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2007 Vol. 29, No. 3

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2007, 29(3): 214-214. doi: 10.11781/sysydz200703214
Abstract(414) PDF-CN(303)
Abstract:
RESERVOIR ROCK CHARACTERISTICS OF PALEOZOIC MARINE FACIES CARBONATE ROCK IN THE TARIM BASIN
Kang Yuzhu
2007, 29(3): 217-223. doi: 10.11781/sysydz200703217
Abstract(677) PDF-CN(387)
Abstract:
Based on study of Paleozoic carbonate reservoir rock in the Tarim Basin,it is discussed in this paper reservoir rock type,reservoir room type,reservoir capacity and carbonate rock diagenesis.Paleozoic carbonate reservoir rock in the Tarim Basin can be classified into 4 types: ancient karst and weathered residuum,shoal and reef,oolitic beach and dolomite.5 stages of tectonic evolution result in 5 stages of ancient karst reservoir,including: Lower Cambrian-Upper Sinian,Middle Ordovician-Upper Ordovician,Silurian-Ordovician,Carboniferous and underlying strata,and ancient karst between Triassic and Pretriassic.Reservoir room is divided into 2 types: pore-vug and fracture.Pore and vug include micropore,intercrystalline pore,dissolution pore and dissolution vug.Fractures include diagenetic fracture,facture related to regional tectonics,fracture related to fold,fracture related to rupture,and fracture related to deep strata charge and pore pressure.Diageneses of carbonate reservoir rock include compaction,pressure solution,cementation,dolomitization,recrystallization,silicification and dissolution.Reservoir rocks include dolomite(fracture-vug type) and limestone(fracture type,with few vug-fracture type and fracture-carven type).Reservoir capacity of dolomite is much better than that of limestone.
OIL MIGRATION AND ACCUMULATION PATTERN IN THE TAHE OILFIELD
Gu Yi, Shao Zhibing, Chen Qianglu, Huang Jiwen, Ding Yong, Chen Zhengfu, Chen Jianghan, Xu Sihuang
2007, 29(3): 224-230. doi: 10.11781/sysydz200703224
Abstract(620) PDF-CN(447)
Abstract:
Based on study of geochemical characteristics,fluid inclusion characteristics,reservoir bitumen,reservoir autogenetic clay minerals,ancient and present tidal current fields,ancient and present fluid potentials,petroleum conduction condition related to petroleum migration and accumulation,petroleum charging process in the Tahe Oilfield can be divided into 3 stages and 5 times: late Hercynian(the 1st time),Indosinian-Yanshanian(the 2nd time),and Himalayan(the 3rd,4th and 5th time).The main accumulation stages are late Hercynian and Himalayan.During late Hercynian,petroleum migrates from south to north.During Himalayan,petroleum migrates from south to north and east to west.Huge Cambrian and Ordovician source rocks provide for multistage hydrocarbon charging and accumulation.Favorable tectonic locations on ancient uplifts and slopes are the target for petroleum migration.Large-scale unconformities,karst passage networks and fractures are channels for petroleum migration and accumulation.Sets of reservoirs,sets of reservoir and seal associations, types of traps and the generation of large-scale carbonate rock karst-fracture reservoirs are the key for the generation of large-scale composite oil-andgas field.Ordovician reservoir in the Tahe Oilfield is characterized by early accumulation transformation and late charging adjustment.Generation and evolution of sealing condition control hydrocarbon accumula-tion in the Tahe Oilfield.
