柴达木盆地盐湖地下卤水开采过程中水文地质参数变化机制研究

The underground brine of Salt Lake in Qaidam Basin belongs to special groundwater. Its particularity show that the salt rock porosity medium of brine aquifer has high soluble and the brine in inter crystalline pores of the salt rock possess the properties of high-salinity, multi-component and easy-crystallize, etc. In the exploitation process, there has a serious fluctuation in seepage field and geochemical field in brine aquifer. The salt bath-salting out effect in brine aquifer is being in a quality conversion process state. Thus causes complicated changes on hydrogeological parameter in brine aquifers. This application choose the brine aquifer in Mahai salt lake as the research region. Obtain hydrogeological information by means of underground brine dynamic monitoring, multipe wells pumping test and hole coring samples collected. This study could master the vary of the hydrogeologic parameters ove the mining process by the means of hydro-geological information system analysis. Based on the data, we could find out the diachronic features of porosity, water level and permeability coefficient. Then study the correlation analysis between the change of hydro -geological parameters and affecting factors, such as groundwater level dynamics, hardness index and chemical components. Discriminant the salt bath-salting out effect in brine aquifer when it is being in a quality conversion process state. Then explore its critical process of the hydrodynamic and hydrochemistry. Screened and identified the main influence who caused the change of the parameters and interpret the main influence mechanisms. Discussing the artificial mining - dynamic control mode that could made the salt bath-salting out effect in a relative balance position. This will provide scientific basis for preventing the reduce of porosity, specific yield and permeability of brine aquifer and the deteriorate of hydrogeological conditions during the exploitation process. And this will also provide scientific basis for the accurate assessment and rational development of underground brine resources.

柴达木盆地盐湖地下卤水属于较为特殊的地下水，其特殊性主要表现为赋存地下卤水的盐岩介质矿物具有较强易溶性，而盐岩介质晶间孔隙卤水又具有高矿化度、多组分、易析出等特点。开采过程中渗流场、化学场剧烈波动变化，含卤水层系统中盐溶-盐析作用及其强度处于差异分化过程，引起水文地质参数复杂变化。本申请以马海盐湖含卤水层为研究对象，以动态监测、抽水试验、样品采集等手段获取水文地质信息。通过对信息系统分析，弄清开采过程中孔隙度、给水度、渗透系数历时变化特征。研究参数变化与卤水黏度、水位动态、卤水矿化度、水化学组分等动态要素间相关关系，筛选、识别参数变化主要动态要素，探索盐溶-盐析作用优/劣势转化的水动力与水化学临界动态特征，阐释参数变化机制。探讨盐溶-盐析作用达到相对平衡状态的人工开采-动态调控模式，为防止开采过程中孔隙度、给水度趋于降低、渗透性趋于减弱以及为卤水资源准确评价与合理开发利用提供科学依据。

由于柴达木盆地盐湖储卤层孔渗性较低，非均质性及各向异性特征明显，水文地质参数在平面及剖面上变化复杂，导致相邻甚近的钻井或层位产卤量差异甚大，因此只有在弄清储卤层孔隙特征、渗透性能及富集规律后，才能准确评价地下卤水资源及合理开采。储卤层空隙是地下卤水储存的场所和运移通道，不同岩性地层正是通过所具有的孔隙、裂隙和溶隙来影响卤水的富集，孔隙度、渗透率越大，储卤层对卤水的富集越有利、富集程度越高，反之则不利于卤水的富集。本研究以马海盐湖储卤层为研究对象，以动态监测、抽水试验、样品采集等为手段，通过系统分析，研究储卤层孔隙度、渗透系数变化特征以及影响因素，揭示参数变化机制，并开展了地下卤水富集特征及机制研究。取得主要进展如下：. （1）对储卤层孔隙度分布变化规律研究发现，不同平面位置、不同层位的储卤层，其孔隙度分布有较大差别。平面上分布方面，盆地上的储卤层孔隙度通常是缓坡大于陡坡。垂向上分布方面，一是孔隙度数值自下而上具有由小到大的变化特征，二是具有旋回性变化，即自下而上孔隙度表现出小-大-小-大的变化特征。. （2）马海盐湖储卤层中的矿物大致可分为盐类矿物及碎屑矿物两大类，其中盐类矿物的质量分数大于50%，盐类矿物在储卤层中起着支撑骨架的作用，而碎屑矿物多充填于盐类矿物晶间。由于碎屑矿物在储卤层中主要充填于石盐晶间及裂隙中，它们对储卤层的孔隙起到了堵塞、孔隙度减小的作用，此作用随着碎屑矿物含量的增加而增强。. （3）首次进行了地下卤水富集性能的差异性分类，提出了研究区储卤层不同特征类型划分方法。通过钻孔岩心岩性、孔隙特征及补给条件等方面分析，揭示了卤水富集性能强的基本条件。依据储卤层渗透性能和卤水富集规律，将马海盐湖试验开采区划分出不同地下卤水富集区段。. 研究结果对于柴达木盆地马海盐湖地下卤水富集规律的深化认识、资源量的精准评价以及卤水资源合理勘探与开发等方面具有重要的科学价值和实际指导意义。