Shallow groundwater nitrogen responses to different land use managements in the riparian zone of Yuqiao Reservoir in North China

This field study investigated the nitrogen concentrations in the shallow groundwater from an ephemeral stream and four land uses： cropland, two-year restored （2yr） and five-years restored （Syr） woodlands, fishponds, and the nitrogen flux in the riparian zone of Yuqiao Reservoir. The groundwater nitrate-N concentrations in cropland were the highest among the four land uses. Total dissolved nitrogen （TDN） and nitrate-N concentrations in the 2yr woodland were significantly （p 〈 0.05） higher than in 5yr woodland. The lowest nitrogen concentrations were detected in fishponds. Nitrate-N was the main form in cropland and 2yr woodland, whereas both nitrate-N and dissolved organic nitrogen （DON） were the main species in 5yr woodland and fishponds. But, ammonium-N was the main form in the ephemeral stream. During the rainy season, the groundwater flow with dissolved nitrogen drains from upland into the reservoir along the hydraulic gradient. The woodland between the cropland and reservoir could act as a buffer to retain shallow groundwater nitrogen. The dominant form of ammonium-N in the groundwater TDN pool in ephemeral stream indicated that nitrogen from the village and orchard in upland flowed into the reservoir via subsurface flow. The fishpond was not an important pollution source for nitrogen transfer via shallow groundwater.

Predicting the height of water-flow fractured zone during coal mining under the Xiaolangdi Reservoir

It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40%of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model, which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and 14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.

Fractal characterization of sediment particle-size distribution in the water-level fluctuation zone of the Three Gorges Reservoir, China

The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landscape. Siltation, eutrophication, enrichment of heavy metals, and methane emissions in the WLFZ have been widely associated with sediment and soil particles generated from the upstream catchment or upland slopes. However, little attention has been paid to the complexity of sediment particle-size distributions in the WLFZ. In the present study, core samples(from a 345 cm thick sediment core from the base of the WLFZ), slope transect surface samples(across/up a WLFZ slope), and along-river/longitudinal surface samples(from the reservoir reaches) were collected. Laser granulometry and a volume-based fractal model were used to reveal the characteristics of sediment particle-size distributions. Results indicate that the alternation of coarse and fine particles in the sedimentary core profile is represented as a fluctuation of low and high values of fractal dimension(D), ranging from 2.59 to 2.77. On the WLFZ slope transect, surface sediment particles coarsen with increasing elevation, sand content increases from 3.3% to 78.5%, and D decreases from 2.76 to 2.53. Longitudinally, surface sediments demonstrate a downstream-fining trend, and D increases gradually downstream. D is significantly positively correlated with the fine particle content. We conclude that D is a useful measure for evaluating sediment particle-size distribution.

Estimation of soil reinforcement by the roots of four postdam prevailing grass species in the riparian zone of Three Gorges Reservoir, China

Soil erosion and bank degradation is a major post-dam concern regarding the riparian zone of the Three Gorges Reservoir. The development and succession of vegetation is a main countermeasure,especially to enhance bank stability and mitigate soil erosion by the root system. In this study, the roots of four prevailing grass species, namely, Cynodon dactylon, Hemarthria altissima, Hemarthria compressa, and Paspalum paspaloides, in the riparian zone were investigated in relation to additional soil cohesion. Roots were sampled using a single root auger. Root length density(RLD) and root area ratio(RAR) were measured by using the Win RHIZO image analysis system. Root tensile strength(TR) was performed using a manualdynamometer, and the soil reinforcement caused by the roots was estimated using the simple Wu's perpendicular model. Results showed that RLD values of the studied species ranged from 0.24 cm/cm3 to20.89 cm/cm3 at different soil layers, and RLD were significantly greater at 0–10 cm depth in comparison to the deeper soil layers(>10 cm). RAR measurements revealed that on average 0.21% of the reference soil area was occupied by grass roots for all the investigated species. The measured root tensile strength was the highest for P. paspaloides(62.26MPa) followed by C. dactylon(51.49 MPa), H.compressa(50.66 MPa), and H. altissima(48.81MPa). Nevertheless, the estimated maximum root reinforcement in this investigation was 22.5 k Pa for H.altissima followed by H. compressa(21.1 k Pa), P.paspaloides(19.5 k Pa), and C. dactylon(15.4 k Pa) at0–5 cm depth soil layer. The root cohesion values estimated for all species were generally distributed at the 0–10 cm depth and decreased with the increment of soil depth. The higher root cohesion associated with H. altissima and H. compressa implies their suitability for revegetation purposes to strengthen the shallow soil in the riparian zone of the Three Gorges Reservoir. Although the soil reinforcement induced by roots is only assessed from indirect indicators, the present results still useful for species selection in the framework of implementing and future vegetation recovery actions in the riparian zone of the Three Gorges Reservoir and similar areas in the Yangtze River Basin.

