Abstract: Geofluids are the focus of current geosciences research, which should include gas, liquid (water and petroleum), magmatic melt and moving matter moved under geostress. There are seven spheres inside the earth within the radius of 6378 km. The fluids in interior earth were less understood, since it is too deep too see. To understand the fluids in earth's interior, it is necessary through the across sphere structures which include:subduction zone which fluids from ocean crust through up the lithosphere and asthenosphere to mantle; deep fluids through mid-ocean ridge to the crust; mantle plume bringing melt and fluid to the crust. Through the study of the fluids in three across sphere structures, the composition, distribution of the fluids in crust, lithosphere, asthenosphere, upper and lower mantle have been learned. This is the important way to know the fluids in deep earth, as well as the crust.
Abstract: Basins, source rock, hydrocarbon accumulation areas controlled by structural systems, hydrocarbon accumulation controlled by stresses, oilfields controlled by subordinate shear structural systems are researched based on structural system theory. The results show that northern China are dominated by Neocathaysian, Western Regions, Latitudinal, Qi-Lyu-He epsilon-type and some other structural systems with stage, migration, inheritance, discrepancy, transition, and complexity features, which controls the generation and development of the Tarim basin, Ordos basin and Songliao basin. The rules of petroliferous basins and hydrocarbon distribution controlled by structural systems are explained, including multi-order, superimposition, conjunction and multi-stage control of structural systems and the control of subordinate shear structural system. The favorable areas for hydrocarbon accumulation are pointed out by taking the structural system theory as the basis and considering the conditions of hydrocarbon accumulation comprehensively. Major breakthroughs and discoveries have been made in the selected favorable areas, which proves the scientificalness and accuracy of the study on the structural system control over oil and the prediction of favorable areas for hydrocarbon accumulation. These favorable areas are also the main targets for hydrocarbon exploration in the long term.
Abstract: Fault is the main type of structural deformation in the eastern part of the middle uplift zone in the Tarim basin, and it is also an important factor controlling hydrocarbon accumulation and distribution. Based on the structural system theory of Professor J.S.Lee, and through the comprehensive analysis of geometry, kinematics and dynamics characteristics of faults in the eastern part of central uplift belt in the Tarim basin, the geodynamics models of "brush structural system" are discussed in this paper. Research results show that:since the early paleozoicera, affected by the three orogenic belts of the Southern Tianshan mountain in the north, the Kunlun mountain in the southwest and the Altun mountain in the southeast and along with the evolutionary process of the three great extension-convergent tectonic cycles, faults, such as the Central Tarim Fault Ⅰ, the Central Tarim Fault 10, the Central Tarim Fault Ⅱ, the Katak southern edge faults and so on, were generated successively and had been active many times. They present as "Y" type structure on the profile, and constrict to the SE direction and spread out to the NW direction on plane, forming as the "brush structure system" together with the Tangnan strike-slip fault and Cheerchen strike-slip fault on the south side. Ever since the early time of Caledonian orogeny, the "brush structure system" experienced two regional stress field conversion history of the tenso-shear stage (early Caledonian orogeny)→ the compresso-shear stage(moddle Caledonian orogeny)→the tenso-shear stage(early Hercynian orogeny) and the compresso-shear stage(late Hercynian orogeny), and basically finalized the design by the time of late Hercynian orogeny, in the meantime, many lower generation faults of NE trend and NEE trend were generated.
Abstract: Geomechanics, founded by Chinese famous geologist J. S. Lee, is an interdisciplinary theory of systematic tectonic geology based on systems theory and centered on tectonic system. Over the past 70 years, it has been widely applied and developed in regional geology, seismic geology, geothermal exploration, quaternary geology, crustal stability evaluation and other aspects. Great achievements have been made in the strategic zones selection, forecast of mineral, petroleum resources, and guidance of the exploration of those resources. In the discovery of the Songliao, Tarim, Jianghan and other important petroliferous basins, geomechanics theory has played a practical role. This paper reviews the history of China's petroleum exploration, summarizes the successful experience of geomechanics theory in China's conventional petroleum exploration, and believes that geomechanics theory will continue to play a leading role in China's deep oil and gas exploration.
