Earth Sciences Research Journal

Letter from the editor

Shear-wave Velocity Structure of Greenland from Rayleigh-wave Analysis

The elastic structure beneath Greenland is shown by means of S-velocity maps for depths ranging from zero to 350 km, determined by the regionalization and inversion of Rayleigh-wave dispersion. The traces of 50 earthquakes, occurring from 1990 to 2011, have been used to obtain Rayleigh-wave dispersion data. These earthquakes were registered by 21 seismic station located in Greenland and the surrounding area. The dispersion curves were obtained for periods between 5 and 200 s, by digital filtering with a combination of MFT (Multiple Filter Technique) and TVF (Time Variable Filtering). Later, all seismic events (and some stations) were grouped to obtain a dispersion curve for each source-station path. These dispersion curves were regionalized and inverted according to the generalized inversion theory, to obtain shear-wave velocity models for a rectangular grid of 16x20 points. The shear-velocity structure obtained through this procedure is shown in the S-velocity maps plotted for several depths. These results agree well with the geology and other geophysical results previously obtained. The obtained S-velocity models suggest the existence of lateral and vertical heterogeneity. The zones with consolidated and old structures present greater S-velocity values than the other zones, although this difference can be very little or negligible in some case. Nevertheless, in the depth range of 15 to 45 km, the different Moho depths present in the study area generate the principal variation of S-velocity. A similar behaviour is found for the depth range from 80 to 230 km, in which the lithosphere-asthenosphere boundary (LAB) generates the principal variations of S-velocity. Finally, the new and interesting feature obtained in this study: the definition of the base of the asthenosphere (for the whole study area and for depths ranging from 130 to 280 km, respectively) should be highlighted.

La estructura elástica bajo Groenlandia es mostrada por medio de mapas de velocidad de onda para profundidades variando desde cero a 350 km, determinada por la regionalización e inversión de la dispersión de onda Rayleigh. Las trazas de 50 terremotos, ocurridos desde 1990 hasta 2011, han sido usados para obtener datos de dispersión de onda Rayleigh. Estos terremotos fueron registrados por 21 estaciones sísmicas localizadas en Groenlandia y el área circundante. Las curvas de dispersión fueron obtenidas para periodos entre 5 y 200 s, por filtrado digital con una combinación de MFT (Técnica de Filtrado Múltiple) y TVF (Filtrado en Tiempo Variable). Después, todos los eventos sísmicos (y algunas estaciones) fueron agrupados para obtener una curva de dispersión para cada trayecto fuente-estación. Estas curvas de dispersión fueron regionalizadas e invertidas de acuerdo con la teoría de la inversión generalizada, para obtener modelos de velocidad de cizalla para una rejilla rectangular de 16x20 puntos. La estructura de velocidad de cizalla obtenida a través de este procedimiento es mostrada in los mapas de velocidad de onda S representados para varias profundidades. Estos resultados muestran buen acuerdo con la geología y con otros resultados geofísicos obtenidos previamente. Los modelos de velocidad de onda S obtenidos sugieren la existencia de heterogeneidad lateral y vertical. Las zonas con estructuras antiguas y consolidadas presentan mayores valores de velocidad de onda S que las otras zonas, aunque esta diferencia puede ser muy pequeña o despreciable en algún caso. No obstante, en el rango de profundidad de 15 a 45 km, las diferentes profundidades del Moho presentes en el área de estudio generan la principal variación de velocidad de onda S. Un comportamiento similar es encontrado para el rango de profundidad desde 80 a 230 km, en el cual la frontera litosfera-astenosfera (LAB) genera las principales variaciones de velocidad de onda S. Finalmente, debería ser destacada la nueva e interesante característica obtenida en este estudio: la definición de la base de la astenosfera (para el área de estudio completa y para profundidades variando desde 130 a 280 km, respectivamente).