Protection and Ecological Restoration of Water Level Fluctuation Zone in the Three Gorges Reservoir

Water level fluctuation zone(hereinafter referred to as "WLFZ") is a transitional ecosystem between terrestrial ecosystem and aquatic ecosystem,and also a key area to control its neighboring terrestrial and aquatic ecosystem. After the Three Gorges Reservoir was put into use,ecological environment of its WLFZ has aroused wide concern from domestic and foreign experts. On the basis of introducing characteristics of WLFZ of the Three Gorges Reservoir,current ecological environment and main problems of this area were analyzed,plant selection and configuration was elaborated as well as the implementation effect of many WLFZ protection and ecological restoration modes. In view of the actual conditions,pertinent suggestions were proposed for WLFZ of the Three Gorges Reservoir,namely classified protection and ecological restoration,enhancing monitoring and assessment of current situation and change tendency,carrying out technical researches and demonstration of WLFZ wetland ecological restoration.

Reservoir Characteristics and Favorable Area Prediction of Chang-6 Reservoir in Zhouguan Area, Ordos Basin

Based on the analysis of a large number of core samples, logging results, logging interpretation data and dynamic data in the study area, the characteristics of Chang 6 reservoir in Zhouguan area of Baihe area are studied, and the favorable reservoir areas in the study area are predicted. The results show that the lithology of Chang 6 reservoir is mainly light gray and gray fine-grained to very fine-grained feldspar lithic sandstone. The pore types are mainly residual intergranular pores and feldspar dissolved pores, including debris dissolved pores and microfractures. The porosity and permeability values are low, which belongs to low porosity-low permeability and ultra-low permeability reservoirs. According to the reservoir distribution characteristics and related data, the Chang 6 reservoir in the study area is divided into two types, mainly Class II and Class III reservoirs. The comprehensive evaluation predicts that the spatial distribution of the favorable area of Chang 6 reservoir is not uniform, but the distribution area is large, which has broad exploration and development value, and provides the necessary conditions for the distribution study of the favorable oil-bearing zone in this area and the preparation for the next exploration and development.

苏北盆地溱潼凹陷古新统阜宁组二段侵入岩围岩变质带储层特征及其成藏意义

火山岩油气藏是油气勘探的重要领域之一。苏北盆地溱潼凹陷侵入岩分布广泛,油气显示活跃,已成为我国东部陆相盆地油气深化勘探和规模增储的重要领域,具备良好的勘探前景。然而,目前针对火山岩对泥页岩围岩储层及其成藏影响的研究较为缺乏,泥页岩围岩变质带能否作为勘探重点领域有待深入评价。为了推动苏北盆地侵入岩围岩变质带新类型油藏勘探,以溱潼凹陷阜二段侵入岩围岩变质带为研究对象,综合岩心、薄片、全岩、测井等资料,系统揭示了泥页岩变质带储层特征,明确了岩浆侵入对阜二段变质带油气成藏的贡献。研究表明,溱潼凹陷阜二段泥页岩受岩浆侵入影响,泥页岩围岩发生蚀变形成环状变质带储层,岩浆的侵入具有明显“增储作用”;变质带储层发育孔隙、裂缝两类储集空间,储层发育程度受侵入岩厚度及烘烤强度控制,岩浆的侵入具有“催熟作用”,同等深度下泥页岩Ro可增加0.4%~0.5%;阜宁组侵入岩形成于吴堡期—三垛期,火成岩侵入形成环状变质带的时间早于油气充注期,具有良好的成藏匹配关系。受岩浆侵入、侵入岩空间分布以及源储匹配关系控制,溱潼凹陷阜二段侵入岩围岩变质带具有源储一体、近源富集的特征,是规模增储的新阵地。

