992 resultados para regional geology
Resumo:
With the rapid increase of the number and influence of floating population in China, it is urgently needed to understand the regional types of China's floating population and their spatial characteristics. After reviewing the current methods for identifying regional types of floating population, this paper puts forward a new composite-index identification method and its modification version which is consisted of two indexes of the net migration rate and gross migration rate. Then, the traditional single-index and the new composite-index identification methods are empirically tested to explore their spatial patterns and characteristics by using China's 2000 census data at county level. The results show: (1) The composite-index identification method is much better than traditional single-index method because it can measure the migration direction and scale of floating simultaneously, and in particular it can identify the unique regional types of floating population with large scale of immigration and emigration. (2) The modified composite-index identification method, by using the share of a region's certain type of floating population to the total in China as weights, can effectively correct the over- or under-estimated errors due to the rather large or small total population of a region. (3) The spatial patterns of different regional types of China's floating population are closely related to the regional differentiation of their natural environment, population density and socio-economic development level. The three active regional types of floating population are mainly located in the eastern part of China with lower elevation, more than 800 mm precipitation, rather higher population densities and economic development levels.
Resumo:
Many mud diapirs have been recognized in southern Okinawa Trough by a multi-channel seismic surveying on R/V KEXUE I in 2001. Gas hydrates have been identified, by the seismic reflection characteristics, the velocity analysis and the impedance inversion. Geothermal heat flow around the central of the mud diapir has been determined theoretically by the Bottom Simulating Reflectors (BSRs). Comparing the BSR derived and the measured heat flow values, we infer that the BSR immediately at the top of the mud diapirs indicate the base of the saturated gas hydrate formation zone (BSGHFZ), but not, as we ordinarily know, the base of the gas hydrate stability zone (BGHSZ), which could be explained by the abnormal regional background heat flow and free gas flux associated with mud diapirs. As a result, it helps us to better understand the generation mechanism of the gas hydrates associated with mud diapirs and to predict the gas hydrate potential in the southern Okinawa Trough. (C) 2008 Elsevier Ltd. All rights reserved.
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Organic carbon (OC) in definitely small area sediments(according to marine dimension)off the Huanghe River Estuary is investigated in order to evaluate the feature of regional difference of physical and chemical properties in marginal sea sediments. The distributions of OC in sediments with natural grain size and the relationship with the pH, Eh,Es and Fe3+/Fe2+ are discussed. In addition,OC decomposition rates in surfacial/subsurfacial sediments are estimated. OC concentrations range from 0.26% to 1.8%(wt)in the study area. Significant differences in OC content and in horizontal distribution as well as various trends in surfacial/subsurfacial sediments exhibit the feature of regional difference remarkably in marginal sea sediments. The complicated distribution of OC in surface sediments is due to the influence of bacterial activity and abundance, bioturbation of benthos and physical disturbance. The OC decomposition rate constant in surfacial/subsurfacial sediments ranges from 0.0097 to 0.076 a(-1) and the relatively high values may be mainly related to bacteria that are mainly responsible for OC mineralization;meio-and macrofauna affect OC degradation both directly, through feeding on it, and indirectly through bioturbation and at the same time coarse sediments are also disadvantageous to OC preservation. In almost all the middle and bottom sediments the contents of OC decrease with the increase of deposition depth, which indicates that mineralization of OC in the middle and bottom sediments has occurred via processes like SO42- reduction and Fe-oxide reduction.
Resumo:
Macro-distribution of residual basins is a basic question in residual basin research,the main object of macro-distribution study is to build strata framework, compute thickness of residual strata and analyze characteristics of residual basins. With the guidance of the theory of integrated geology and geophysical research, the paper assembled series of methods and established the technical chart based on gravity and magnetic data, with restriction of geology, seismic and drilling data. Based on potential field data processing and analysis, forward and inverse computation, region potential field analysis and potential field separation, etc. it computed depth of gravity/magnetic basement and got strata framework. It had got effective results in the research of macro-distribution of residual basin research in the Dagang area. It did the wavelet transform of gravity/magnetic data with multi-kind of wavelet basis using a trou algorithm. From comparison of processing result and their spectral of wavelet analysis, up continuation and filter method, the wavelet approximation is better to fit the regional potential field, and it is an effective method to separate gravity/magnetic effect caused by deep geology bodies. The experiment of matching pursuit shows that te transform domain methods have great advantage in potential data analysis. From the integrated geophysical study of rock property study, gravity/magnetic basement inversion and fault system analysis of the Dagang area, it gets the strata framework and the thickness of pre-Cenozoic residual strata. Comprehensive study with gravity and magnetotelluric profile inversion and interpretation, three prospect plays of macro-distribution of residual basins are fingered out. It has great residual strata thickness in the northern part of Chengning Uplift and there is thrust fault in the deep zone and good up-Paleozoic hydrocarbon source rocks in this area. With integrated analysis, this area will be the most prospective hydrocarbon location of pre-Cenozoic residual basins.