Oxygen and Carbon Isotopic Composition of Carbonate Rocks of the Permian Qixia Formation, Sichuan Basin: Thermal Effects of Emeishan Basalt

The late Permian thermal events related to Emeishan Basalt has made a great impact on the underlying carbonate rock properties in the western margin of the Yangtze Platform. In this paper, we investigate the carbon and oxygen isotopic composition of the Qixia Formation carbonates from two sections: the Qiaoting Section in the northeastern part of the Sichuan Basin and the Changjianggou Section at the northwestern edge of the Basin. The data reveal that: (i) Samples from Qiaoting section show a relatively narrow range of δ13C and δ18O, varying from 2.7‰ to 5.2‰ with an average of 4.2‰, and -3.8‰ to -7.8‰ with an average of -5.4‰, respectively. In contrast, Samples from Changjianggou section exhibit larger magnitude of variation in δ13C and δ18O, ranging from -1‰ to 3.8‰ with an average of 1.5‰, and -2.1 to -9.2‰, with an average of -6.0‰ respectively; (ii) δ13C and δ18O records in carbonates from Qiaoting section are similar to those of Middle Permian seawater whereas carbonates from the Changjianggou section are depleted in 13C and18O compared to contemporary seawater; (iii) On the basis of combined petrographic and paleo-heat flow evidence, the lower carbon and oxygen isotopic composition of the carbonates from the Changjianggou section are interpreted to be the results of thermal effects of Emeishan Basalt because of its proximity to the eruption center of the basalt. The high temperature reduced the δ18O values of the carbonates and forced the organic matter to mature at an early stage, thus producing 13C-enriched carbon dioxide to participate in the formation of carbonates.

Los eventos térmicos del Pérmico tardío relacionados con el Basalto Emeishan han tenido un gran impacto en las propiedades de las rocas de carbonato subyacentes en el margen occidental de la plataforma Yangtze. En este artículo se investiga la composición isotópica de carbonatos de la formación Qixia en dos secciones: la sección de Qiaoting en la parte nororiental de la cuenca Sichuan y la sección Changjianggou, en el noroccidente de la cuenca. La información evidencia que, (i) las muestras de la sección Qiaoting tienen un espectro más angosto que va de δ13C a δ18O, con variación de 2.7 ‰ a 5,2 ‰, con un promedio de 4.2 ‰, y -3.8 ‰ a -7.8 ‰, con una media de -5.4 ‰, respectivamente. En contraste, las muestras de la sección Changjianggou tienen una variación de mayor magnitud en δ13C a δ18O que va desde -1 ‰ hasta 3.8 ‰, con un promedio de 1.5 ‰, y de -2.1 a -9.2 ‰, con una media de -6.0 ‰, respectivamente; (ii) los registros de δ13C y δ18O en carbonatos son similares a los de agua marina del pérmico medio, mientras que los carbonatos de la sección Changjianggou se ven empobrecidos en 13C y 18O comparados al agua marina de esta edad; con base en la petrografía combinada y la evidencia del flujo paleotérmico, la baja composición isotópica de oxígeno y carbón de los carbonatos en la sección de Changjianggou se interpretó como resultado de los efectos térmicos del Basalto Emeishan debido a la proximidad con el centro de erupción. La alta temperatura redujo los valores de δ18O de los carbonatos y llevó a la maduración temprana de la materia orgánica, lo que produjo dióxido de carbono enriquecido en 13C durante la formación de los carbonatos.

Petrologic significance of Fe-rich staurolite in pelitic schists of the Silgará Formation, Santander Massif

Medium grade metapelites of the Silgará Formation at the Santander Massif (Colombian Andes) have been affected by a medium-pressure/high-temperature Barrovian type of metamorphism, developing a sequence of metamorphic zones (biotite, garnet, staurolite and sillimanite). These rocks record a complex tectono-metamorphic evolution and reaction history. Metapelitic rocks from the staurolite zone are typically foliated, medium- to coarse-grained, pelitic to semipelitic schists that contain the mineral assemblage biotite + garnet + staurolite ± kyanite; all contain muscovite + quartz + plagioclase with minor K-feldspar, tourmaline, apatite, zircon, epidote, calcite, and Fe-Ti oxides. Field and microscopic evidences reveal that Fe-rich staurolite in pelitic schists is involved in several chemical reactions, which explains its formation and transformation to other minerals, which are very important to elucidate the reaction history of the Silgará Formation metapelites.

