稠油火驱过程焦炭的化学性质与微观形貌特征分析

为了认清稠油火驱过程中焦炭的化学性质与微观形貌特征，利用室内高温高压反应釜开展了焦炭的生成实验，并对生成的颗粒状的焦炭的样品开展了有机元素、傅里叶变换红外光谱、岩石热解、扫描电镜（SEM）、CT扫描三维重建等方面的研究。研究表明：稠油火驱过程中生成的焦炭中氧元素含量增加近3倍，与原油相比具有富氧贫碳的特点，焦炭中存在含氧的官能团主要以以醛、酮、羧酸、酯、醇等大分子化合物的形式存在；焦炭的有机质成分以可裂解的S2为主，可以为稠油火驱的持续燃烧提供燃料，存在的残碳（RC）是稠油在高温高压条件下裂解缩聚生成的大分子极性化合物，在高温含氧的条件下也可以作为火驱的燃料；SEM与CT观察发现，焦炭的孔隙空间是由一系列大小不一的有机质孔洞组合而成，小孔洞与大孔洞相互连通组成一个系统的孔隙空间网络，有利于火驱过程中与氧气的充分接触。该研究将有利于认识火驱高温氧化过程中生成的焦炭的化学性质与微观形貌特征，为火驱开发的机理深化与开发方案的调整提供有力支撑。

Analyses on the Chemical Properties and Microstructures of Coke Generated by In-situ Combustion of Heavy Oil

This paper is aimed at understanding the chemical properties and microstructures of coke during in-situ combustion of heavy oil. It was achieved by conducting a coke generation experiment in an indoor high-temperature and high-pressure reactor. To begin with, the organic elements of the generated granular coke samples were studied, in addition to the findings on its Fourier transform infrared spectroscopy (FTIR), rock pyrolysis, scanning electron microscopy (SEM), and CT three-dimensional reconstruction. The experimental results suggest that the coke generated herein by in-situ combustion of heavy oil oxygen content that increased by nearly three times. The coke saw enriched oxygen levels but more deficient carbon levels compared with crude oil, with significant structural break in long-chain fatty acids and intensified aromatization. Due to the introduction of oxygen, oxygenated functional groups in the coke existed mainly in such macromolecular forms as aldehyde, ketone, carboxylic acid, ester and alcohol. Degradable S2 was the leading organic composition in the coke, which continued to break down into hydrocarbons of smaller molecular weight at high temperatures, providing fuel for sustained in-situ combustion of heavy oil. Carbon residue in coke is a type of polar macromolecular compounds of heavy oil through pyrolysis and polycondensation under high temperature and high pressure that may fuel the in-situ combustion at high temperature in an oxygenated environment. Moreover, observations using SEM and CT also showed that pore spaces of the coke consisted of a series of organic holes with different sizes. A large number of inter-connecting holes form a network of pore spaces that are indeed conducive to sufficient contact with oxygen in the process of in-situ combustion. As shown from the findings, this research may facilitate a better understanding of the chemical properties and microstructures of coke generated via high temperature oxidation during in-situ combustion, and may serve as valuable supporting references for the further mechanism development of fire flooding and for adjustment of relevant development schemes.