Abstract: Southeastern Guizhou is located in the Rongjiang Caledonian fold belt, which is very undeveloped in caprock. In order to find out the state of crustal stress in this area, the hydraulic fracturing stress measurements of 7 boreholes were carried out. A comparative study was made on the distribution differences of crustal stress in the southeast, west and northwest of southeastern Guizhou, combining with the research results of west Guizhou and crustal measurement data of a borehole in northwestern Guizhou. Finally the fault stability around the sampling borehole area was discussed in association with fault activities and the Byerlee criterion. The results demonstrate that the horizontal principle stress is dominant in the study area, and the maximum horizontal principal stress is in the N-W direction; according to the Anderson fault theory, the relative magnitude of the three-direction principal stress is favorable to the movement of the thrust fault and strike-slip fault, which corresponds to the nature of the active fault developed in the study area; the linear fitting results of the maximum and minimum horizontal principal stresses show that the gradient of horizontal principal stress is larger than that of the coal seam area in western Guizhou, the northeastern Guangxi basin and the whole country, and the maximum horizontal principal stress is larger than that of western Guizhou, northwesternern Guizhou and the northeastern Guangxi basin at the similar depth; there are high tectonic stresses near the Sandu fault zone, and the μm value (the ratio of the maximum shear stress to the average principal stress) is higher, which indicates that the fault is in the state of friction limit equilibrium; the tectonic action on both sides of the Sanjiang-Rongan fault is obviously different, and the tectonic action on the west side is stronger than that on the east side; although μm values are high in some boreholes, the direction of regional stresses intersect with the fault at a larger angle, so the fault is stable, which is consistent with the seismicity in the study area.
Abstract: There are various types of strike-slip faults in Halahatang area, Tarim basin, which show obvious segmentation in the plane and characteristics of multistage and inheritance development during the active period. With the help of innovative geophysical method, the author identified the characteristics of faults spreading in the plane. In addition, combining with the nature of stress we studied the development characteristics of strike-slip faults in Block A of Halahatang oilfield and clarified their control effects on differential enrichment of hydrocarbons. The study shows that there are three main faults in this area which can be divided into 12 segments, such as transtensional, transpressional, strike-slip section. Deep fault plays an important role in the development of reservoirs, and the development of karst reservoir and accumulation of oil and gas are controlled by different stress segments of faults. Large fracture-cavity aggregate is easy to be formed in high tectonic position of transtensional and transpressional section of strike-slip fault which is the advantage area for high quality reservoir and hydrocarbon accumulation.
Abstract: Seepage characteristics of tight sandstone are of great significance for tight reservoir evaluation and exploitation. The fluid-solid-heat coupling control equation was built, and the COMSOL Multiphyics software was used to carry out a numerical simulation study for the distribution law of fluid seepage velocity and formation pore pressure under different production time in a 3D tight reservoir in No.4 block of central Dzungaria Basin. The results are as follows:(1) The maximum values of fluid seepage velocity appeared in the wellhead and its surrounding areas, and the velocity of fluid seepage in the transition zone of fault breakage was higher than that in the surrounding continuous formation and nuclear part of the fault. (2) With the increase of the distance from the wellhead, the variation of fluid seepage velocity changed from increasing first, then decreasing, and finally tending to be stable to gradually increasing first, then gradually tending to be stable. (3) In the initial stage of production, the pore pressure isobar was located around the wellhead, distributed with circular line and then the low stress zone extended along the direction of the fault. (4) The pore pressure was decreasing as the production time increased, at the same time, the farther from the wellhead, the larger the pore pressure was and the smaller the decrease amplitude was. The research results provide technical support for the correct prediction of development and production indexes and improvement of exploration and development effect of tight oil and gas.
Abstract: The determination of lower limits of effective reservoir physical properties is an important basis for effective thickness statistics, reservoir division and reservoir reserve estimation. The carboniferous igneous rock in the study area is characterized by multi-period diagenesis, multiple rock types and strong heterogeneity, and the lower limits of effective reservoir physical properties lack systematic research. The distribution function curve method and the physical oil test method are used to study physical property lower limits and the results of two methods are mutually compared to avoid the randomness of a single method. On this basis, the lower limit values of physical properties of different strata in the study area are obtained, and the fitting equation of lower limit value and buried depth of reservoir is established. The results show that the reservoirs in the study area are mostly low-porosity and medium-low-permeability reservoirs, with relatively high porosity and permeability in the central area and good physical property, and the physical properties gradually become worse in the north and south. The effective reservoir porosity of the carboniferous system in the study area from 1500 meters to 1900 meters and from 1900 meters to 2300 meters is 5.09% and 4.93%, respectively, and the lower limit of permeability is 0.252 mD and 0.198 mD, respectively. The lower limit of the effective reservoir property of the carboniferous igneous rock in the study area is negatively correlated with the buried depth of the reservoir.