Medium grade metapelites of the Silgará Formation en el Macizo de Santander (Andes Colombianos) han sido afectadas por un metamorfismo de tipo Barroviense, el cual se ha producido en condiciones de media presión y alta temperatura, desarrollando una secuencia de zonas metamórficas (biotita, granate, estaurolita y silimanita). Estas rocas registran una evolución tectono-metamórfico e historia reacción compleja. Las metapelitas de la zona de la estaurolita están representadas por esquistos pelíticos a semipelíticos de grano medio a grueso típicamente foliados que contienen la paragénesis mineral biotita + granate + estaurolita ± cianita; todos contienen moscovita + cuarzo + plagioclasa con menor feldespato potásico, turmalina, apatito, zircón, epidota, calcita, y óxidos de Fe-Ti. Evidencias de campo y microscópicas revelan que la estaurolita rica en Fe en esquistos pelíticos se involucró en varias reacciones químicas a partir de las cuales esta se formó o transformó a otra fase mineral, lo cual es muy importante para dilucidar la historia de reacción de los metapelitas de la Formación Silgará.

Estimation of IDF Curves of Extreme Rainfall by Simple Scaling in Northern Oueme Valley, Benin Republic (West Africa)

Rainfall intensity-duration-frequency (IDF) curves are of particular importance in water resources management, for example, in urban hydrology, for the design of hydraulic structures and the estimation of the flash flood risk in small catchments. IDF curves describe rainfall intensity as a function of duration and return period, and they are significant for water resources planning, as well as for the design of hydraulic constructions and structures. In this study, scaling properties of extreme rainfall are examined to establish the scaling behavior of statistical non-central moment over different durations. IDF curves and equations are set up for all stations by using the parameter obtained from scaling behavior, the location and scale parameters μ24 and σ24 of the Gumbel distribution (EVI) sample of annual maximum 1440 min rainfall data. In another hand, we have established the IDF curves for ten selected rain gauge stations in the Northern (Oueme Valley) parts of Benin Republic, West Africa by using the simple scaling approach. Analysis of rainfall intensities (5 min and 1440 min rainfall data) from the ten rainfall stations shows that rainfall in north-Benin displays scales invariance property from 5 min to 1440 min. For time scaling, the statistical properties of rainfall follow the hypothesis of simple scaling. Therefore, the simple scaling model applies to the rainfall in (Oueme Valley). Hence, the simple scaling model is thought to be a viable approach to estimate IDF curves of hourly and sub-hourly rainfall form rainfall projections. The obtained scaling exponents are less than 1 and range from 0.23 to 0.59. The empirical model shows that the scaling procedure is a good estimator as it is more efficient and gives more accurate estimates compared with the observed rainfall than the traditional method which only consists the Gumbel model in all stations for lower return periods (T<5 years) but not for higher return periods.

Las curvas de precipitación Intensidad-Duración-Frecuencia (IDF) son de particular importancia en el manejo de los recursos hídricos, como es el caso de la hidrología urbana o para el diseño de estructuras hidráulicas y la estimación del riesgo de crecidas en pequeñas captaciones. Las curvas IDF describen la intensidad de las precipitaciones como una función con períodos de duración y recurrencia, lo que las hace significativas en la planeación de recursos hídricos así como en el diseño de construcciones y estructuras hidráulicas. Este estudio examina las propiedades de escala en precipitaciones extremas para establecer un comportamiento en momentos estadísticos marginales en diferentes períodos de duración. Se establecieron las curvas IDF y las ecuaciones para todas las estaciones a partir del parámetro obtenido del comportamiento de escala, la ubicación y los parámetros de escala μ24 and σ24 de la muestra de información de precipitación máxima anual de 1440 minutos de la distribución de Gumbel (EVI). Por otro lado, se establecieron las curvas IDF para 10 estaciones pluviométricas seleccionadas en el Valle Oueme, al norte de la República de Benín (África occidental), con el uso de aproximación simple de escala. El análisis de las intensidades de precipitación en las diez estaciones pluviométricas muestra que la precipitación en el norte de Benín expone propiedades de poca variación en la escala 5 min y 1440. En el tiempo de escala, las propiedades estadísticas de precipitación confirman la hipótesis de escala simple; además, este modelo so corresponde a la precipitación del Valle Oueme. Por lo tanto, el modelo de escala simple se considera una aproximación viable para estimar las curvas IDF en las proyecciones de precipitación de cada hora y sub-hora. Los exponentes de escala obtenidos son menores a 1 y oscilan de 0,23 a 0,59. El modelo empírico muestra que el procedimiento de escala es un buen estimativo, más eficiente y con cálculos más exactos que el método tradicional, el cual consiste solamente en el modelo Gumbel aplicado en todas las estaciones pluviométricas en períodos de menor recurrencia (T<5 años) pero no en lapsos de mayor recurrencia.

