Study on the Generation Features of Gaseous Hydrocarbon in Different Source Ro cks —— Evidences from DTA coupled with chromatography thermal simulation
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摘要: 运用差热—色谱联机分析仪对不同煤阶的标准煤样及泥岩和碳酸盐岩烃源岩的热模拟研究表明,低成熟的煤具有更强的放热反应和较大的失重量,其放热反应第一峰温度和失重温度相对较低。低煤阶煤在热模拟过程中比高煤阶煤具有更强的生烃能力。烃源岩气态烃的生成量和特征不仅受控于烃源岩中有机质的丰度而且与其岩石类型、干酪根类型、成熟度等存在着密切关系。成熟度较高的烃源岩属耗尽了的烃源岩,其生烃能力相对较弱。含Ⅰ、Ⅱ型干酪根烃源岩生成的气态烃中重组分含量普遍较高,含Ⅲ型干酪根烃源岩生成的气态烃中甲、乙烷等轻组分含量普遍较高。碳酸盐岩烃源岩在热模拟的高温阶段往往能生成比较大量的气态烃。Abstract: To understand the thermal evolution process and hydrocarbon-forming mech anism of organic matter, the researchers have done lots of hydrocarbon-generatio n experiments on the sediment and rock-containing organic matter. In this paper we have adopted the method DTA coupled with chromatography to simulate the gener ation of gaseous hydrocarbon from the standard coal samples of different ranks a nd oth er source rocks. The method is of the following advantages: (1) rapid temperatur e-rising speed and without influence of pressure; (2) continuous sampling; (3) o nly gaseous hydrocarbon analysed; (4) directly comparing gas-forming state of so urce rock with DTA and weight loss features; (5) less human-induced influence on experiment results. By use of the new analysis method, we have concluded that the low-mature c oal has the strongest exothermic reaction and weight loss in relatively lower th e first temperature of exothemic reaction and weight loss temperature. And the c oal sample with low rank has much stronger hydrocarbon-generating capacity than those with high rank in the course of the themal simulation. The generation amou nt and features of the gaseous hydrocarbon are dependent not only on the abundan ce of organic matter,but also rock types,kerogen types,maturation degree and so on. Source rocks with higher maturation degree belongs to the exhausted rock of the weaker hydrocarbon-generating capacity. Gaseous hydrocarbon produced from th e source rock containing Ⅰ and Ⅱ-type kerogens is generally of the high conten t of heavy components, whereas those formed from the source rock bearing Ⅲ-type kerogen is mainly composed of the light components such as methane and ethane. Carbonate source rocks have weaker hydrocarbon-generating capacity in the proces s of the thermal simulation due to their low content of organic carbon, but the much higher temperature can increase the internal pressure of the inclusion in c arbonate crystals resulting in explosion to release "effective hydrocarbon". Thus, carbonate source rock can usually produce large amounts of gaseous hydroc arbon at the higher temperature stage during thermal simulation.
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