Safety assessment for dams of the cascade reservoirs system of Lancang River in extreme situations

Numerous dams have been constructed in the midstream and downstream regions of Lancang River, which form a complex cascade reservoirs system. The safety of dams is critical for water resource management of the whole system. To check the safety of dams, this study used the MIKE 11 model to simulate flood routing along the Lancang River from Xiaowan dam to Jinghong dam under extreme situations of 100-, 500-, 1000-, 5000-, and 10,000-year design floods throughout the whole cascade reservoirs system. The design flood events used as the input for the MIKE 11 model contains the design flood hydrograph of the upstream reservoirs and corresponding flood hydrographs of the intermediate areas. The design flood hydrograph of the upstream reservoirs was obtained using the Equal Frequency Factor Method, and the corresponding flood hydrograph of the intermediate areas was obtained using the Equivalent Frequency Regional Composition Method. The results show that all dams are safe for the 100-, 500-, 1000-, and 5000-year design flood situations throughout the whole cascade reservoirs system, whereas the Manwan and Jinghong dams have a risk of overtopping under a 10,000-year design flood. The curves showing the relationship between the highest water level and return period for the dams are also presented.     

塔里木盆地库车坳陷烃源岩生成甲烷的动力学参数及其应用

根据压力下黄金管封闭体系热模拟实验结果 ,应用 Kinetics和 GOR- Isotope Kinetics专用软件 ,获得了塔里木盆地库车坳陷三叠系—侏罗系烃源岩的生烃动力学参数及碳同位素动力学参数。库车坳陷侏罗系煤、煤系泥岩及三叠系泥岩热解生成甲烷具有各自的活化能分布范围 ,分别是 197～ 2 6 8k J/ mol、180～ 2 6 0 k J/ mol、2 14～2 89k J/ m ol,频率因子各为 5 .2 6 5× 10 1 3s- 1、9.76 1× 10 1 1 s- 1、2 .2 70× 10 1 4s- 1 ,反映它们的生烃行为有所差异 ;其相应的碳同位素动力学参数也有差别 ,平均活化能分别是 2 2 8k J/ mol、2 0 5 k J/ mol、2 31k J/ mol。在此基础上 ,应用这些动力学参数 ,并结合地质背景 ,进一步探讨了依南 2气藏天然气的成因和运聚成藏模式。研究表明 ,依南 2气藏天然气主要来源于库车坳陷阳霞凹陷中心侏罗系煤系烃源岩 ,主要聚气时间为 5～ 0 Ma,对应 Ro 为 1.2 5 %～ 1.95 % ,天然气散失率为 2 5 %～ 30 %。该研究对塔里木盆地 ,乃至我国其他地区天然气藏的成因评价与成藏过程研究具有参考和借鉴意义。     

松南油伴生CO2气的成因及其对油气藏的影响

以松辽盆地南部长岭断陷油伴生气和含片钠铝石砂岩为对象,研究松南伴生CO2气的成因,并在此基础上,讨论幔源-岩浆CO2混入对油气动态成藏的影响。通过对伴生气组分,碳、氧及氦同位素数据的分析,发现松南油伴生CO2气的体积分数为1.57%～75.25%,主体在20%以上,δ13 CCO2值为-9.90‰～-4.00‰,R/Ra为0.95～4.46,说明松南油伴生气中CO2的体积分数很高,伴生CO2气主体为幔源-岩浆成因。如果幔源-岩浆CO2气大量混入油藏,将发生CO2驱油,形成次生油气藏。由松南油气藏的典型剖面特征及片钠铝石中原生烃类包裹体的发现,证实松南存在幔源-岩浆CO2驱油的事实。在幔源-岩浆CO2与油气混合成藏地区,寻找幔源-岩浆CO2充注驱油成因的次生油气藏已成为新的勘探思路。     

Evidence of return of chum salmon released from Tangwang River by strontium marking method

In order to assess the effect of enhancement release of chum salmon (Oncorhynchus keta), otolith strontium (Sr) marking method was used to tag chum salmon released in Tangwang River in 2016. The homing chum salmon were detected and the samples were collected in Tangwang River, Ussuri River and Suifen River in the autumn of 2018. The samples were analyzed by examining Sr and calcium (Ca) fingerprints in the otolith using electron probe microanalysis. The results suggested that two samples collected in Tangwang River had the marking ring near the core of otolith where the Sr concentration and Sr/Ca ratio were significantly higher than comparative samples. Proving that the two fish belonged to the released population in Tangwang River in 2016. This article indicated the success of the enhancement release of chum salmon from the Tangwang River for the first time and also confirmed the validity of Sr marking in enhancement release of fishes.     

松辽盆地上白垩统青山口组介形虫群集性死亡事件成因

松辽盆地上白垩统青山口组发育含大量介形虫化石的介形虫层,介形虫层的单层厚约5～200cm。介形虫层具有低伽马、高电阻、低声波等测井响应特征。以测井资料识别介形虫层为基础,研究了介形虫层在平面上不同相带及其在纵向高频层序格架下的分布规律,探讨了介形虫群集性死亡的原因。介形虫层平面上主要分布在大庆、龙虎泡—红岗阶地、黑帝庙等环坳带,盆地东部相对不太发育,滨浅湖是介形虫生存的有利环境;纵向上主要分布在青一段上部及青二段。高频层序旋回控制了介形虫的繁殖与死亡,介形虫群集性死亡事件主要发生在基准面下降期间。介形虫的群集性死亡与湖泊面积扩大无关,更与海侵事件无关。基准面下降造成水体变浅、矿化度增高以及砂岩进入滨浅湖可能是导致介形虫群集性死亡的直接原因。     