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The engineering geological properties of Neogene hard clays and related engineering problems are frontiers in the fields of Engineering Geology, Soil Mechanics and Rock Mechanics. Recently, it has been recognized that Neogene hard clay is the intermediate type of material between the soil and the rock. Many aspects of them, such as sampling, testing, calculating and engineering process, are special, which could not be researched by means of theories and methods of traditional Soil Mechanics of Rock Mechanics. In order to get real knowledge and instruct the engineering practice, intersect studying of multiple disciplines, including Engineering Geology, Soil Mechanics and Rock Mechanics, etc., is necessary. Neogene hard clay is one of the important study objects of regional problem rocks & soils in our country, which extensively distributed in China, especially in Eastern China. Taking the related areas along the middle line of the Project of Transferring Water from the South to the North (e.g. Nanyang basin, Fangcheng-Baofeng area and Handan-Yongnian area), South-west of Shandong, Xu-Huai area and Beijing area, etc. as main study areas, the paper divided Neogene hard clays into reduction environment dominated origin and oxidation environment dominated origin, which distributed on areas western and eastern to Mount Taihangshan respectively. Intermediate types are also existed in some areas, which mainly distribute near the edges of depositional basins; they are usually of transitions between diluvial and lacustrine deposits. As to Neogene hard clays from Eastern China, the clay particle content is high, and montmorillonite or illite/montmorillonite turbostratic mineral is the dominating clay mineral. The content of effective montmorillonite is very high in each area, which is the basis for the undesirable engineering properties of Neogene hard clays. For hard clays from the same area, the content of effective montmorillonite in gray-greenish hard clay is much higher than that in purple-brownish or brown-yellowish hard clay, which is the reason why the gray-greenish hard clay usually has outstanding expansive property. On the other hand, purple-brownish or brown-yellowish hard clay has relatively less montmorillonite, so its property is better. All of these prove that the composition (clay mineral) of Neogene hard clay is the control factor for the engineering properties. Neogene hard clays have obvious properties such as fissured, overconsolidated and expansive, which are the main reasons that many engineering problems and geological harzards usually occur in Neogene hard clays. The paper systematically elaborates the engineering properties of Neogene hard clays from Eastern China, analyses the relationships between engineering properties and basic indexes. The author introduces the ANN method into the prediction of engineering property indexes of hard clays, which provides a new way for quantitatively assessment and prediction of engineering property indexes. During investigation in the field, the author found that there exists obvious seam-sheared zone between different hard clays in Miocene Xiacaowan formation in Xu-Huai area. Similar phenomenon also exists near the borderline between Neogene hard clays and underlying coal measures in the Southwest of Shandong province, which could be observed in the cores. The discovery of seam-sheard zone has important theoretical and practical significance for engineering stability analysis and revealing the origin of fissures in Neogene hard clays. The macrostructure, medium structure and microstructure together control the engineering properties of hard clays. The author analyses and summarizes the structural effects on hard clays in detail. The complex of the strength property of hard clays is mostly related to the characteristics of fissures, which is one of the main factors that affect the choice of shear strength parameters. So structure-control theory must be inseparably combined with composition-control theory during the engineering geological and rock/soil mechanics research of hard clays. The engineering properties, such as fissured, overconsolidated and expansive, control the instability of engineering behaviors of Neogene hard clays under the condition of excavation, i.e. very sensitive to the change of existence environment. Based on test data analysis, the author elaborates the effects of engineering environment change on the engineering properties. Taking Nanyang basin as example, the author utilizes FEM to study the effects of various factors on stability of cutting canal slopes, than sets forth the characteristics, development laws and formation mechanism of the deformation and failure of hard clay canal slopes, summarizes the protection and reinforcement principles, as well as the protection and remedy steps. On the basis of comparison of engineering properties of domestic and foreign Neogene muddy deposits, in the view of whole globe and associated with the geological characteristics of China, the paper demonstrates that the intermediate type of the material between the soil and the rock, named "hard clay/soft rock", which can not be separated abruptly, really exists in China. The author has given a preliminary classification based on its geological origin and distribution law, which is very significant for promoting the mixture of Engineering Geology, Soil Mechanics and Rock Mechanics. In the course of large scales engineering construction in China, many engineering experiences and testing data are gained, summarizing these testing results and automatically managing them with computer technology are very necessary. The author develops a software named "Hard Clay-Soft Rock Engineering Geological Information Management and Analysis System (HRGIMS)", realizes the automatic and visual management of geo-engineering information, on the basis of information management, the functions of test data analysis and engineering property prediction are strengthened. This system has well merits for practice and popularization.
