多次酸化砂岩在三轴循环压缩中的变形特征分析

 通过对同一岩样进行多次注酸酸化处理后再进行多次三轴循环加、卸载试验，由试验中得到的结果，分析酸化对岩石变形特征的影响。试验结果表明：注酸酸化处理及注酸量的大小对岩石变形影响很大，第一次注酸酸化处理对岩石变形特性的影响尤为显著，岩石在加、卸载过程中弹性模量和泊松比均呈现快速下降趋势。随着注酸酸化处理的继续，岩石中可溶解、易溶解部分的量逐渐减少，岩石变形受注酸的影响逐渐变小，随着多次注酸酸化处理及注酸量的增大，弹性模量在加、卸载过程中呈缓慢下行，泊松比在加载过程中同样缓慢下行，前期弹性模量和泊松比变化大，后期弹性模量和泊松比的变化趋向平缓，而泊松比在卸载过程中规律性不强。当达到循环上限应力时，随着对岩石注酸量的增加，岩石的轴向变形逐渐增大。因此，酸是影响砂岩力学特性不可忽视的重要因素之一，在油气工业中，当岩石用酸进行处理后，应充分重视酸作用对岩石承载能力的改变及这种改变对后期工程作业可能带来的不利影响。

ANALYSIS OF DEFORMATION OF SANDSTONE WITH MULTIPLE ACID TREATMENTS UNDER TRIAXIAL CYCLIC COMPRESSION

Based on the results of triaxial cyclic on/off loading experiment using the same sample treated by multiple acid，the influence of acid treatment on deformation feature of rock has been analyzed specifically. The results show acid treatment and the quantity of acid flooding have significant effect on deformation of rock. The effect of the acid flooding for the first time is obvious，and the elastic modulus and Poisson’s ratio decrease dramatically in the process loading/unloading. However，the effect is tapering off when the quantity of acid flooding is large enough because of decrease of the lyotrope and dissoluble mineral. Elastic modulus in the process of loading/unloading is decreasing with the increasing of multiple acid treatments，so is the Poisson’s ratio. The changes of elastic modulus and Poisson’s ratio in the early stage are greater，and tend to smooth in the later stage. And the regularity of Poisson’s ratio in the process of loading/unloading is indistinct. When the clyclic load reaches to the maximum value，the axial deformation is increasing gradually with the increasing of quantity of acid flooding. Therefore，acid treatment is one of the important factors that affect the mechanical deformation behavior of rock. In the gas and oil industry，the alternation of loading capacity of rock treated by acid and the negative impacts in the later engineering operation should be noticed.