2012 Vol. 18, No. 2

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STUDY ON THE GEOMECHANICAL MODEL OF LANDSLIDE WITH LOW DIP ANGLE STRATA STRUCTURE:TAKING FENGDIAN LANDSLIDE AS AN EXAMPLE
WANG Zhi-hua, DU Ming-liang, GUO Zhao-cheng, JIA Wei-jie
2012, 18(2): 97-109, 186.
Abstract (170) HTML (63) PDF (730KB)(15)
Abstract:
On the basis of research at home and abroad, starting from the landslide mechanism establish geomechanical model of landslides with low dip angle strata, all the parameters in the model, such as landslide size, slip angle, back edge ripping slot seeper depth and so on, were obtained by digital landslide technology and fields investigation and put them into the model formula then landslide critical friction coefficient can be obtained, and landslide total down-slide and total resistance slippery force shall be get. This is the first putting forward the concept of critical friction coefficient and calculating methods, and the coefficient directly related to the slippery ability or stability of the landslide. Analysis shows that the critical friction coefficient and landslide sliding body size (the length and width of the sliding surface), sliding plane obliquity are positive correlation, with landslide weight inversing relationship. The influence of the dip angle of the back wall changing in 60°-90° on slippery ability of the landslide with low angle strata is very weak.
NUMERICAL SIMULATION OF STRUCTURAL FRACTURES CONTROLLED BY PIQIANG STRIKE-SLIP FAULT
ZHANG Qing-lian, HOU Gui-ting, PAN Wen-qing, HAN Jian-fa, LI Le, JU Wei
2012, 18(2): 110-119.
Abstract (236) HTML (100) PDF (573KB)(7)
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Based on the intensive research on development of structural fractures that controlled by the Piqiang strike-slip fault, this paper has simulated the distribution of structural fractures under the influence of the regional deviatoric stress, the width and trend of the strike-slip fault through the "ANSYS" finite element method. The simulating results indicated that the width of the fractures increased linearly with the increase of the regional deviatoric stress, decreased linearly with the increase of the width of the faulted belt, and decreased linearly with the increase of the angle between regional deviatoric stress and the fault trend. The regional deviatoric stress is the main factor that controls the development of the fractures.
CONTROLLING OF STRUCTURAL STRESS FIELD TO THE FRACTURES IN XUANHAN-DAXIAN REGION, NORTHEASTERN SICHUAN BASIN, CHINA
TANG Yong, MEI Lian-fu, CHEN You-zhi, TANG Wen-jun, XIAO An-cheng
2012, 18(2): 120-139.
Abstract (167) HTML (60) PDF (1545KB)(11)
Abstract:
Structural stress field is one of the main reasons on fracture formation. It is the key of prediction structural fracture that paleostructure stress field is microscopically quantitative calculated.So we can well understand the fracture distribution in underground strata based on careful analysis to geological structure and numerical model coincides with the practice about the region of interest.It was influenced due to squeezing process from the SE direction during Late Crataceous and compressed from the NE direction in the period of Late Eocene-Early Oligocene in the Xuanhan-Daxian area of the northeast of Sichuan, China. The structural fracture development in Feixianguan formation in Lower Triassic series was effected by the two periods of structural action in Xuanhan-Daxian region. The fracture is an important geologic factor affecting the development of the oilfield. Through analysis of interaction in rock layers, calculation results on conjugate joints and mechanical twinning and using three dimensional finite element analysis method, we have obtained paleostructure stress in Feixianguan Formation of Xuanhan-Daxian region. We well know the distribution feature of paleostructure stress on the two periods. By threshold value-limited of the carbonatite burst, fracture area in Puguang and Maobawe blocks was predicted prediction. The integrated fracture rates give the basis to evaluate fracture strength. It provides the scientific geological basis for increasing the rate of drilling fractures and reducing the risk and cost of exploration and development.
