菱铁矿对烃源岩中有机质热解的影响

Effect of siderite on pyrolysis of organic matters in source rocks

烃源岩中有机质热解受无机矿物影响,利用热重实验分析柴北缘大煤沟组含菱铁矿烃源岩的热失重特征,揭示菱铁矿在有机质热解过程中的作用。热重实验结果表明,菱铁矿对烃源岩中有机质热解具有促进作用,一方面使有机质热解速率明显增大,另一方面使有机质主要热解温度提前。热动力学计算结果表明,菱铁矿对有机质热解的促进作用主要通过降低热解反应的活化能,从而改变了有机质的热解速率以及热解时机。菱铁矿对有机质热解的影响作用分为两个阶段:中-低温阶段(A1~A2),菱铁矿产生促进作用;高温阶段(A2~A3),菱铁矿热分解生成含铁氧化物与二氧化碳,其对有机质热解的促进作用可能包括多种来源。菱铁矿对有机质热解具有促进作用,这与方解石、白云石等其他碳酸盐矿物对有机质热解的影响不同。

The pyrolysis of organic matters in source rocks is influenced by inorganic minerals.Thermogravimetric experiment was conducted to analyze the thermal weight loss characteristics of the siderite-bearing source rocks of the Dameigou Formation in northern Qaidam Basin,and to reveal the role of siderite on the pyrolysis of organic matters.Thermogravimetric experiment showed that siderite promoted the pyrolysis of organic matters by increasing the pyrolysis rate.On the other hand,the main pyrolysis periods of organic matters were advanced.Siderite promotes the pyrolysis of organic matters by reducing the activation energy of the pyrolysis reaction;as a result,the rate and periods of hydrocarbon generation change.The effects of siderite on the pyrolysis of organic matters can be divided into two stages:in the low-middle temperature stage,Siderite works,in high temperature stage,siderite is thermally decomposed to form iron oxides and carbon dioxide,the promotion may include multiple ways.Siderite promotes the pyrolysis of organic matters,which is different from that of calcite,dolomite and other carbonate minerals.