Geospatial Analysis for the Determination of Hydro-Morphological Characteristics and Assessment of Flash Flood Potentiality in Arid Coastal Plains: A Case in Southwestern Sinai, Egypt

Coastal plains with a unique geographic setting and renewable natural resources are promising for sustainable development; however, these areas may be subjected to some environmental hazards due to their geological setting. One of those hazards is the seasonal flash flood that can threaten existing and future development projects in such critical areas. Southwestern Sinai, Egypt, is a coastal plain that is characterized by complex geological setting an arid climate with seasonal rainfall which can result in a high runoff. The aim of this work is to model spatially the runoff amount and density related to flash flood development and to create a flash flood hazard map of the plain as an example of coastal plain in a desert environment with large and complex hydrologic setting. In this research, ASTER images are used to develop a digital elevation model (DEM) and land use/land cover (LULC) data sets of the study area. Geographic information system (GIS) was used to perform runoff and flash potential flood analyses of the created databases and to show distributed runoff and flooding potential in spatial maps. A module was created in a GIS environment to develop a flash flood potential index map. It was clear that the main two factors controlling runoff amounts and flash flood potential in such kinds of areas are the slope and soil types. The final dataset map procedure by this work can be very helpful in land use planning by highlighting the areas subjected to flash floods.

Las llanuras costeras que poseen recursos naturales renovables y una configuración geográfica única son promisorias para el desarrollo sostenible. Estas áreas, sin embargo, son objeto de algunas amenazas ambientales debido a su escenario geológico. Una de estas amenazas es la temporada de inundaciones rápidas que pueden poner en riesgo los proyectos de desarrollo existentes y los futuros en estas zonas críticas. El suroccidente de Sinaí, Egipto, es una llanura costera que se caracteriza por su compleja configuración geológica de clima árido, con temporadas de lluvia que pueden resultar en una gran escorrentía. El objetivo de este trabajo fue modelar espacialmente la cantidad y densidad de escorrentía relacionada al desarrollo de inundaciones rápidas y elaborar un mapa de amenazas de inundación rápida en este valle, como un ejemplo de llanura costera en un ambiente desértico con un escenario hidrológico grande y complejo. En este trabajo se utilizaron imágenes ASTER para desarrollar un Modelo de Elevación Digital (DEM, en inglés) y establecer la información de uso del suelo/cobertura del suelo (LULC, en inglés) en el área de estudio. A partir del Sistema de Información Geográfica (GIS) se analizaron la escorrentía y el potencial de inundación de las bases de datos creadas, y se mostró la escorrentía y el potencial de inundación en mapas espaciales. Se creó un módulo en un ambiente del GIS para desarrollar un mapa del índice inundación rápida potencial. Se estableció que los dos factores que controlan la cantidad de escorrentía y el potencial de inundaciones rápidas en estas áreas son la inclinación y los tipos de suelo. El mapa final de procemiento con el conjunto de datos de este trabajo es de gran ayuda en la planeación del uso de suelos, ya que evidencia las áreas con posibilidad de inundaciones rápidas.

The effects of ex-situ oil shale mining on groundwater resources in Siwaqa area, southern Jordan, using DRASTIC index and hydrochemical water assessment

Energy resources in addition to water resources are the most limited resources in Jordan, being one of the fourth poorest countries in water resources, and limitation of surface water resources put huge pressure on groundwater which is the main resource there. High expenses and the increasing prices of oil over all worlds increase the feasibility to mining the oil shale that exists in southern Jordan area, Siwaqa. This study took place to clarify the possible effects of mining and energy production activities on the water resources in that area. Groundwater vulnerability mapping was done for many areas all over the country, including this part. The initiative of this work is to determine the vulnerability under the conditions of removing the bedrock of the oil shale which is described as a confining layer. Results that are obtained by this work conclude that the oil shale area becomes highly vulnerable to the human activities because of the existing geological structures while it is small and medium vulnerable in the fields in which there are no geological structures. In addition to the structural features and adding the possibility of the oil shale mining from the outcropped areas which will decrease the depth to water table and hence will affect the vulnerability values.