深层超深层油气藏高应力下数字岩心构建方法

深层超深层油气藏由于埋藏深,其地应力达200 MPa,会显著改变储层岩石孔隙的微观结构。数字岩心是孔隙尺度数值模拟的重要载体,但是现有数字岩心重构方法是基于常温常压下岩心的扫描图像重构,不能反映高应力下的孔隙结构。为此,提出了一种基于离散元法考虑高应力影响的数字岩心重构方法。首先,采用分水岭算法分割CT图像,利用球面谐波分析方法建立轮廓数据库,并在PFC^(3D)中建立Clump(团簇)模板库;然后,根据孔隙度和粒径分布使用模板库中的Clump建立离散元模型,并用两点相关和线性路径相关函数曲线评价模型的准确性;随后,标定颗粒间微观力学参数,并加载应力模拟得到不同应力下的数字岩心;最后,分析了不同应力下数字岩心的孔隙几何拓扑结构,计算孔隙度和渗透率。以Bentheim砂岩为例,构建了其不同应力下的数字岩心,研究结果表明,应力增大,导致孔隙和喉道半径缩小、喉道伸长、连通性变差、孔隙度和渗透率减小。研究结果为深层超深层油气藏孔隙尺度模拟提供了技术途径。

沾化凹陷垦西斜坡带沙河街组三段下亚段沉积特征及有利储层预测

垦西斜坡带构造处于沾化凹陷中部,孤岛潜山西南倾末端,西北为渤南洼陷,南边过垦西断层为三合村洼陷,是由孤西断层与一组近东西向垂直于孤西断层的断裂构建的“梳状断裂构造带”。研究区沙河街组三段下亚段油气充足,深部储层只要位于沟通油源的通道处,均有可能成藏。但早期研究认为该区沙河街组三段下亚段沉积类型为远源的三角洲水道沉积.

王洼煤矿水库坝体下工作面安全开采高度研究

为解决水库坝体下开采安全性,提高煤炭资源回收率,以王洼煤矿水库坝体下110505工作面为研究背景,通过物理仿真模拟、数值模拟及理论分析等方法对覆岩裂隙发育规律及导水裂隙带高度展开研究。为避免矿井开采对地表水坝与水体破坏,针对导水裂隙带高度分析结果,提出了110505工作面限高开采方案。结果表明:工作面开采后地表形成“凹”型盆地,并产生拉伸裂隙,致使地表水位下降78%;现场实测导水裂隙高度为170.76 m,物理仿真模拟试验、数值计算、传统经验公式得出三者的导水裂隙带高度分别为162,164 m和120.57 m;方差修正系数对经验公式做出修正后,反推出限高开采的安全开采高度为2.6 m。研究揭示了工作面覆岩导水裂隙带高度发育规律及水库水体受采动影响的规律,为王洼煤矿后续此类条件下安全措施的制定提供了依据。

倾角测井资料在冷湖地区含气储层评价中的应用

柴达木盆地北缘山前带存在着一套以侏罗系煤系烃源岩为主的含气储层,沿着冷湖构造带呈条带状展布,已成为天然气勘探的重要领域。目前,关于冷湖地区气层解释评价研究往往集中在岩性及孔隙结构评价方面,针对含气储层与浅表滑脱断层的关系研究相对匮乏。利用地层倾角资料解释处理,首先对比四类软件进行处理参数优选,然后综合地震剖面及测录井资料,多井对比明确了含气储层与断裂带的关系,研究揭示了含气显示集中段主要分布在滑脱断层带下盘,且距离断点位置越近,具有含气性越好的特征,这一认识有效支持了老井复查挖潜工作并取得实效。

