Accumulation Mechanisms and Evolution History of the Giant Puguang Gas Field,Sichuan Basin,China

Solid bitumens were found throughout the carbonate reservoirs in the Puguang gas field, the largest gas field so far found in marine carbonates in China, confirming that the Puguang gas field evolved from a paleo-oil reservoir. The fluid conduit system at the time of intensive oil accumulation in the field was reconstructed, and petroleum migration pathways were modeled using a 3-D model and traced by geochemical parameters. The forward modeling and inversion tracing coincided with each other and both indicated that oils accumulated in the Puguang-Dongyuezhai structure originated from a generative kitchen to the northwest of the Puguang gas field. The deposition of organic-rich Upper Permian source rocks dominated by sapropelic organic matter in the Northeast Sichuan Basin, the development of fluid conduit system that was vertically near-source rock and laterally near-generative kitchen, and the focusing of oils originated from a large area of the generative kitchen, were the three requirements for the formation of the giant paleo-oil reservoir from which the giant Puguang gas field evolved. The Puguang gas field had experienced a three-stage evolution. The post-accumulation processes, especially the organic-inorganic interaction in the hydrocarbon-water-rock system, had not only profoundly altered the composition and characteristics of the petroleum fluids, but also obviously changed the physicochemical conditions in the reservoir and resulted in complicated precipitation and solution of carbonate minerals.     

Reserve and Pressure Change of Paleo-oil Reservoir in Puguang Area,Sichuan Basin

The Puguang (普光) gas field is the largest gas field found in marine carbonates in China.The Feixiangnan (飞仙关) and Changxing (长兴) reservoirs are two such reservoirs that had been buried to a depth of about 7 000 m and experienced maximum temperature of up to 220 ℃ before uplift to the present-day depth of 5 000-5 500 m,with present-day thermal maturity between 2.0% and 3.0% equivalent vitrinite reflectance (Ro).Bitumen staining is ubiquitous throughout the Feixianguan and Changxing formations,with the greatest concentrations in zones with the highest porosity and permeability,suggesting that the solid bitumen is the result of in-situ cracking of oil.According to the distribution of bitumen in the core,the paleo-oil boundary can be approximately determined.The paleo-oil resource is calculated to be about (0.61-0.92)×109 t (average 0.76×109 t),and the cracked gas volume is about (380.80-595.80)×109 m3 (average 488.30×109 m3); at least 58.74% of cracked gas is preserved in Puguang gas field.The study area experienced not only the cracking of oil but also thermochemical sulfate reduction,resulting in large quantities of nonhydrocarbon gas,with about 15.2% H2S and 8.3% CO2,together with the structural reconfiguration.During the whole process,the great change of volume and pressure compels the PVTsim modeling software to simulate various factors,such as the cracking of oil,the thermochemical sulfate reduction (TSR) and the tectonic uplift in both isolated and open geological conditions,respectively.The results show that although any one of these factors may induce greater pressure changes in an isolated system than in a closed system,the oil cracking and C3+involving TSR lead to overpressure during the early stage of gas reservoir.Therefore,the tectonic uplift and the methane-dominated TSR,as well as the semi-open system contribute to the reducing pressure resulting in the current normal formation pressure.     

Analysis and application of carbon-bearing rate of reservoirs in the Puguang gas field, northeastern Sichuan Basin

With wells Puguang 2 and 6 in the Puguang gas field as the research objects by choosing organic carbon as characterization reservoir carbon(indirectly reflecting the bitumen contents),this paper discusses the relationship between bitumen contents and lithologic characteristics,reservoir characteristics,and calculates the volume of paleo-oil and oil cracked gas.The study shows that the organic carbon contents of the reservoirs are related to lithologic characteristics.Due to variations in the particle size or structure of rocks,the porosity of the reservoirs varies,furthermore,it will influence the contents of organic carbon.And the relationship between these two parameters is positive.Based on the analysis,the relationship between total organic carbon(TOC)and the contents of reservoir bitumen also appears to be positive.The volume of paleo-oil and cracked gas of the Changxing-Feixian’guan Formation are respectively 495 million tons and 360.4 billion m3 through the calculation of reservoir’s organic carbon.Therefore,the relationship between carbon-bearing rate and characteristics of the reservoirs can be used to indirectly evaluate reservoir types.Besides,the carbon-bearing rate of the reservoirs also reflects the contents of reservoir bitumen,paleo-oil as well as natural gas.It makes a new approach for the study of the types of reservoirs and the amounts of paleo-oil and oil cracked gas in northeastern Sichuan Basin.     

