Geophysical evaluation methods for buried hill reservoirs in the Jiyang superdepression of the Bohai Bay basin, eastern China

The Jiyang superdepression is one of the richest hydrocarbon accumulations in the Bohai Bay basin, eastern China. Comprehensive seismic methods have been used in buried hill exploration in Jiyang to describe these fractured reservoirs better. Accurate seismic stratigraphic demarcation and variable-velocity mapping were applied to reveal the inner structure of the buried hills and determine the nature of the structural traps more precisely. Based on the analysis of rock properties and the characteristics of well-developed buried hill reservoirs, we have successfully linked the geology and seismic response by applying seismic forward technology. Log-constrained inversion, absorption coefficient analysis and tectonic forward-inversion with FMI loggings were applied to analyse and evaluate the buried hill reservoirs and gave satisfying results. The reservoir prediction was successful, which confirmed that the comprehensive utilization of these methods can be helpful in the exploration of buried hill reservoirs.

海拉尔盆地贝尔凹陷基岩潜山特征及储层预测

The lithology of the buried hill of Triassic Budate group in Beier depression is epimetamorphic clastic rock and volcanic clastic rock stratum. Recently the favorable hydrocarbon show was discovered in buried hill of base rock, and large-duty industrial oil stream was obtained in some wells in Beier depression. Based on the information of seismos and wells, the tectonic framework, tectonic deformation times and faulted system of the Beier depression are comprehensively studied, then configuration, evolutional history, genetic type and distributed regularity of buried hill are defined. According to observing description and analysis of core sample, well logging and interpretive result of FMI, the lithological component, diagenetic type and diagenetic sequence of buried hill reservoir are confirmed, then reservoir space system of buried hill is distinguished, and vegetal feature, genetic mechanism and distributed regularity of buried hill fissure are researched, at the same time the quantitative relationship is build up between core fissures and fissures interpreted by FMI. After that fundamental supervisory action of fault is defined to the vegetal degree of fissure, and the fissure beneficial places are forecasted using fractal theory and approach. At last the beneficial areas of Budate group reservoir are forecasted by reservoir appraisal parameters optimization such as multivariate gradually regression analysis et. al. and reservoir comprehensive appraisal method such as weighing analyze and clustering procedure et. al. which can provide foundation for the next exploratory disposition. Such production and knowledge are obtained in this text as those: 1. Four structural layers and two faulting systems are developed, and four structural layers are carved up by three bed succession boundary surfaces which creates three tectonic distortional times homology. Three types of buried hill are divided, they are ancient physiognomy buried hill, epigenetic buried hill, and contemporaneous buried hill. 2. Reservoir space of Budate buried hill is mainly secondary pore space and fissure, which distributes near the unconformity and/or inside buried hill in sections. The buried hill reservoir experienced multi-type and multi-stage diagenetic reconstruction, which led to the original porosity disappeared, and multi secondary porosity was created by dissolution, superficial clastation and cataclasis et. al. in diagenetic stage, which including middle crystal pore, inter crystal pore, moldic pore, inter particle emposieu, corrosion pore space and fissure et. al. which improved distinctly reservoir capability of buried hill. 3. The inner reservoir of buried hill in Beier depression is not stratigraphic bedded construction, but is fissure developing place formed by inner fault and broken lithogenetic belt. The fissures in inner reservoir of buried hill are developed unequally with many fissure types, which mainly are high angle fissure and dictyonal fissures and its developing degree and distribution is chiefly controlled by faulting. 4. The results of reservoir comprehensive evaluate and reservoir predicting indicates that advantageous areas of reservoir of buried hill chiefly distributes in Sudeerte, Beixi and Huoduomoer, which comprehensive evaluate mainly Ⅱand Ⅲ type reservoir. The clues and results of this text have directive significance for understanding the hydrocarbon reservoir condition of buried hill in Beier depression, for studying hydrocarbon accumulated mechanism and distributed regularity, and for guiding oil and gas exploration. The results of this text also can enrich and improve nonmarine hydrocarbon accumulated theory.