定边油田油房庄区延9_(3)地质特征研究及有利区预测

定边油田油房庄区主要含油层位延9_(3)、长4+5_(2),该区北部延9_(3)油藏早在上世纪90年代就投入开发,南部则在2010年以后开始开发,但由于种种原因,只是零星动用,并未规模开发。目前,该区面积大,井数少,地质认识不清,且存在生产井产能低、注采井网不完善、水驱控制程度和油藏动用程度较低等开发难题,油藏特征及富集规律认识有待进一步深化。因此,在油田开发方案制定前,需开展该区延9_(3)油层组地质特征研究,为开发方案的制定提供技术支撑。

基于Markov模型的三峡上游消落带土地利用变化预测

三峡水库蓄水后形成高程差30 m的消落带,以蓄满水位175 m为基准水平外扩150 m得到交错缓冲区。缓冲区土地利用情况较复杂,本研究通过研究库区上游缓冲区近20年土地利用的变化情况,分析前20年上游发展模式。通过马尔可夫函数来预测未来20年的土地利用变化可能,为上游区域未来规划发展方向提出建议。研究表明:(1)上游在发展过程中持续紧抓农业用地,可按目前的模式继续发展;(2)生态方面,森林、灌丛、草地等与生态环境相关的地类占比是有所提高的,目前发展政策是有利生态环境的,但由于水域面积增长导致裸岩增加,水土流失风险增加,需更加重视水土流失的防治;(3)经济发展与城镇化密切相关,城乡建设用地与道路占比不断上升,上游经济形势一片大好。综合来说,可按照2000~2020年的发展模式继续开发建设,但应在此基础上更加重视经济与环境的协同发展,尽量建设森林城市,通过工程护坡、生态护坡等技术来加强两岸土地的水土保持力度。

珠江口盆地深水区古潜山强风化淋滤带储层分布规律及其主控因素

珠江口盆地深水区古潜山钻井资料极少,严重制约了古潜山有利储层的预测和天然气勘探进程。为此,以该盆地白云凹陷东部古潜山为例,综合利用井资料和高精度三维地震数据,对该古潜山的强风化淋滤带储层分布进行了重点解剖,在明确其储层微观和测井响应特征的基础上,通过井—震标定,依托高精度三维地震数据揭示了古潜山强风化淋滤带储层的分布规律,并探讨其主控因素。研究结果表明:①古潜山强风化淋滤带储层具有低密度的测井响应特征,其内部斜长石和云母等矿物严重蚀变,斜长石内的裂缝因强烈的溶蚀改造变宽和不同程度弯曲;②古潜山强风化淋滤带储层在地震剖面上呈空白反射,且具有明显的垂向非均质性,分布在古潜山现今地貌西部的高点和东部的斜坡上;③在始新世早期及其之前,该区古潜山均位于古地貌高点,长期的强风化淋滤作用有效地促进了强风化淋滤带的形成,中—晚始新世,东强西弱的差异伸展导致西部强风化淋滤带仍处于地貌高点,而东部则由于断块旋转和岩浆底侵导致的抬升转变为现今的斜坡部位。结论认为,大气降水沿古潜山内幕断裂的差异渗流导致了差异风化,造就了古潜山强风化淋滤带储层的垂向非均质性;古地貌是主控古潜山强风化淋滤带储层东西差异分布的主要因素。

高强度堵剂优化及其在高含水油藏靶向调堵中的应用

针对河南油田高渗高凝特高含水砂岩油藏,对双激发无机堵剂的配方优化、耐温耐盐性能、封堵性能、耐冲刷性能、粒径匹配等多方面进行系统研究。结果表明,缓凝剂和离子平衡剂是控制体系凝固时间的主导因素,随着主剂与激发剂浓度以及温度的增加,双激发无机堵剂固结速度增大。配液水中矿化度较高时,硫酸根和氯盐会加快体系固结时间。双激发无机堵剂封堵能力强,耐冲刷能力和深部液流转向效果较好,可对高渗透层大孔道有效封堵,提高低渗岩芯分流率,其封堵率高于98.5%。现场应用效果证实,双激发无机堵剂能够实现深部靶向封堵,具有强度高、有效期长、成本低等优点,调堵后含水率大幅下降。

水库近坝高位滑坡滑带抗剪强度参数综合确定研究

滑坡滑带的抗剪强度参数是进行滑坡稳定性评价和滑坡涌浪等灾害链研究必需的数据基础,科学合理确定滑带物理力学参数至关重要.本研究以澜沧江GS水电站MLS滑坡为依托,采用现场调查、大型原位剪切试验、室内重塑样剪切试验、室内原状样剪切试验、工程地质类比法及参数反分析法,综合确定滑带抗剪强度参数.采用数值模拟软件运用所得参数对滑坡进行变形破坏分析.数值计算结果与现场滑坡监测变形数据相吻合,验证了采用多方法综合选取滑带抗剪强度参数的准确性和合理性.研究成果可为MLS滑坡稳定评估和防治工程设计等提供技术支撑和参考借鉴依据.

