1998 Vol. 4, No. 3

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INNOVATION AND DEVELOPMENT OF GEOMECHANICS
Sun Dianqing, Dong Shuwen
1998, 4(3): 1-8.
Abstract (127) PDF (281KB)(9)
Abstract:
The innovation of geomechanics created by Professor J.S.Lee(Li Siguang) is expounded and discussed from scientific innovation system,technological innovation system,application and dissemination system.In the transition from the old contrary to the new authors put forward how to develop geomechanics from the geodynamical theory,the new dynamics theory of East Asian Continent,material accommodation under the action of tectonic force and its metallogenetic mechanism,evaluation of the stability of Earth crust and nonlinear engineering geomechanics,evaluation of oil and gas in China and petroleum geomechanics,environmental change of Meso-Cenozoic East Asian Continent and the mode of E-W-trending tectonic upwarping and downwarping and their dynamics,and the evaluation and planning of territory resource and their relation to the Earth system theory.
MECHANICAL PROPERTIES OF THE STRUCTURAL ELEMENTS OF THE GLOBAL TORSION TECTONIC SYSTEM
Zhang Yonghong
1998, 4(3): 9-19.
Abstract (114) PDF (539KB)(6)
Abstract:
The divsion and displacement of the plates of the world are not random.They are combined into a unified stress field by a tectonic framework of different mechanical properties to form a global torsion tectonic system.The system consists of a NWW-trending helix shaped torsion compressed fracture belt which is a major structural element,an associated NNE-trending extension fracture belt,and some meridional shearing split belts and latitudinal cutting shear belts.This paper tries to identify the system by analyzing the mechanical properties of structural elements of this system.
ON THE EFFECT OF ALTERNATING STRESS RESULTING FROM THE TIDAL FORCE AND ITS BEARING ON GEODYNAMICS
Wu Zhenhan
1998, 4(3): 20-27.
Abstract (160) PDF (309KB)(4)
Abstract:
Under the action of tidal force of the Sun and Moon a periodic tidal force and the westward tidal drag occur in the Earth,the former belonging to a symmetric cyclic alternating stress results in the tectonic stress which is the order of magnitude of 104Pa roughly equal to static tectonic stress of 105 Pa and plays a prominent role in the triggering of earthquake;the later causes the westward shear stress belonging to pulsating cyclic alternating stress which is the order of magnitude of 105Pa roughly equal to static tectonic stress of 106 Pa and makes an important contribution to the horizontal movement of lithosphere and asthenosphere and is a fundamental dynamical factor resulting in the tectonic movement.
MODELLING OF PROGRESSIVE FAILURE OF BRITTLE DISORDERED MATERIALS E. G. SANDSTONE
Xing Jibo, Yu Liangqun, Wang Yongjia
1998, 4(3): 28-35.
Abstract (111) PDF (388KB)(4)
Abstract:
In this paper the beam-particle model at a fine structural scale is presented for analysis of the progressive failure of such brittle disordered materials as sandstone by diffe rent loadings.In the model,the media are divided as an assembly of particle elements linked by elastic brittle beam elements.The mechanical behaviour of particle elements is determined by the distinct element method and finite element method.As soon as a particular beam element is stressed beyond its assigned strength it is removed from the computation in simulation of the rupturing of the material.Two physical experiments are performed to verify the numerical results.The rupturing model and load-displacement response obtained are in good agreement with the experimental results.Moreover,the influence of heterogeneity on fracture patterns is also discussed and the correlation between the fracture distribution and the loads imposed is characterized in fractal dimensions.
A NEW METHOD TO DETERMINE THE DIFFERENTIAL STRESS OF DIP-SLIP FAULTS
Chen Shuping, Zhong Jianhua, Song Quanyou
1998, 4(3): 36-40.
Abstract (168) PDF (201KB)(5)
Abstract:
Structural geology seeks to approach its subject of study in a quantitative way.Stress and strain analysis of structures are essential to this approach.In the stress analysis,we can often determine the directions of the principal stresses,instead of their magnitudes.In this paper,we develop the equations to determine the differential stresses for normal and reverse faults,which increase with depth and are related to the initial shear strength and the angle of inner fraction of rocks on the surface.These equations can be used in combination with those in calculating the differential stress from conjugate joints to obtain the differential stress in certain area.
STRUCTURAL SYSTEMS IN THE WEST QINLING AND ADJACENT REGION AND THEIR EVOLUTION
Du Zitu, Wu Ganguo, Lü Guxian, Wang Ping'an, Dong Faxian
1998, 4(3): 41-49.
Abstract (132) PDF (446KB)(11)
Abstract:
A study of the division of structural systems in the West Qinling and its adjacent region and their evolution is made. First, we have the tectonic systems prior to the Indosinian movement. Next we come to the major Meso-Cenzoic systems which can be divided into the E-W-trending. N-S-trending, NE-trending,NWN-trending systems and an arcuate system. Last, we have a discussion of the history of their deformation and interrelation, and origin.
TECTONIC SYSTEMS IN TARIM BASIN CONTROLLING OVER OIL AND GAS
Kang Yuzhu
1998, 4(3): 50-57.