金川镍矿岩体移动与开采稳定性研究

The two major issues in mining industry are work safety and protection of ground environment when carrying on underground mining activities. Cut-and-fill mining method is increasingly applied in China owing to its advantages of controlling ground pressure and protecting the ground environment effectively. However, some cut-and-fill mines such as Jinchuan nickel mine which has big ore body, broken rock mass and high geostress have unique characteristics on the law of ground pressure and rock mass movement that distinguish from other mining methods. There are still many problems unknown and it is necessary for the further analysis. In this dissertation, vast field survey, geology trenching and relative data analysis are carried out. The distribution of ground fissures and the correlation of the fissures with the location of underground ore body is presented. Using of monitoring data by three-dimension fissure meter and GPS in Jinchuan Deposit Ⅱ, the rule of the surface deformation and the reason of ground fissures generation are analyzed. It is shown that the stress redistribution in surrounding rocks resulting from mining, the existence of the void space underground and the influence of on-going mining activities are three main reasons for the occurrence of ground fissures. Based on actual section planes of No.1 ore body, a large-scale 3D model is established. By this model, the complete process of excavation and filling is simulated and the law of rock mass movement and stability caused by Cut-and-fill Mining is studied. According to simulation results, it is concluded that the deformation of ground surface is still going on developing; the region of subsidence on the ground surface is similar with a circle; the area on the hanging wall side is larger than one on the lower wall side; the contour plots show the centre of subsidence lay on the hanging wall side and the position is near the ore body boundary of 1150m and 1250m where ore body is the thickest. Along strike-line of Jinchuan Deposit Ⅱ, the deformation at the middle of filling body is larger than that in the two sides. Because of the irregular ore body, stress concentrates at the boundary of ore body. With the process of excavation and filling, the high stress release and the stress focus disappear on the hanging wall side. The cut-and-fill mechanism is studied based on monitoring data and numerical simulation. The functions of filling body are discussed. In this dissertation, it is concluded that the stress of filling body is just 2MPa, but the stress of surrounding rock mass is 20MPa. We study the surface movement influenced by the elastic modulus of backfill. The minimal value of the elastic modulus of backfill which can guarantee the safety production of cut-and-fill mine is obtained. Finally, based on the real survey results of the horizontal ore layer and numerical simulation, it is indicated that the horizontal ore layer has destroyed. Key words: cut-and-filling mining, 3D numerical simulation, field monitoring, rock mass movement, cut-and-filling mechanism, the elastic modulus of backfill, the horizontal ore layer

大型反倾岩体变形破坏机制及稳定性分析———以金沙江宽谷坝址龙蟠边坡为例

A large number of catastrophic accidents were aroused by the instability and destruction of anti-dip rock masses in the worldwide engineering projects, such as hydropower station, mine, railways and so on. Problems in relation to deformation and failure about anti-dip rock slopes are significant for engineering geology research. This dissertation takes the Longpan slope in the Jinsha River as a case to study the deformation mechanism of large-scale anti-dip rock masses and the slope stability analysis method. The primary conclusions are as follows. The Dale Reach of Jinsha River, from Longpan to the debouchment of Chongjiang tributary, is located in the southeastern margin of the Qinghai-Tibet Plateau. Longpan slope is the right embankment of Dale dam, it is only 26 km to the Shigu and 18 km to Tiger Leaping Gorge. The areal geology tectonic structures here area are complicated and blurry. Base on the information of geophysical exploration (CSAMT and seismology) and engineering geological investigation, the perdue tectonic pattern of Dale Reach is put forward for the first time in this paper. Due to the reverse slip of Longpan fault and normal left-rotation of Baihanchang fault, the old faulted valley came into being. The thick riverbed sediments have layered characters of different components and corresponding causes, which attribute to the sedimentary environments according with the new tectonic movements such as periodic mountain uplifting in middle Pleistocene. Longpan slope consists of anti-dip alternate sandstone and slate stratums, and the deformable volume is 6.5×107m3 approximately. It was taken for an ancient landslide or toppling failure in the past so that Dale dam became a vexed question. Through the latest field surveying, displacement monitoring and rock masses deforming characters analyses, the geological mechanism is actually a deep-seated gravitational bending deformation. And then the discrete element method is used to simulate the deforming evolution process, the conclusion accords very well with the geo-mechanical patterns analyses. In addition strength reduction method based on DEM is introduced to evaluate the factor of safety of anti-dip rock slope, and in accordance with the expansion way of the shear yielding zones, the progressive shear failure mechanism of large-scale anti-dip rock masses is proposed for the first time. As an embankment or a close reservoir bank to the lower dam, the stability of Longpan slope especially whether or not resulting in sliding with high velocity and activating water waves is a key question for engineering design. In fact it is difficult to decide the unified slip surface of anti-dip rock slope for traditional methods. The author takes the shear yielding zones acquired form the discrete element strength reduction calculation as the potential sliding surface and then evaluates the change of excess pore pressure and factor of stability of the slope generated by rapid drawdown of ponded water. At the same time the dynamic response of the slope under seismic loading is simulated through DEM numerical modeling, the following results are obtained. Firstly the effective effect of seismic inertia force is resulting in accumulation of shear stresses. Secondly the discontinuous structures are crucial to wave transmission. Thirdly the ultimate dynamic response of slope system takes place at the initial period of seismic loading. Lastly but essentially the effect of earthquake load to bringing on deformation and failure of rock slope is the coupling effect of shear stresses and excess pore water pressure accumulation. In view of limitations in searching the critical slip surface of rock slope of the existing domestic and international software for limit equilibrium slope stability analyses, this article proposes a new method named GA-Sarma Algorithm for rock slope stability analyses. Just as its name implies, GA-Sarma Algorithm bases on Genetic Algorithm and Sarma method. GA-Sarma Algorithm assumes the morphology of slip surface to be a broken line with traceability to extend along the discontinuous surface structures, and the slice boundaries is consistent with rock mass discontinuities such as rock layers, faults, cracks, and so on. GA-Sarma Algorithm is revolutionary method that is suitable for global optimization of the critical slip surface for rock slopes. The topics and contents including in this dissertation are closely related to the difficulties in practice, the main conclusions have been authorized by the engineering design institute. The research work is very meaningful and useful for the engineering construction of Longpan hydropower station.

