有机酸对长石溶解度影响的热力学研究  

THE EFFECT OF ORGANIC ACID ON FELDSPAR SOLUBILITY: A THERMODYNAMIC STUDY

作　　者：罗孝俊[1] 杨卫东[1] 

机构地区：[1]中国科学院地球化学研究所矿床开放实验室,贵阳550002

出　　处：《矿物学报》2001年第2期183-188,共6页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目 (批准号 :49773 179)

摘　　要：为明确认识有机酸 (草酸、醋酸 )对长石溶解度及储层次生孔隙发育的影响 ,本文利用热力学方法 ,计算了不同温度、酸度下钾长石在含有醋酸根 0 .0 5mol/L、草酸 0 .0 0 55mol/L的溶液中的溶解度及草酸和醋酸对溶液酸度的影响。计算的结果表明醋酸根与铝的络合作用只发生在偏酸性的溶液体系中 ,并且随温度升高要求酸度增加 ,实际的络合能力降低。醋酸根的络合作用对长石溶解度的增加作用极其有限 ,最高时不足一倍 ;但醋酸能有效地缓冲溶液酸度 ,从而提高长石溶解度。草酸根与铝的络合作用发生在弱碱性至酸性条件下 ,温度升高 ,络合能力增加。络合效应对长石溶出量的增加最多可达 2个数量级以上。草酸的浓度太低无法通过缓冲溶液在较高的酸度下来促进长石的溶解。草酸和醋酸能否促进储层次生孔隙的发育取决于盆地流体的酸度及组成流体的缓冲体系。To understand the effect of acetate on the solubility of feldspar and the development of secondary porosity, the solubility of K\|feldspar has been calculated in \{0.05\} mol/L acetate\|bearing solution and \{0.0055\}mol/L oxalate\|bearing solution at different temperatures over a wide pH range, and the effect of both acetic acid and oxalic acid on the acidity of solution was also estimated. The result shows that Al\|acetate complex only occurs in slightly acidic aqueous solution. With increasing temperature, the pH complexion decreased and the ability of acetate to complex aluminum decreased, too. Al\|acetate complex's contribution to the solubility of feldspar is negligible. But acetate acid can buffer pH to improve the dissolution of feldspar. On the contrary, Al\|oxalate complex occurs in weakly alkaline and acidic solutions. With the rise of temperature, the ability of oxalate to complex aluminum increased. Al\|oxalate complexion can significantly enhance the solubility of feldspar by 1～2 orders of magnitude at proper pH. Due to low contents in solution, oxalic acid can't improve the solubility of feldspar by buffering pH to a low value. Whether acetic and oxalic acids can promote secondary porosity development depends on the pH and buffer system of fluids in the basin.

关 键 词：有机酸阴离子-铝络合物 长石 次生孔隙 热力学 有机酸 溶解度 储层 

分 类 号：P618.130.2[天文地球—矿床学]