Resumo:
According to the basic geologic conditions, the paper is directed by the modem oil-gas accumulation theory and petroleum system in which typical oil pools are analyzed and the shape of lithologic trap and geologic factors are pointed out. The process during which oil and gas migrate from source rock to lithologic trap is rebuilt, and the accumulation model of oil pool is set up. With the comprehensive application of seismic geologic and log data and paying attention to the method and technology which is used to distinguish lithologic accumulation. Promising structural-lithofacies zones are got and the distribution rule of various lithologic accumulation is concluded. With making use of the biologic mark compound, different reservoirs are compared. As a result, the oil and gas in HeiDimiao come from Nenjiang Group's source rocks; in SaErTu from QingShenkou Group's and Nenjiang Group's, and in PuTaohua. GaoTaizi and FuYang from QingShankou Group's. According to the development and distribution of effective source rock, oil distribution and the comparison in the south of SongLiao basin, the characteristic of basin structure and reservoir distribution is considered, and then the middle-upper reservoir of SongLiao basin south are divided into two petroleum system and a complex petroleum system. Because of the characteristic of migration and accumulation, two petroleum systems can furtherly be divided into 6-7 sub-petroleum systems,20 sub-petroleum systems in all. As a result of the difference of the migration characteristic, accumulation conditions and the place in the petroleum system, the accumulation degree and accumulation model are different. So three accumulation mechanism and six basic accumulation model of lithologic trap are concluded. The distribution of lithologic pools is highly regular oil and gas around the generation sag distribute on favorable structural-lithofacies zones, the type of lithological pool vary regularly from the core of sandstone block to the upper zone. On the basic of regional structure and sedimentary evolution, main factors which control the form of trap are discovered, and it is the critical factor method which is used to discern the lithologic trap. After lots of exploration, 700km~2 potential trap is distinguished and 18391.86 * 10~4 tons geologic reserves is calculated. Oil-water distribution rule of pinch-out oil pool is put up on plane which is the reservoirs can be divided into four sections. This paper presented the law of distribution of oil and water in updip pinch-out reservoir, that is, hydrocarbon-bearing formation in plane can be divided into four zones: bottom edge water zone, underside oil and water zone, middle pure oil zone and above residual water zone. The site of the first well should be assigned to be middle or above pure oil zone, thus the exploration value of this type of reservoir can be recognized correctly. In accordance with the characteristics of seism and geology of low permeability thin sandstone and mudstone alternation layer, the paper applied a set of reservoir prediction technology, that is: (1)seism multi-parameter model identification; (2) using stratum's absorbing and depleting information to predict reservoir's abnormal hydrocarbon-bearing range. With the analysis of the residual resource potential and the research of two petroleum system and the accumulation model, promising objective zones are predicted scientifically. And main exploration aim is the DaRngZi bore in the west of ChangLin basin, and YingTai-SiFangZi middle-upper assembly in Honggang terrace.
