川东北黄金口背斜ZK001钻孔流体地球化学及含锂特征

Geochemical and Li-bearing Characteristics of Fluids from Borehole ZK001 in Huangjinkou Anticline of the Northeastern Sichuan, China

伴随着中国高镁低锂老卤溶液提纯碳酸锂的关键技术取得突破,卤水提锂日益受到重视。深地资源勘查开发专项中的锂能源金属矿产基地深部探测技术示范项目在川东北宣汉地区布置了3 227 m深钻孔(ZK001),主要研究目的是探讨深部是否存在富锂卤水。随钻流体(常用钻探循环泥浆气体)分析是常规井口流体实时监测的主要手段,但因Li化学性质活泼,气体组分难以全面反映Li的富集浓度,故本次对钻孔流体(包含深部卤水、随钻流体、钻孔洗井水)及钻孔周边地表水、地下水进行了取样分析,首次获得了川东北黄金口ZK001钻孔流体组分特征,初步归纳了钻孔流体中Li及其他主要组分的变化规律。结果表明:川东北黄金口各类型水样品Li质量浓度从大到小依次为深部卤水、钻孔洗井水、随钻流体、地下水、地表水;比较ZK001钻孔随钻流体组分随深度变化特征,发现0～500 m深度随钻流体Li质量浓度相对较高,Mg/Li值较低,且流体Li质量浓度异常与深度成正比,Mg/Li值与深度成反比;ZK001钻孔3 000 m深度处采集的黄色卤水Na、K、Rb、Sr等有用组分达到卤水工业品位,Li质量浓度(10 556μg·L^(-1))接近边界品位(24 599μg·L^(-1))的一半,Mg/Li值为33.92。上述钻孔流体特征将为下一步钻探工程布置提供科学支撑。

Since great breakthrough was made in purifying lithium carbonate from brine with high content of magnesium and low content of lithium, extracting lithium from brine has obtained increasing attention in China. Potassium-rich brine in the northeastern Sichuan contains many kinds of rare metals such as lithium which is urgently demanded in strategic emerging industries, while associated lithium resources of potassium-bearing brine are rarely considered in previous studies. A borehole(ZK001) with the depth of 3 227 m was arranged in deep exploration project in Xuanhan area of the northeastern Sichuan, of which the main goal is to investigate lithium-bearing brines in the deep. Analysis of fluids during drilling(conventional circulating drilling gas) is a main method of conventional real-time monitoring of wellhead fluids. As a result of lithium’s active property, it is difficult to reveal enrichment features of lithium by gas component only. Fluids of borehole ZK001(include deep brine, fluids during drilling, drilling-washing water), surface water and groundwater around borehole ZK001 were collected and analyzed;the characteristics of fluids during drilling were obtained for the first time;and the vertical variations of lithium and other components of drilling fluids in borehole ZK001 were summarized. The lithium concentrations in different types of water around borehole ZK001 show a rule that deep brine, drilling-washing water, fluids during drilling, groundwater, and surface water in descending order. By comparing the profile characteristics of the composition of fluids during drilling in borehole ZK001, it is discovered that lithium concentration of fluids during drilling in the depth of 0-500 m is relatively high while the ratio of Mg/Li is low. It is revealed that lithium concentration of fluids during drilling is proportional to the depth, and the ratio of Mg/Li is inversely proportional to depth. Lithium concentration of yellow brine collected at the depth of 3 000 m from borehole ZK001 is 10 556 μg·L-1(the ratio of Mg/Li is 33.92), which almost reaches the half of the cut-off grade(24 599 μg·L-1). In addition, Na, K, Rb, Sr components of the yellow brine from borehole ZK001 reach industrial grade. These features of fluids from borehole ZK001 will provide scientific support for future arrangement in drilling engineering.