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1.
The compressibility of shale matrix reflects the effects of reservoir lithology, material composition, pore structure and tectonic deformation. It is important to understand the factors that influence shale matrix compressibility (SMC) and their effects on pore size distribution (PSD) heterogeneity in order to evaluate the properties of unconventional reservoirs. In this study, the volumes of pores whose diameters were in the range 6–100 nm were corrected for SMC for 17 shale samples from basins in China using high-pressure mercury intrusion and low-temperature nitrogen gas adsorption analyses, in order to investigate the factors influencing the SMC values. In addition, the variations in fractal dimensions before and after pore volume correction were determined, using single and multifractal models to explain the effects of SMC on PSD heterogeneity. In this process, the applicability of each fractal model for characterizing PSD heterogeneity was determined using statistical analyses. The Menger and Sierpinski single fractal models, the thermodynamic fractal model and a multi-fractal model were all used in this study. The results showed the following. The matrix compression restricts the segmentation of the fractal dimension curves for the single fractal Menger and Sierpinski models, which leads to a uniformity of PSD heterogeneity for different pore diameters. However, matrix compression has only a weak influence on the results calculated using a thermodynamic model. The SMC clearly affects the multifractal value variations, showing that the fractal dimension values of shale samples under matrix compression are small. Overall PSD heterogeneity becomes small for pores with diameters below 100 nm and the SMC primarily affects the PSD heterogeneity of higher pore volume areas. The comparison of fractal curves before and after correction and the variance analysis indicate that the thermodynamic model is applicable to quantitatively characterize PSD heterogeneity of shale collected from this sampling area. The results show that PSD heterogeneity increases gradually as micro-pore volumes increase.  相似文献   

2.
Quantitative analyses of the spatial distribution of fault structures can provide a theoretical basis for forecasting prospective ore deposits. Characteristics and complexity of fault structure distribution in the Qitianling area, Southern Hunan Province, China, were quantitatively calculated and appraised by fractal and multifractal methods to evaluate the relation between fault structures and ore-prospecting potential. The results show that the lengths of faults can be modeled as multifractals. Multifractal spectra evidently reflect the characteristics of the scaling of fault structures. The boxcounting dimension value(D) of fault structures is equal to 1.656, as indicates complexity of the spatial distribution of faults and favorable structural conditions for the formation of ore deposits. Moreover, the D values of sub-regions were calculated and isopleths of their fractal dimension values were plotted accordingly. Overlay analyses of isopleths of fractal dimension values and distributions of known ore deposits show that areas with the larger fractal dimension values of fault structures have more ore deposits. This spatial coupling relationship between D values and ore deposits can be used to forecast and explore other ore deposits. On the basis of complexity theory for ore-forming systems, three exploration targets with high D values were delineated as prospective ore deposits.  相似文献   

3.
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4.
The properties of feldspar and quartze are studied in this article from a fractal point of view using gray-scale micro-images of granite samples collected at the Fangshan (房山) granite body in Hebei (河北) Province, China, which can be regarded as an ideal granite in the sense of Vistelius. We found that there exist power-law relationships between the eigenvalues of the gray-scale matrices and their ranks for the feldspar and quartz. The fractal model used here is a λ-R model similar to the N-λ model proposed by Qiuming Cheng in 2005. Meanwhile, we found that average variances for the gray-scale matrices of feldspar are larger than those of quartz on the same sections, and this may be useful for auto-identification of feldspar and quartz as well as other minerals.  相似文献   

5.
Frequency-size relation of earthquakes in a region can be approximated by the Gutenberg-Richter law(GR). This power-law model involves two parameters: a-value measuring seismic activity or earthquake productivity, and b-value describing the relation between frequencies of small and large earthquakes.The spatial and temporal variations of these two parameters, especially the b-value, have been substantially investigated. For example, it has been shown that b-value depends inversely on differential stress. The b-value has also been utilized as earthquake precursor in large earthquake prediction.However, the physical meaning and properties of b-value including its value range still remain as an open fundamental question. We explore the property of b-value from frequency-size GR model in a new form which relates average energy release and probability of large earthquakes. Based on this new form of GR relation the b-value can be related to the singularity index(1-2/3 b) of fractal energy-probability power-law model. This model as applied to the global database of earthquakes with size M ≥ 5 from 1964 to 2015 indicates a systematic increase of singularity from earthquakes occurring on mid-ocean ridges, to those in subduction zones and in collision zones.  相似文献   

