Design and operation problems related to water curtain system forunderground water-sealed oil storage caverns

The underground water-sealed storage technique is critically important and generally accepted for the national energy strategy in China. Although several small underground water-sealed oil storage caverns have been built in China since the 1970s, there is still a lack of experience for large-volume underground storage in complicated geological conditions. The current design concept of water curtain system and the technical instruction for system operation have limitations in maintaining the stability of surrounding rock mass during the construction of the main storage caverns, as well as the long-term stability. Although several large-scale underground oil storage projects are under construction at present in China, the design concepts and construction methods, especially for the water curtain system, are mainly based on the ideal porosity medium flow theory and the experiences gained from the similar projects overseas. The storage projects currently constructed in China have the specific features such as huge scale, large depth, multiple-level arrangement, high seepage pressure, complicated geological conditions, and high in situ stresses, which are the challenging issues for the stability of the storage caverns. Based on years’ experiences obtained from the first large-scale （millions of cubic meters） underground water-sealed oil storage project in China, some design and operation problems related to water curtain system during project construction are discussed. The drawbacks and merits of the water curtain system are also presented. As an example, the conventional concept of “filling joints with water” is widely used in many cases, as a basic concept for the design of the water curtain system, but it is immature. In this paper, the advantages and disadvantages of the conventional concept are pointed out, with respect to the long-term stability as well as the safety of construction of storage caverns. Finally, new concepts and principles for design and construction of the underground water-sealed oil storage caverns are proposed.

Key issues in water sealing performance of underground oil storage caverns: Advances and perspectives

Water sealing performance is important for underground water-sealed oil storage(UWSOS).The key issues concerning water sealing performance mainly include the permeability of fractured rock mass(FRM),water-sealed safety(WSS),water curtain performance,and prediction and control of water inflow.This paper reviews the progress of above four key issues on water sealing performances.First,the permeability of an FRM is the basis of water sealing performance,and several commonly used permeability test methods and spatial variation characteristics of permeability are outlined.Second,the current water sealing criteria are compared,and the evaluation methods of WSS are summarized.Third,the design parameters and efficiency evaluation of water curtain systems(WCSs)are introduced.The water inflow of oil storage caverns(OSCs)can reflect the water sealing effect,and the prediction methods and control measures of water inflow are also summarized.Finally,the advantages and disadvantages of the current research are discussed,and the potential research directions are pointed out,such as optimization of water sealing criteria and FRM model,quantitative evaluation of WCS efficiency,accurate prediction of water inflow,and improvement of grouting technology.

Experimental study of water curtain performance for gas storage in an underground cavern

An artificial water curtain system is composed of a network of underground galleries and horizontal boreholes drilled from these galleries.Pre-grouting measures are introduced to keep the bedrock saturated all the time.This system is deployed over an artificial or natural underground cavern used for the storage of gas（or some other fluids） to prevent the gas from escaping through leakage paths in the rock mass.An experimental physical modeling system has been constructed to evaluate the performance of artificial water curtain systems under various conditions.These conditions include different spacings of caverns and cavern radii located below the natural groundwater level.The principles of the experiment,devices,design of the physical model,calculation of gas leakage,and evaluation of the critical gas pressure are presented in this paper.Experimental result shows that gas leakage is strongly affected by the spacing of water curtain boreholes,the critical gas pressure,and the number and proximity of storage caverns.The hydraulic connection between boreholes is observed to vary with depth or location,which suggests that the distribution of water-conducting joint sets along the boreholes is also variable.When designing the drainage system for a cavern,drainage holes should be orientated to maximize the frequency at which they encounter major joint sets and permeable intervals studying in order to maintain the seal on the cavern through water pressure.Our experimental results provide a significant contribution to the theoretical controls on water curtains,and they can be used to guide the design and construction of practical storage caverns.

A study of water curtain parameters of underground oil storage caverns using time series monitoring and numerical simulation

Water curtain systems(WCSs)are key components for the operation of underground oil storage caverns(UOSCs)and their optimization and design are important areas of research.Based on the time series monitoring of the first large-scale underground water-sealed storage cavern project in China,and on finite element analysis,this study explores the optimum design criteria for WCSs in water-sealed oil caverns.It shows that the optimal hole spacing of the WCS for this underground storage cavern is 10 m in order to ensure seal effectiveness.When the WCS is designed with a 10-m horizontal hole spacing and a water curtain pressure(WCP)of 80 kPa,a water curtain hole(WCH)has an influence radius of approximately 25 m.The smaller the vertical distance is between a WCH and the main cavern,the greater the water inflow into the main cavern.The vertical hydraulic gradient criterion can be satisfied when this distance is 25 m.It shows that the optimal WCP is 70 kPa,which meets sealing requirements.