Millstone Hill电离层F层等效风场的气候学研究

Neutral winds and electric fields in the ionospheric F layer play important roles in the variations of the ionosphere, and also affect the thermospheric circulation via the close coupling between the ionosphere and the thermosphere. By now, the neutral winds and electric drifts are generally observed with ground-based Fabry-Perot interferometers (FPI) and incoherent scatter radars (ISR), rockets, and satellite-borne instrument. Based on the servo theory, the ionospheric equivalent winds, which include the information of both the neutral winds and electric fields, can be derived from these characteristic parameters observed by ionosondes. This indirect derivation has potential values in climatological researches and space weather forecast. With the data set of the incoherent scatter radar observations at Millstone Hill, USA, from 1976 to 2006, we statistically analyzed the climatological variations of the vertical component of the equivalent winds (VEWs) over Millstone Hill, which are derived from the ionospheric key parameters (the peak electron number density and peak height of the F2 layer, NmF2 and hmF2) on the basis of the servo theory, Liu's method, and measurements from the ion line-of-sight velocity as well. The main results of this analysis are summarized as follows: (1) The values of VEWs over Millstone Hill during nighttime are stronger than in the daytime, and the upward drift dominates most of the day. In 1993, Hagan found that the component of the neutral winds in the magnetic meridion in daytime is weaker than during nighttime under both solar maximum and minimum conditions; he also found that the equatorward winds dominate most of the day. Both results suggest that the thermosphere in Millstone Hill is modulated by the aurorally driven high-latitude circulation cell; that is, during geomagnetic quiet periods, the average auroral activity is strong enough to drive thermospheric circulation equatorward for most of the day at Millstone Hill. Moreover, since ion drag is the strongest during daytime when F region densities are enhanced by photoionization, the wind speeds are smaller during the daytime than in the nighttime. (2) There is equinoctial symmetry in VEWs at Millstone Hill. The amplitudes and phases of VEWs in spring are quite similar to those in autumn. In contrast, the nighttime upward drift in winter is weaker than in summer and the difference becomes more significant with increasing solar activity. This solstice asymmetry indicates that, the aurorally driven circulation in the northern hemisphere at Millstone Hill latitude is weaker in winter due to arctic darkness, because the subsolar point is in the southern hemisphere. (3) The comparison of the VEWs derived from three methods, i.e., the servo theory, Liu's method, and the ISR ion line-of-sight velocity measurements, indicates that the amplitudes and main phase tendencies of these VEWs accord well with each other during nighttime hours. However, the case in the daytime is relatively worse. This daytime discrepancy can be explained in terms of the effects of photochemical processes and the choices of the servo constants. A larger servo constant gives a stronger plasma drift in daytime. Therefore, this study tells how important to choose a suitable constant for deriving VEWs at Millstone Hill.