6.
Semivariogram is applied to fracture data obtained from detailed scanline surveys of nine field sites in western New York, USA in order to investigate the spatial patterns of natural fractures. The length of the scanline is up to 36 m. How both fracture spacing and fracture length vary with distance is determined through semivariogram calculations. In this study, the authors developed a FORTRAN program to resample the fracture data from the scanline survey. By calculating experimental semivariogram, the authors found five different types of spatial patterns that can be described by linear, spherical, reversed spherical, polynomial I (for a<0) and polynomial II (for a>0) models, of which the last three are newly proposed in this study. The well-structured semivariograms of fracture spacing and length indicate that both the location of the fractures and the length distribution within their structure domains are not random. The results of this study also suggest that semivariograms can provide useful infor  相似文献   

7.
A number of fractal/multifractal methods are introduced for quantifying the mineral de-lmsit spectrum which include a number-size, grade-tonnage model, power spectrmn model,multi-fractal model and an eigeavalue spectrmn model The first two models characterize mineral deposits spec-tra based on relationships among the measures of mineral deposits.These include the number of deposits,size of deposits,concentration and volume of mineral deposits.The last three methods that deal with the spatial-temporal spectra of mineral deposit studies are all expected to be popularized in near future.A case study of hydrothermal gold deposits from the Abitibi area,a world-class mineral district is used to demonstrate the principle as well as the applications of methods proposed in this paper,It has been shown that fractal and multifractal models are generally applicable to modeling of mineral deposits and occurrences.Clusters of mineral deposits were identified by several methods including the power spectral eral deposits in the Timmins and Kirkland Lake camps.  相似文献   

8.
The Guandishan granitoids consist mainly of various granitoid intrusions with different scales, including the Huijiazhuang intrusion, Shizhuang intrusion and Hengjian intrusion, which were formed between 1906 Ma and 1848 Ma. On the basis of geological and petrological characteristics, these granitoids can be classified into two groups： the earlier gneissic granodiorites and monzogranites, and the later massive leuco-monzogranites. Their geochemical and Nd isotopic features indicate that they could be derived from complicated partial melting of supracrustal rocks with an affinity of continental arc materials, such as sandy shale and pelite, and with garnet, pyroxene, hornblende and plagioclase as residual phases. Biotite, feldspar and other minerals were most likely fractionated during the magma evolution. Their source may have an affinity with continental arcs, and the granitoids could be derived from the main syn-collisional to late-orogenic tectonic environment, which may be related to the final amalgamation between the Eastern and Western continental blocks in the North China Craton.  相似文献   

9.
The IAPWS-95 formulation explicit in Helmholtz free energy proposed by Wagner and Proβ(2002) is the best equation of state of water,from which all thermodynamic properties can be obtained over a wide T—p range from 273.16 to 1273 K and from 0 to 1000 MPa with experimental accuracy.This paper reports the applications of the IAPWS-95 formulation in fluid inclusion and mineral-water phase equilibria. A reliable and highly efficient calculation method is presented for the saturated properties of water so that the formulation can be conveniently applied in the study of fluid inclusion,such as calculating homogenization pressures,homogenization densities(or molar volumes),volume fractions and isochores.Meanwhile,the univariant curves of some mineral-dehydration reactions are calculated based on the IAPWS-95 formulation.The computer code of the IAPWS-95 formulation can be obtained from the corresponding author.  相似文献   