Resumo:
Based on geodynamic analysis of sedimentary basins, combined sedimentology with structural geology and other methods, the author studied the Honghe basin located in Yunnan province of Southwestern China. Sandstone slice grain size analysis, combined with field geology and indoors study indicate that a set of inland alluvial fan diposits, fluvial deposites, delta deposits and some lacustrine sediments are in Honghe basin. Studying on shape of the Honghe basin, sedimentary and structural characteristic and distribution of different kinds of conglomerate and its structural significance, we hold the idea that the formation and evolution of Honghe basin are controlled by the activity of Red River faut. Correlation of lithostratic cross section in Honghe basin and studying on activity of Red River fault indicate that Honghe basin was formed in two stages. It is a complex basin constitutes of the first-stage trans-releasing basin and the second-stage trans-downfaulted basin. Due to the uplift of Qinghai-Xizang plateau and deformation of orogeny, the western Yunnan and adjacent area move to SE direction as a result of Tectonic Escape. Right lateral strike slip occurred along Red River fault, trans-releasing basin formed at the bend part of the fault due to stress relexation. As the block escaping, it moves away from the other block of the Red River fault, the upper block move down obliquely and trans-downfaulted basin formed. Combined the age of phytolite and regional structural events, we think the first-stage transreleasing basin was formed in late Miocene, on the other words, the dextral strike slip of Red River fault may began in late Miocene (10-7Ma). The second-stage trans-downfaulted basin may be formed in early stage of Pliocene (about 4.7Ma). Subsequently, the bilateral faults dipping to the inside of the plateau and thrusting outwards occurred in the marginal region of Qinghai-Xizang plateau during its uplifting as a fan-shaped mountain body, this results in the uplift of the strata to the east of Red River fault and supply large quantity of provenance for the Honghe basin. In last Pliocene (about 3Ma), strong uplift of Qinghai-Xizang plateau leads to massive clastic sediment entered Honghe basin and causes its closure. As a kind of trans-tentional basin, trans-releasing basin is different to pull-apart basin. The author compared the Mosha trans-releasing basin with Jinggu pull-apart basin in SW Yunan, China, and described their character correspondingly. Otherwise, the author combined the predecessors' studding with conclusion of own study, discussed the kinematics of Ailaoshan-Red River belt in Cenozoic, and the relationship between the formation of Honghe basin and uplifting of Qinghai-Xizang plateau.
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Since the discovery of coesite-bearing eclogites in Dabie and Sulu region over ten years ago, the Dabie collisional orogen has been the "hot-spot" across the world. While many great progresses have been made for the last decade in the researches on the Dabie and Sulu UHP metamorphic rocks in the following fields, such as, petrology, mineralogy, isotope chronology, and geochemistry, the study of the structural geology on the Dabie orogen is still in great need. Thrust and nappe tectonics commonly developed in any collisional orogenic belt during the syncollisional process of the orogen. It is the same as the Dabic collisional orogen is concerned. The paper put much stress on the thrust and nappe tectonics in the Dabic orogenic belt, which have been seldom systematically studied before. The geometric features including the division and the spatial distribution of various thrust and nappe tectonics in the Dabie orogen have been first studied, which is followed by the detailed studies on their kinematic characteristics in different scales varying from regional tectonics to microtectonics. In the thesis, new deformation ages have been obtained by the isotopic methods of ~(40)Ar-~(39)Ar, Sm-Nd and Rb-Sr minerals-whole rock isochrons on the mylonites formed in three ductile shear zones which bounded three different major nappes in the Dabie collisional orogenic belt. And the petrological, geochemical characteristics of some metamorphic rocks as well as the geotectonics of their protoliths, which have also deformed in the ductile shear zone, are analyzed and discussed. In the paper, twelve nappes in the Dabie orogen are first divided, which are bounded by various important NWW or NW-strike faults and three NNE-strike faults. They are Shangcheng Nappe, Huoshan Nappe, Yuexi Nappe, Yingshanjian-Hengzhong Nappe, Huangzhen Nappe, Xishui-Huangmei Nappe, Zhoudang Nappe, Suhe-Huwan Nappe, Xinxian Nappe, Hong'an Nappe, Mulan Nappe and Hhuangpi-Susong Nappe. In the Dabie orogen, three types of thrust and nappe tectonics belonging to two stages have been confirmed. They are: (1) early stage ductile thrust -nappe tectonics which movement direction was top-to-the-south; (2) late stage brittle to ductile-brittle thrust-nappe tectonics which are characterized by double-vergence movement, including top-to-the-north and top-to-the-south; (3) the third type also belongs to the late stage which also characterized by double-vergence movement, including top-to-the-east and