RELATIONSHIP BETWEEN CENOZOIC TIANSHAN MOUNTAIN UPLIFTING AND CURRENT TECTONIC TOPOGRAPHY IN NORTH MARGIN OF TARIM BASIN:AN EVIDENCE FORM ROCK ACOUSTIC EMISSION
ZHANG Yu-hang
2012, 18(2): 140-148, 194.
Abstract (221) HTML (107) PDF (568KB)(8)
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Strongly tectonic activity had been observed by field outcrop in the northern margin of the Tarim Basin. In order to find out regional stress field setting of active structure movement, the authors collected rock acoustic emission samples in Sishichang and Kuqa River section in the north margin of the Tarim Basin, and then experiment with Silurian, Triassic, Permian samples, rock ground stress test of acoustic emission. The recorded results of the maximum principal stress were 57.74 MPa, 57.73 MPa and 58.86 MPa respectively. Summarized previous research results of study area, the rocks recorded the ground stress of the Himalayan movement about 57 MPa, in the northern margin of the Tarim Basin. Late Himalayan period had been suffered intensively, during the geology history stage of the northern margin, since Silurian period. Today's tectonic features were formed. It is intimately relation to Cenozoic Tianshan Mountain uplifting; the main kinetic factor is Eurasian plate and India plate collision.
THE INVESTIGATION OF NORMAL FAULT UNDER UPWELLING FORCE AND ITS CRITICAL STRESS STATE
SONG Sui-hong, CHEN Shu-ping, HE Ming-yu
2012, 18(2): 149-157.
Abstract (196) HTML (93) PDF (308KB)(9)
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The investigation of normal fault formed under tectonic setting of upwelling force and its critical stress state is of significance in the structural interpretation and the hydrocarbon migration. Based on the theory of parabolic Mohr failure envelope, and certain assumptions, mathematical derivation and theory modeling being carried out, quantitative functions of geometric shape of normal fault and its critical stress state were given. It is found that the fault dip becomes smaller from shallow to deep, being a listric fault. The rate of dip change is only related to the properties of strata. And the rate of dip change is faster in isotopic sandstone than in mudstone. It is also proved that the depth of the fault is linear against the amplitude of upwelling force. A typical ramp-flat normal fault can be drawn from the fracture modeling of interbedded sandstone-mudstone rock body. Not only are these conclusions consistent with the natural phenomena and general cognition, but also they can explain the geometric shape of faults quantitatively and find the critical stress state.
NUMERICAL SIMULATION OF HOLE CREEP SHRINKAGE FOR COMPOSITE ROCK SALT LAYERS
ZENG De-zhi, LIN Yuan-hua, LU Ya-feng, ZHU Da-jiang, LI Liu-wei
2012, 18(2): 158-164.
Abstract (123) HTML (85) PDF (341KB)(6)
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Salt rocks have very strong creep behaviors in HTHP environment in deep formations, complex accidents such as hole shrinkage, drill pipe sticking, etc. occurring frequently. Current methods to calculate the safe drilling mud density are mainly used in circumstances of homogeneous earth stress. The 3-D finite element analysis (FEA) model of borehole creep shrinkage concerning salt rock and sand shale was established in this paper under triaxial earth stress. On the basis of deep wells of Yangtake in Tarim, laws of borehole creep shrinkage vs time were studied under the condition of heterogeneous earth stress, and values of borehole diameter in different times are obtained when the mud density is specified. Results calculated are very close to the safety drilling mud density field used in rock salt layers, thus verifying the reasonableness and reliability of the model established in the paper. Research results can provide technical support for safe drilling in rock salt layers.
POTENTIAL GENESIS OF THE TRENDING CHANGES OF JINNING PERIOD AND CALEDONIAN STRUCTURAL LINEAMENS IN MIDDLE-SOUTHERN HUNAN
BAI Dao-yuan, JIA Bao-hua, ZHONG Xiang, JIA Peng-yuan, LIU Yao-rong
2012, 18(2): 165-177.
