塔里木盆地塔中19井奥陶系蓬莱坝组云灰互层段的 岩性旋回特征与“顶侵型”埋藏云化模式的建立
- 中国石油塔里木油田分公司勘探开发研究院博士后工作站 新疆库尔勒 841000
- 收稿日期:
1900-01-01
- 修回日期:
1900-01-01
- 刊出日期:
2009-04-10
摘要: 在塔里木盆地西部台地区奥陶系蓬莱坝组地层中，发育了厚层的白云岩与灰岩的互层段，其中塔中19井蓬莱坝组云灰互层段存在着相对固定的岩性旋回，每个旋回上段为泥晶灰岩，中段为粉晶云岩，下段为硅化砂屑灰岩。对旋回3段泥晶灰岩/粉晶云岩/硅化砂屑（球粒）灰岩进行了地球化学研究发现：1）微量元素组成上，相比于泥晶灰岩与砂屑灰岩，白云岩富集大多数种类的微量元素。一般来说，白云岩样品的稀土总量（6.17×10-6～18.62×10-6）都高于互层的灰岩样品(2.86×10-6～6.80×10-6)，但在PAAS标准化图解上，两者的配分模式却很一致，指示了白云岩为灰岩云化的产物。2）白云岩化分为两个期次，分别形成了高钡云岩与低钡云岩。高钡云岩表现出了高S特征，指示了Ba以重晶石形式在白云岩中富存；同时高钡云岩其高Fe、Mn含量特征指示了高钡云岩云化卤水来自热液。3）高钡云岩与低钡云岩表现出了不同的碳、氧同位素特征，指示了两期白云岩化事件。高钡云岩δ13C值与灰岩相当，δ18O值较高（-6.0‰～-3.2‰），可能指示了交代流体来源于岩浆热液;低钡云岩δ13C值为-1.7‰～-1.5‰，高于泥晶灰岩，δ18O值变化为-9.7‰～-8.5‰，低于泥晶灰岩，推测交代流体为海水演化热液。4）灰岩87Sr/86Sr值变化很小，为0.708 983～0.709 039，粉晶云岩白云岩87Sr/86Sr值较高，并且变化范围较大，为0.708 914～0.709 409，可能由成岩作用演化造成。由于粉晶云岩沿低孔渗条件的泥晶灰岩下层分布，热液流体进入云化体系的方式只能为流体从底部通过裂缝向上运移，遇盖层封堵而沿盖层下层流动发生云化。我们将这种云化模式定义为“顶侵型埋藏云化模式”，该模式下形成的白云岩与其上泥晶灰岩构成了良好的储盖组合，具有广阔的勘探前景。
The Petrologic Rhythm of Lower Ordovician Penglaiba Formation Encoun tered by Well Tazhong 19 and New Dolomitization Model, Tarim Basin
- Tarim Oil Field Company Exploration and Development Research Institute, Korla Xinjiang 841000
- Received Date:
1900-01-01
- Rev Recd Date:
1900-01-01
- Publish Date:
2009-04-10
Abstract: In the lower Ordovician Penglaiba Formation of Tarim basin occur thick strata of interbeded dolostone and limestone, which show a relatively constant petrologic rhythm in Tazhong19 well: three parts can be observed in every rhythm, the upper part is microlite limestone, middle part is dolostone, and lower part is siliceous granular limestone. The geochemical research on the limestones and dolostones show: 1) compared with limestones, dolostones are enriched in most of trace elements. Dolostones show a higher content of total rare earth elements than limestones but similar PAASnormalized patterns were demonstrated between limestones and dolostones, which indicates that the rare earth elements in dolostones might have come from limestones by dolomitization. 2) There are two dolomitization events and the productions are Barich dolostones and Bapoor dolostones, respectively. Ba content in Barich dolostone is as high as 2 312×10-6. Meanwhile, high sulfur concentrations were demonstrated in Barich dolostones, which indicate that the Formation of Ba in dolostones is hydrothermal BaSO4. High Fe, Mn content in Barich dolostones also showed the hydrothermal origin of dolomitization fluid. 3) An obvious difference in carbon and oxygen isotope composition was shown between Barich dolostone and Bapoor dolostone. The carbon isotope compositons in Barich dolostone were similar to limestones, with values ranging from 2.5‰～2.3‰, but a higher oxygen isotope with value ranging from 6.0‰～3.2‰, maybe as a result of dolomitization by magmatic hydrothermal fluid; In Bapoor dolostone, δ18O values vary in a lower range of9.7‰～8.5‰, and a higher range of 1.7‰～1.5‰ for carbon isotope compositions, maybe as a result of dolomitization by evolved hydrothermal seawater; 4) 87Sr/86Sr values of dolostones vary in 0.708 914～0.709 409, higher than limestones (0.708 983～0.709 039), maybe as a result of the later diagenesis alternations. Because of the spatial relations between microlite limestone and dolostones, the dolomitization fluids can not penetrate the limestone to dolostone layers, therefore, the dolomitizations fluids must have originated from deep hydrothermal fluid. By some cleavage or tectonic movement the hydrothermal fluids upwelled, encountered the microlite limstones and started dolomitization along the bottom of limestones. We can define the model as “up erosion model”, by which the dolostones and the upper limestone will construct very good reservoircover combinations.
陈永权. 塔里木盆地塔中19井奥陶系蓬莱坝组云灰互层段的 岩性旋回特征与“顶侵型”埋藏云化模式的建立[J]. 沉积学报, 2009, 27(2): 202-211.
| 引用本文: |
陈永权. 塔里木盆地塔中19井奥陶系蓬莱坝组云灰互层段的 岩性旋回特征与“顶侵型”埋藏云化模式的建立[J]. 沉积学报, 2009, 27(2): 202-211.
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CHEN Yongquan. The Petrologic Rhythm of Lower Ordovician Penglaiba Formation Encoun tered by Well Tazhong 19 and New Dolomitization Model, Tarim Basin[J]. Acta Sedimentologica Sinica, 2009, 27(2): 202-211.
| Citation: |
CHEN Yongquan. The Petrologic Rhythm of Lower Ordovician Penglaiba Formation Encoun tered by Well Tazhong 19 and New Dolomitization Model, Tarim Basin[J]. Acta Sedimentologica Sinica, 2009, 27(2): 202-211.
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