FORMATION AND DISTRIBUTION FEATURES OF LARGE-MEDIUM OIL-AND-GAS FIELDS IN MAIN FAULT DEPRESSIONS IN THE SONGLIAO BASIN
Wu Yuyuan, Zhou Liqing
2007, 29(3): 231-237. doi: 10.11781/sysydz200703231
Abstract(675) PDF-CN(287)
Abstract:
More than 30 Mesozoic fault depressions develop in the center of the Songliao Basin.The discovered large-medium oil-and-gas fields mainly locate in the petroleum-rich deep fault depressions named Xujiaweizi,Shiwu and Changling on the two sides of the NNE oriented Sunwu-Shuangliao lithospheric fracture in the center of the basin.Study of the petroleum generating geologic condition of deep fault depressions and the distribution characteristics of large-medium oil-and-gas fields shows that,large-medium oiland-gas fields mainly locate in the EW oriented inherited nose-like structures in the central fault horst zone,the gentle slope break zone,the gentle slope horst zone and the steep slope break zone around hydrocarbon generating center of half-graben deep faults and the lithospheric overlapping pinch and lithologic traps.The central uprising belts between two deep fault depressions are usually where large oil-and-gas fields can be found.The future exploration should be focused on the above-mentioned regions in deep fault depressions.
PROGRESSIVE DEFORMATION IN YANGTZE PLATE——SERIES 2 OF THE SOUTHERN STRUCTURE STUDIES
Ding Daogui, Liu Guangxiang
2007, 29(3): 238-246. doi: 10.11781/sysydz200703238
Abstract(694) PDF-CN(645)
Abstract:
From Indosinian to early Yanshanian,ancient Tethys basin closed.The continent margin of Yangtze Plate was extruded and collided,forming the Jiangnan-Xuefeng basement decoupling structure(zone A) in the plate.Due to the massive horizontal extrusion effect from SE to NW(E to W,S to N at the meanwhile),Meso-Paleozoic basins in Yangtze Plate were deformed progressively.At the front,the following zones were formed: high-obliquity thrust and fault-bend fold zone(zone B),overthrust and fault-propagation fold zone(zone C),detachment fault and detachment fold zone(zone D),conjugate thrust and kink fold zone(zone E),and ancient uplift and monocline zone(zone F).At the back,decollement fault and detachment fold zone(zone F) was formed.In different deformation zones,horizontal displacement and compressive deformation,placement of thrust fault and fold,as well as tectonic trap types and preservation are all different,hence controlling petroleum accumulation and distribution of different types.
NAPPE STRUCTURE CHARACTERISTICS AND EXPLORATION POTENTIAL FORECAST IN LONGMENSHAN, THE WEST OF SICHUAN PROVINCE
He Li, Liu Liping, Luo Xiao, Lü Zhizhou, Wang Yingrong
2007, 29(3): 247-252. doi: 10.11781/sysydz200703247
Abstract(690) PDF-CN(348)
Abstract:
The Longmenshan nappe structure in the west of Sichuan Province can be divided into three parts in plane: the Indosinian fold in the north,the Yanshanian fold in the middle and the Himalayan fold in the south.There are 3 layers vertically: the Indosinian autochthon at the bottom,the Yan-shanian nappe structure in the middle and the Himalayan gliding nappe and superposition at the top.The Longmenshan structure has undergone multiple-epoch structural movements with strong deformation,thus its sealing conditions of preservation are the key factor to form reservoirs.In the north,faults are cut through and objective intervals are exposed,thus oil and gas reservoirs are destroyed.In the middle,objective intervals are exposed and sealed half-and-half and the preservation condition is general.In the south,the Middle and Lower Jurassic red bed,which is exposed to surface,develops continuous deformation resulting in seal to the fractured structure,thus the preservation condition has been improved. Hereby,it is concluded that the structural belt from Gaojiachang to Lianhuashan in the southern Longmenshan is the most favorable zone in which large and medium oil and gas fields may be discovered.The fault-fold zone in the middle is the favorable zone in which medium and small oil and gas fields may be found.Oil and gas reservoirs in the north have been destroyed in which small residual heavy oil and gas reservoirs may be discovered.In addition,Dayi,Yazihe,Jinma and Juyuan in the subtle area of the front of mountain should be paid more attention to.