Las fuentes de energía y agua son las más limitadas en Jordania, uno de los cuatro países más pobres en recursos hídricos; además, las limitadas fuentes superficiales hacen de las aguas subterráneas las más importantes. Las ganancias y el precio del petróleo, por su parte, incrementan la viabilidad de la minería de esquistos bituminosos en el sur de Jordania, en la región de Siwaqa. Este estudio se realiza con el fin de establecer los posibles efectos de las actividades de producción de energía y minería en las fuentes hídricas de la zona. Se elaboró un mapa de vulnerabilidad para las fuentes de agua subterránea en varias regiones del país, incluida el área de estudio. La iniciativa de este trabajo es determinar la vulnerabilidad si se remueve el lecho rocoso del esquisto bituminoso, que funciona como una capa de confinamiento. Los resultados obtenidos evidencian que el esquisto bituminoso se torna bastante vulnerable a las actividades humanas debido a la presencia de estructuras geológicas, mientras que su vulnerabilidad es media o baja en aquellos lugares donde no hay estructuras geológicas. Además de los rasgos estructurales, existe la posibilidad de que la minería del esquisto bituminoso en las áreas de afloramiento podría descender hasta la capa freática y allí afectar los valores de vulnerabilidad.

Assessment by multivariate analysis of groundwater-surface water interactions in the Coal-mining Exploring District, China

This paper applies for cluster analysis and factor analysis theory to statistically analyze environmental isotope (δ18O,δ²H, 3H, 14C) and water chemistry (K+, Na+, Ca2+, Mg2+, HCO3 -, SO4(2-), Cl-) test data from different water bodies in the coal-mining exploring district. The result shows that groundwater can be clustered into four categories, namely GA, GB, GC and GD classes. Deep karst groundwater and spring were grouped into GA class, and the contour map of the second-factor scores shows that karst water and spring of the GA group is in the same area, indicating the same recharging source from the northern mountainous area. Deep fissure water was clustered into GC class with the lowest second-factor scores, and cation exchange plays a central role, then did not detect tritium with 14C of lower levels, indicating the late Pleistocene rainfall recharging. Shallow pore water and surface water were clustered into GB class with the high third factors scores, indicating surface water leakage recharging. The water samples of GD class have the highest three factors score, pointing out that the shallow pore water and surface water were polluted. The results of this study provide a scientific basis for assessing groundwater circulation mechanism in the coal-mining exploring district.

Este estudio utiliza la teoría del análisis de grupos y del análisis factorial para examinar estadísticamente la información de pruebas al isótopo ambiental (δ18O,δ²H, ³H, 14C) y a la química del agua (K+, Na+, Ca2+, Mg2+, HCO3 -, SO4(2-), Cl-) en diferentes cuerpos de agua en el distrito de exploración carbonífera. El resultado muestra que el agua subterránea puede ser agrupada en cuatro categorías, nombradas Clase GA, Clase GB, Clase GC y Clase GD. El agua subterránea del karst profundo y el agua de manantial fueron agrupadas en la Clase GA; el mapa topográfico de los marcadores de segundo factor muestra que el agua del karst y el agua de manantial del grupo GA se encuentran en la misma área, lo que indica que tienen la misma fuente de recarga, en la región montañosa al norte del distrito. El agua de las fisuras profundas fue agrupada en la Clase GC con los marcadores más bajos de segundo factor y donde el intercambio de cationes es determinante; no se detectó tritio con los bajos niveles de 14C, lo que indica una recarga por lluvia en el Pleistoceno tardío. El agua poco profunda y el agua superficial fueron agrupadas en la Clase GB, con los mayores marcadores de tercer factor, lo que indica una recarga por vertido superficial. Las muestras de agua de la Clase GD tienen los mayores marcadores de los tres factores, lo que señala que las aguas poco profundas y las superficiales están contaminadas. Los resultados de este estudio proveen una base científica para la evaluación del mecanismo de circulación del agua subterránea en el distrito de exploración carbonífera.

