酸性流体对碳酸盐岩储层的改造作用

Effect of acid fluid on carbonate reservoir reconstruction

普遍认为CO2、有机酸及H2S是碳酸盐岩储层溶蚀作用的酸性流体。CO2对碳酸盐岩储层的溶蚀作用已有不少学者进行了研究,本文则以一个全新的模拟实验方式对不同类型碳酸盐岩在有机酸和H2S水溶液中的相对溶蚀能力进行了研究,结果发现随温度从常温升高至200℃,有机酸对碳酸盐岩的溶蚀能力由弱变强再变弱,在90℃左右溶蚀能力最强。而H2S水溶液对碳酸盐岩的溶蚀作用则明显不同,60℃时基本达到最大溶蚀率,温度继续升高后,溶蚀能力一直维持在较高的水平并略有增加,150℃后突然降低。由于H2S主要是硫酸盐高温热还原产物(TSR),因而在碳酸盐岩成岩早期阶段,溶蚀作用的流体可能主要是有机酸和CO2,而在深埋阶段,H2S水溶液则可能是溶蚀作用的主要流体。

CO2, organic acid and H2S are commonly regarded as acid fluid which can cause erosion of carbonate rocks. Many data and discussions about carbonate rock dissolution in CO2 solution have been published. In this paper, special simulation experiments were carried out in order to understand the dissolution behaviors of carbonate rocks in organic acid and H2S solution. The results show that, as the temperature rises from 20 ℃ to 200 ℃, the dissolution rate of carbonate rock in organic acid increases with temperature below 90 ℃ and decreases above 90 ℃. But the erosion of carbonate rock in H2S solution is quite different. As the temperature rises from 20 ℃ to 200 ℃, the dissolution rate of the carbonate rock in H2S solution increases below 60 ℃ and decreases above 150℃, with a top dissolution rate at a temperature range from 60 ℃ to 150 ℃. It may be included that organic acid and CO2 solution are the main fluids which cause the erosion of carbonate rock in early diagenetic stage, and H2S solution is the main fluid which causes the erosion of carbonate rock in deeply buried stage.