急倾斜金属矿体开采岩体移动规律与变形趋势预测研究

Rockmass movement due to mining steep metallic ore body is a considerable question in the surface movement and deformation issue caused by underground mining. Research on coal mining induced rockmass movement and its prediction problem have been performed for a long-term, and have achieved great progress at home and abroad. However, the rockmass movement caused by mining steep metal mine is distinctivly different from coal seam mining.. Existing surface movement laws and deformation prediction methods are not applicable to the rockmass movement caused by mining steep metal mine. So far the home and abroad research to this theory is presently at an early stage, and there isn’t mature theory or practical prediction method, which made a great impact on production. In this paper, the research object—Jinchuan nickel mine, which is typical steep metal mine, characterized by complex geological conditions, developed faults, cracked rockmass, high geostress, and prominent engineering stability problems. In addition, backfill mining method is used in the mine, the features of rockmass movement caused by this mining method are also different from other mining methods. In this paper, the laws of rock mass movement, deformation and destroy mechanism, and its prediction were analyzed based on the collection of data, detailed in-sit engineering geology survey, ground movement monitoring by GPS, theoretical analysis and numerical simulation. According to the GPS monitoring of ground surface movement, ground subsidence basin with apparent asymmetry is developing, the influence scope is larger in the upper faulted block than in the lower faulted block, and the center of ground movement is moving along the upper faulted block direction with increasing depth of mining. During the past half and seven years, the largest settlement has amounted to 1287.5mm, and corresponding horizontal displacement has amounted to 664.6mm. On the ground surface, two fissure belts show a fast-growing trend of closure. To sum up, mining steep metal mine with backfill method also exist the same serious problem of rockmass movement hazards. Fault, as a low intensity zone in rockmass, when it located within the region of mining influence, the change of potential energy mainly consumed in fault deformation associated with rockmass structure surface friction, which is the essence of displacement and stress barrier effects characterized by fault rupture zone. when steep fault located in the tensile deformation region incurred by underground excavation, no matter excavation in hangingwall or in footwall of the fault, there will be additional tensile stress on the vertical fault plane and decrease in the shear strength, and always showing characteristics of normal fault slip, which is the main reason of fault escarpment appeared on the ground surface. The No.14 shaft deformation and failure is triggered by fault activation, which showed with sidewall move, rupture, and break down features as the main form of a concentrated expression of fault effects. The size and orientation of principal stress in surrounding rock changed regularly with mining; therefore, roadway deformation and damage at different stages have different characteristics and distribution models. During the process of mining, low-intensity weak structures surface always showed the most obvious reaction, accompany with surface normal stress decrease and shear strength bring down, to some extent, occurred with relative slide and deformation. Meanwhile, the impact of mining is a relatively long process, making the structure surface effect of roadway deformation and damage more prominent than others under the influence of mining. Roadway surrounding rockmass deformation caused by the change of strain energy density field after excavation mainly belongs to elastic deformation, and the correspondented damage mainly belongs to brittle rupture, in this circumstance, surrounding rockmass will not appear large deformation. The large deformation of surrounding rockmass can only be the deformation associated with structure surface friction or the plastic deformation of itself, which mainly caused by the permanent self-weigh volume force，and long-term effect of mining led to the durability of this deformation Good pitting fill effect and supporting effect of backfill, as well as the friction of rockmass structure surface lead to obvious macro-rockmass movement with long-lag characteristics. In addition, the loss of original intensity and new structure surface arisen increased flexibility in rockmass and fill deformation in structure surface, which made the time required for rockmass potential energy translate into deformation work associated with plastic deformation and structure surface friction consumed much, and to a large extent, eliminated the time needed to do those plastic work during repeated mining, all of which are the fundamental reason of rockmass movement aftereffect more significant than before. Mining steep deposits in high tectonic stress area and in gravity stress area have different movement laws and deformation mechanism. The steep deposit, when the vertical size of the mining areas is smaller than the horizontal size of the orebody, no matter mining in gravity stress area or in high tectonic stress area, they have similar features of ground movement with mining horizontal orebody; contrarily, there will appear double settlement centers on the ground surface under the condition of mining in high tectonic stress area, while there will always be a single center under the other condition. Meanwhile the ground movement lever, scale of mining influence area and macro features of ground movement, deformation and fracture are also different from mining in gravity stress area, and the fundamental reason lies in the impact of orientation of the maximum principal stress on rock movement features in in-site rock stress field. When mining thick and steep deposit, the ground surface movement and deformation characteristic curves are significantly different from excavating the horizontal ore bed and thin steep deposit. According to the features of rockmass movement rate, the development process of mining-induced rockmass movement is divided into three stages: raising stage, steadily stage and gradually decay stage. Considering the actual exploitation situation, GPS monitoring results and macro-characteristics of surface movement, the current subsidence pattern of Jinchuan No.2 mine is in the early stage of development. Based on analysis of surface movement rate, surface subsidence rate increase rapidly when mining in double lever at the same time, and reach its peak until the exploitation model ended. When double lever mining translate into single, production decreased, surface subsidence rate suddenly start to reduce and maintain a relatively low value, and the largest subsidence center will slowly move along with the hangingwall ore body direction with increasing depth of mining, at the same time, the scope and extent of subsidence in footwall ore body will begin magnify, and a sub-settlement center will appear on ground surface, accompanied with the development and closure trend of ground fissure, the surrounding rockmass of shaft and roadway will be confronted to more frequent and severe deformation and failure, and which will have a negative impact on the overall stability of No.2 mine mining. On the premise of continuity of rockmass movement, gray system model can be used in ground rockmass movement prediction for good results. Under the condition of backfill mining step by step, the loose effect of compact status of the hard, broken rockmass led to lower energy release rate, although surrounding rockmass has high elastic energy, loose and damage occurred in the horizontal ore body, which made the mining process safety without any large geological hazards. During the period of mining the horizontal ore body to end, in view of its special “residual support role”, there will be no large scale rockmass movement hazards. Since ground surface movement mainly related to the intensity of mining speed and backfill effect, on the premise of constant mining speed, during the period of mining the horizontal ore body to end, the rate of ground surface rockmass movement and deformation won’t have sudden change.

