有机土酸对花岗岩力学性能影响试验研究

Experimental Study on Effects of Organic Soil Acid on the Mechanical Properties of Granite

以采自青海共和盆地的花岗岩样品为研究对象,利用电液伺服万能试验机对3种不同乙酸浓度的土酸溶液浸泡后的花岗岩试件进行岩石力学试验。通过测量3种溶液浸泡过程中各溶液的pH变化、浸泡岩样的质量变化,分析化学溶液对岩石的腐蚀程度,进而探讨乙酸在化学刺激剂中的作用以及有机土酸与储层反应机理。研究了有机土酸对储层的化学刺激效果以及溶蚀特征,获得不同浓度乙酸溶液对花岗岩强度的影响规律。结果表明,在增强型地热系统(EGS)中,乙酸不仅仅作为有机弱酸参与储层激发,同时还作为缓冲液维持酸岩反应体系的低pH值,强化腐蚀反应。对花岗岩力学性质的影响不同,花岗岩单轴抗压强度、抗拉强度随乙酸浓度增加而降低,且花岗岩的内聚力随浸泡溶液的乙酸浓度增加而减小,而内摩擦角随着乙酸浓度增加微增。室内试验结果可为构建花岗岩化学腐蚀条件下本构模型提供重要的试验资料。

Taking the granite samples from Gonghe Basin in Qinghai Province as the research object,the rock mechanics tests of three kinds of granite samples immersed in soil-acid solution with different acetic acid concentration were carried out by using electro-hydraulic servo universal testing machine.Through measurement of the PH change of each solution and the quality change of rock samples during the soaking process of three solutions,the corrosion degree of chemical solution to rock was analyzed,andtherole of acetic acid in chemical stimulant and the reaction between organic earth and reservoir were discussed.The chemical stimulation effect and dissolution characteristics of organic earth acid on reservoir were studied,and the influence of different concentration of acetic acid solution on the strength of granite was obtained.The results showed that in EGS project,acetic acid not only participated in reservoir stimulation as weak organic acid,but also acted as buffer,which can maintain low pH value of acid-rock reaction system to strengthen corrosion reaction.Te effect on the mechanical properties of granite was different,with the increase of acetic acid concentration in immersion solution,the uniaxial compressive strength and tensile strength of granite decreased,and the cohesion of granite decreased.The laboratory test results can provide important experimental data for the construction of constitutive model of granite under chemical corrosion conditions.