top-to-the-west, and related to the strike-slip movement. The deformation ages of both Wuhe-Shuihou ductile shear zone and Taihu-Mamiao ductile shear zone have been dated by ~(40)Ar-~(39)Ar method. ~(40)Ar/~(39)Ar plateau ages of biotite and mica from the mylonites in these two shear zones are 219.57Ma and 229.12Ma. The plateau ages record the time of ductile deformation of the ductile shear zones, which made the concerned minerals of the mylonites exhume from amphibolite facies to the middle-upper crustal conditions by the early stage ductile thrust-nappe tectonics. The mineral isochons of Sm-Nd and Rb-Sr dating on the same mylonite sample of the metamafic rocks are 156.5Ma and 124.56Ma respectively. The two isochron ages suggest that the mylonitic rock strongly deformed in the amphilbolite facies at 156Ma and then exhumed to the upper crustal green schist condition at 124Ma with the activities of the Quiliping-Changlinggang ductile shear zone which bounded to the southen edge of Xinxian Nappe. Studies of the petrological and geochemical characteristics of some meta-mafic rocks and discussion on the geotectonics of their protoliths indicate that their protoliths were developped in an island arc or back-arc basin or active continental margin in which calc-alkline basalts formed. This means that arc-accretion orogeny had evolved in the margins of North china plate and/or Yangtze plate before these two plates directly collided with each other during the evolution process of Dabie orogen. Three-stage evolution of the thrust-nappe tectonics in Dabie collisional orogen has been induced based on the above-mentioned studies and previous work of others. And a possible 3-stage exhumation model (Thrust-Positive Flower Structure Model) has also been proposed.
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Since 1970s, igneous reservoirs such as Shang741, Bin674 and Luol51 have been found in Jiyang depression, which are enrichment and heavy-producing. Showing good prospect of exploration and development, igneous reservoirs have been the main part of increasing reserves and production in Shengli oilfield. As fracture igneous reservoir being an extraordinary complex concealed reservoir and showing heavy heterogeneity in spatial distribution, the study of recognition, prediction, formation mechanism and the law of distribution of fracture is essential to develop the reservoir. Guided by multiple discipline theory such as sedimentology, geophysics, mineralogy, petroleum geology, structural geology and reservoir engineering, a set of theories and methods of recognition and prediction of fractured igneous rock reservoir are formed in this paper. Rock data, three-dimensional seismic data, log data, borehole log data, testing data and production data are combined in these methods by the means of computer. Based on the research of igneous rock petrography and reservoir formation mechanism, emphasized on the assessment and forecast of igneous rock reservoir, aimed at establishing a nonhomogeneity quantification model of fractured igneous rock reservoir, the creativity on the fracture recognition, prediction and formation mechanism are achieved. The research result is applied to Jiyang depression, suggestion of exploration and development for fractured igneous rock reservoir is supplied and some great achievement and favourable economic effect are achieved. The main achievements are gained as follows: 1. The main facies models of igneous rock reservoir in JiYang depression are summarized. Based on data and techniques of seism, well log and logging,started from the research of single well rock facies, proceeded by seismic and log facies research, from point to line and line to face, the regional igneous facies models are established. And hypabyssal intrusion allgovite facies model, explosion volcaniclastic rock facies model and overfall basaltic rocks facies model are the main facies models of igneous rock reservoir in JiYang depression. 2. Four nonhomogenous reservoir models of igneous reservoirs are established, which is the base of fracture prediction and recognition. According to characteristics of igneous petrology and spatial types of reservoir, igneous reservoirs of Jiyang depression are divided into four categories: fractured irruptive rock reservoir, fracture-pore thermocontact metamorphic rock and irruptive rock compound reservoir, pore volcanic debris cone reservoir and fracture-pore overfall basaltic rock reservoir. The spatial distribution of each model's reservoir has its features. And reservoirs can be divided into primary ones and secondary ones, whose mechanism of formation and laws of distribution are studied in this paper. 3. Eight geologic factors which dominate igneous reservoirs are presented. The eight geologic factors which dominates igneous reservoirs are igneous facies, epigenetic tectonics deformation, fracture motion, intensity of intrusive effect and adjoining-rock characters, thermo-contact metamorphic rock facies, specific volcano-tectonic position, magmatic cyclicity and epigenetic diagenetic evolution. The interaction of the eight factors forms the four types nonhomogenous reservoir models of igneous reservoirs in Jiyang depression. And igneous facies and fracture motion are the most important and primary factors. 