Abstract (85) PDF (347KB)(4)
Abstract:
The Tarim Basin is a promising petroliferous area where many tectonic systems are known to compound each other. The research results show that the second-order tectonic systems in the Basin control the oil-generating depression and the zone of oil and gas enrichment, and the third-or fourth-order shear tectonic systems the oil and gas fields. The Basin is characterized by containing a good number of source beds, not single type of oil/gas pools, many different petroliferous domains and a multi-phase in oil/gas accumulation.
THE THREE-DIMENSIONAL FINITE ELEMENT NUMERICAL SIMULATION OF MODERN STRESS FIELD AND ITS SIGNIFICANCE IN THE OIL DEVELOPMENT OF THE JING'AN AREA IN THE CENTRAL SHAANXI-GANSU-NINGXIA BASIN
Zeng Lianbo, Xiao Shurong, Luo Anxiang
1998, 4(3): 58-63.
Abstract (129) PDF (268KB)(9)
Abstract:
On the basis of the establishment of geological, mechanical and computation models for the Jing'an area, the spatial distribution of modern stress field in the Yanchang Series of Triassic System in the area has been studied by the three-dimensinal finite element method. The results will have an important bearing on the disposition of oil wells, plan of modification of hydrofracturing and the design of horizontal well and water injection management.
CHARACTERISTICS OF CAP ROCKS IN CUOQIN BASIN,TIBET
Song Quanyou, Chen Qinghua, Chen Shuping
1998, 4(3): 64-69.
Abstract (116) PDF (242KB)(5)
Abstract:
China National Petroleum Corporation has conducted petroleum exploration in Qinghai-Tibetan Plateau since 1994.Several sets of source rocks have been discovered after 4 years' geological reconnaissance in the Cuoqin Basin of northern Qinghai-Tibetan Plateau.The cap rocks essential to the oil and gas preservation have been evaluated from their lithology,thickness and microstructure.Mudstones,volcanic rocks and carbonates are suggested to be the dominant cap rocks for oil pools,then come the dense siltstones.
FRACTURES PREDICTION OF MAIN RESERVOIR BED IN KEERKANG OILFIELD OF ZHANGQIANG DEPRESSION IN WESTERN LIAONING PROVINCE
Zhou Xingui, Sun Baoshan, Li Yaohui
1998, 4(3): 70-75.
Abstract (123) PDF (272KB)(5)
Abstract:
The development and distribution of fractures in the main reservoir bed-Shaha Formation-at Keerkang Oilfield of Zhangqiang Depression are studied by means of F-index method based on observations of core fractures and stress field modelling. An evaluation of the fracture development in different area of the oilfields is given, and the promising oil-bearing positions are proposed.
GEOCHEMISTRY OF THE EARLY CARBONIFEROUS WUSU VOLCANIC,MOJIANG COUNTY,YUNNAN, AND ITS TECTONIC SIGNIFICANCE
Han Song, Qian Qing, Xu Ping, Jia Xiuqing
1998, 4(3): 76-83.
Abstract (97) PDF (349KB)(5)
Abstract:
The Wusu volcanics,west of the Ailaoshan Suture Zone,are located in the Simao Massif.They are composed of basalt,pillow lava,dacite,rhyolite and tuff,about 800m thick,occurring in the early Carboniferous sequence.As compared to N-MORB,the Wusu basalt has a higher content of TiO2 and REE,and higher Ti/V and Zr/Y ratios characteristic of E-MORB.The basalts are LREE-enriched,with LaN/YbN=1.9-2.4,YbN=11-23.The rhyolites are higher in REE than the basalts,but with LaN/YbN=2.0-2.8.This shows that both of them may have the same origin,i.e. the bi-modal type.Such composition of the Wusu basalt indicates an extension environment rather than an island arc environment.The higher Th/Ta ratios (1.4-4.0) may imply a hibridization with the continental crust during its rise to the surface.
GOLD MINERALIZATION ALONG THE JIGUANSHAN FAULT IN MESOZOIC VOLCANIC ROCK AREA,WESTERN LIAONINIG PROVINCE
Tian Xiaojuan, Meng Xiangang, Chen Hongxin, Qu Wei, Chen Zhengle
1998, 4(3): 84-90.
Abstract (218) PDF (304KB)(5)
Abstract:
The rhyolitic volcanic rocks erupted during 167-135Ma in Erdaogou area,Beipiao County,and emplacement of the South Jinchanggouliang granitic stock and Duimiangou porphyritic granodioritic stock took place during 128Ma and 126-121Ma to the two sides of the area.The Jinchanggouliang,Erdaogou and Changgaogou gold deposits occurred in the radial fractures produced by the emplacement of the stocks.It is suggested that volcanic rock and granite are controlled by compounding of the EW-trending faults and the NW-trending faults,and the NW-trending Jiguanshan fault serves as the major channel-way for magmatic intrusion and gold mineralization.
DETERMINATION OF ROCK DEFORMATION BASED ON ANALYSIS OF IMAGES OF MICROSTRUCTURES
Shi Lei, Huang Weiping, Meng Xiangang
1998, 4(3): 91-96.
Abstract (90) PDF (242KB)(4)
Abstract:
From the mathematical statistics of the images of such microstructures as pressure shadow,subgrain,dislocation,dynamic recrystallization grain,one can infer the environment including the state of stress under which the rocks were deformed.