Laboratory investigation of hydraulic fracture propagation using real-time ultrasonic measurement in shale formations with random natural fractures

The significance of natural fractures in unconventional shale hydrocarbon formations has opened new research frontiers in hydraulic fracturing. Among many of its unique contributions to gas production, the interaction between natural fractures and hydraulic fractures has long been experimentally and computationally investigated. Here, we experimentally investigated the evolution of the fracturing network with a self-developed ultrasonic testing system. Laboratory experiments are proposed to study the propagation of hydraulic fracture in naturally fractured model blocks that contain random micro-fractures. Our analysis suggests that the total fracture width obtained by ultrasonic pulse velocity (UPV) can reflect the dynamic evolution of the fracturing network. The nonlinear fracturing network evolution process is closely related to the variation of the total fracture width. It is suggested from the total fracture width that the maximum fracture network can be realized with greater natural fracture density, large injection rate, and smaller stress ratio. The study presents a better insight into the response of random naturally fractured shale formation under hydraulic fracturing treatment by analyzing the variation of UPV in real time.     

Local normal height connection across sea with ship-borne gravimetry and GNSS techniques

Heights as the basic geographical information are very important to study marine geophysics, geodesy and oceanography. Based on the astronomical leveling principle, we put forward a new method to unify the normal height (NH) datum along one ship route across sea with the ship-borne gravimetry and global navigation satellite system (GNSS) techniques. Ship-borne gravimeter can precisely measure gravity anomalies and the GNSS technique is used to measure precise sea surface heights (SSHs) along the ship track across sea. Precisions of ship-borne gravities and SSHs are improved with the colinear adjustment. To remove the effects of sea wave and wind, the Gaussian filter is used to filter residuals both between the ship-borne and modeled gravities from EGM2008 to degree 2160, and the measured and modeled SSHs from DTM10MSS, respectively. Deflections of the vertical (DOVs) along the ship route are estimated from the measured gravities with the least squares collocation method. The astro-geodetic survey is made on continent and island to improve the accuracy of DOVs along the route. We use the new method to connect NHs on the coastal sea of Shandong Peninsula, China. The results indicate that the method is very efficient to precisely connect the NH along the ship route across sea.     

Applying image recording and identification for measuring water stages to prevent flood hazards

Information on river stages can be transmitted to relevant management offices over a network by using an automatic stage gauge so that management offices can effectively evaluate whether a river stage is exceeding the warning line and take action if necessary. However, current river stage measurement methods can present this information only in data form because the methods cannot simultaneously obtain images such as the rising or overflow of the river stage. In addition, the stage gauge can fail or be washed away when the river stage is high. To solve these problems, this research evaluates a novel measurement method involving a video surveillance system that exhibits features such as easy installation, low maintenance cost, and low failure possibility. Through on-site image recording, this measurement method involves using image identification technology to read water level figures automatically. This method offers instant river stage figures and on-site video so that disaster prevention measures can be implemented accordingly. The results of a dynamic water flow test conducted in an indoor experimental channel indicated that all of the average absolute error levels of river stage identification were less than ±1.2 %, meaning that the image identification technology could achieve identification results at any flow level. By contrast, the findings of a rainfall simulation experiment suggest that the average absolute error of river stage identification was less than ±2.5 %, meaning that the measurement technology and method used in this research are useful and feasible at various rainfall intensities.     

Crustacean zooplankton distribution patterns and their biomass as related to trophic indicators of 29 shallow subtropical lakes

A comparative limnological study was carried out to present a snapshot of crustacean zooplankton communities and their relations to environmental factors to test whether there is a consistent relationship between crustacean biomass and trophic indicators among lake groups with similar trophic conditions. The study lakes showed a wide range of trophic status, with total phosphorus (TP) ranging from 0.008 to 1.448 mg L⁻¹, and chlorophyll a from 0.7 to 146.1 μg L⁻¹, respectively. About 38 species of Crustacea were found, of which Cladocera were represented by 25 taxa (20 genera), and Copepoda by 13 taxa (11 genera). The most common and dominant species were Bosmina coregoni, Moina micrura, Diaphanosoma brachyurum, Cyclops vicinus, Thermocyclops taihokuensis, Mesocyclops notius and Sinocalanus dorrii. Daphnia was rare in abundance. Canonical correspondence analysis showed that except for four species (D. hyalina, S. dorrii, C. vicinus and M. micrura), almost all the dominant species had the same preference for environmental factors. Temperature, predatory cyclopoids and planktivorous fishes seem to be the key factors determining species distribution. TP was a relatively better trophic indicator than chlorophyll a to predict crustacean biomass. Within the three groups of lakes, however, there was no consistent relationship between crustacean biomass and trophic indicators. The possible reason might be that top-down and bottom-up control on crustaceans vary with lake trophic state. The lack of significant negative correlation between crustacean biomass and chlorophyll a suggests that there was little control of phytoplankton biomass by macrozooplankton in these shallow subtropical lakes.     

