Application of sulfur and carbon isotopes to oil-source rock correlation: A case study from the Tazhong area, Tarim Basin, China
Application of sulfur and carbon isotopes to oil-source rock correlation: A case study from the Tazhong area, Tarim Basin, China
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DOI：
10.1016/j.orggeochem.2015.03.012
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发表时间：
2015-06-01
影响因子：
3
通讯作者：
Zhang, Baoshou
中科院分区：
文献类型：
--
作者：
Cai, Chunfang;Zhang, Chunming;Zhang, Baoshou
到目前为止，人们一直认为塔中隆起古生代储层中的石油来源于上奥陶统烃源岩。最近在塔中1井和塔中5井中寒武统和下寒武统产出的石油为中国塔里木盆地塔中隆起石油的烃源岩提供了线索。在本研究中，对潜在烃源岩以及寒武系和奥陶系储层中的石油测定了分子组成、正构烷烃整体及单体的δC - 13值以及烷基二苯并噻吩单体的δS - 34值，以确定石油的来源，并探讨δC - 13和δS - 34值是否可有效地用于油 - 源岩对比。塔中1井和塔中5井的寒武系石油以及奥陶系储层中的其他六种石油未受到热化学硫酸盐还原作用（TSR）的显著改造。塔中1井的石油以及大多数其他石油在C - 27 - C - 29甾烷分布上呈“V”形，正构烷烃整体及单体的δC - 13值主要在 - 31‰至 - 35‰（相对于维也纳盆地白垩系箭石化石标准，VPDB）之间，烷基二苯并噻吩整体及单体的δS - 34值在15‰至23‰（相对于维也纳峡谷地沥青标准，VCDT）之间。这些特征与某些寒武系烃源岩相似，这些烃源岩的干酪根δC - 13值在 - 34.1‰至 - 35.3‰之间，δS - 34值在10.4‰至21.6‰之间。英买2井中下奥陶统产出的石油与塔中1井寒武系石油具有相似特征。这些新的证据表明，与先前的解释相反，塔中隆起的大多数石油可能来源于寒武系烃源岩，而非上奥陶统。相反，由于热化学硫酸盐还原作用（TSR），塔中1井寒武系石油的δC - 13和δS - 34值已显示向更正的值偏移。因此，δC - 13和δS - 34值可作为有效的工具用于证明油 - 源岩的相关性，但这仅仅是因为该区域受TSR影响很小或没有受到影响。（C）2015爱思唯尔有限公司。保留所有权利。
Up until now, it has been assumed that oil in the Palaeozoic reservoirs of the Tazhong Uplift was derived from Upper Ordovician source rocks. Oils recently produced from the Middle and Lower Cambrian in wells ZS1 and ZS5 provide clues concerning the source rocks of the oils in the Tazhong Uplift, Tarim Basin, China. For this study, molecular composition, bulk and individual n-alkane delta C-13 and individual alkyl-dibenzothiophene delta S-34 values were determined for the potential source rocks and for oils from Cambrian and Ordovician reservoirs to determine the sources of the oils and to address whether delta C-13 and delta S-34 values can be used effectively for oil-source rock correlation purposes. The ZS1 and ZS5 Cambrian oils, and six other oils from Ordovician reservoirs, were not significantly altered by TSR. The ZS1 oils and most of the other oils, have a "V'' shape in the distribution of C-27-C-29 steranes, bulk and individual n-alkane delta C-13 values predominantly between -31% to -35% VPDB, and bulk and individual alkyldibenzothiophene delta S-34 values between 15% to 23% VCDT. These characteristics are similar to those for some Cambrian source rocks with kerogen delta C-13 values between -34.1% and -35.3% and delta S-34 values between 10.4% and 21.6%. The oil produced from the Lower Ordovician in well YM2 has similar features to the ZS1 Cambrian oils. These new lines of evidence indicate that most of the oils in the Tazhong Uplift, contrary to previous interpretations, were probably derived from the Cambrian source rocks, and not from the Upper Ordovician. Conversely, the delta C-13 and delta S-34 values of ZS1C Cambrian oils have been shown to shift to more positive values due to thermochemical sulfate reduction (TSR). Thus, delta C-13 and delta S-34 values can be used as effective tools to demonstrate oil-source rock correlation, but only because there has been little or no TSR in this part of the section. (C) 2015 Elsevier Ltd. All rights reserved.