Transient electromagnetic detection method in water-sealed underground storage caverns

Taking advantage of the water sensitivity of the transient electromagnetic method(TEM),this study assesses the effectiveness of the water curtain system for underground LPG storage caverns during the excavation period.It also detects fracture water flow during the excavation process in light of the practice of two pilot large underground LPG storage caverns in China.Comparative maps of apparent resistivity derived from TEM measurements before and after water-filling during the excavation process have been discussed to improve the quality of the water curtain system.This is the first case to apply TEM to detect the quality of the water curtain system during the construction of underground LPG storage cavern projects,and it is found to be practical,more visualized and worth popularizing.

基于两相流的水封油库油气泄漏运移规律及控制措施

地下水封油库运行的关键是保持一定的水封厚度,为确定合适的水封厚度,基于气液两相流理论,采用有限元数值模拟方法,以我国某石油储备地下水封洞库为依托,模拟了地下水封石油洞库储油运行期油气的泄漏运移演变过程。结果表明:施工期不设置水幕系统情况下,洞室顶部出现了大面积的疏干区,造成后期无法储油;设置水幕系统情况下,洞库上方能够维持一定水封厚度,洞库周围岩层油气泄漏范围和泄漏量均与储油运行时间呈正幂函数关系;水封厚度越大油气泄漏范围和泄漏量越小,但过大的水封厚度会大大增加工程成本,所对应的案例在水封厚度为30 m时对油气泄漏控制最为经济合理,《地下水封石洞油库设计标准》推荐的水封厚度合理且有一定安全裕度。研究成果可为水封油库工程的设计及油气泄漏控制提供一定理论参考。

地下水封石油洞库竖直水幕设计参数及其影响分析

滨海地区地下水封石油洞库工程中,需要增设竖直水幕系统,以满足其水封性和控制海水入侵。为研究竖直水幕系统的设计方法与参数,以滨海地区某地下水封石油洞库为例,通过有限元数值模拟方法获得了竖直水幕孔距主洞室距离d、竖直水幕孔间距b、竖直水幕孔长度l和竖直水幕孔注水压力p_(i)4个参数对洞库周围地下水渗流场、水封性、涌水量以及海水分布范围的影响规律,并与现有结果进行了对比验证。研究表明:竖直水幕孔距主洞室距离主要影响竖直水幕孔的埋深范围,长度的影响范围取决于超出主洞室的变化位置,间距和注水压力影响整个深度范围;4个参数对水封性和抑制海水入侵的影响程度顺序分别为:b<l<d<p_(i),d<b<l<p_(i);研究中共7个工况存在海水入侵洞室的风险,需进一步增强淡水补给。研究结论可为滨海地区地下水封石油洞库的竖直水幕设计参数提供一定理论依据。

基于地下水化学特征的水封油库水幕系统有效性评价

水幕系统有效性是地下水封油库安全稳定运行的重要基础条件,然而目前评价水幕系统有效性的方法并不高效便捷。以我国首个大型地下水封油库工程为背景,采集油库运行期现场水样和岩样进行水质检测分析和电镜扫描试验,获取库址区地下水水化学类型和岩石的矿物成分组成特征。采用数理统计方法,基于地下水水化学特征获得了不同部位地下水之间的水力联系,开展水幕系统有效性评价。研究表明:油库运行初期库址区地下水主要为HCO^(3)—Na•Ca型水,围岩中的钾长石、钠长石和钙长石发生水化学反应,地下水中的K^(+)、Na^(+)、Ca^(2+)和HCO_(3)^(-)浓度总体呈上升趋势,pH值总体呈下降趋势;Cl^(-)浓度低于造成钢筋腐蚀的浓度,地下水对洞库支护系统无明显腐蚀作用;洞库周边监测孔地下水与水幕供水的水化学特征相似,说明水幕系统与油库围岩之间存在较好的水力联系,形成良好的水封效果。该研究可为判断地下水封油库运行情况提供重要依据,并为评价水幕系统有效性提供了一种科学方法。

MICP技术在地下水封油库渗控注浆中的应用潜力

地下水封油库在建设及运营过程中洞室涌水量大小是影响洞库水封安全和运营成本的重要因素。目前地下水封油库工程建设中采用传统的注浆方式难以将围岩渗透性降低到设计要求,因此洞室涌水量得不到很好的控制。微生物诱导碳酸钙沉淀(MICP)技术具有注浆黏度低、环境适应性强、生成矿化物质稳定等显著优点,引起了学术界与工程界广泛的兴趣和研究。本文首先分析了地下水封油库涌水量控制中存在的相关问题,然后阐述了MICP技术对裂隙渗流控制的机理、影响因素以及对裂隙渗透性的影响效果,最后探讨了MICP技术在地下水封油库中应用的关键问题。通过分析表明,MICP作为地下水封油库渗流控制的一种辅助注浆方式,可以较为准确地控制围岩渗透性变化,达到对洞室涌水量有效控制的目的。