GIS-based assessment of aquifer vulnerability using DRASTIC Model: A case study on Kodaganar basin

Groundwater is vulnerable and more susceptible to contamination from various anthropogenic elements. Various steps are taken to measure the groundwater vulnerability for a sustainable groundwater development. The present study estimates the aquifer vulnerability by applying DRASTIC model in the Geographic Information System (GIS) environment. The DRASTIC model uses seven hydrological parameters which include depth to water level, net recharge, aquifer media, soil media, topography, the impact of vadose zone and hydraulic conductivity. DRASTIC index was calculated from DRASTIC model that ranged from 31 to 154. All these parameters characterize the hydrological setting for evaluating aquifer vulnerability. Sensitivity analyses have also been performed to determine the sensitivity of every individual DRASTIC parameter towards the aquifer vulnerability. Sensitivity analysis indicated that all the parameters have an almost similar influence on vulnerability index. Depth to water parameter inflicts larger impact on aquifer vulnerability followed by recharge, topography and soil Media. The whole of Kodaganar basin is classified into very low, low, moderate and high vulnerable zones. Nearly three-fourth of the basin has very low and low vulnerability. Incorporating DRASTIC model in the GIS environment has proved efficient in handling large volumes of data and in determining the groundwater vulnerability.

El agua subterránea es vulnerable y más susceptible a la contaminación de varios elementos antropogénicos. Se midió la vulnerabilidad del agua subterránea en varias etapas para establecer el desarrollo sustentable de la fuente acuífera. Este trabajo estima la vulnerabilidad del agua subterránea por la aplicación del método DRASTIC en el entorno del Sistema de Información Geográfica (GIS, en inglés). El método DRASTIC utiliza siete parámetros hidrológicos: profundidad del agua subterránea, recarga neta, litología del acuífero, tipo de suelo, topografía naturaleza de la zona no saturada y conductividad hidráulica del acuífero. El índice DRASTIC fue calculado a través de este método y que oscila entre 31 y 154 unidades. Estos parámetros caracterizan la configuración hidrológica para la evaluación de vulnerabilidad del acuífero. También se realizaron los análisis de susceptibilidad para determinar la respuesta de cada parámetro DRASTIC frente a la vulnerabilidad del agua subterránea. El análisis de susceptibilidad indicó que todos los parámetros tienen una influencia similar en el índice de vulnerabilidad. El parámetro de profundidad ocasiona un mayor impacto en el índice de vulnerabilidad, seguido por la recarga, la topografía y el tipo de suelo. Toda la cuenca de Kodaganar se clasifica en zonas de vulnerabilidad muy baja, baja, moderada y alta. La incorporación del método DRASTIC en el entorno GIS prueba la eficiencia en el manejo de grandes volúmenes de información y en la evaluación de vulnerabilidad de aguas subterráneas.

Rb-Sr Isotopic Geochronology and Geological Implications of Dongfeng Gold Deposit in Jiaodong Area

The superlarge Dongfeng gold deposit is located in the Potouqing faults-alteration belt of the eastern part of the 'Zhao-Lai-gold ore belt', which belongs to the northwestern part of the Jiaodong area. Tectonically, ore bodies are controlled by faults and gold mainly occurs in the pyrite and polymetallic sulfide-bearing quartz vein. In this paper, Rb-Sr isotopic analysis is carried out with the beresite, which formed by hydrothermal metasomatism, and the Rb-Sr isochron age is 125.5±6.7Ma, indicating this deposit set up in the early Cretaceous of the late Yanshanian. Based on the relationship between the Dongfeng gold deposit and the Mesozoic granite, it is suggested that the formation of the gold deposit is a complex geological process of gradual enrichment and precipitation of the ore-forming elements. The initial 87Sr/86Sr ratio of the beresite is 0.711502±0.000069, which indicates the ore-forming materials mainly come from the crust. Combined with the complex mineralization process of the Dongfeng gold deposit and the reported H-O isotopic data, it is suggested that the ore-forming materials are mainly derived from the crust with some mantle materials, while the ore-forming fluids are originated primarily from magmatic hydrothermal and mantle with some precipitate water.