PETROLEUM GEOLOGICAL FEATURES AND EXPLORATION POTENTIAL ANALYSES OF NORTH CARNAVON BASIN, AUSTRALIA
Bai Guoping, Yin Jinyin
2007, 29(3): 253-258. doi: 10.11781/sysydz200703253
Abstract(806) PDF-CN(276)
Abstract:
The North Carnarvon Basin is the premier oil and gas producing basin in Australia and one of the world-class gas-rich basins.It experienced pre-rifting,early rifting,late rifting,and post-rifting passive margin development stages.The basin was filled with about 15 km thick sediments,which are overwhelmingly dominated by the Mesozoic.Four sets of source rocks were developed in the Triassic-Lower Cretaceous succession.Oil,condensate and gas are mainly reservoired in the Upper Triassic,Upper Jurassic and Lower Cretaceous.Regionally,oil is mostly distributed in the Barrow and Dampier Sub-basins whereas the Exmouth Plateau and Rankin Platform contain bulk of the condensate and gas.By the end of 2004,5.27×108 tonnes of oil and 28 424×108 m3 of gas had been discovered in the basin.Integrated petroleum geological analyses indicate that the basin has a considerable hydrocarbon prospectivity.The moderately explored Exmouth Plateau,Exmouth Sub-basin and Beagle Sub-basin comprise the most promising areas with the best exploration potential.
EFFECTS OF DEEP-SOURCED FLUIDS ON THE FORMATION OF NATURAL GAS RESERVOIRS
Shen Baojian, Huang Zhilong, Liu Hongwen, Xu Cheng, Yan Zaifei, Chen Mi
2007, 29(3): 259-264. doi: 10.11781/sysydz200703259
Abstract(848) PDF-CN(264)
Abstract:
The deep-sourced fluids are important in material and energy transfer on earth interior.Deep-sourced fluid is a kind of supercritical fluid composed of vast of gases.These gases will move to the shallow through earthquake or deep fault belt.The temperature and pressure will reduce during the fluid uplifting.A mass of gases will extract from fluid or magma.On the other hand,it can transmit energy and material,which obviously contributes hydrogen to hydrocarbon generation.Appling models of stable carbon isotope and rare gas geochemistry,the natural gases along Tanlu Fault Belt were studied.The result shows that the deep-sourced fluid effects on natural gas formation and migration.The same result was obtained with an experimental simulation of natural gas formation.The recent researches on the relationship between deep-sourced fluids and the formation of natural gas reservoir have important theoretic and practice significance to natural gas origin.
ORDOVICIAN PALAEOKARST LANDFORM AND ITS CONTROL ON RESERVOIRS IN WEST LUNGU REGION, THE TARIM BASIN
Liu Xiaoping, Sun Dongsheng, Wu Xinsong
2007, 29(3): 265-268. doi: 10.11781/sysydz200703265
Abstract(637) PDF-CN(334)
Abstract:
Karst landform is the result of the compositive process of karst and various geology.And various shapes of karst landforms also control the karst reservoir development.The palaeokarst landform in west Lungu region was restored by using seismic horizon flattening technique.The results show that the surface of the karst is undulate greatly,and develops the landform combination of peak cluster depression,peak forest valley and peak forest plain from east to west.The vertical karst facies belts in different landform was divided according to the data of well logging,drilling and geological log.Then,the development characteristics of reservoirs in different landforms are discussed.Research results indicate that the great differences of cavern development and filling status exist among various palaeokarst landforms and karst facies belts,which reflect that the palaeokarst landforms control the spatial development of karst facies belt and reservoirs.
TECTONIC DEFORMATION CHARACTERISTICS OF THE SOUTH DABA TECTONIC BELT DURING MESOZOIC AND CENOZOIC
Pei Zhenhong
2007, 29(3): 269-274. doi: 10.11781/sysydz200703269
Abstract(1892) PDF-CN(321)
Abstract:
Compressed from both Qinling and Xuefeng directions,the South Daba Tectonic Belt,known as a typical thrust and fold belt,has experienced long history of development ever since the Indo-Chinese period.The composite stress displays a clockwise movement during the early stage and an anticlockwise movement during the late stage respectively.Because of the time and spatial changes in stress direction and the existence of multiple layers of detachment,deformations during Mesozoic and Cenozoic are cha-racterized by multiple phases,multiple directions,multiple layers and multiple phases'composition.The tectonic deformations include gentle fold(late Indo-Chinese),fold generation(early Yanshanian),thrust and fold(middle Yanshanian),thrust(early Himala-yan) and uplift and erosion(late Himala-yan).The major compression comes from Qinling and the minor from Xuefeng Mountain as well as Micang and Longmen Mountains.Tectonic deformations during Mesozoic and Cenozoic are controlled by either simultaneous or un-simultaneous composite actions.Due to the southward shoaling of stress in its transfer process and the existence of plastic layers,the deformation exhibits a vertical and planar pattern of multiple layers.Influenced by the multiple originated and multiple directional compression simultaneously or un-simultaneously,the deformation in this area is both complicated and complex.