地下水封储油洞库惰性气体注入系统分析

首先对地下水封储油洞库惰性气体注入的重要性进行了说明。然后对氮气的生产工艺原理进行了介绍,并通过工程设计实例对比分析了3种惰性气体注入系统的优缺点、投资额,对水封洞库氮气置换对建设工期的影响进行了分析,最后分析说明了地下水封洞库惰性气体注入系统分析结论及设计建议,为后续项目设计及生产运营提供了决策依据。

地下水封洞库水幕孔注水试验渗流场及稳压时间分析

近年来我国建设的地下水封储油洞库均采用了水平水幕系统,水幕系统对于保证洞库水封性至关重要。水幕系统往往进行了大量的水力学试验,但如何拟定合理的试验方法和试验过程,如何有效利用试验数据并合理评价水封效果,还需结合工程实践进行深入研究。文章以某水封洞库为依托,基于单一水幕孔注水-回落试验,对试验的理论背景、试验过程的合理性及数据分析等进行了研究。首先,分析了单一水幕孔注水试验的试验过程和本质特征;然后,基于非稳定流分析原理推导了注水-回落试验的解析方程,并进一步分析了注水试验的水幕孔水压力、注水量与试验时间、岩体渗透参数的关系;最后,以某水封洞库为例,基于试验数据和理论分析,对注水试验的稳压时间进行了计算和分析,并建议了合理的试验过程和稳压时间控制要求。研究结果可为地下水封洞库水幕系统渗透性试验方法的建立提供理论参考依据。

大型地下水封石油洞库主洞室群间距分析

大型地下水封石油洞库往往由多个洞室构成,在工程设计中洞室群之间的距离不仅影响洞室围岩的稳定性,同时还能够影响工程建设的经济性。目前大型地下水封石油洞库地下洞室群间距多是根据洞室截面尺寸和洞室围岩质量,按照工程经验来确定,缺乏合理的解释。通过数值分析,模拟实际工程地下洞室开挖过程,根据围岩的空间位移分析洞室群中洞室开挖对其相邻已开挖洞室围岩的影响,确定其影响距离,从而提出合理的洞室间距。数值分析以某地下水封洞库为例,分析8种不同洞室间距工况下两相邻洞室围岩变形变化规律及其相互影响,构建了大型地下水封石油洞库地下洞室围岩关键位置位移立方与洞室间距之间的关系,为该地下水封石油洞库设计提供了参考。

大型地下水封洞库油气处理技术研究

油气处理技术是困扰大型地下水封洞库建设及进油投产的一大难题,国内尚没有形成系统性的技术、标准和装置。开展地下水封洞库油气处理技术与工艺的研究,提出解决油气处理问题的新思路和方法,既能增强我国地下水封洞库建设及运行的可靠性,又能提升我国油气装备制造水平。本文介绍了水封洞库油气的生成及处理主要技术措施,并以两个地下水封洞库为例,根据进油条件和运行工况,分析了油气焚烧和油气回收技术方案的特点。在油气回收技术研究中,将冷凝法+活性炭真空吸附法(CVA)与活性炭真空吸附法(CVA)+溶剂吸收法(CLA)进行了深入的对比分析,提出了地下水封洞库油气处理建议,有效解决了同类工程油气处理技术缺乏实践比选经验的难题。

某地下水封石油洞库地下水渗流场及涌水量模拟

地下水封石油洞库是通过人工开挖建于地下,利用稳定地下水的水封作用密封储存在洞室内的石油。具有占地少、投资少、损耗少等优点,但对地下水环境影响相对较大。为评价地下水封石油洞库施工期和运营期对地下水环境的影响,以某大型地下水封石油储库为研究对象,结合现场试验数据,利用GMS软件,建立了非均质、各向异性、三维非稳定地下水流模型和溶质运移模型。研究结果表明:有水幕系统时预测水位高于设计水位3 m以上,可以保证洞库的水封效果,且石油局限于洞室周围不外泄,为后期制定地下水污染防治措施及长期监测计划提供了依据。

