, leading to rapid maturing of source rock within 5 Ma and a large quantity of hydrocarbon being generated and expelled. The thick neotectonic strata can form high quality reservoirs with the proved gas and oil reserves accounting for 5% and 27% of the total reserves, respectively. 86% of the structural traps were formed in the neotectonic movement period. The faults formed during the neotectonic movement serve as important migration pathways and they exist in the region where the hydrocarbon reservoirs are distributed. Abnormally high pressure caused by the intense lateral compression, thick neotectonic strata deposition and rapid hydrocarbon generation provide driving force for hydrocarbon migration. The accumulation elements match each other well over a short period, leading to many large gas fields formed later in the Kuqa Foreland Basin.
基金supported by the Major National Oil&Gas Specific Project of China(No.2011ZX05044)
文摘The resistivity experimental measurements of core samples drilled from low permeability reservoirs of Ordos Basin, Northwest China, illustrate that the cementation factors are not agminate, but vary from 1.335 to 1.749. This leads to a challenge for the estimation of water and hydrocarbon sa- turation. Based on the analysis of Purcell equation and assumption that rock resistivity is determined by the parallel connection of numerous capillary resistances, a theoretical expression of cementation factor in terms of porosity and permeability is established. Then, cementation factor can be calculated if the parameters of porosity and permeability are determined. In the field application, porosity can be easily obtained by conventional logs. However, it is a tough challenge to estimate permeability due to the strong heterogeneity of low permeability reservoirs. Thus, the Schlumberger Doll Research （SDR） model derived from NMR logs has been proposed to estimate permeability. Based on the analysis of the theoretical expressions of cementation factor and SDR model, a novel cementation factor prediction model, which is relevant to porosity and logarithmic mean of NMR T2 spectrum （T21m）, is derived. The advantage of this model is that all the input information can be acquired from NMR logs accurately. In order to confirm the credibility of the novel model, the resistivity and corresponding laboratory NMR measurements of 27 core samples are conducted. The credibility of the model is confirmed by compar- ing the predicted cementation factors with the core analyzed results. The absolute errors for all core samples are lower than 0.071. Once this model is extended to field application, the accuracy of water and hydrocarbon saturation estimation will be significantly improved.
基金supported by the National Science and Technology Major Project (No. 2011ZX05043-005)Chinese Geological Survey based comprehensive geological research Project (No. 1212011120181)
文摘The Triassic Lower Karamay Formation（T2k1） is one of the main oil-bearing stratigraphic units in the northwestern margin of Junggar Basin（NW Junggar）, China. Based on an integrated investigation of outcrops, well logs and seismic data of NW Junggar, the Lower Karamay Formation is subdivided into 2 sets, 6 beds and 13 layers. Also, it is considered that the alluvial fan, the braided river, the meandering river and the shore-shallow lacustrine were developed during the early period of Middle Triassic in Karamay districts Ⅰ, Ⅲ. The Lower Karamay Formation deposits the following 9 sedimentary subfacies： the lower fan, the middle fan, the upper fan, the braided channel, the overflow bank, the river flood of braided river, the meandering channel, the river flood of meandering river, the shore-shallow lacustrine. Seventeen microfacies such as the braided stream channel, the alluvial sand floodplain, the alluvial glutenite floodplain, the water channel, the channel bar etc. have been identified in subfacies as well. The thickness of strata is firstly up-thinning and then thickening upward to the top, it is a process from large-scale lacustrine transgression to partly lacustrine regression. Furthermore, the microfacies planar distributing law proves that the remaining oil may enrich along the margin of microfacies because of the planar microfacies changes. Therefore, this research is beneficial for searching remaining oil in NW Junggar and providing information to the project ＂The Secondary Exploration＂ of PetroChina.
基金Supported by the PetroChina Science and Technology Project(2021DJ0501,2018A-0105).
文摘In 2022,the risk exploration well Chongtan1(CT1)in the Sichuan Basin revealed commercial oil and gas flow during test in a new zone–the marl of the second submember of the third member of Leikoupo Formation(Lei-32)of Middle Triassic,recording a significant discovery.However,the hydrocarbon accumulation in marl remains unclear,which restricts the selection and deployment of exploration area.Focusing on Well CT1,the hydrocarbon accumulation characteristics of Lei-32 marl are analyzed to clarify the potential zones for exploration.The following findings are obtained.First,according to the geochemical analysis of petroleum and source rocks,oil and gas in the Lei-32 marl of Well CT1 are originated from the same marl.The marl acts as both source rock and reservoir rock.Second,the Lei-32 marl in central Sichuan Basin is of lagoonal facies,with a thickness of 40–130 m,an area of about 40000 km^(2),a hydrocarbon generation intensity of(4–12)×10^(8) m^(3)/km^(2),and an estimated quantity of generated hydrocarbons of 25×10^(12) m^(3).Third,the lagoonal marl reservoirs are widely distributed in central Sichuan Basin.Typically,in Xichong–Yilong,Ziyang–Jianyang and Moxi South,the reservoirs are 20–60 m thick and cover an area of 7500 km^(2).Fourth,hydrocarbons in the lagoonal marl are generated and stored in the Lei-32 marl,which means that marl serves as both source rock and reservoir rock.They represent a new type of unconventional resource,which is worthy of exploring.Fifth,based on the interpretation of 2D and 3D seismic data from central Sichuan Basin,Xichong and Suining are defined as favorable prospects with estimated resources of(2000–3000)×10^(8) m^(3).
基金Gratitude is extended to Wei Luo,the corresponding author for the article.The authors would also like to acknowledge the support provided by the National Natural Science Fund Project(61572084)major national projects(2017ZX05030-005,2016ZX05056004-002,2016ZX05046004-003).
文摘Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inclined and even vertical sections of gas wells.To grasp the flow law of slug flow and guide engineering practice,the flow law of slug flow at various inclination angles(30°~90°)is studied by means of the combination of laboratory experiments(including high frequency pressure data acquisition system)and finite element numerical simulation.The results reveal that because of the delay of pressure variation at the corresponding position of pipeline resulting from gas expansion,the highest point of pressure change curve corresponds not to the highest point of liquid holdup curve(pressure change lags behind 0.125 s of liquid holdup change).Thus,the delay of pressure should be highlighted in predicting slug flow using pressure parameter change;otherwise the accuracy of prediction will be affected when slug flow occurs.It is generally known that liquid holdup and pressure drop are the major factors affecting the pressure variation and stable operation of pipelines.Accordingly,the results of finite element numerical simulation and Beggs-Brill model calculation are compared with those of laboratory experiments.The numerical simulation method is applicable to predicting the pressure drop of the pipeline,while the Beggs-Brill model is more suitable for predicting the liquid holdup variation of the pipeline.The research conclusion helps reveal the slug flow law,and it is of a scientific guiding implication to the prediction method of flow parameters under slug flow pattern in the process of gas well exploitation.