Calculating Pollution Indices by Heavy Metals in Ecological Geochemistry Assessment and a Case Study in Parks of Beijing

Pollution index is a powerful tool for ecological geochemistry assessment. The commonly used pollution indices by heavy metals in soils and sediments were classified as two types of single index and integrated index in an algorithm point of view. Four single indices of contamination factor (or concentration factor), ecological risk factor, enrichment factor, and index of geo-accumulation were illustrated, and the reference values for calculating single indices were distinguished into background levels and threshold pollution values. Eight integrated indices were divided into two groups. One group is suitable for the normal distribution single indices including the sum, average, weighted average,vector modulus, and Nemerow pollution indices, and the other for log-normal distribution including the product, root of product, and weighted power product pollution indices. Using background levels as reference values, five contamination classes were divided, and the terminologies are suggested for the single and integrated indices to unify the assessment results. Software of EGAPI was developed in a single document interface to calculate the four single and eight integrated indices by heavy metals to assess the quality of soil and sediment ecological geochemistry. Pollution indices by heavy metals of Cu,Pb, and Zn in soils in parks of Beijing were calculated using EGAPI software, and these five contamination classes and terminologies suggested in this study were evaluated and used. Results ofintegrated indices of Cu, Pb, and Zn in soils indicated that the soil qualities are unpolluted as a whole and varied from low polluted to unpolluted status from the center to the outskirts of Beijing City.     

苍山5.2Ms级地震前后地震前兆综合危险度的变化

地震前兆综合危险度是以系统论为基础的一种综合地震预报的新方法。利用山东省每年年底的地震会商报告给出的地震前兆异常,而不是取震后的震例总结或论文给出的异常,通过“专家系统”的思想,对每一异常事件进行综合评估,计算出无量纲的、归一化的地震前兆综合危险度,分析了１９９５年９月２０日山东苍山５２Ｍｓ级地震前综合危险度的变化特征。震前综合危险度出现了一次明显的高值异常变化,震后危险度很快下降恢复到正常水平。     

综合台站观测资料信息管理系统的技术特点

介绍了为配合闽南地震示范工程的开展而开发的《综合地震台观测资料信息管理系统》程序设计的基本原则、总体结构及功能,并给出了操作流程示意图和简要说明。     

大亚湾大鹏澳养殖海区水化学指标的变化及营养状况分析

根据 １９９４年 ７月和 １０月、１９９５年 １月和 ４月对大亚湾大鹏澳养殖海区的现场调查,统计了各水化学指标的变化范围和平均值;讨论了Ｎ／Ｐ值的季节变化;以ＣＯＤ、ＴＩＮ、ＰＯ~３－_４－Ｐ和Ｃｈｌ－ａ为分析指标,用营养状态质量指数（ＮＱＩ）分析了该海区的营养状态;并用叶绿素法估算了养殖海区的初级生产力。     

On crustal movement in Mt. Qomolangma area

Mt. Qomolangma lies in the collision zone between the fringe of Eurasia plate and Indian plate. The crustal movement there is still very active so far. In the past three decades China carried out five geodetic campaigns in Mt. Qomolangma and its north vicinal area, independently or cooperatively with other countries, including triangulation, leveling, GPS positioning, atmospheric, astronomical and gravity measurements. On the basis of the observation results achieved in the campaigns the crustal movements in the area were studied and explored. A non-stationary phenomenon both in time and space of the crustal vertical movement in the area is found. There seems to be some relevance between the phenomenon of non-stationary in time and seismic episode in China. The phenomenon of non-stationary in space is possibly relevant to the no-homo- geneity of crustal medium and non-uniform absorption of terrestrial stress. The horizontal crustal movement in the area is in the direction of NEE at a speed of 6–7 cm per year, and the trend of strike slip movement is manifested evidently in the collision fringe of Indian plate and Qinghai-Xizang block.