基于红外光谱测试的腐殖煤生烃热压模拟及干酪根化学结构演化的地质意义

Pyrolysis simulation of humus coal generating hydrocarbon based on FTIR and geological significance of chemical structure evolution of kerogen

为了探究不同流体压力下有机质生烃过程中干酪根化学结构的变化特点,采用DK‑Ⅲ型地层孔隙热压生排烃模拟系统得到了2、40、80 MPa 3种不同流体压力下完整成熟度系列的样品。对3种系列样品进行了傅里叶变换红外光谱(FTIR)测试,通过对波长为3100~2700 cm^(-1)和2000~800 cm^(-1) FTIR曲线特征峰段的分峰拟合,并计算了4大类参数,获取了脂肪烃结构参数和芳香烃结构参数随热裂解过程的变化规律。结果表明:长昌组腐殖煤以芳香基结构和含氧官能团结构为主,脂肪族结构相对较少,干酪根生烃过程中主要是长链脂肪族和含氧官能团不断脱落,芳香族缩聚反应,还包含一定的脂肪族芳构化过程;而流体压力的显著增加减缓了已生成烃类的排出,部分未排出烃类进一步缩合到残余固体有机质中,从而为更高演化阶段保留了一定的生烃潜力。研究成果为更深层油气勘探提供了理想的气源保障。

In order to study chemical structure variation characteristics of kerogen during hydrocarbon generation of organic matters with different fluid pressure,complete maturity series of sample are obtained by using DK-Ⅲforma‑tion pores pyrolysis hydrocarbon generation and expulsion simulation system with 3 different fluid pressures of 2,40 and 80 MPa.3 sample series are tested by FTIR.4 types of parameters are calculated and variation laws of ali‑phatic structural parameters and aromatic hydrocarbons parameters with pyrolysis process are obtained by peak fit‑ting FTIR curve characteristics peak segments with wave lengths of 3100~2700 cm^(-1) and 2000~800 cm^(-1).The re‑sults show that humic coals in Changchang Formation are mainly dominated by aromatic structures and oxygen-con‑taining functional group structures,with relatively less aliphatic structures.Kerogen generating hydrocarbon pro‑cess mainly includes continuous shedding of long chain aliphatic groups and oxygen-containing functional groups,aromatic polycondensation reactions,and certain process of aliphatic aromatization.Significant increase of fluid pressure retards the expulsion of generated hydrocarbon,and some undischarged hydrocarbon is further condensed into residual solid organic matters,thereby retaining certain hydrocarbon generation potential for higher evolution stages.The research provides ideal gas source guarantee for deeper oil and gas exploration.