10.
Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computational treatments.The flow velocity has a large spatial differentiation which is more likely to produce non-linear flow and additional head losses on and nearby intersections in such shaped fractures,therefore it is necessary to understand and quantify them.In this study,both laboratory experiments and numerical simulations were performed to investigate the total head loss on and nearby the intersections as well as the local head loss exactly on the intersections,which were not usually paid sufficient attention or even ignored.The investigation results show that these two losses account for 29.17%-84.97%and 0-73.57%of the entire total head loss in a fracture,respectively.As a result,they should be necessarily considered for groundwater modeling in fractured rocks.Furthermore,both head losses become larger when aperture and flow rate increase and intersection length decreases.Particularly,the ratios of these two head losses to the entire total head loss in a fracture could be well statistically explained by power regression equations with variables of aperture,intersection length,and flow rates,both of which achieved high coefficients of determination.It could be feasible through this type of study to provide a way on how to adjust the groundwater head from those obtained by numerical simulations based on the traditional linear flow model.Finally,it is practicable and effective to implement the investigation approach combining laboratory experiments with numerical simulations for quantifying the head losses on and nearby the intersections between disc-shaped fractures.  相似文献   

11.
By PVT fractionation experiments to model phase-controlled and gaw-washing fractionations during the formation of petroleum reservoirs,the authors measured the physical and chemical properties of products formed in different fractionation staes and made a correlative analysis of the influence of depressurization and gas washing on oil/gas molecular composition and the rule of fractionation.The analytical results showed that gas washing is an important factor affecting the physical properties of crude oils.and also can be regarded as a good genetic interpretation of marine wax-high oils in the Tarim region,Xinjiang,China.Phase-controlled and gaw-washing fractionations can lead to the formation of condensates and their differences in chemical composition from crude oils are a direct reflection of evaporating fractionation.Phasecontrolled and gaw-washing fractionations have a great influence on the composition of molecular compounds and relevant parameters.So phase-controlled and gas-washing fractionations during the formation of petroleum reservoirs are not only favorable to identifying different processes of formation of petroleum reservoirs,but also to the scientific application of routine geochemical parameters.  相似文献   

12.
The“tailing”effect caused by residual non-aqueous phase liquids(NAPLs)in porous aquifers is one of the frontiers in pollution hydrogeology research.Based on the current knowledge that the residual NAPLs is mainly controlled by the pore structure of soil,this study established a method for evaluating the residual saturation of NAPLs by investigating the fractal dimension of porous media.In this study,the soil column experiments of residual light NAPLs(LNAPLs)in sandy aquifer with different ratios of sands and soil were carried out,and the correlation between the fractal dimension of the medium,the residual of LNAPLs and the soil structure parameters are statistically analyzed,and its formation mechanism and main control factors are discussed.The results show that:Under our experimental condition:(1)the fractal dimension of the medium has a positive correlation with the residual saturation of NAPLs generally,and the optimal fitting function can be described by a quadratic model:SR=192.02 D2-890.73 D+1040.8;(2)the dominant formation mechanism is:Smaller pores in the medium is related to larger fractal dimension,which leads to higher residual saturation of NAPLs;stronger heterogeneity of the medium is related to larger fractal dimension,which also leads to higher residual saturation of NAPLs;(3)the micro capillary pores characterized by fine sand are the main controlling factors of the formation mechanism.It is concluded that both the theory and the method of using fractal dimension of the medium to evaluate the residual saturation of NAPLs are feasible.This study provides a new perspective for the research of“tailing”effect of NAPLs in porous media aquifer.  相似文献   

13.
Three kinds of spatial analysis methods （geostatistics, concentration-area fractal model and the multifractal analysis called the moment method） were used for almost 50 elements, including heavy metals, disperse elements, rare elements and even others, in 6586 top soil （0-20 cm） samples and 1833 deep soil （150-200 cm） samples from Chengdu metropolitan area of 12400 km^2, southwestern China. The ranges of spatial correlation revealed by variograms are quite different for different kinds of elements in the top and deep soils. The most interest is the fact that the multifractal spectra of environmentally important elements such as Pb, Cr, Cd and Ni in top soils in the metropolitan area show systematic change from those in the deep soils, revealing a strong anthropogenic addition, while Hg, Zn, As, Cu and all common elements show no such kind of addition. In terms of multifractal properties based on the multifractal spectrum curves, those disperse and rare elements show great deviation from other major and trace elements, which is also of great interest.  相似文献   

