深层温压条件下有机酸热稳定性模拟研究

深层、超深层中有机酸的分布特征及其热稳定性对储层物性有着重要影响。采用高温高压水—岩模拟装置对储层中典型一元和二元有机酸（乙酸和乙二酸）的分解反应进行了模拟，对动力学参数进行了计算，并分析其影响因素。结果显示:乙二酸比乙酸更容易分解，且分解反应的速率更高；乙酸和乙二酸分解反应的起始温度分别为230 ℃和180 ℃，其反应速率随着温度的升高而急剧增加。反应体系中高pH值和钾长石的存在明显提高了乙酸和乙二酸分解反应的反应速率，但对起始温度影响较小。高流体压力和静岩压力均会抑制乙酸和乙二酸的分解，在提高有机酸分解反应起始温度的同时降低分解反应速率。从地质意义上来讲，相对高压、低地温的地层环境更有利于有机酸的保存，因此具有低地温梯度的沉积盆地形成深层—超深层优质储层的可能性更高。

Simulation Study of the Thermostability of Organic Acid at the Temperature and Pressure Conditions of Deep Layers:A case study of acetic acid and oxalic acid

The distribution and thermal stability of organic acids in deep hydrocarbon reservoirs significantly affects the reservoir properties. The decomposition reactions of typical monocarboxylic and dicarboxylic acids （acetic and oxalic acids） were studied using high?temperature and high?pressure water?rock simulation for which the influence factors and kinetic parameters were analyzed and calculated. The results show that the decomposition reaction occurs more readily for oxalic acid than for acetic acid. The rate of the decomposition reaction of oxalic acid is also more rapid than for acetic acid. The critical decomposition reaction temperature for acetic acid is 230 °C， and is 180 °C for oxalic acid. Their rates of decomposition reaction increase sharply with increasing temperature. High pH and the presence of potash feldspar in the reaction system increase the decomposition reaction rates of both acids， but have little influence on the critical temperature of their decomposition reactions. Large lithostatic and fluid pressures hinder the decomposition reactions of these acids by reducing the rate and raising the critical temperature of the decomposition reaction in both cases. It was found that high pressure at low temperature favors the preservation of organic acids， from which it is inferred that sedimentary basins with a low temperature gradient is more likely to form high?quality reservoirs in deep and ultra?deep rock.