石膏对白云岩溶解影响的实验模拟研究

表生到埋藏成岩作用的温度与压力（４０-１３０℃、常压－３０ＭＰａ）条件下，含膏与不含膏白云岩的溶解实验证明:在表生与相对浅埋藏的温压条件（低于７５℃，２０ＭＰａ）下，石膏（或硬石膏）的存在可不同程度地加速白云岩的溶解，随着实验温度和压力的升高，石膏（或硬石膏）对白云岩溶解的这种积极作用逐渐降低。在相对深埋藏的温压条件（高于７５℃、２０ＭＰａ）下，石膏（或硬石膏）的存在显著阻止白云岩的溶解，随着实验温度和压力的继续升高，石膏（或硬石膏）对白云岩溶解的这种消极作用也逐渐增加。从实验的这种结果可以预测，在近地表条件下和埋藏成岩作用的早期阶段，由溶解作用造成的含膏白云岩地层的次生孔隙将比不含膏的白云岩地层更为发育，因而在经历了古风化作用的地层中，含膏白云岩层更易形成良好的储层；与之相反，在相对高温高压的深埋藏成岩阶段，不含膏的白云岩地层中将更容易因酸性水的溶解作用而形成次生孔隙。因而在非蒸发沉积环境中形成的白云岩体（如正常海沉积环境的灰岩中的白云岩透镜体）更易因深埋藏溶蚀作用而形成良好的储层。

Effects of Gypsum (or Anhydrite) on Dissolution of Dolomite under Different Temperatures and Pressures of Epigenesis and Burial Diagenesis

Exeperiments of dissolution for dolomite with and without gypsum (or anhydrite) have been made under different temperatures and pressures (40-130℃, normal atmospheric pressure-30MPa) of epigenesis and burial diagenesis conditions.The results show that the effect of presence of gypsum(or anhydrite) on dissolution of dolomite is positive when temperature is below 75℃ and pressure below 20MPa, but it is negative when temperature is higher than 75℃ and pressure higher than 20MPa. Based on the results we can predict that under the conditions of epigenesis and relatively shallow burial diagenesis the dissolution and formation of secondary porosity of dolomite with gypsum (or anhydrite) should be more common than that of dolomite without gypsum (or anhydrite), but under the deeper burial conditions the dissolution and formation of secondary porosity of dolomite without gypsum (or anhydrite) should be more common than that of dolomite with gypsum (or anhydrite).