14.
Based on the analysis of newly collected data of plate tectonics, distribution of active faults and crustal deformation, the Taiwan area is divided into two seismic regions and six seismic belts. Then, correlation fractal dimensions of all the regions and belts are calculated, and the fractal characteristics of hypocenteral distribution can be quantitatively analyzed. Finally, multifractal dimensions Dq and f(α) are calculated by using the earthquake catalog of the past 11 years in the Taiwan area. This study indicates that (1) there exists a favorable corresponding relationship between spatial images of seismic activity described with correlation fractal dimension analysis and tectonic settings; (2) the temporal structure of earthquakes is not single but multifractal fractal, and the pattern of Dq variation with time is a good indicator for predicting strong earthquake events.  相似文献   

15.
The Salmas geothermal field is located in NW Iran. Subduction of Neo-Tethys oceanic crust beneath the Iranian microcontinent caused to propagation of the magmatic-Arc. Fractures and faults in the convergent zone have created path-ways for the circulation of geothermal fluid. Fracture concentration in the Salmas geothermal field has been characterized using of the fractal method and creation of a fracture density map that shows the highest concentration in the central part of the study area. The permeability of fractures has been evaluated by analyzing their orientation in respect to the paleostress axes. Also, the fractal analyzing result indicates the maximum fractal dimension (1.96) is around the thermal spring outlet. Paleostress analyzing revealed that in the central part of the study area, σ1 axes orientation is S90°W/10° and the σ2 dip is near to the vertical in this stress field, where strike slip faults can be propagated. In the SE part near the recharge of the thermal springs, the σ3 plunge increases to 70? and σ1 orientation is N15°E/20°, in this local tectonic regime thrust fault developed. Fractures have an important role in the circulation of fluid and the fractal dimension increases near the thermal springs in the Salmas geothermal field. Regarding the paleostress data fracture with N-S direction such as the F1 fault zone (parallel to the σ1 axes), a suitable pathway for deep circulation of geothermal fluid flow has been created.  相似文献   

16.
This paper presents a detailed study on the textural and geochemical characteristics of the proglacial sediments near the edge of modern Nelson Ice Cap, Antarctica. The grain size distributions of the proglacial sediments are characteristic of glacigenic deposits, but very different from those of aeolian and lacustrine sediments. Moreover, the grain size distributions of the proglacial sediments are fractal with a dimension of about 2.9, and the fractal dimensions can be used as another summary statistical parameter for quantifying the relative amounts of coarse and fine materials. Correlations between the absolute element abundances of the proglacial sediments are very weak due to mineral partitioning and other effects of glacial processes, but correlations between the element/Rb ratios are statistically significant. This finding indicates that element/Rb ratios can be used to reduce or eliminate the effects of glacial processes, evaluate geochemical data and determine the sediment provenance in the for  相似文献   

17.
http://www.sciencedirect.com/science/article/pii/S1674987111000764   总被引：1，自引：0，他引：1  
The Jinding Zn-Pb deposit has been generally considered to have formed from circulating basinal fluids in a relatively passive way,with fluid flow being controlled by structures and sedimentary facies,similar to many other sediments-hosted base metal deposits.However,several recent studies have revealed the presence of sand injection structures,intrusive breccias,and hydraulic fractures in the open pit of the Jinding deposit and suggested that the deposit was formed from explosive release of overpres-sured fluids.This study reports new observations of fluid overpressure-related structures from underground workings(Paomaping and Fengzishan).which show clearer crosscutting relationships than in the open pit.The observed structures include:I) sand(±rock fragment) dikes injecting into fractures in solidified rocks:2) sand(±rock fragment) bodies intruding into unconsolidated or semi-consolidated sediments;3) disintegrated semi-consolidated sand bodies;and 4) veins and breccias formed from hydraulic fracturing of solidified rocks followed by cementation of hydrothermal minerals.The development of ore minerals(sphalerite) in the cement of the various clastic injection and hydraulic fractures indicate that these structures were formed at the same time as mineralization.The development of hydraulic fractures and breccias with random orientation indicates small differential stress during mineralization,which is different from the stress field with strong horizontal shortening prior to mineralization. Fluid flow velocity may have been up to more than 11 m/s based on calculations from the size of the fragments in the clastic dikes.The clastic injection and hydraulic fracturing structures are interpreted to have formed from explosive release of overpressured fluids,which may have been related to either magmatic intrusions at depth or seismic activities that episodically tapped an overpressured fluid reservoir.Because the clastic injection and hydraulic structures are genetically linked with the mineralizing fluid source,they can be used as a guide for mineral exploration.  相似文献   

