察尔汗盐湖固体钾盐溶解对溶剂注入速率响应机制研究

察尔汗盐湖浅部储卤层赋存有储量可观的固体钾盐资源, 目前正处于溶解液化开采阶段。储卤层中固体钾盐矿物溶解及储卤层结构变化特征受到溶剂注入速率控制, 但其控制机制尚不明确。本文以察尔汗盐湖浅部储卤层典型钻孔岩芯为研究对象, 通过开展室内岩芯柱渗流模拟实验, 研究岩芯在三种流速条件下储卤层渗透系数和固体钾盐矿物溶出的变化规律。结果表明: (1)随着注入溶剂速率的增大, 岩芯渗透系数呈现逐渐增大的趋势, 渗出液中钾离子浓度呈现持续减小的趋势, 但在流速改变的时间节点处, 岩芯渗透系数和其对应溶出液中钾离子浓度均出现异常增加现象。矿物的溶解引起储层孔隙度增加, 而溶剂流速的改变会导致松散盐类矿物颗粒重组。(2)储卤层岩芯固体钾盐矿物溶解受到溶剂注入速率的影响明显。注入速率增加引起矿物颗粒重组以及滞留孔隙高浓度水体释放是造成渗出液中K+浓度短暂性升高的主要原因。本次实验研究对于研究区低品位固体钾盐的水溶开采具有一定理论指导意义。

A Study on the Mechanism of Influence of the Dissolution of Solid Potassium Salt in Qarhan Salt Lake to the Rate of Solvent Injection

The shallow brine reservoir of Qarhan Salt Lake contains considerable reserves of solid potash resources, and it is currently at the stage of liquefaction mining. The dissolution of solid potassium salt minerals in the brine reservoir and the structural changes of the brine reservoir are controlled by the solvent injection rate, however, the control mechanism is still unclear. In this paper, a typical borehole core in the shallow brine reservoir of Qarhan Salt Lake was investigated. Through the indoor core column seepage simulation experiment, the permeability coefficient of the brine reservoir and the dissolution of solid potash minerals under three flow rates are studied. The results show that: (1) With the increase of the solvent injection rate, the core permeability coefficient shows a gradually increasing trend, and the potassium ion concentration in the exudate shows a continuous decreasing trend, but at the time node when the flow velocity changes, the rock core both the core permeability coefficient and the potassium ion concentration in the corresponding dissolution liquid showed an abnormal increase. The dissolution of minerals causes the porosity of the reservoir to increase, and the change of the solvent flow rate causes the reorganization of loose salt mineral particles. (2) The dissolution of solid potash minerals in the brine core was significantly affected by the solvent injection rate. The increase in injection rate causes the reorganization of mineral particles and the release of high-concentration water from the retained pores, which were the main reasons for the temporary increase of K+ concentration in the exudate. This experimental study has certain theoretical guiding significance for the water-soluble mining of low-grade solid potassium salt in the study area.