THE NEW RECOGNITION OF RESERVOIR-FORMING CONDITION OF KONGQUEHE PALAEOSLOPE IN THE TARIM BASIN
Yang Ming, Tang Dazhen, Xing Weixin, Li Xiaolin, Ma Xinhai, Li Ying
2007, 29(3): 275-279. doi: 10.11781/sysydz200703275
Abstract(603) PDF-CN(396)
Abstract:
The Well Yuli 1 is the first well which drills through Sinian System on the northeast margin of the Tarim Basin.This is on the significance to know reservoir-forming condition and to determine the favourable exploration targets of the Kongquehe palaeoslope area by drilling consequent analysis of the Well Yuli 1.The results of observation of core,the analysis of the rock sample component by electron microprobe's method,the pyrogenation analysis and the basin modeling comprehensive research show that the thermal evolution of organic matter of Cambrian-Lower Ordovician source rocks in the Kongquehe palaeoslope approach coal and the Cambrian-Lower Ordovician source rocks are not the capability of secondary hydrocarbon generation after its experienced one buried depth in its burial history.The main reservoir space of Cambrian-Lower Ordovician paleo-reservoir is crack and corrosion hole which were formed early period.Reservoir-forming characteristic in the Kongquehe is early reservoir-forming,self-generating and self-storing,one stage destroying,tow stage adjusting.By discussing the favourable exploration trap in the Kongquehe area,we get the following conclution: transverse nose-shaped trap is not favourable trap; the Lower Palaeozoic paleo-anticline is more better exploration trap and breaking-anticline;lithologic trap and unconformit trap is good exploration trap.
THE POTENTIAL OF GENERATING HEAVY OIL AND SOLID BITUMEN OF EXCELLENT MARINE SOURCE ROCKS
Qin Jianzhong, Li Zhiming, Liu Baoquan, Zhang Qu
2007, 29(3): 280-285. doi: 10.11781/sysydz200703280
Abstract(715) PDF-CN(397)
Abstract:
It is concluded that excellent marine source rocks have the great potential of generating heavy oil and solid bitumen,by combining the results of a great deal thermal pressure hydrocarbon generation and expulsion simulating experiments of marine source rocks,pelagic algae and benthic algae with the reservoir solid bitumen and their characteristics in marine carbonate rock in Southern China.The main evidences are as follows:(1) Thermal pressure simulating experiments of oil generation of the pelagic algae as the main hydrocarbon generation organism in marine source rock show that the maximum yield of oil appears at the early mature stages(Ro=0.45%-0.7%),a great quantity of heavy oil with asphaltene and non-being dominant can be generated at this stage,and the peak value of yield per ton TOC can reach to 1 000 kg.The heavy oil is the main component of forming solid bitumen in reservoirs.(2) Immature excellent marine source rock(type Ⅰ-Ⅱ1 kerogen and TOC2%) can also generate a mass of heavy oil dominated by asphaltene and non-hydrocarbons at early mature stage.The total oil yield per ton TOC can reach to 300 kg,which accounts for about 50% maximum oil yield and 40% of the total hydrocarbon yield.The total yield of heavy oil gradually decreases following the kerogen type becoming poor,the organic matter content decreasing(TOC2.0%) and the carbonte content(5%) reducing.(3) The heavy oils generated from the excellent marine source rock at the early mature stage and the suspending organic matters moving out at the penecontemporaneous to early diagenesis in the Permian and Silurian stratums in Southern China,can form lots of soild bitumens by later burial and high tempe-rature cracking and polymerization.