Abstract: Liaoxi sag is a Cenozoic marginal sag, which is located in the northeast of the Bohai sea. Exploration proved that a series of fault block traps developed in the role of No.1 fault system in the steep slope of the southern sub-sag of Liaoxi, with different oil and gas enrichment degree. Based on the analysis of the static characteristics and dynamic evolution of No.1 fault and its regulative faults in the south of Liaoxi sag, and the controlling roles of different types of faults on hydrocarbon accumulation are mainly analyzed. The study shows that the No.1 fault system include the No.1 fault and its regulative faults, and they have the characteristics of "early break and late decline" and "middle break and late decline" activity, respectively. The "S" increasing section caused the uplift effect of the steep slope and the development of the regulative faults in the stage of E3d, both of which control the development of the compressive structural trap. The regulative fault has a piecewise control effect on oil and gas migration and accumulation, and the slope segment of the fault has the properties of compression and torsion, and the fracture structure is relatively compact, which is beneficial to the sealing of oil and gas; The sag segment of the fault has the tensile property, the fracture structure is relatively loose and is beneficial to the migration of oil and gas. The hydrocarbon enrichment degree is controlled by the angle between the compressive segmentation of regulative fault and the main strike-slip displacement zone, which has a negative correlation with the angle size.
Abstract: A set of lacustrine and fluvial red clastic sedimentary rocks are exposed in east Sichuan, and the slope structures with low dip angles are widely distributed. Due to its special engineering characteristics and environmental conditions, geological hazards occur frequently, among which collapse is one of the main forms and a great threat to the safety of local residents, transportation, urban construction. By summarizing the previous research results and analyzing a lot of engineering mapping and geotechnical mechanics in the field, we proposed four kinds of basic collapse types based on the environment background conditions in east Sichuan, which are penetrating-topple, penetrating-slide, non-penetrating-shearfault and non-penetrating-pullfault. Their lithologic association characteristics, slope structure characteristics, evolution process and security quantitative evaluation are summarized systematically, which provide reference for the treatment and research of similar geological hazard in the region.
Abstract: The deep coal-rock combinations vibrate under the action of vertical disturbance. When the horizontal impact overcomes the friction resistance between blocks, it is very easy to produce ultra-low friction rock burst. In this paper, the combination block of fine sandstone-coal-fine sandstone is regarded as the research object. Considering the mining condition of the roof-coal-floor near the working face, numerical simulation method was used to establish the numerical block model under confining pressure and impact disturbance. The horizontal displacement and vertical acceleration difference value of coal block are defined as characteristic parameters of ultral-low friction effect. The influence of confining pressure, vertical impact and horizontal impact on the characteristic parameters are analyzed. The results show that the residual and horizontal displacement peaks increase exponentially with the increase of confining pressure under the interaction of vertical impact and confining pressure. And under the interaction of vertical and horizontal impacts and confining pressure, the strength and duration of ultra-low friction effect also increase with the increase of confining pressure. The vertical impact has the most significant effect on the ultra-low friction effect in coal-rock combination block.
Abstract: The process of anti-slide pile bearing load is accompanied by damage accumulation of pile structure. For the purpose of knowing the condition of damage evolution of anti-slide pile, this paper induced damage factor expressions varying with strain based on Najar damage theory, and established the concrete damage model of anti-slide pile under the action of tension and pressure loads. This damage model was embedded in the built-in concrete damage model of Abaqus/CAE program, and then this paper drew the following conclusions by analyzing the damage condition of anti-slide pile of 1# landslide in Erlang Mountain:the simulated horizontal displacement was 30.3 cm by using the damage model of anti-slide pile under the action of tension and pressure loads, which was consistent with the figure of crack width observed on site, concluding that the increased landslide load was the immediate cause to the large deformation of 1# landslide in Erlang Mountain; the value of compression damage was less in the process of the large displacement happened to the anti-slide pile and no compressive damage occurred to the pile structure; but tensile damage was severe at the sliding surface near the landslide during the large displacement occurred to the anti-slide pile and tensile damage occurred on the pile, with the damage zone reaching the 3/4 of the cross-sectional area, which is an important position that requires attention to the restoration of the anti-slide pile.