墨西哥湾Alaminos Canyon、Bush Hill冷泉碳酸盐岩有机地球化学与沉积环境

本文通过对墨西哥湾Bush Hill 的5个冷泉碳酸盐岩样品和Alaminos Canyon 的1个冷泉碳酸盐岩样品的总有机质含量、可溶有机质含量、饱和烃、芳烃、脂肪酸、δ13C组成分布特征和部分地球化学参数的研究，探讨了冷泉碳酸盐岩中有机质来源、成熟度和沉积环境。 Bush Hill的冷泉碳酸盐岩样品的总有机碳为0.78-9.02%，可溶有机质含量5.77-65.06mg/g。总有机碳达9.02%的GC-B样品高碳数正构烷烃奇偶优势明显，存在荧蒽、芘和苝系列化合物，表明该样品有陆源物质的输入，并明显受深部渗漏原油的影响，其中烷烃的δ13C为-27.64～-32.36‰，正构脂肪酸δ13C为-26.52～-39.99‰，与现代菌藻类及下伏油气藏的δ13C值（-27～-31‰）相似，表明样品中的有机质主体可能来源于深部油气藏。其余4个Bush Hill冷泉碳酸盐岩样品和1个Alaminos Canyon冷泉碳酸盐岩样品正构烷烃的低碳优势明显，而奇偶优势不明显，低碳数分布的环己烷和长链烷基苯，以及三芳甾烷和甲基三芳甾烷的存在，推断这些样品的母质以菌藻类来源为主。 所有分析样品的甾烷成熟度参数C29ββ/(ββ+αα)为0.28-0.40，C2920S/(20S + 20R)为0.42-0.61、及C20-C21三芳孕甾烷TA(Ⅰ)/C26-C28三芳甾烷TA(Ⅱ)为0.49都说明样品的有机质成熟度较低,。 AC深水区AC-E样品UCM隆起不明显，Bush Hill浅水区样品（GC-B、GC-D、GC-F、GC-G，GC-H）UCM隆起均十分明显，这种隆起的形成是因为正烷烃、甚至五环三萜烷遭受生物降解。被微生物降解的正构烷烃与未被降解的环烷烃和支链烷烃等形成不能被溶解的复杂混合物（UCM）。因此，UCM隆起通常被认为是有机质遭受生物降解最直接的证据。深水区AC-E和Bush Hill浅水区GC-F样品中芴、氧芴和硫芴之间的丰度关系为硫芴﹥芴﹥氧芴，表明其为弱氧化-弱还原的沉积环境。具有较负碳同位素组成（-63.95‰ ~ -50.48‰）的异构/反异构脂肪酸是硫酸盐还原细菌的典型生物标志化合物，进一步证实冷泉碳酸盐岩的形成与甲烷缺氧氧化作用有关。 关键词：墨西哥湾 冷泉碳酸盐岩 有机质组成分布 单体烃碳同位素 沉积环境