GEOCHEMICAL CHARACTERISTIC OF THE LOWER SILURIAN OIL SANDSTONES IN WELL ZHONG 1 ZONE, NORTH WESTERN TAZHONG AREA
Qian Yixiong, Ma Anlai, Chen Qianglu, Shao Zibing, You Donghua
2007, 29(3): 286-291. doi: 10.11781/sysydz200703286
Abstract(547) PDF-CN(220)
Abstract:
The lower part of the Lower Silurian sandstones is one of the most important hydrocarbon exploration play in Tarim Basin Based on systematic analysis of the petroleum family composition,various biomarkers and distribution of isotope of petroleum family composition in the saturated fraction from extracts of the Lower Silurian oil sandstones in Well Zhong 1 zone,the results show that the contents of saturated hydrocarbon is from 51.31%～60.15%,the ratio for saturated and aromatics is from 1.68～1.94 in Well Zhong 1,in contrast,the contents of saturated hydrocarbon is 30%,the average ratio for saturated and aromatics is 1,the distribution for n-alkanes is nC12 to nC39 with the major contents of n-alkanes from nC17 to nC19,OEP is from 0.91 to 1.08 in Well Zhong 13. Moreover,the latter is characteristic of a certain content of tricyclic and tetracyclic terpane,C27>C28<29 in consist of steranen and the raising line for isotope of petroleum family composition in the saturated fraction.It therefore can be inferred that the oil for the Lower Silurian oil sandstones is mostly origined from the Middle and Lower Cambrian mixing with a certain of the Upper Ordovician source rocks.
ISOTOPIC CHARACTERISTICS OF OIL FILED WATERS FROM ORDOVICIAN OIL ACCUMULATIONS IN TAHE OILFIELD AND ITS GEOLOGICAL SIGNIFICANCES
Jia Cunshan, Ma Xujie, Rao Dan, Gao Renxiang
2007, 29(3): 292-297. doi: 10.11781/sysydz200703292
Abstract(640) PDF-CN(421)
Abstract:
Hydrogen isotope values(δD) of oil field waters from the Ordovician oil accumulations in Tahe oilfield cover -44.7‰～-61.0‰(SMOW),from which one can conclude that the oilfield waters are mostly paleo-atmospheric waters mixed with original sediment seawater.Based on the transverse change trends of the parameters in these oilfield waters,such as high pressure physical parameter,carbon isotope of CO3- electronegative ion and 87Sr/86Sr ratio of strontium isotope,one can roughly deduce that the predominant flow direction of paleo-atmospheric water is from the northeastern tectonic high position to the southwestern plunge end of the Arkekule nose salient.In this process,the current flowed from axis to two wings of the tectonic,which would cut through weakness belt of faults or cracks and enlarge the space by carbonates corrosion,finally formed complicated karst fracture-cavity system of the Ordovician carbonates in Tahe Oilfield.Therefore,the flow direction of paleo-atmospheric water controled the distribution of fracture-cavity system and connectivity of fracture-cavity cells.
A STUDY OF THE PYROLYSIS PARAMETER Tmax AND VITRINITE REFLECTANCE FROM MIXED COAL SAMPLES
Sun Lizhong, Lee Hsientsung, Tsai Louis L
2007, 29(3): 298-300. doi: 10.11781/sysydz200703298
Abstract(959) PDF-CN(287)
Abstract:
Reworked sedimentary materials were simulated by mixing of high and low rank coals in various proportions,so as to evaluate the variation of Tmax from Rock-Eval pyrolysis.The results indicate that(1) once the low rank coal is mixed with high rank coal,the Tmax is close to that of the low rank coal,whatever the mixing ratio is;(2) care must be taken for reworked samples,especially for organic materials with high maturity,even dealing with a very small amount of sample mixing;(3) Because of the fast dropping of Tmax after increasing mixed ratio of low rank coal,the correlation of Ro and Tmax is quite different from the linear trend possessed by type-Ⅲ kerogen.
