Multi-tier interactive genetic algorithms for the optimization of long-term reservoir operation

Genetic algorithms (GAs) are well known optimization methods. However, complicated systems with high dimensional variables, such as long-term reservoir operation, usually prevent the methods from reaching optimal solutions. This study proposes a multi-tier interactive genetic algorithm (MIGA) which decomposes a complicated system (long series) into several small-scale sub-systems (sub-series) with GA applied to each sub-system and the multi-tier (key) information mutually interacts among individual sub-systems to find the optimal solution of long-term reservoir operation. To retain the integrity of the original system, over the multi-tier architecture, an operation strategy is designed to concatenate the primary tier and the allocation tiers by providing key information from the primary tier to the allocation tiers when initializing populations in each sub-system. The Shihmen Reservoir in Taiwan is used as a case study. For comparison, three long-term operation results of a sole GA search and a simulation based on the reservoir rule curves are compared with that of MIGA. The results demonstrate that MIGA is far more efficient than the sole GA and can successfully and efficiently increase the possibility of achieving an optimal solution. The improvement rate of fitness values increases more than 25%, and the computation time dramatically decreases 80% in a 20-year long-term operation case. The MIGA with the flexibility of decomposition strategies proposed in this study can be effectively and suitably used in long-term reservoir operation or systems with similar conditions.     

Intensive Observation of Reservoirinduced Seismicity and Preliminary Analysis on the Causes of Earthquakes in the Three Gorges Reservoir Area,Yangtze River

In accordance with the requirements of the National Key Technology R&D Program of the 11th "Five-year Plan",a densified seismic network consisting of 26 seismic stations was established at the Three Gorges Reservoir area in the section of Hubei Province in March 2009(21 short-period seismographs,5 broadband digital seismographs).From March to December,2009,a total of 2,995 ML-0.8~2.9 earthquakes were detected during the trial impounding of the Three Gorges Reservoir(water level rose from 145 m to 172.8m).Using the double difference earthquake location algorithm,2,837 earthquakes were precisely re-located.The results show that the pattern of small local earthquake swarms in the Three Gorges Reservoir area took on a linear distribution or mass-like cluster distribution,the mass-like clusters of events were generally within a distance of 5 km from waterfront,and the linear distribution of the earthquakes could be extended to a distance of 16 km away from the waterfront.In the Hubei section of the Three Gorges Reservoir,earthquakes were mainly concentrated in the northern end of the Xiannvshan and Jiuwanxi faults near the Xiangxihe River,and along the banks of the Yangtze River at the west of Xietan township and the Shenlongxi area on the northern bank in the Badong region,with focal depths less than 10km,and 4km in average.Earthquake frequency in the reservoir region had a positive correlation with reservoir water level fluctuations,indicating that the seismicity belongs to reservoir induced earthquakes.Along the Shenlong River in the reservoir area,earthquakes showed three linear distributions in the northern Badong county,and distributed according to Karst distribution.There are underground rivers in the carbonate strata.When the reservoir was impounded,water permeated into the underground rivers,thus inducing earthquakes.Earthquakes in the areas on the cross-river segment of Xiannvshan fault,the Jiuwanxi fault and at the areas west of Xietan,Shazhen and Xizhen,may be related to the softening of discontinuities,such as the Nukou fault,the Xiannvshan fault,or the bedding joints,which would lead to failure of rock masses,thus,inducing earthquakes.However,convincing conclusions about the triggering mechanism still need further study.Additionally,near the areas south of Wenhua and Yanglin of Zigui county and at Rangkou town east of Badong county,mining-induced earthquakes occurred at the mines nearby,and on the shores of the reservoir are some collapse earthquakes.     

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孔隙结构对低渗-特低渗砂岩储层渗流特征的影响段储层为例——以鄂尔多斯盆地东部上古生界盒8段储层为例

通过铸体薄片显微镜下观察、孔喉图像、毛细管压力、恒速压汞、气水相对渗透率、核磁共振等多种分析实验手段,研究了鄂尔多斯盆地东部上古生界盒8段低孔、低渗-特低渗砂岩储层的微观孔隙结构和渗流特征,探讨了孔隙结构对储层渗流特征的影响。结果表明,孔隙结构特征是影响低孔、低渗-特低渗砂岩储集性能与渗流特征的主要因素。而砂岩的孔隙结构特征主要受砂岩原生矿物组合与成岩演化过程及其产物的控制,盒8段各砂岩类型由于其矿物成分不同导致孔隙结构的差异,也是各砂岩类型储集性能与渗流能力存在差别的直接原因。在孔隙结构参数中,喉道的大小、有效孔隙与喉道的体积及其连通性是决定储层储集与渗流能力的关键。大孔喉对储层渗流能力的贡献更大,中-小孔喉则对储集能力的贡献相对较高。微裂缝是除孔隙结构以外影响砂岩储集性能与渗流特征的重要因素。     

