贵州水城煤中基质镜质体生烃潜力、烃类组成及生烃模式

基质镜质体是华南晚二叠世煤中的主要组分之一,其在煤中含量的多少、生烃潜力的大小、生烃特性等直接影响到该区煤成油气资源的评价。采用岩石热解、热解气相色谱以及开放体系下热模拟等方法,对贵州水城晚二叠世(P21)龙潭组煤中基质镜质体的生烃潜力、烃类组成特征、生烃模式进行了研究。结果表明:本区基质镜质体的生烃潜力、氢指数分别为191.99mg/g和250mg/gTOC,远高于丝质体的生烃潜力(26.17mg/g)和氢指数(35mg/gTOC),而小于树皮体的生烃潜力(297mg/g)和氢指数(491mg/gTOC);基质镜质体热解烃类组成中以轻质烃为主,湿气次之,可见本区基质镜质体不但能生成气态烃,而且能生成一定量的液态烃,这归因于其中所含大量的超微类脂体;基质镜质体“生油窗”温度范围为375～475℃,主要生烃温度区间为400～450℃,其中415～430℃为生烃高峰期,420℃处产烃率最高。基质镜质体这种在高成熟度下(大于VRo1.0%)大量生烃的特点对在成熟度普遍较高的华南地区寻找油气田具有重要的意义。

Characteristics of Hydrocarbon Generation Potential, Hydrocarbon Composition and Hydrocarbon Generating model of Desmocollinite from Late Permian Coals in Shuicheng, Guizhou Province

Desmocollinite is one of the major macerals of Late Permian Longtan Formation coals in Shuicheng, Guizhou Province, Southwest China. The characteristics of hydrocarbon generation of desmocollinite are important to evaluate and explore oil and gas resources derive from coals. In this paper, Rock eval, Py GC and experimental simulation in an open system were used to study hydrocarbon generation potential, hydrocarbon composition, hydrocarbon generation model and thermoevolutional characteristics of desmocollinite. The results indicate that desmocollinite has high hydrocarbon generation potential, with (S ₁+S ₂) of 191.6mg/g, which is higher than that of fusinite (S ₁+S ₂ is 26.2mg/g,), and lower than of barkinite (S ₁+S ₂ is 297mg/g); light hydrocarbon (C ₆-C ₁₄ )and wet gas (C ₂-C ₅)are the main hydrocarbon composition; the "oil window" of desmocollinite is within 375～475 ℃, the main temperature range of hydrocarbon generation is at 400～450 ℃ with a peak range of 410～430 ℃, and the temperature of maximum hydrocarbon generating rates is at 420 ℃. These studies show that desmocollinite from barkinite rich coal is one of oil generated macerals, which is attributed to abundant submicro liptinites in desmocollinite,and desmocollinite also can generate a large amount of hydrocarbon in higher mature degree, these hydrocarbon generating model of desmocollinite is favorable for exploring oil and gas resources in South China.