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Linking source rock to expelled hydrocarbons using diamondoids: an integrated approach from the Northern Gulf of Mexico
Journal of Petroleum Science and Engineering ( IF 5.168 ) Pub Date : 2020-10-13 , DOI: 10.1016/j.petrol.2020.108015
R. Forkner , A. Fildani , J. Ochoa , J.M. Moldowan

Nanodiamonds (diamondoids) are the ideal geochemical tool for hydrocarbon-source correlation in high-maturity fields since they are thermally stable and outlast biomarkers (molecular fossils), which deteriorate with thermal maturity. Diamondoids form in the shallow subsurface as organic material reacts with clay minerals in source rock, thereby preserving information about the precursor organic compounds and parent minerals. The unique suites of diamondoids generated by these combinations allow direct linkage between expelled hydrocarbons and source rock facies. We compared diamondoid distributions obtained from oils produced from both Eagle Ford Fm. and Austin Chalk Fm. in South-Central Texas, to rock extracts taken from equivalent intervals in a cored pilot hole. The targeted well is in the gas window where biomarkers are of limited use. Diamondoid distributions from oils produced from laterals in the Eagle Ford Fm. and the Austin Chalk Fm. matched extracts from those formations, proving that local sourcing is recognizable in expelled hydrocarbons.

A second phase of this project included a direct comparison of results from pilot hole extracts to diamondoids analyzed from 15 oils selected from producing Eagle Ford wells. We showed a close match between the diamondoid chemistry of produced oils regionally and source samples from the Eagle Ford Formation in the cored pilot well. However, samples from immediately adjacent formations (Buda and Upson) were discordant, containing higher concentrations and different distributions of diamondoids when compared to the Austin and Eagle Ford systems.

These results spurred a third phase of investigation that included generating diamondoid data from extracts of known Mesozoic Northern Gulf of Mexico (NGoM) source rocks stratigraphically beneath the Austin and Eagle Ford system. These included The Aptian-Albian Pearsall group and several Jurassic formations (Oxfordian Smackover Fm., Kimmeridgian Haynesville Fm., and Tithonian Bossier Fm.). The outlier samples from phases 1 and 2 are matched with deeper source rocks when comparing their diamondoid geochemistry to those of extracts from cored Jurassic source samples. These Jurassic intervals and migration pathways were then vetted with seismic data and integrated attribute analysis.

The results of this work show: 1. expelled hydrocarbons can be linked to parent source rock using diamondoid composition; 2. diamondoids can be used to discriminate co-sourcing in intervals where routine biomarker analyses would fail; 3. Samples of well-known Mesozoic source rocks in the northern Gulf of Mexico (Cenomanian-Turonian Eagle Ford, Tithonian Bossier, Kimmeridgian Haynesville, and Oxfordian Smackover) can be independently recognized using diamondoids, and 4. seismic anisotropy and fluid escape attributes helped delineate both deep-seated, through-going faults and intervals of high fracture density, allowing for connectivity and migration from the deeper source rocks illuminated by diamondoid analyses.



中文翻译:

使用类金刚石将烃源岩与排出的烃类联系起来:墨西哥北部湾的一种综合方法

纳米金刚石(菱形化合物)是高稳定性油田中烃源相关性的理想地球化学工具,因为它们具有热稳定性,并且生物标志物(分子化石)的寿命也随着热成熟而变差。当有机物质与烃源岩中的粘土矿物发生反应时,类金刚石会在浅层地下形成,从而保留了有关前体有机化合物和母体矿物的信息。通过这些组合生成的独特类钻,可以将驱出的烃类与烃源岩相直接联系起来。我们比较了从两种Eagle Ford Fm生产的机油获得的类金刚石分布。和Austin Chalk Fm。在得克萨斯州中南部的一个带孔的先导孔中以等间隔提取岩石提取物。目标井位于生物标志物使用受限的气窗中。Eagle Ford Fm的分支油中的类金刚石分布。和Austin Chalk Fm。与这些地层的提取物相匹配,证明在驱出的碳氢化合物中可以识别本地采购。

该项目的第二阶段包括直接比较试验孔提取物与类金刚石的结果,该类金刚石是从从Eagle Ford井中选择的15种油中分析出来的。我们显示出该地区采出油的类金刚石化学与有芯中试井中伊格尔福特地层的源样品之间的匹配程度很高。但是,与奥斯汀和伊格福特系统相比,紧邻地层(布达和厄普森)的样品不一致,含有更高的浓度和类金刚石的不同分布。

这些结果激发了第三阶段的研究,包括从奥斯汀和伊格福特系统的地层下从已知的中生代墨西哥北部湾(NGoM)烃源岩提取物中生成类金刚石数据。这些包括Aptian-Albian Pearsall组和几个侏罗纪地层(Oxfordian Smackover Fm。,Kimmeridgian Haynesville Fm。和Tithonian Bossier Fm。)。当将第一阶段和第二阶段的离群样品的类金刚石地球化学与取自有芯侏罗纪源样品的提取物进行比较时,它们与较深的烃源岩相匹配。然后,通过地震数据和综合属性分析,对这些侏罗纪层段和偏移路径进行了审查。

这项工作的结果表明:1.排出的碳氢化合物可以通过类金刚石成分与母源岩联系起来;2.类钻可以在常规生物标志物分析失败的时间间隔内区分共同来源;3.可以使用类金刚石来独立地识别墨西哥湾北部著名的中生代烃源岩样品(西诺曼尼亚-突尼斯的伊格福特,蒂通尼的波西尔,基米第吉安的海恩斯维尔和牛津的Smackover),以及4.地震各向异性和流体逸出属性有助于描绘了深部贯穿的断层和高裂缝密度的层段,允许通过类钻分析得到的较深烃源岩的连通性和运移。

更新日期:2020-10-13
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