Genetic Relationship between Natural Gas Dispersal Zone and Uranium Accumulation in the Northern Ordos Basin, China

The Ordos Basin is well-known for the coexistence of oil, natural gas, coal and uranium. However, there has been little research to discuss the genetic relationship between them. In this paper, a case study of the Zaohuohao area in Dongsheng, Inner Mongolia, China, is conducted to investigate the genetic relationship between the natural gas and the uranium accumulation. Fluid inclusion data from the uranium-bearing sandstone samples indicate that the fluid inclusions formed in a gas-water transition zone. Using the homogeneous temperatures of aqueous inclusions coeval with hydrocarbon-bearing inclusions, combined with the buried history and paleo-temperature data, the gas-water transition zone reached the area at about 110 Ma. On the basis of this, the contents of Uranium （U） and Total Organic Carbon （TOC） of the samples were analyzed, and there was no obvious relation between them. With regard to the available data from both publications and this study, it is found that the U mineralization has a spatiotemporal accordance with the gas-water dispersal zone. Thus, it is believed that the natural gas in the gas-water zone is an effective reducer to the U-bearing ground water abundant in oxygen, which is the main factor to U accumulation. This result can be used as the reference to the U mines predicting and prospecting.     

Hydrocarbon Accumulation Mechanism of Sinian Reservoir in Anpingdian-Gaoshiti Structure,Middle Sichuan Basin

The Sinian reservior in Anpingdian (安平店)-Gaoshiti (高石梯) structure,Middle Sichuan (四川) basin,is of great importance to prospect for oil and gas.This article dissects the hydrocarbon accumulation mechanism of this area on the basis of comprehensive methods of organic geochemistry,fluid inclusion,modeling of hydrocarbon generation and expulsion from source rocks,and by combining structure evolutions and analyzing the key geologic features of hydrocarbon origin and trap.According to the fluid inclusion homogenization temperature analysis,there exist at least three stages of fluid charging in the Sinian reservoir.From Middle-Late Jurassic to Early Cretaceous,oil cracked to gas gradually owing to high temperature at 200-220 ℃.The Sinian gas pool was mainly formed at the stage when natural gas in trap was released from water and paleo-gas pools were being adjusted.It was a process in which natural gas dissipated,transferred,and redistributed,and which resulted in the present remnant gas pool in Anpindian-Gaositi tectonic belt.The authors resumed such an evolution process of Sinian reservoir as from paleo-oil pools to paleo-gas pools,and till today's adjusted and reconstructed gas pools.     

Types, Evolution and Pool-Controlling Significance of Pool Fluid Sources in Superimposed Basins： A Case Study from Paleozoic and Mesozoic in South China

Having multiple tectonic evolution stages, South China belongs to a superimposed basin in nature. Most marine gas pools became secondary pools. The pool fluid sources serve as the principal pool-controlling factors. On the basis of eight typical petroleum pools, the type, evolution in time-space, and the controlling of petroleum distribution of pool fluid sources are comprehensively analyzed. The main types of pool fluid sources include hydrocarbon, generated primarily and secondly from source rocks, gas cracked from crude oil, gas dissolved in water, inorganic gas, and mixed gases. In terms of evolution, the primary hydrocarbon was predominant prior to Indosinian; during Indosinian to Yen- shanian the secondary gas includes gas cracked from crude oil, gas generated secondarily, gas dissolved in water, and inorganic gas dominated; during Yenshanian to Himalayan the most fluid sources were mixed gases. Controlled by pool fluid sources, the pools with mixed gas sources distributed mainly in Upper Yangtze block, especially Sichuan (四川) basin; the pools with primary hydrocarbon sources distributed in paleo-uplifts such as Jiangnan (江南), but most of these pools became fossil pools; the pools with secondary hydrocarbon source distributed in the areas covered by Cretaceous and Eogene in Middle-Lower Yangtze blocks, and Chuxiong (楚雄), Shiwandashan (十万大山), and Nanpanjiang (南盘江) basins; the pools with inorganic gas source mainly formed and distributed in tensional structure areas.     