地下水封石油洞库建设管理过程中关键点控制探讨

目前,用于储存原油、成品油、液化石油气等介质的地下水封洞库工程陆续建设,工程发展呈现储存规模大型化、储存介质多样化的趋势。地下水封石油洞库作为一种安全、经济、环保的储存方式,逐渐在世界范围内得到广泛应用。基于此,文章分析地下水封石油洞库的特点及建设要求,从优化设计方案、把控施工质量、强化安全管理等方面总结建设管理过程中的核心控制点,同时强调科学合理的施工组织设计和严格的过程监控,从而为类似工程的建设管理提供有益的参考和借鉴。

某水封洞库工程防渗灌浆策略研究

通过实施地下水封洞库围岩灌浆,降低围岩渗透系数,是实现提高洞库水封性和控制洞库渗水量双重目标的重要手段。笔者依托国内某在建水封洞库工程,结合已实施的不同类型灌浆数据,对预灌浆和后灌浆的灌浆效果进行对比分析,总结出灌前透水率-单位耗灰量的变化规律。结果表明:预灌浆效果优于后灌浆;在现有灌浆压力条件下,灌浆部位围岩结构没有发生明显非线性变化,可以进一步提高灌浆压力;相当部分灌浆孔的灌前透水率接近于0 Lu,单位耗灰量也仅为封堵灌浆孔的耗灰量,灌浆判据有进一步调整优化的空间。研究成果对后续水封洞库灌浆具有很强的指导作用和参考价值。

地下储氢技术现状及在中国加快发展的可行性

随着能源转型升级需求的日益迫切,氢能以其零污染、零碳排、无次生污染的优势,将成为中国能源体系的重要组成部分,也是中国石化新能源业务的主要主攻方向。目前,中国主要采用高压气态储氢、低温液态储氢和固态合金储氢等地面储氢方式,其储氢成本高,储氢效率低。与地面储氢相比,地下储氢以其规模大、成本低、更高的安全性,展现出更为广阔的发展潜力和应用前景。在国际上,混合储氢技术已在法国、德国等国家实现了一定规模的应用;纯氢气地下存储技术在美国取得较好的应用效果,但在中国这一领域的应用和研究近乎空白,尚处于起步阶段。针对氢气强流动性、高泄漏风险及强腐蚀性的特点,通过研究明确地下储氢面临的技术挑战,包括对圈闭密封性、地层条件、完井材料、地面工艺等方面。从枯竭油气藏资源、盐岩资源、储气库建设与运行管理技术等方面出发,分析中国开展地下储氢技术的可行性。中国西部和中东部拥有多个大型油气藏,枯竭油气藏资源丰富,具备开展地下混合氢储试验和氢储能的条件;盐岩分布广泛,用盐穴储存纯氢或氢储能切实可行;中国在气藏型储气库和盐穴型储气库建设与运行管理技术方面已积累了丰富经验和技术储备。综合分析认为中国具备了开展地下储氢的条件和技术。

地下水封石油洞库渗流场的数值分析

对研究区水文地质条件和地下水封石油洞库、水幕系统进行了概化,利用Visual MODFLOW软件,建立了某地下水封石油洞库无水幕和有水幕条件下的三维地下水数值模拟模型,模拟了地下水封石油洞库区的渗流场。利用所建模型预报了2种条件下涌入地下水封石油洞库的涌水量、区域地下水降落漏斗扩展情况及洞库上方地下水位变化情况等。由预测结果可知,2种条件下洞库涌水量均逐渐减小并趋于稳定,而有水幕条件下的地下漏斗扩展范围和速度均比无水幕条件小;在洞库开挖初期水幕作用较小,随时间延长作用愈加明显,因此水幕系统在保证地下水封石油洞库的储油安全和保护周围地下水资源方面都起到重要作用。

水封油库地下水位动态变化特性数值研究

为认识水封石油洞库区地下水位的动态变化过程,以黄岛地下水封石油洞库的基本地质条件为依据,采用饱和非饱和非恒定流数值分析方法,对水封油库在施工期和运行期可能出现工况下的地下水位变化情况进行了全过程数值仿真计算,分析了不同时期洞库区附近岩体的地下水位分布特点及变化过程。研究表明水封油库区内的地下水位变化过程主要受岩体渗透系数、洞库开挖方式和运行方式的影响;当洞库区岩体渗透系数大于1.0×10 7m/s时,洞顶上方岩体中的地下水将被疏干,必须设置水幕系统来保证洞库的水封效果。

地下水封储油库库址的水文地质工程地质问题

将石油储存于地下水封洞库是建设大型石油储备基地的重要发展方向。由于建设地下水封储油洞库的地质条件、设计和施工的复杂性,为满足建设的安全性和经济性,需要综合考虑水文地质、工程地质、环境地质问题。文章考虑了建设地下水封油库的原则和外部依托条件,特别针对库址选择时应注意的水文地质、工程地质问题,提出了相应的认识。