准南大黄山芦草沟组油页岩热解气相色谱特征

Pyrolysis-gas chromatography of the oil shale in Lucaogou Formation,Dahuangshan,Southern Junggar Basin

热解气相色谱能提供热解产物的详细组成,是研究油页岩品质的有利手段。大黄山油页岩矿区位于准噶尔盆地南缘博格达山北麓油页岩矿带的主体位置,大黄山油页岩的热解产物以正构烃为主,约占热解产物的90%。热解时干酪根核外的脂族基团断裂,形成烷基自由基,其得、失氢自由基就生成正构烷烃、烯烃。受空间位阻影响,烯烃的生成需要更多的能量,且短链烷基自由基(C14-)生成烯烃的几率大于长链烷基自由基(C15+)。利用C1—C4、C5—C14、C15+三段正构烃的相对百分含量能较好地区分不同类型干酪根。正构烷烃/正构烯烃值也能准确地区分不同类型的干酪根,Ⅰ型干酪根该比值小于2.17,Ⅱ型干酪根该比值大于2.17。该地区油页岩与美国绿河页岩相似,热解产物绝大部分为高蜡石蜡基原油。

Dahuangshan oil shale mine is located at the main position of oil shale deposit belt in Northern Bog＆ Mountain. The majority of the pyrolysis products of Dahuangshan oil shale are n alkanes and n alkenes, which approximately account for 90% of total products. Aliphatic groups break from kerogen nuclear when heated and turn into alkyl radicals. Alkyl radicals, which are very active, quickly turn into n-alkanes or n alkenes depending on capturing or losing hydrogen radicals. Due to the effect of space steric hindrance, the formation of n-alkenes need more energy than n-alkanes, and the formation ratio of short chain n-alkenes （C14- ） is bigger than long chain walkenes （C15＋）. The relative contents of C1 -C4 n-alkanes and walkenes, C5- C14 n-alkanes and n alkenes, and C15- n- alkanes and n-alkenes are effective parameters to distinguish kerogen type, as proved. Also the composition ratio of all n-alkanes and all n-alkenes is also an accurate parameter, for the type Ⅰ kerogen is below 2. 17 while the type Ⅱ is above it. The pyrolysis products of Dahuangshan oil shale are mainly high wax paraffinic oil, which is similar to that of Green River shale in America.