拉尼甘杰页岩热解S2-峰值特征对干酪根动力学与其它热成熟度进程的复杂反映

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拉尼甘杰页岩热解S2-峰值特征对干酪根动力学与其它热成熟度进程的复杂反映

Ager,2018, 2(4): 343-368

原文网址：http://www.astp-agr.com/index.php/Index/Index/detail?id=76

  印度拉尼甘杰盆地的二叠纪页岩经历了岩浆侵入（白垩系）之前的快速下沉（侏罗纪早期白垩系）、快速上升和侵蚀（晚白垩第三纪）的戏剧性埋藏史。从早期成熟到过度成熟，这些页岩具有干酪根显微组分和典型的热信号，这体现了它们热解S2-峰值的特征。其中一些页岩100年以前到达热成熟的峰值，并持续到现在。在这些页岩中开采页岩气资源具有很大的潜能，并且它们的S2-峰值特征有助于我们找到开发的最有效点。

在不同的热成熟阶段，该论文分析了这些页岩的单速率和多速率发热坡板岩石热解数据。从S2峰值的形状可以清楚的了解热演化中的干酪根动力学。然而，用干酪根动力学混合模型拟合峰值形状的详细拟合结果表明：除了静态一级反应动力学，S2峰值的形状特征还受其他因素的影响。这些因素有可能包括：在有些干酪根成分上受硫磺和炭影响的催化效应、复杂埋藏和热成熟史期间干酪根孔径分布的改变。达到成熟峰值的页岩已经产出页岩气，并且有可能含有大量的页岩气，这些页岩气赋存在一些干酪根纳米孔道中，也许会在S2热解发热坡道期间释放出来，而不在S1发热坡道期间释放。这使得S2峰值在成熟页岩中扩大，这一特点可以被用来作为区域勘探的标识，也最适合页岩气开发利用。

Pyrolysis S2-peak characteristics of Raniganj shales (India) reflect complex combinations of kerogen kinetics and other processes related to different levels of thermal maturity

David A. Wood, Bodhisatwa Hazra

(Published: 2018-08-01)

CorrespondingAuthor and Email: David A. Wood, dw@dwasolutions.com

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Citation: Wood, D.A., Hazra, B. Pyrolysis S2-peak characteristics of raniganj shales (India) reflect complex combinations of kerogen kinetics and other processes related to different levels of thermal maturity. Advances in Geo-Energy Research, 2018, 2(4): 343-368, doi: 10.26804/ager.2018.04.01.

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ArticleType: Original article

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Abstract：

    The Permian shales of the Raniganj basin, India, have experienced a dramatic burial history of rapid subsidence (Jurassic-Early Cretaceous) followed by igneous intrusion (Cretaceous) and rapid uplift and erosion (Late Cretaceous-Tertiary). This has left these shales with mixed kerogen macerals with a characteristic thermal signature, ranging from early mature to post mature, which is reflected in the characteristics of their pyrolysis S2 peak. Many of these shales are today at peak thermal maturity but reached that condition more than 100 million years ago. They have significant potential to be exploited as a shale gas resource and their S2 peak characteristics should help to identify sweet spots for such exploitation. Here we analyze single-rate and multi-rate heating ramp Rock-Eval data from a suite of these shales at varying stages of thermal maturity. The S2 peak shapes provide significant insight to the kerogen kinetics involved in their thermal evolution. However, detailed fitting of the peak shapes with kerogen-kinetic mixing models indicate that factors other than static first-order reaction kinetics are also involved in their S2-peak-shape characteristics. Such factors likely include the catalytic effects, influenced by sulfur and charcoal, on some kerogen components, and kerogen pore-size distribution changes during their complex burial and thermal maturation histories. It is likely that the peak-mature shales contain significant, already generated, gas trapped within some of the kerogen nanopores that may be released during the S2 pyrolysis heating ramp rather than during the S1 heating ramp. This causes the S2 peak to broaden in the mature shales, a characteristic that could be used as an exploration marker for zones best suited to shale gas exploitation.

Keywords: Kerogen kinetics from pyrolysis, gas-prone shales India, Rock-Eval variable heating rates, shale kinetic/physical properties, S2-peak-shape characterization.