18.
As typical carbonate geothermal reservoirs with low porosity in northern China, the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration. The Jixianian System comprises the Gaoyuzhuang, Yangzhuang, Wumishan, Hongshuizhuang, and Tieling formations. The characteristics, formation periods, and controlling factors of reservoir tectonic fractures have been determined based on analyses of outcrops, cores, thin sections, and image logs. The results show that unfilled fractures account for over 87% and most tectonic fractures are high-angle shear fractures with angles concentrated at 40° to 70° and the fracture porosity increases linearly with an increased fracture aperture. Within the same tectonic setting and stress field, the lithology and layer thickness are the dominant factors governing the development of tectonic fractures, which are the most developed in dolomites and thin layers. Tectonic fractures were most likely formed in regions near faults or areas with larger stress gradients. The tectonic fractures in the carbonate geothermal reservoirs are roughly divided into four sets: NNW–SSE and NNE–SSW oriented ‘X’-conjugated shear fractures formed from the Paleozoic to the pre-Yanshanian Movement; NE–SW-oriented shear fractures, formed in episode B of the Yanshanian Movement, occurred at the Early Cretaceous; nearly E–W-oriented tensional fractures formed in the late Yanshanian Movement at the Late Cretaceous to Paleogene, and NEE–SW-oriented shear fractures formed during the Himalayan movement.  相似文献   

19.
This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray diffraction analysis of 25 black shale outcrops and samples. Two main types of shale gas reservoirs were determined, i.e., fractures and pores. Fractures were classified into five categories, i.e., giant, large, medium, small, and micro, according to the features of the shale gas reservoirs, effect of fracture on gas accumulation, and fracture nature. Pore types include organic matter pores, mineral pores (mineral surface, intraparticle, interparticle, and corrosional pore), and nanofractures. The various fracture types, fracture scales, pore types, and pore sizes exert different controls over the gas storage and production capacity. Pores serve as a reservoir for gas storage and, the gas storage capacity can be determined using pores; fractures serve as pathways for gas migration, and gas production capacity can be determined using them.  相似文献   

20.
The Cenozoic rift basins in eastern China show a clear temporal and spatial zonation and episodic tectonic evolution, which control their episodic hydrocarbon generation and zonal accumulation. In this paper, based on the study of depositional architecture, hydrocarbon migration system and dynamic evolution in the rift basins, combinations of hydrocarbon accumulation elements were analyzed using sequence stratigraphy. Hydrocarbon distribution in system tracts with different sequence orders was further studied. And we summarized stacking patterns and horizontal combination relationships for different types of reservoirs, such as lithological, tectonic-lithological, tectonic and stratigraphical reservoirs which can be observed from depression center to basin margin. The result reveals that various scales of pools exhibit significant distribution and evolution orderliness in different pool-forming units, i.e., depositional systems, plays and depressions. The regular distribution of various scales of pools is closely related to tectonic evolution and depositional filling in the rift basins. The result can be applied to the fine petroleum exploration in rift basins in eastern China. It will promote the scientific prediction and evaluation of reservoir types and their spatial distribution, lead to the active shifts of exploration targets in different zones, and thus support the stable progress of fine exploration in mature exploration areas.  相似文献   

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