Variable-Permeability Well-Testing Models and Pressure Response in Low-Permeability Reservoirs with non-Darcy Flow

This paper proposes the concept of variable-permeability effect and sets up the one-dimensional and two-dimensional non-Darcy well testing models. The finite difference algorithm is employed to solve the differential equations of the variable-permeability model, and the non-convergence of the numerical solutions is solved by using the geometric mean of permeability. The type curves of pressure and pressure derivative with variable-permeability effect are obtained, and sensitivity analysis is conducted. The results show that the type curves upturn in the middle and late sections, and the curves turn more upward with the severer of the variable-permeability effect. The severer the non-Darcy effect is, the less obviously the curve upturns caused by boundary effect. Furthermore, the boundary effect is increased by increasing the number of impermeable boundaries or decreasing the distance between the well and boundary.

Research on Test-bench for Sonic Logging Tool

In this paper, the test-bench for sonic logging tool is proposed and designed to realize automatic calibration and testing of the sonic logging tool. The test-bench System consists of Host Computer, Embedded Controlling Board, and functional boards. The Host Computer serves as the Human Machine Interface (HMI) and processes uploaded data. The software running on Host Computer is designed on VC++, which is developed based on multithreading, Dynamic Linkable Library (DLL) and Multiple Document Interface (MDI) techniques. The Embedded Controlling Board uses ARM7 as the microcontroller and communicates with Host Computer via Ethernet. The Embedded Controlling Board software is realized based on embedded uclinux operating system with a layered architecture. The functional boards are designed based on Field Programmable Gate Array (FPGA) and provide test interfaces for the logging tool. The functional board software is divided into independent sub-modules that can repeatedly be used by various functional boards and then integrated those sub-modules in the top layer. With the layered architecture and modularized design, the software system is highly reliable and extensible. With the help of designed system, a test has been conducted quickly and successfully on the electronic receiving cabin of the sonic logging tool. It demonstrated that the system could greatly improve the production efficiency of the sonic logging tool.

Geochemical Characteristics and Paleoenvironmental Significance of the Ordovician Paleokarst Reservoir in the Maigaiti Slope of Tarim Basin

The Ordovician carbonatites of the Maigaiti slope have formed the conditions for the development of large oil and gas fields with karst reservoirs. This study systematically analyzed the isotopic characteristics of carbon, oxygen, and strontium and enrichment trace elements regularity to examine the geochemical features of the paleo-karstification products, various periods of paleo-karstification, and paleoenvironmental conditions of the Ordovician. Affected by terrigenous clasts, the Lianglitage Formation is composed of limestone with a relatively high 87Sr/86Sr value and a frequently fluctuating sea level, which exhibits an overall increasing-to-decreasing trend variation. Of all samples affected by the atmospheric freshwater leaching effect, δ18O values were negative, and δ13C values varied greatly toward both ends. The fissure/cave infills were rich in Fe and Mn but poor in Sr, and the Sr/Ba value was considerably less than 1, which confirms the existence of ancient weathered crust and the development of an atmospheric freshwater karst environment. Four different paleo-karstification periods were identified according to the carbon and oxygen isotopic characteristics of calcite. Combined with the trace element characteristics of the infills, the paleo-karstification in the Yingshan Formation was subdivided based on three hydrological environment conditions. Erosion modification of buried acid compaction-released water from late-period corrosion pores, caves, and fissures formed by syndiagenetic paleo-karstification and weathered crust bare paleo-karstification due to atmospheric freshwater leaching can significantly improve the reserving and permeability characteristics of the karst reservoir to develop a large paleokarst reservoir.

Numerical Simulation of Shock Response and Dynamic Fracture of a Concrete Dam Subjected to Impact Load

The shock response and dynamic fracture of concrete gravity dams under impact load are the key problems to evaluate the antiknock safety of the dam. This study aims at understanding the effects of impact shock on the elastic response and dynamic fracture of concrete gravity dams. Firstly, this paper uses acceleration records of a concrete gravity dam under impact to establish the correct way to determine the concrete gravity dam of the fundamental frequency and present cut sheets multi-degree-of-freedom dynamic modeling. Under strong impact loading, the constitutive relation of concrete gravity dam and the highest frequency of the impact are uncertain. So, the main advantage of this method is avoiding the use of elastic modulus in the calculation. The result indicates that the calculation method is a reliable computational method for concrete gravity dams subjected to impact. Subsequently, the failure process of dam models was numerically simulated based on ABAQUS commercial codes. Finally, this paper puts forward suggestions for future research based on the results of the analysis.