Abstract: Active faults of different properties, types and characteristics, developing on the southeastern margin of the Tibetan Plateau, are relatively active. Since the Wenchuan earthquake in 2008, there have occurred several earthquakes, including the Yushu earthquake, Lushan earthquake, Ludian earthquake and other earthquakes, which induced a large number of geological disasters and leaded to catastrophic losses of life and property. Based on data collection and analysis, advances in the earthquake geohazard on the southeastern margin of the Tibetan Plateau are summarized. Geohazard effect of active faults including the main control factors of geological disaster, spatial distribution regularity, evolution pattern and formation mechanism, the geological environment effect such as active faults with different properties, the difference between two plates, ground motion parameters and topography, and mechanical effects of geological hazards are analyzed. Then the main problems or key research directions in the study of the geological disaster effect of active faults, such as the correlation between the active faults with different properties, the earthquake with magnitude and geological disasters, and the seismic geological disaster monitoring and risk assessment, are put forward. The results can provide strong support for the study of the mechanism, risk assessment, disaster prevention and reduction of seismic geological disasters.
Abstract: Rock is a collection of mineral particles and an important heterogeneous material. Understanding its mechanical characteristics plays an important role in guiding geotechnical engineering and mining. As a typical granular material, the proportion of particle size distribution in granular element body certainly affects the macroscopic mechanical behavior of rock. PCF2D software was used to simulate the mechanical characteristics of rock models with different proportions of the same granular material element body by setting the granular material element bodies with different volume proportions. The simulation results show that the proportion of particle elements has obvious influence on the mechanical characteristics of rock. In the simulation process, the proportion of large particles significantly affects the compressive strength of rocks. The higher the content of large particles is, the greater the compressive strength is. The proportion of fine particles affects the tensile strength of rocks. The higher the content of fine particles is, the greater the tensile strength will be; however, excessive fine particles will reduce the tensile strength of rocks. Considering the influence of fracture morphology in the process of rock mass compression, penetrating fractures are formed by rock model with particle proportions of 1:1:1, 5:2:3 and 7:2:1, while those of 1:2:7 and 3:2:5 fail to form penetrating fractures. Moreover, the higher the proportion of fine particles is, the higher the probability of high number of fractures is.
Abstract: Ground Penetrating Radar (GPR) has the characteristics of strong operability, high resolution, deep detection depth, no damage to the surface environment and repeatable detection, so it is widely-used in active fault detection. In order to assess the effects of GPR for imaging the shallow subsurface geometry in active fault, the 25 MHz, 100 MHz, 250 MHz and 500 MHz GPR frequency antenna were firstly conducted on the Minzhu site of the Yushu active fault zone for the fault detecting. Moreover, the multi-frequency GPR profiles were compared with the three trench section, which were excavated by the previous researches. The research results show that:the low GPR frequencies (25 MHz and 100 MHz) were applied to delineate an excellent general view of deformation zones at a much wider area and greater depth (up to 32 m). The distribution and the direction of the active fault and the horst structure can be deduced on the GPR profiles. The high GPR frequencies (250 MHz and 500 MHz) provided more detailed analysis of the shallow subsurface geometry within 3 m depth. The GPR results are consistent with the surface morphology and trench wall, and the result show that multi-frequency GPR antenna is valuable for imaging the shallow subsurface geometry of the Yushu acive fault, and also provide multi-scale data and method for active fault study.
Abstract: For the crustal stability assessment of the cross-sea channel engineering in the Qiongzhou Strait, geophysical survey methods including side-sweep sonar, single channel seism and multi-beam were applied to investigate the topography and geomorphology of the Qiongzhou Strait. The side sweep sonar images, topographic and the distribution of active faults were obtained. The engineering geological evaluation shows that the fault, earthquake, and volcanic activities in the planned area of the line are weak, the seabed water depth is shallow, the terrain is relatively flat, and the landform is simple. The low liquid limit clay of the formation and the Pliocene neritic facies sand layer could be used as the basic supporting layers, and the mechanical properties of geotechnical engineering are acceptable, which are conducive to the construction of bridges across the sea. Research demonstrates that the planned line passes through an erosion trench, affecting a length of about 5 kilometers, with a terrain height difference of 60 meters and a sea kettle to the east of the line, along with steep slopes as well as slump deposits in some parts of the area. It is proposed that the northern section of the line be partially moved about 1.5 kilometers westward. At the same time, attention will be paid to the erosion of trenches in the West mouth, muddy soft soil in the southern part of the planning area, sandy soil deposits in ancient rivers, and active sand waves at the bottom of the strait.