Tectonic and Geodynamic Setting of Oil and Gas Basins in China

About 26 sedimentary basins bearing oil and gas are developed in China. They can be classified into two main types , extensional basins and foreland basins . The former are chiefly distributed in the eastern part and the latter in the central and northwestern parts of the country . The present paper discusses the structural characteristics of these basins , including subsidence history , thermal history and structural style and kinematics . Combined with tectonic setting analysis of geophysical data and eruptive rocks , the geodynamic setting of the basins is established , and the formation mechanism of the basins is deduced to have been related to the subduction of the Izanagi and west Pacific plates and the closing of the Tethys ocean.     

Evolution of the Moxizhuang Oil Field, Central Junggar Basin, Northwest China

Current oil saturation in the Moxizhuang (莫西庄) Oil Field in central Janggar (准噶尔) basin was evaluated by logging interpretation and measured on core samples, and the paleo-oil saturation in both the pay zones and water zones was investigated by graln-containing-oil inclusion (GOI) analysis.The pay zones in this field have low oil saturation and display low resistivity and small contrast between pay zones and water zones, and are classified as low-porosity, low oil saturation, and low resistivity reservoirs. Both the current low oil-saturation pay zones and the water zones above 4 365 m have high GOI values (up to 38%), suggesting high paleo-oil saturation. The significant difference between current oil saturation from both logging interpretation and core sample measurement and paleo-oil saturation indicated by GOI analysis suggests that this low oil-saturation field evolved from a high oil-saturation pool. Lateral re-migration and spill of formally trapped oil owing to changes in structural configuration since Neogene was the most plausible mechanism for oil loss in the Moxizhuang Oil Field.The combined effects of differential accumulation in the charge phase and the differential re-migration and spill of accumulated oil in Neogene are responsible for the complicated correlation between residual oil saturation and porosity/permeability of the reservoir sandstones and the distribution of low oil-saturation pay zones and paleo-oil zones (current water zones).     

Geological features and hydrocarbon accumulation in the Xinken oil field, Tarim Basin

Recently,a large-scale Ordovician oil and gas pool has been discovered in Xinken,north of the Tarim Basin,and it has strongly heterogeneous reservoirs and complicated fluid distribution.Through analyzing oil,gas and water samples collected from this area,in combination of field production and testing data,this study reveals that the Xinken oil pool contains dominantly normal oil characterized by low viscosity,low sulphur,and high wax.It has a low content of natural gas,which presents typical characteristics of wet gas and is oil-associated gas.Oil-gas correlation shows that the oil was from the Middle-Upper Ordovician source rocks and the charge and accumulation of oil and gas took place in the Late Hercynian Period.Controlled by paleogeomorphology,sedimentary facies,ancient karstification,faults,and other factors in the Caledonian Period,the Ordovician carbonate reservoirs are dominated by dissolved pores,cavities and fractures.The reservoir body of fractures and cavities is distributed in the shape of strip and laminate along faults and excellent reservoirs are mostly in the range of 70–100 m below the top of the Yijianfang Formation.As a whole,the Xinken oil pool is a fracture-cavity pool controlled by interbedded karst reservoirs and is a complex composed of stacked karst fractures and cavities of various sizes.It contains oil in large areas horizontally,which is quasi-laminated in distribution,and the accumulation of oil and gas is controlled by the distribution and development degree of the Ordovician carbonate reservoirs.The study shows that this area has abundant resources and a great exploration potential for oil and gas.     

The Statistical Prediction of the Vitrinite Reflectance and Study of the Ancient Geothermal Field in Songliao Basin,China

The resource of the gas from coal and coal measures deep in Songliao Basin hasbeen drawing more and more attention to.It is necessary to find out the evolution regulari-ty of the geothermal field of the basin in addition to a series of geological studies in orderto predict its resources because the ancient geothermal field of the basin is one of themain factors controlling the generation,evolution and disappearance of oil and gas.Inthe recent twenty years,it is generally believed that vitrinite reflectance is the best quanti-tative marker for the ancient geothermal field.In the present paper,a systematic studyof the vitrinite reflectance value of Songliao Basin and its influence factors is made by mul-tiple statistical analysis so as to reconstruct the evolutional process of the Moho and thecorresponding geothermal field.Then,an overall prediction is made of the vitrinitereflectance and the distribution of J_3-K_1 fault basin group at the bottom of SongliaoBasin,which provides the evidence for the furth     