4. Identification patterns of seismic, well log and logging facies of igneous rocks are established. Igneous rocks of Jiyang depression show typical reflecting features on seismic profile. Tabular reflection seismic facies, arc reflection seismic facies and hummocky or mushroom reflection seismic facies are the three main facies. Logging response features of basic basalt and diabase are shown as typical "three low and two high", which means low natural gamma value, low interval transit-time, low neutron porosity, high resistivity and high density. Volcaniclastic rocks show "two high and three low"-high neutron porosity, high interval transit-time, low density, low-resistance and low natural gamma value. Thermo-contact metamorphic rocks surrounding to diabase show "four high and two low" on log data, which is high natural gamma value, high self-potential anomaly, high neutron porosity, high interval transit-time and low density and low-resistance. Based on seismic, well log and logging data, spatial shape of Shang 741 igneous rock is described. 5. The methods of fracture prediction and recognition for fractured igneous reservoir are summarized. Adopting FMI image log and nuclear magnetic resonance log to quantitative analysis of fractured igneous reservoir and according to formation mechanism and shape of fracture, various fractures are recognized, such as high-angle fracture, low-angle fracture, vertical fracture, reticulated fracture, induced fracture, infilling fracture and corrosion vug. Shang 741 intrusive rock reservoir can be divided into pore-vug compound type, pore fracture type, micro-pore and micro-fracture type. Physical properties parameters of the reservoir are computed and single-well fracture model and reservoir parameters model are established. 6. Various comprehensive methods of fracture prediction and recognition for fractured igneous reservoir are put forward. Adopting three-element (igneous facies, fracture motion and rock bending) geologic comprehensive reservoir evaluation technique and deep-shallow unconventional laterolog constrained inversion technique, lateral prediction of fractured reservoir such as Shang 741 is taken and nonhomogeneity quantification models of reservoirs are established.
Resumo:
Jurassic is an important hydrocarbon-bearing formation in Junggar Basin. Analyzing in strata sequence stratigraphy and hydrocarbon formation has both theoretical and practical values. First of all, strata sequence stratigraphy of continental facies is a new development and supplement in the theory of stratigraphic geology. Stratum of continental facies, unlike sea facies, has rich sup-plements, rapid facies changes, and was influenced slightly by sea level changes. The structural background and sedimentary environment of the basin in west China are greatly different from those of the basins in east China. So it is important to build the patterns of strata sequence stratigraphy in west China basins. Secondly, it is also of significance to find out all kinds of traps, for the dominant types are structural ones so far. After 50 years exploration, the stratigraphic or litholigic traps have become the main concern. This desertation is mainly focused on establishing the isochronal strtaum frame for Junggar Basin to show the evolvement characters of the basin sediment system and the regionalstuctrue background. By analyzing the conditions and patterns of the regional oil and gas bearing formations with typical cross-sections, we have established the patterns of sedimentary conditions for different reserviors. By authur's study, several fruitful results have been obtained in the following: Strata sequence frame and evolvement characteristics of Jurassic: By studing strata sequence, Jurassic has been divided into 2 second rank strata sequences and 3 third rank strata sequences based on the interface unconformities. Only 2 fourth rank strata sequences were grouped in BaDaoWan group. Also different seismic facies and sediment units have been recognized with the establishment of the of sediment system model. The oil-gas system characteristics in Jurassic: We conclude that hydrocar bon resources have the best oil potential. Potential of coal, carbonaceous and dark mudstone were reduced in turn. In this thesis we have made the evaluation of three hydrocarbon sources and the distribution oil-gas resource, and studied the potentials of hydrocarbon and evolvement for each kind of micro-component of the two main resource rocks. Prediction of paleo-temperature: In Junggar basin the evolvement of paleo-ground temperature can be divided into three stages. From Carboniferous to early Permian grads of ancient ground temperature was 8-5 ℃/100m, 5-3 ℃/100m from later period of Permian to end Trias, 3-2 ℃/100m from Jurassic to early Tertiary. Patterns of Jurassic hydrocarbon-bearing reserviors: There were two kinds of hydrocarbon source of Permian and Jurassic. They form different hydrocarbon - bearing systems. Six fundamental hydrocarbon - bearing trap modeS have been established. Directions for later exploration: There were two kinds of regional belts in Jurassic, One is structural belt caused by Yanshan and Ximalaya process, and the other was the stratum one caused by paleostructural rises.