Theoretical study on the reactivity of sulfate species with hydrocarbons

The abiotic, thermochemically controlled reduction of sulfate to hydrogen sulfide coupled with the oxidation of hydrocarbons, is termed thermochemical sulfate reduction (TSR), and is an important alteration process that affects petroleum accumulations in nature. Although TSR is commonly observed in high-temperature carbonate reservoirs, it has proven difficult to simulate in the laboratory under conditions resembling nature. The present study was designed to evaluate the relative reactivities of various sulfate species in order to provide greater insight into the mechanism of TSR and potentially to fill the gap between laboratory experimental data and geological observations. Accordingly, quantum mechanics density functional theory (DFT) was used to determine the activation energy required to reach a potential transition state for various aqueous systems involving simple hydrocarbons and different sulfate species. The entire reaction process that results in the reduction of sulfate to sulfide is far too complex to be modeled entirely; therefore, we examined what is believed to be the rate limiting step, namely, the reduction of sulfate S(VI) to sulfite S(IV). The results of the study show that water-solvated sulfate anions are very stable due to their symmetrical molecular structure and spherical electronic distributions. Consequently, in the absence of catalysis, the reactivity of is expected to be extremely low. However, both the protonation of sulfate to form bisulfate anions () and the formation of metal-sulfate contact ion-pairs could effectively destabilize the sulfate molecular structure, thereby making it more reactive.Previous reports of experimental simulations of TSR generally have involved the use of acidic solutions that contain elevated concentrations of relative to . However, in formation waters typically encountered in petroleum reservoirs, the concentration of is likely to be significantly lower than the levels used in the laboratory, with most of the dissolved sulfate occurring as , aqueous calcium sulfate ([CaSO₄]_(aq)), and aqueous magnesium sulfate ([MgSO₄]_(aq)). Our calculations indicate that TSR reactions that occur in natural environments are most likely to involve bisulfate ions () and/or magnesium sulfate contact ion-pairs ([MgSO₄]_CIP) rather than ‘free’ sulfate ions () or solvated sulfate ion-pairs, and that water chemistry likely plays a significant role in controlling the rate of TSR.     

Groundwater recharge and discharge in a hyperarid alluvial plain (Akesu,Taklimakan Desert,China)

Groundwater recharge and discharge in the Akesu alluvial plain were estimated using a water balance method. The Akesu alluvial plain (4842 km²) is an oasis located in the hyperarid Tarim River basin of central Asia. The land along the Akesu River has a long history of agricultural development and the irrigation area is highly dependent on water withdrawals from the river. We present a water balance methodology to describe (a) surface water and groundwater interaction and (b) groundwater interaction between irrigated and non‐irrigated areas. Groundwater is recharged from the irrigation system and discharged in the non‐irrigated area. Uncultivated vegetation and wetlands are supplied from groundwater in the hyperarid environment. Results show that about 90% of groundwater recharge came from canal loss and field infiltration. The groundwater flow from irrigated to non‐irrigated areas was about 70% of non‐irrigated area recharge and acted as subsurface drainage for the irrigation area. This desalinated the irrigation area and supplied water to the non‐irrigated area. Salt moved to the non‐irrigation area following subsurface drainage. We conclude that the flooding of the Akesu River is a supplemental groundwater replenishment mechanism: the river desalinates the alluvial plain by recharging fresh water in summer and draining saline regeneration water in winter. Copyright © 2007 John Wiley & Sons, Ltd.     

活动造山带地区河流阶地与下切速率及其时空分布样式

河流下切带动区域地貌的演化,因此河流下切速率及其时空分布样式是解析构造、地表过程和气候变化之间广泛相互作用的关键切入点之一。根据阶地的保存状况,利用河流阶地的累积下切量和下切时间可以直接测得千年到百万年时间尺度的下切速率。鉴于此河流下切速率是链接不同时间和空间尺度上地貌侵蚀速率的关键所在,并具有较精细的时空分辨率。计算河流下切速率时,累积下切量上限是阶地基座的拔河高度,下界最优选择是低级阶地基座,而累积下切时间的最佳约束是尽量靠近阶地基座的冲洪积物的沉积时间;运用河流下切速率获得岩石抬升速率和区域构造变形量时,通常假定区域地貌处于均衡状态,河流下切速率代表着岩石抬升速率。但是由于气候变化,河流下切过程具有较强的时空不稳定性,导致这些假设经常失效。此外,河流加积和下切的转换与第四纪冰期-间冰期的变化并不一定存在时间上的一一对应关系,这可能是由于河流裂点的溯源迁移以及河流对气候变化的响应方式与强度存在差异。因此,实际工作中需要多方面获得不同时空尺度和分辨率的构造变形、气候变化以及地表过程的基本信息,借助地貌数值模拟程序,定量解析构造、气候和地表过程之间的广泛而复杂的相互作用。

     

2005年11月26日九江—瑞昌5.7级地震浅析

对赣北及邻区2014年以来的地震条带及视应力进行了分析。结果表明：江西丰城—安徽蒙城2014年10月—2015年6月快速形成M_L≥3.0地震条带,地震条带及周边地区的视应力均值为0.49 MPa,条带上的地震视应力高于条带以西地区,低于条带以东的江苏北部地区。2009年4月以来江西瑞昌—南黄海出现M_L≥4.0地震条带,条带及周边地区的视应力均值为1.72 MPa,条带上的视应力水平高于条带外。视应力总体呈现随震级增大而增大的特点。