塔里木盆地顺北1号断裂带奥陶系碳酸盐岩储层结构表征及三维地质建模

综合利用地震、测井、岩心以及动态生产资料,对塔里木盆地顺北1号断裂带断控型碳酸盐岩储集体的内部结构进行了层级划分;基于层级划分,通过地震资料属性提取与转换、深度学习、基于目标示性点过程模拟以及离散裂缝网络模拟(DFN)等方法建立了三维地质模型,并以模型进行油气储量和油藏数值模拟,将拟合结果与实际生产数据进行对比。研究结果表明:(1)顺北1号断裂带奥陶系断控型储层按层级由大到小分为走滑断裂影响带、断控体、类洞穴、类洞穴内簇充填和裂缝带共5个层级。(2)走滑断裂影响带受应力差异影响具有分段性,可细分为挤压段、拉分段和平移段;断控体在拉分段发育断裂交会型、单支走滑型,在平移段发育双断裂交错型和两断裂交会型,在挤压段发育双断裂扭曲型和双断裂交会型,共有6种平面组合样式;类洞穴在地震剖面上呈串珠状反射特征;类洞穴内部分为栅体与栅间(基岩),其中栅体又可进一步分为簇(角砾带)、簇间(裂缝带),整体表现为栅状结构,簇的物性更好;裂缝带为类洞穴的主要储集空间,在簇内部比簇间更发育,在一间房组比鹰山组更发育,一间房组和鹰山组均以发育高角度裂缝为主,在两者连接处则以发育水平缝为主。(3)地质模型预测的油气储量与地质分析储量误差为1.75%,模型模拟的生产井地层压力及累产液结果与生产动态吻合度较高,拟合误差小于10%。

太行山东南麓断裂带水文地球化学特征及水热成因模式

太行山东南麓断裂带发育,赋存丰富的中低温地热资源,然而,该地区深部地热水的水热成因模式依然不清楚。通过55组地热水和38组浅层地下水的水化学组分特征,研究离子组分来源及其运移规律,并借助同位素特征分析地热水补给来源,在此基础上分析深部热储的水岩平衡状态、热储温度和热循环深度。结果表明:研究区属对流—传导复合型地热系统,地热水整体处于氧化环境,离子组分以HCO_(3)^(-)和Na^(+)为主,主要受盐岩和碳酸盐岩等矿物的溶解及阳离子交替吸附作用控制;地热水的补给高程为1010~1153m,表明地热水补给区位于太行山东南麓西部的太行山地区;地热水循环深度范围为1125~4468 m;混合比例法估算汤阴断陷深层热储温度达到110~160℃,而汤阴断陷东部的内黄凸起地区为80~110℃,二者热储温度差别源自汤阴断陷两侧深切地幔的汤东、汤西深大断裂导热导水条件良好,以及内黄凸起的基岩埋深较浅,上伏盖层薄,热能更容易散失。本研究揭示了太行山东南麓地热系统的水文地球化学特征和水热成因模式,为该区地热资源开发利用提供重要依据。

基于分形理论的三峡库区消落带岸线形态特征研究

以消落带为基础数据,采用网格法计算了不同水位及各段岸线的分形维数,对其分布特征和空间分布规律进行了研究。结果表明:(1)145 m水位岸线、175 m水位线和消落带整体形态的分维值D分别为1.1996,1.3216,1.3192;(2)消落带145 m水位线相对于175 m水位线和消落带整体形态而言,相对平直简单,与岸线实际情况相符合;(3)消落带网格单元分维值整体均值为1.24,最大值为1.40,主要分布在1.05~1.3之间。