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Nansha Islands as sacred territory of China, containing abundant natural resources is the important area of sustaining development of Chinese people. Safeguarding and developing Nansha Islands has become one important part to develop ocean resource of China in 21 century. Engineering geological problems will be faced inevitably in the processes of engineering construction. Coral reef is a new kind of soil and rock and has special engineering characteristics. This doctoral dissertation researches deeply and systematically the regional engineering geology environmental properties and quality, engineering geological characteristics of coral reefs sand on the basis of synthetic analysis of hydrology, climate, geology, geomorphology and engineering field exploration information and combining the experimental data. 1. Put forward the division program of engineering geological environment of Nansha Islands according to the data of hydrology, geology and sediments, and also deeply study the properties of each division. Evaluate the quality of engineering geological environment by fuzzy mathematics and draw the evaluation map of quality of engineering geological environment. The research work provides background support of engineering geological environment to program of resource development in Nansha Islands. 2. Structures of coral reefs have been analyzed. The model of engineering geological zone has been proposed on the basis of geomorphologic zone and combining the strata and ocean dynamic environment. The engineering construction appropriation of each zone is praised. 3. The physical and mechanical properties of coral sands are researched. The results show that coral sands have high void ratio, non-regular shape, easy grain crushing and large compressibility. Shear-expansion takes place only at very low confining pressure and shear-contraction of volumetric strain occurs at higher confining pressure. Internal friction angle decreases with the increasing of confining pressure. The grain crushing property is the main factor influencing the mechanical characteristics. 4. A revised E-ν constitutive model is proposed which considers the change of internal friction angle with confining pressure, and parameter values are also determined. 5. The stability of Yongshu Reef by is analysed for the purpose of serving engineering struction. The process and mechanism of deformation and failure of foundation and slope is analyzed by finite-element method.
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Based on the principle and methods of carbonate sedimentology and reservoir geology, and guided by the theories of carbonate reservoir geology, the palaeokarst of Ordovician carbonate rocks in Tarim Basin has been comprehensively studied with multiple methods from different branches of geology. It is indicated that the features and distribution of palaeokarstification have developed in Ordovician carbonates. The controlling of karstification to Ordovician carbonate reservoirs has been discussed. Regional distribution of carbonate reservoirs controlled by karstification has been predicted within this basin. The main consents and conclusions of the this dissertation is as follows: Nine key indicators to the recognition of palaeokarst are proposed in terms of careful observation upon the well cores, lithological and geochemical analyses, and drilling and logging responses to the karst caves and fractures. The time and environment of cave filling are documented from careful research of lithofacies, mineralogy, and geochemistry of the physical and chemical fillings within karst caves. The caves in Ordovician carbonates were filled in Early Carboniferous in Lunnan area. The muddy filling in upper caves was deposited under subaerial fresh-water setting, while the muddy filling in lower caves was formed in the mixed water body of fresh-water and dominated sea water. Although most chemical fillings are suggested being precipated in the burial diagenetic environment after karstification but mineralogic and geochemical characteristics of some chemical fillings indicates they formed in meteoric environment during the karstification. It is obvious that the palaeokarst has been zoned in vertical profile. It can be divided into four units from top to bottom: surface karst, vadose karst, phreatic and tranquil flow zones. Between two types of limestone karst and dolostone karst are firstly differentiated in Tarim Basin, based on the comparison of features of each karst zone in limestone and dolostone regions. In Tabei area, the lowest depth of karstification is approximately 300 m below the Upper Ordovician unconformity interface, while the bottom depth of karstification in Tazhong area ranges commonly from 300 to 400 m, in rare cases may be up to 750 m below the upper Ordovician unconformity interface. In Lunnan and Tazhong areas, the palaeokarst morphology and the surface hydrosystem are firstly reconstructed based on the top of carboniferous "Shuangfeng limestone bed (Double-Peaks limestone)" as basal. According to the palaeomorphologic feature, karst topography can be divided into three units: karst upland, karst slope, and karst valley. Vadose zone was well developed in karst upland, and it can be found in a quite depth. Both vadose and phreatic zones were well developed in karst slope and upstream valley. In downstream valley, the karstification is not strong, the vadose and phreatic zones are thin in thickness. In Tazhong and Yingmaili areas, karstification is also developed in relict carbonate palaeo-hills which existed as isolated blocks admits clastic strata.