Contact metamorphism around the Stawell granite, Victoria, Australia

The contact metamorphosed metapelitic and metapsammitic rocks surrounding the Stawell granite, western Victoria, Australia, are divided into three zones: the low-grade zone, the medium-grade zone and the high-grade zone. Detailed petrological study shows consistency of element distributions, implying that equilibrium was widely attained in the rocks, although equilibrium volumes are generally small (millimetre scale) and considerable mineral chemical variations exist between adjacent domains. The metamorphic mineral assemblages are generally of high variance (KFMASH variance ≤ 2). Consequently, the chemical evolution of assemblages is controlled largely by bulk composition and metamorphic temperature, the former factor being more important in most rocks. The chemographic relations of mineral assemblages in low- and medium- to high-grade zones are presented in compatibility diagrams projected from biotite, quartz and H₂O, and biotite, K-feldspar and H₂O, respectively. These compatibility diagrams have the advantage of showing both quartz-bearing and quartz-absent assemblages. The metamorphic reactions are modelled successfully by a calculated petrogenetic grid that combines both KFASH and KMASH equilibria. Based on petrographic observations and with constraints from the calculated petrogenetic grid, the following KFMASH reactions, in the order of increasing metamorphic grade, are responsible for producing the various mineral assemblages in the Stawell rocks: chl + mu + q = bi + cd + V, chl + q + cd = g + V, mu + bi + q = ksp + cd + V, mu + q = ksp + and + cd + V (or KASH mu + q = ksp + and + V), mu + cd = ksp + and + bi + V, mu + bi + and = ksp + sp + V, and + bi = ksp + sp + cd + V, mu + bi = ksp + cor + sp + V, mu = ksp + cor + and + sp + V (or KASH mu = ksp + cor + V), bi + cd + q = g + ksp + V. The combined KFASH and KMASH grid provides constraints on reaction coefficients in the above sequence of reactions and on temperature and pressure of metamorphism.     

岩土颗粒介质在应力波作用下的接触力与变形关系

为了描述岩土颗粒介质在应力波作用下的接触力与变形关系,运用接触力学和刚体动力学等理论方法,考虑颗粒体之间的局部非线性相互作用,通过引入恢复系数,导出了适用于低速冲击情况下的颗粒介质弹塑性接触模型,通过几种算例的比较分析,说明了该计算方法的合理性。结果表明：本文给出的接触力与变形关系,避开了复杂的增量形式和非线性动态接触问题,且反映了颗粒体的冲击速度、物理力学性质、几何特征以及表面物理条件等因素对接触过程的影响,便于工程推广应用。     

Disequilibrium in the Ross of Mull Contact Metamorphic Aureole, Scotland: a Consequence of Polymetamorphism

The Ross of Mull pluton consists of granites and granodioritesand intrudes sediments previously metamorphosed at amphibolitefacies. The high grade and coarse grain size of the protolithis responsible for a high degree of disequilibrium in many partsof the aureole and for some unusual textures. A band of metapelitecontained coarse garnet, biotite and kyanite prior to intrusion,and developed a sequence of textures towards the pluton. InZone I, garnet is rimmed by cordierite and new biotite. In ZoneII, coarse kyanite grains are partly replaced by andalusite,indicating incomplete reaction. Coronas of cordierite + muscovitearound kyanite are due to reaction with biotite. In the higher-gradeparts of this zone there is complete replacement of kyaniteand/or andalusite by muscovite and cordierite. Cordierite chemistryindicates that in Zone II the stable AFM assemblage (not attained)would have been cordierite + biotite + muscovite, without andalusite.The observed andalusite is therefore metastable. Garnet is unstablein Zone II, with regional garnets breaking down to cordierite,new biotite and plagioclase. In Zone III this breakdown is welladvanced, and this zone marks the appearance of fibrolite andK-feldspar in the groundmass as a result of muscovite breakdown.Zone IV shows garnet with cordierite, biotite, sillimanite,K-feldspar and quartz. Some garnets are armoured by cordieriteand are inferred to be relics. Others are euhedral with Mn-richcores. For these, the reaction biotite + sillimanite + quartz garnet + cordierite + K-feldspar + melt is inferred. Usinga petrogenetic grid based on the work of Pattison and Harte,pressure is estimated at 3·2 kbar, and temperature atthe Zone II–III boundary at 650°C and in Zone IV asat least 750°C. KEY WORDS: contact metamorphism; disequilibrium     

