乙酸溶蚀方解石影响因素探究及特征分析

碳酸盐岩储层是全球油气主要储集体,对油气储层的开发有十分重要的意义。通过对典型碳酸盐在不同条件下的溶蚀实验,厘清其溶蚀控制因素以及热力学与动力学关系,进而探讨其发育机理。为此,以高纯度方解石为研究对象,在不同温度、矿化度、离子类型以及p H条件下进行方解石溶蚀模拟实验,通过原子吸收光谱仪(AAS)、X射线荧光光谱仪(XRF)、X射线衍射仪(XRD)以及扫描电镜(SEM)等分析手段,并结合热力学计算,探究了不同地层条件下方解石溶蚀曲线变化规律、热力学与动力学之间关系以及溶蚀形貌特征。结果表明:(1)方解石的溶蚀量以及Ca~(2+)释放规律均随温度、矿化度、离子类型以及p H呈现规律性的变化;(2)中深埋层(100~130℃)、适中矿化度(29.25 g/L)、较小p H的地层条件更有利于方解石矿物的溶解,促进优质方解石矿物储层的形成;(3)相对封闭的地层环境下,乙酸溶蚀方解石的溶蚀速率r与反应ΔG关系式为r=2.047×10~(-8)[1+e~*+(0.748(ΔG+18.61))]-4.11×10~(13);(4)方解石溶蚀反应优先发生在具有高自由能表面和活性位点的表面断裂、凸凹点及边缘处,并且由溶孔到溶蚀坑,再到溶蚀带,随后形成溶蚀晶锥,最后裸露出新的晶面的过程进行。

Study on dissolution factors of calcite and characteristic analysis in acetic acid

In order to study the influencing factors and characteristics of calcite dissolution under acetic acid conditions, the formation conditions of high quality reservoirs. In this paper, high-purity calcite was used as the research object, and calcite experiment was carried out under different temperature, salinity, ion type and pH. By means of atomic absorption spectrometry(AAS), X-ray fluorescence spectrometer (XRF), X-ray diffractometer (XRD)and scanning electron microscopy(SEM), variation law of dissolution curve ,the relationship between thermodynamic and dynamics and dissolution characteristics of calcite under different influencing factors were explored.The results show that: (1) the dissolution of calcite and the law of ion release change with temperature, salinity, ion type and pH regularity; (2) the condition of mid-deep buried layer (100-130 C), salinity (<29.25g/L), and smaller pH were more beneficial to the dissolution of calcite,promote the formation of high-quality mineral reservoirs ;(3)In the relatively closed formation environment, the relation between thermodynamics and dynamics was: ;(4) the dissolution reaction of calcite occurs first in the surface with high free energy and active sites of the surface fracture, convex and concave and the edge; And from the hole to the dissolution of the pit, and then to the dissolution zone, followed by the formation of dissolved crystal cone, and finally exposed the new crystal surface .