浅水湖盆三角洲储层构型模式探讨

针对浅水湖盆三角洲储层构型模式研究的不足,在考察鄱阳湖现代浅水湖盆三角洲沉积和解剖扶余油田扶余油层古代浅水湖盆三角洲储层构型的基础上,综合应用卫星照片、岩心、测井等资料,建立了浅水湖盆三角洲平原分流河道和三角洲前缘水下分流河道的沉积构型模式。研究结果表明:浅水湖盆三角洲主要发育三角洲平原上部曲流型分流河道、三角洲平原下部顺直型分流河道和三角洲前缘顺直型水下分流河道3种砂体类型,曲流型分流河道主要为侧积的点砂坝沉积构型模式,顺直型分流河道主要为垂积的心滩坝沉积构型模式,顺直型水下分流河道主要为垂积的分流砂坝沉积构型模式。同时从沉积亚相、砂体几何形态、夹层倾向及倾角、废弃河道、决口扇、粒度分析等几个方面总结了不同类型的分流河道及水下分流河道砂体的判别标志,为浅水湖盆三角洲储层内部构型及地质建模研究工作奠定了基础。     

准噶尔盆地中-东部石炭系火山岩储集空间特征研究

通过岩心观察、显微鉴定、扫描分析和成像测井等对准噶尔盆地火山岩油气储层的储集空间进行系统分类并分析其组合特征。结果表明,准噶尔盆地火山岩储层的储集空间可划分为原生孔隙、次生孔隙和裂缝3大类,进一步可细分出4种原生孔隙、5种次生孔隙和4种裂缝。其中,次生孔隙和裂缝对火山岩储集性能的改善具关键作用;储集空间组合类型包括构造缝-溶蚀缝-溶孔组合、原生气孔-构造缝-溶蚀缝-溶蚀孔组合和晶间孔-原生孔-构造缝-溶蚀孔组合等3种类型;孔缝组合整体表现为类型多样、形态各异、结构复杂、分布不均、连通性差、裂缝改善明显等特点。     

海河流域大型水库饮用水水源地水环境安全评价及应用

对水库型水源地水环境安全评价的理论和方法进行研究,构建了基于驱动力-压力-状态-影响-风险模型(DPSIR)的水库型水源地水环境安全评价指标体系,综合评价指标体系包括了降水、污染物入库量、水质状态指标、水质达标率以及水华爆发影响因子5个方案,11项指标。将该指标体系应用于岳城水库水环境安全评价,其结论主要有:(1)该模型的驱动力是降水带入面源污染,压力是流域输入水库的污染负荷,状态指标是TN、TP以及COD_Mn等水质参数,影响指标是水库水质达标率,风险指标则是氮磷比、水温等;(2)岳城水库4、5、6和9月处于较安全状态,但由于受地表径流污染负荷影响,在7、8月处于预警状态。将评价结果与实际水环境安全状况进行比较,吻合程度好,因此该模型可应用于海河流域大型水库饮用水水源地水环境安全评价。     

双塔水库水质对人类活动的响应分析

选取1993～2008年瓜州县人类活动数据及双塔水库水质指标年平均值进行主成分分析,去除冗余信息后进行多元线性回归分析,得到四组反映人类活动对水库水环境影响情况的回归方程。说明对双塔水库水质起主要影响作用的是农业活动和因农业活动引起的土地利用变化,农业活动的非点源污染是水库水质的主要污染源,水库水质仍存在富营养化的风险;工业活动对水库水质的影响没有在回归方程中体现出来。在农业活动过程中,耕地面积每增加10 000亩促使pH值上升0.062、溶解氧值下降0.046、高锰酸钾指数上升0.103、COD值上升0.617;而每增加10 000t的氮肥施用量会引起pH值升高1.837;总人口每增加1万人,COD值上升0.798。     

2003年3月北大西洋上两个爆发性气旋的“吞并”过程及发展机制分析

本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)提供的0.125(°)×0.125(°)的ERA-Interim再分析资料、美国国家航空航天局(National Aeronautics and Space Administration,NASA)提供的MODIS(Moderate Resolution Imaging Spectroradiometer)可见光云图、气象卫星合作研究所(Cooperative Institute for Meteorological Satellite Studies,CIMSS)提供的GOES-EAST红外卫星云图等资料以及WRF(Weather Research and Forecasting)数值模式的模拟结果,对2003年3月北大西洋上一个爆发性气旋B“吞并”另一个气旋A后快速发展机制进行了分析。气旋A和B均生成于美国东部,气旋A于2003年3月5日06 UTC生成,气旋B于6日00 UTC生成,且比气旋A向东北方向移动得更快,7日18 UTC达到最大加深率3.27 hPa·h^-1。在北大西洋中部地区,从8日00 UTC开始,气旋B吞并气旋A后形成气旋C,8日12 UTC气旋C中心气压达到最低值938.3 hPa。高空急流、低空水汽输送和潜热释放为气旋A和气旋B的快速发展提供了有利的环流背景场。气旋B吞并气旋A的过程经历三个阶段:前期阶段、吞并阶段、完成阶段。利用WRF模式模拟结果的分析表明,气旋A和B之间建立水汽输运通道,水汽从气旋A向气旋B输送。气旋B吞并气旋A后形成气旋C快速发展的主要原因是暖平流的作用。     

长周期潮汐与全球地震能量释放

采用1850-2012年期间USGS全球M≥5.0地震目录资料,构成全球地震能量-时间序列,进行小波变换和准周期分析. 结果表明,全球地震能量释放的时间序列存在9年、19年和45年的3个准周期,其中,45年准周期最为突出. 结合起潮力周期的物理背景,对长周期潮汐起潮力与地震能量释放准周期的关系进行了探讨,没有发现全球地震活动的能量释放与潮汐短周期相关的准周期.