ORGANIC MACERAL CHARACTERISTICS AND HYDROCARBON-GENERATING POTENTIALS OF SOURCE ROCKS IN THE PEARL RIVER MOUTH BASIN
Zhu Junzhang, Shi Hesheng, Shu Yu, Du Jiayuan, Wu Jianyao, Luo Junlian
2007, 29(3): 301-306. doi: 10.11781/sysydz200703301
Abstract(780) PDF-CN(433)
Abstract:
Organic maceral and sub-maceral characteristics of source rocks in Paleogene in the Pearl River Mouth Basin have been studied by means of compositive optics of organic petrology.It is also discussed the hydrocarbon generating potentials and features by element analyses on kerogen,rock-eval analyses and high temperature and pressure simulation on source rocks.Relatively abundant exinite and exinite-vitrinite A rich in hydrogen result in oil-prone type Ⅰ-Ⅱ1 of organic matter in medium-deep lacustrine facies.Relatively abundant exinite-vitrinite B pool in hydrogen and vitrinite result in gas and condensate-prone type Ⅲ-Ⅱ2 of organic matter in shore-shallow lacustrine and swamp facies.Sapropelinite and intertinite contents are low.The two types of source rocks have different hydrocarbon-generating features in various phases. Those conclusions are important for the further studies of organic facies and exploration potential and prospect in different depressions(sags) in the basin.
APPLICATION OF MICROELEMENTS ANALYSIS IN IDENTIFYING SEDIMENTARY ENVIRONMENT——TAKING QIANJIANG FORMATION IN THE JIANGHAN BASIN AS AN EXAMPLE
Liu Gang, Zhou Dongsheng
2007, 29(3): 307-310. doi: 10.11781/sysydz200703307
Abstract(1115) PDF-CN(529)
Abstract:
The compositions of microelements in clay minerals,mud rock and gypsum in lake sediments are very sensitive to the change of sedimentary environment.It may reveal lake-level change.The lithology change of sediment in saline lake in vertical is distinct,this change is controled by the balance in supply,evaporation and sediment of the river,which lead to the change of lake level.The paper mainly introduces using microelements,B,S,Ba,Ti,Fe,P,Mn etc.,in the Qianjiang Sag of the Jianghan Basin as an indication for sedimentary environment change to analyse the characteristics of change in different sequence and different systems tract,and discusses paleoclimate and sedimentary environment in different sequence.The content of B in sedimentary rock is more then in igneous rock commonly.The content of B is 135×10-6 in shale and(1～40)×10-6 in sand rock.The content of Sr is 0.8‰～1‰ in saline lake and 0.1‰～0.3‰ in freshwater.
EXPERIMENTAL STUDY TO IMPROVE CRUDE OIL RECOVETY EFFICIENCY IN LOW PERMEABILITY RESERVOIRS——TAKING THE FANG48 BLOCK IN THE NORTH OF THE SONGLIAO BASIN AS AN EXAMPLE
Zhao Mingguo, Chen Dingfeng
2007, 29(3): 311-314. doi: 10.11781/sysydz200703311
Abstract(695) PDF-CN(250)
Abstract:
Taking the Fang48 Block in the Daqing Oil Field as an example,it is studied the relationship between crude oil recovery efficiency and pressure when displaced by CO2,N2 and natural gas respectively through slim tube experiment.The minimum miscible pressures(MMP) of CO2,N2,natural gas and crude oil are measured.In the Fang48 Block,the MMP of CO2 is 29 MPa and that of natural gas is 40 MPa.N2 is not miscible from crude oil at the highest experiment pressure(44 MPa).Gas injection has been carried out in the Fang48 Block.Below the formation fracture pressure(31 MPa),CO2 is miscible while natural gas and N2 are not.When immiscible,the recovery efficiency with CO2 displacing is the highest,natural gas the second and N2 the lowest under the same condition.