Optimization of land use at Mt. Yuelu scenic area: an analysis using the ecological green equivalent

This study applies the ecological green equivalent approach to evaluating the land use structure of Mt. Yuelu scenic area in Hunan Province, China. A mathematical model is established based on land use and land cover data, and then ArcGIS used to extract the spatial extent of the ecological green equivalent within each of the relevant elements. Results show that the area has a relatively reasonable land use structure even though the forest coverage rate is slight below the optimum. The overall green equivalent (1.13) was higher than the optimum forest coverage ecological green equivalent (1.00). The distribution of forest was uneven, with most of the forest within the site; the area's land use structure could thus be improved by extending the green area outside of Mt. Yuelu. We conclude by reiterating that landscape and infrastructure development should consider ecological system conditions.

Development of Tropical Lowland Peat Forest Phasic Community Zonations in the Kota Samarahan-Asajaya area, West Sarawak, Malaysia

Logging observations of auger profiles (Tarmizi, 2014) indicate a vertical, downwards, general decrease of peat humification levels with depth in a tropical lowland peat forest in the Kota Samarahan-Asajaya área in the región of West Sarawak (Malaysia). Based on pollen analyses and field observations, the studied peat profiles can be interpreted as part of a progradation deltaic succession. Continued regression of sea levels, gave rise to the development of peat in a transitional mangrove to floodplain/floodbasin environment, followed by a shallow, topogenic peat depositional environment with riparian influence at approximately 2420 ± 30 years B.P. (until present time). The inferred peat vegetational succession reached Phasic Community I at approximately 2380 ± 30 years B.P. and followed by Phasic Community II at approximately 1780 ± 30 years B.P., towards the upper part of the present, ombrogenic, peat profile. Observations of the presence of large, hollow, Shorea type trees, supports that successive vegetational zonation of the tropical lowland peat dome may have reached Phasic Community II. Some pollen types were found that are also known to occur in the inferred vegetational zonation of Phasic Community III and IV or higher. Pollen analyses indicates that estuarine and deltaic, brackish to saline water influence may have gradually ceased at approximately 0.5 m below the lithological boundary between peat and underlying soil (floodplain deposit) in the tropical lowland peat basin.

Engineering Innovation of a Length of Nearly 3300m large Diameter Pipeline Installed by HDD

The Yangtze River Crossing Project, which is part of the Chinese gas pipeline trunk network and aims to transmit the natural gas to the Yangtze River Delta area, sets up a record for the length of Horizontal Directional Drilling(HDD) in the world. The term of pipeline installed is 3300m, and the diameter is 40in. Many technical difficulties have been inevitably encountered in a large diameter hole reaming in fine sand, the calculation of section scour depth which determines the minimum buried depth of the pipe, protection of outside coating and the method of long distance pilot hole drilling, such other challenges. In view of this,it was recommended that two pipelines of 711mm should be installed to replace the existing one of 1016mm in diameter and 1% flooding scour depth obtained by reliable statistical analysis. In period of installation, application glass fiber reinforced epoxy resin as a protective coating, executing the pilot hole by Intersect Method.As a result, this super project is finished successfully on May 21.2013. The experience can be applied to any pipeline engineering the installed by horizontal directional drilling or similar works.

Geological Characteristics of Unconventional Gas in Coal Measure of Upper Paleozoic Coal Measures in Ordos Basin, China

There are enormous resources of unconventional gas in coal measures in Ordos Basin. In order to study the geological characteristics of unconventional gas in coal Measures in Ordos Basin, we analyzed and summarized the results of previous studies. Analysis results are found that, the unconventional gas in coal measures is mainly developed in Upper Paleozoic in Eastern Ordos Basin, which including coalbed methane, shale gas and tight sandstone gas. The oil and gas show active in coal, shale and tight sandstone of Upper Paleozoic in Ordos Basin. Coalbed methane reservoir and shale gas reservoir in coal measures belong to "self-generation and self-preservation", whereas the coal measures tight sandstone gas reservoir belongs to "allogenic and self-preservation". The forming factors of the three different kinds of gasses reservoir are closely related and uniform. We have the concluded that it will be more scientific and reasonable that the geological reservoir-forming processes of three different kinds of unconventional gas of coal measures are studied as a whole in Ordos Basin, and at a later stage, the research on joint exploration and co-mining for the three types of gasses ought to be carried out.