内蒙古白乃庙地区外接触变质带内──阳起石～钙质斜长石带

白乃庙地区绿色片岩主要为阳起石＋钙质斜长石组合，形成不同矿物组合和亚带。白乃庙地区花岗质侵入岩体侵入到岛弧蛇绿岩中形成外接触变质带内—阳起石～钙质斜长石带。该带的确立为建立阳起石～钙质斜长石角门岩相及分布其中的接触变质型铜钼矿床提供依据。     

金家堡子地段岩体接触带深部延伸特征

岩体接触带为金家堡子地段主要的控矿构造,根据其走向与深部分布形态复杂的特征,选择音频大地电磁测深进行了深部地质构造的应用研究,通过资料综合对比分析,基本查明了岩体接触带的深部延伸特征以及与成矿关系密切的岩体凸起的分布范围,为区内铀矿勘查提供了基础资料。     

湘南姑婆山岩体北西侧侵入接触带构造控矿研究

位于湖南南部的姑婆山岩体北西侧侵入接触带受断裂构造控制明显,表现复杂多样,是该区钨、锡多金属矿床的主要控矿构造.根据接触带不同成矿区段的空间展布特点、构造变形和矿化蚀变特征,认为该区接触带构造是岩体侵位和区域应力双重作用的结果,并首次将该侵入接触带构造划分为3种类型,即侵入接触-断裂复合型、双侵入接触-断裂复合型以及捕虏体接触-断裂复合型.明确提出了侵入接触带构造控矿的观点,从而为进一步研究其成矿及控矿作用提供必要的理论依据.     

Fenton试剂氧化-微电解-接触氧化法处理丙烯腈废水实验研究

实验采用Fenton试剂氧化-微电解-接触氧化组合工艺处理丙烯腈废水。研究了各单元工艺的最佳控制参数和操作条件。结果表明,在废水pH值为3左右、反应时间2 h的前提下,双氧水投加量40 mL/L,二价铁离子质量浓度为0.4 g/L,再经过微电解处理后的出水进入接触氧化阶段。在溶解氧为4.5 mg/L左右,水力停留时间为10 h、容积负荷1.0 kg COD_Cr/（m³·d）左右的条件下,出水COD_Cr小于100 mg/L,可达到国家对丙烯腈废水处理要求的一级标准。     

Contact metamorphism of pelitic,psammitic and calcareous sediments in the Southern Highlands of New South Wales

Contact metamorphism has been recognized along a 4 km wide belt adjacent to the shallow‐dipping eastern margin of the Arthursleigh Tonalite, an Early Devonian pluton of the Marulan Batholith, eastern New South Wales. In Ordovician psammitic and pelitic rocks three zones of progressive contact metamorphism range from muscovite + biotite + chlorite assemblages in the outer zone to K‐feldspar + cordierite assemblages adjacent to the pluton and in metasedimentary xenoliths. Retrograde phenomena include extensive replacement of metamorphic minerals by ‘sericite’ and chlorite. Calcareous metasediments adjacent to the tonalite typically contain assemblages of quartz + calcic plagioclase + ferrosalite + sphene, or wollastonite + calcite + diopside with minor grossularite and vesuvianite. Thermal effects in volcanic rocks along the western margin of the pluton are confined to recrystallization of the groundmass.

The regional geology indicates confining pressures of approximately 1 kbar at the time of emplacement of the tonalite. Contact metamorphic temperatures were estimated from two‐feldspar geothermometry to attain a maximum of approximately 590°C for rocks in the innermost zone of the aureole and 700°C for the xenoliths. Fluid compositions attending progressive contact metamorphism were water‐rich (Xco₂<0.2) and, during cooling, these fluids probably account for the extensive retrograde hydration observed in the aureole.     

CSAMT法在内蒙古卫境地区接触交代型铀矿勘查中的应用

介绍了CSAMT法在内蒙古卫境地区接触交代型铀矿勘查中的应用实例。通过对成果资料的综合分析,发现CSAMT测量成果能够较清楚地反映花岗岩、变质岩及其接触带的空间展布特征,能够在接触交代型铀矿勘查中取得较好的应用效果,可以为类似地区进行间接找矿提供参考。     

桩土接触面单元参数分析

桩的抗拔特性与接触面的特性密切相关，正确选定接触面的力学参数对于分析桩的抗拔机理有重要意义。根据桩土接触面点面接触模型和库仑摩擦变形原理，在10组土－结构（钢、混凝土）剪切摩擦试验分析的基础上，对桩土接触面摩擦参数的取值问题进行了研究，得到了一些结论，对于桩土接触面力学参数正确取值有一定的参考价值。