A METHOD FOR BIOMARKER STUDY FROM RESERVOIR BITUMEN AND INCLUSIONS
Qin Shengfei, Pan Wenqing, Han Jianfa, Zhao Mengjun
2007, 29(3): 315-318. doi: 10.11781/sysydz200703315
Abstract(693) PDF-CN(295)
Abstract:
The study on biomarkers from bitumen and inclusion in reservoir has attracted many petroleum geologists.Since there is no good method to divide the biomarkers from bitumen and inclusions,this study has not been developed much up to present days.This paper selected carbonate reservoir samples from Lunxi thick oil area in the Tarim Basin.Some special methods have been tried to abstract biomar-kers from bitumen and inclusions,and then compared the biomarkers from thick oil.A set of effective method has been established to get biomarkers from bitumen and inclusions.The base line on saturated hydrocarbon chromatogram from thick oil waved seriously and contented abundant 25-norhopane, showing obvious biodegradation.However,the biomarkers from inclusion appear biodegradation phenomenon.This indicates that the forming time of inclusions is earlier than that of effective oil accumulation are different.
A METHOD FOR GAS HYDRATE RESOURCE ESTIMATION——AN EXAMPLE OF PRELIMINARY ESTIMATION OF GAS HYDRATES IN THE NORTHERN CONTINENTAL SLOPE, SOUTH CHINA SEA
Lu Zhenquan, Wu Bihao, Jin Chunshuang
2007, 29(3): 319-323. doi: 10.11781/sysydz200703319
Abstract(848) PDF-CN(366)
Abstract:
In this paper one method for estimating gas hydrate potentials was put forward based on the general gas hydrate thermodynamics and the basic calculus theory;subsequently a preliminary estimation of gas hydrates possibly occurring in the northern continental slope of the South China Sea(SCS) was carried out.Firstly the gas hydrate potential area was divided into various micro-volume blocks,and the whole gas hydrate potential volume was calculated by the integral accumulations.Afterwards the multiplication of the gas hydrate potential volume by the relevant subsurface sediment porosity,gas hydrate saturation and the hydration coefficient,which are referenced to the world well-known gas hydrate parameterizations,was conducted to estimate the gas hydrate potential resource in the northern SCS.The calculated result approximately corresponds to 6.3×1013 m3 of methane at the STP.It means that the estimated gas hydrate amount is generally equivalent to the magnitude of the Blake Ridge offshore America,the Nankai Trough offshore Japan,and the northern Gulf of Mexico offshore America(1013 m3 of methane) respectively.This suggests a huge gas hydrate potential resource in the northern continental slope of SCS.Of course it still needs to be checked or confirmed by the field investigation.
PHYSICAL SIMULATION EXPERIMENT AND EXAMPLE FOR THE STRUCTURES FORMING BY INVASION OF IGNEOUS ROCK
Tan Junmin, Sun Zhixin
2007, 29(3): 324-328. doi: 10.11781/sysydz200703324
Abstract(935) PDF-CN(281)
Abstract:
In the instance of overlying strata being transverse homogeneous medium,the results of physical simulation experiment for the special structure formed by invasion of igneous rock indicate that the process of magma invasion spirals up snake-shapedly in the upper direction,and ascends oscillatingly in the profile.Top structural configuration is rounded or near round arch,and its boundaries are blocking faults.The process of magma invasion to brittle strata is alternative with stress accumulation and release,in which microseism leap and irregular channel of magma are shown.In the course of magma invasion to plastic strata,the stress varies smoothly and consecutively,the channels of magma obviously spread around,the diameter of the channels increasies,and the structural configuration of the top strata has the characteristics of inheritance.The result of simulation test can logically interpret the developing mechanism of SH24 structure in Jiyang Depression.Exploration results indicate that this kind of derived structures in the process of magma invasion is very benefit to reservoir formation.The results of this experiment fill up the blank of domestic physical simulation for the structure formed by invasion of igneous rock and have acquired the related experiment parameters,which provides experience and reference for the future analogous experiments.

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