察尔汗盐湖低品位固体钾盐资源丰富,是我国钾盐工业可持续发展的重要后备资源.充分了解储卤层中钾盐矿物的溶解机理有助于提高资源开采的效率.本研究以察尔汗盐湖浅部储卤层中含有不同钾盐矿物的3种典型钻孔岩芯为研究对象,通过室内渗流溶解实验,开展储卤层中固体矿物的溶解效率、孔隙度以及渗透性变化特征模拟研究.室内渗流-溶解实验结果表明,3种储卤层中的钾盐矿物溶出率皆近100%,其中主要含光卤石的岩芯样品溶解速度最快,含钾石盐岩芯次之,含杂卤石岩芯最慢.实验过程中,溶解反应后的储卤层固相骨架皆未塌陷,表明饱和NaCl卤水起到了很好的保护作用.由于石盐析出和不溶矿物的运移堵塞,3种岩芯的孔隙度皆降低,其中含光卤石岩芯孔隙度降低了26%,含钾石盐岩芯孔隙度降低了20%,含杂卤石岩芯孔隙度降低了32%.受控于盐类矿物溶解、石盐的析出和不溶矿物的运移堵塞,各储卤层岩芯渗透性降低幅度为40%~70%,降幅显著.
Qarhan Salt Lake is endowed with abundant low-grade solid potassium salt resources,playing a crucial role in the sustainable development of the potash industry in China.A thorough understanding of the dissolution mechanism of potassium salt minerals in brine reservoirs is essential to optimize resource exploi-tation.In this study,three representative drill cores containing different types of potassium salts from the shallow brine reservoir of Qarhan Salt Lake were selected for investigation.Through a laboratory seepage dissolution experiment,the efficiency of solid minerals'dissolution,as well as changes in porosity and per-meability of the drill cores,was simulated.The results of the percolation-dissolution experiment revealed that the potassium salt minerals in the three drill cores were totally dissolved.Among the core samples,those containing carnallite exhibited the highest dissolution rate,followed by sylvite-rich core samples,while,polyhalite-rich core samples showed the lowest dissolution rate.Throughout the experiment,the skeleton of the brine reservoirs did not collapse after the dissolution reaction,indicating effective protection provided by NaCl-saturated brine.The porosities of the three core samples declined due to halite precipita-tion and the migration of insoluble minerals.Specifically,the porosity of the carnallite-rich core decreased by 26%,while that of the sylvite-rich and polyhalite-rich cores decreased by 20%and 32%,respectively.Controlled by the dissolution of salt minerals,precipitation of halite,and migration/blockage of insoluble minerals,the core permeabilities of brine reservoirs diminished by 40%-70%.This research highlighted the importance of considering complex factors for a comprehensive understanding of the changes in the reser-voir's physical properties during the seepage-dissolution process.