乌审旗地区盐下奥陶系流体来源及其油气成藏意义
- 收稿日期:
2023-09-14
- 网络出版日期:
2024-01-05
摘要: 鄂尔多斯盆地乌审旗地区奥陶系马家沟组盐下碳酸盐岩储层中发育多期含有烃及沥青包裹体的方解石，对流体来源和油气成藏过程具有重要指示作用。通过岩心观察、岩石薄片鉴定、阴极发光、稀土元素、C、O、Sr同位素、显微荧光及激光拉曼等实验方法，划分方解石发育期次，分析成脉流体来源，开展流体包裹体研究，揭示与烃类伴生的流体活动对油气成藏的意义。研究结果表明，乌审旗地区碳酸盐岩储层中发育4期方解石脉（C1、C2、C3、C4），而且不同期次方解石脉特征及来源不同。C1和C4成脉流体来源于围岩溶解，其碳氧锶同位素与奥陶纪海水碳氧锶同位素一致，稀土配分模式具有海水特征。C2方解石脉具有很负的碳同位素值，较高87Sr/86Sr值和总稀土含量，Eu正异常，流体来源于外部地层。C3方解石具有较负的碳同位素值，更高的87Sr/86Sr值和总稀土含量，流体同样来源于外部地层。此外，C2和C3两期方解石脉上发育沥青包裹体，表明油气进入储层后发生裂解。方解石脉的研究有助于约束鄂尔多斯盆地及其他盆地的油气成藏过程。
The origin of the pre-salt Ordovician fluid and its significance for hydrocarbon accumulation in Wushenqi area
- Received Date:
2023-09-14
- Available Online:
2024-01-05
Abstract: Calcite containing hydrocarbon and asphalt inclusions developed in the Ordovician Majiagou Formation subsalt carbonate reservoir in the Wusenqi area of Ordos Basin, which is an important indicator of fluid source and hydrocarbon accumulation process. Through core observation, rock thin section identification, cathodoluminescence, rare earth elements, C, O, Sr isotopes, microfluorescence and laser Raman spectroscopy analysis, the calcite development stages were divided, the sources of vein forming fluids were analyzed, and the fluid inclusions were studied to reveal the significance of hydrocarbon activities on oil and gas accumulation. The results show that 4 stages of calcite veins (C1, C2, C3, C4) are developed in the carbonate reservoir in Wushenqi area, and the characteristics and sources of secondary calcite veins are different in different periods. The C1 and C4 vein forming fluids are derived from the dissolved surrounding rocks, and their isotopes of strontium carbon and oxygen are consistent with those of Ordovician seawater, and the rare earth partition pattern is characteristic of seawater. C2 calcite veins have very negative carbon isotope values, high 87Sr/86Sr values and total rare earth content, positive Eu anomaly, and the fluid comes from external fluids. C3 calcite has a negative carbon isotope value, higher 87Sr/86Sr values and total rare earth content, and the fluid is derived from external fluids. In addition, asphaltic inclusions developed on calcite veins of C2 and C3 stages, indicating that oil and gas cracked after entering the reservoir. The geochemical characteristics of calcite veins in the study area provide a theoretical basis for oil and gas accumulation in Ordos Basin and other basins.
张洁, 贾连奇, 范立勇, 马占荣, 罗晓容, 秦彪, 王怡帅. 乌审旗地区盐下奥陶系流体来源及其油气成藏意义[J]. 沉积学报. doi: 10.14027/j.issn.1000-0550.2023.136
The origin of the pre-salt Ordovician fluid and its significance for hydrocarbon accumulation in Wushenqi area[J]. Acta Sedimentologica Sinica. doi: 10.14027/j.issn.1000-0550.2023.136
| Citation: |
The origin of the pre-salt Ordovician fluid and its significance for hydrocarbon accumulation in Wushenqi area[J]. Acta Sedimentologica Sinica. doi: 10.14027/j.issn.1000-0550.2023.136
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