Abstract (158) HTML (102) PDF (1007KB)(7)
Abstract:
There existed visible lateral variations of the Jinning Period and Caledonian structural lineaments in middle-southern Hunan. The Jinning Period and Caledonian structural lineaments in Tongdao-Xupu-Anhua-Taojiang area showed an arc bulging to northwest. The Jinning Period lineaments trend in Liuyang-Chuankou area of eastern Hunan changed from EW to NE-NNE from north to south. The Caledonian structural lineaments in Jiuyishan area and Penggongmiao-Rucheng area in southern Hunan took on EW-trend, while in Dupangling-Tashan uplift and Gaoguashan-Guandimiao uplift took on NE-NNE-trend, and in Dachengshan-Longshan area in middle Hunan took on EW-trend. Geological and geophysical data suggested that the boundary between Qinzhou-Hangzhou juncture and Yangtze block in Hunan Province might extends along Nanqiao-Xinhua-Longhui-Miaoershan with change of EW-to NNE-trend from east to west, and the boundary between the juncture and Cathaysian block extends along Chuankou-Changning-Shuangpai with NE-trend. Combined with regional compressional stress field, the trend of the boundaries can be taken to explain the dynamic mechanisms of the lateral changes of Jinning Period and Caledonian structural lineaments.
MOLYBDENITE Re-Os ISOTOPIC DATING OF SANGBUJIALA COPPER DEPOSIT IN THE SOUTH MARGIN OF THE EASTERN GANGDESE SECTION, TIBET, AND ITS GEOLOGICAL IMPLICATIONS
ZHAO Zhen, HU Dao-gong, WU Zhen-han, LU Lu
2012, 18(2): 178-186.
Abstract (156) HTML (100) PDF (701KB)(6)
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Located in north side of Yaluzangbujiang Suture, Sangbujiala skarn-type copper deposit is one of the typical polymetallic deposits in the south subzone of the Gangdese metallogenic belt. For the purpose of finding out the mineralization time, the authors selected eight molybdenite samples from Sangbujiala ore district to perform the Re-Os dating. The age of Re-Os isotime line from molybdenite is 93.3±4.1 Ma, with an average model age of 94.5±1.6 Ma. Therefore, the Sangbujiala ore formed during Late Cretaceous, which belongs to the Neo-Tethys subduction stage. The Sangbujiala ore and other Cenozoic deposits showed that the Gangdese metallogenic belt occurring large-scale mineralization in the subduction stage, main collision stage, late collision stage and post-collisional stage, and to form a complete series of metallogenic evolution.
STRUCTURAL CHARACTERISTICS OF TONGCHENG FAULT AND HYDROCARBON ACCUMULATION IN JINHU SAG
YE Shao-dong
2012, 18(2): 187-194.
Abstract (193) HTML (81) PDF (479KB)(4)
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Tongcheng Fault is a second class fault which controlls the development of Tongcheng structural belt in Jinhu Sag.It is divided into two parts by its faulted feature showing reverse fault character at the south part and normal fault feature at the north part.There are different views about its character and evolvement.Tongcheng fault is considered as a typical strike-slip fault based on the structural analysis of seismic profiles.Varied directions of dip result in normal fault and reverse fault alternatively occurring along the fault because of strike-slip movement. Tongcheng strike-slip fault can not only form different types of traps, but also improve physical property of low-permeability reservoir, which is of great advantage to oil and gas accumulation.
EVALUATION OF WATER SOLUBLE HELIUM RESOURCES IN WEIHE BASIN
ZHANG Fu-li, SUN Qi-bang, WANG Xing-yun, ZOU Yan-rong
2012, 18(2): 195-202.
Abstract (137) HTML (64) PDF (268KB)(7)
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The discovery of water soluble helium in Weihe Basin was introduced in this paper.Researches showed that the water soluble helium resources in Weihe Basin the resources are widely distributed and highly graded in Weihe Basin. The cause types of water-soluble gas are of different rock multi-source mixed characteristics, and the water soluble helium gas mainly comes from the shell source gas, with uranium rich granite being the main source rock; four reservoir models build in deep basin geothermal water soluble helium; two kinds of methods to obtain the basin water soluble helium resources with quantity of (984.2-1141.31)×108 m3.