鄂尔多斯盆地西部奥陶纪乌拉力克期岩相古地理特征【鄂尔多斯盆地乌拉力克组海相页岩气勘探专辑】
- 收稿日期:
2024-05-06
- 网络出版日期:
2024-10-09
摘要: 【目的】鄂尔多斯盆地西部中上奥陶统乌拉力克组发育一套黑色海相页岩，近年来多口乌拉力克组海相页岩气探井获得工业油气流，展现出良好的油气勘探潜力，而研究盆地西部奥陶纪岩相古地理有利于明确页岩气烃源岩、储层的展布及海相页岩气下步勘探方向。【方法】本文通过大量野外露头、钻井岩心、岩石薄片、元素地球化学等资料，综合研究了乌拉力克组岩石学特征、沉积相类型及沉积演化特征。【结果】研究结果表明：（1）乌拉力克组发育硅质页岩、钙质页岩、黏土质页岩、混合页岩、颗粒石灰岩等岩石类型，其中纹层型硅质页岩是最有利于页岩气勘探的岩石类型；（2）鄂尔多斯盆地西部乌拉力克期水体西深东浅，自西向东依次发育盆地相、广海陆棚相、斜坡相、碳酸盐岩台地相等四种沉积相类型；（3）鄂尔多斯盆地西部在乌拉力克期经历了多次海侵海退过程，水体逐渐变浅，沉积环境由深水向浅水过渡。【结论】综上，本文认为鄂尔多斯盆地西部乌拉力克期发育一套碳酸盐岩台地边缘沉积，其中广海陆棚相、斜坡相和颗粒滩亚相是下一步天然气有利的勘探相带。
Lithofacies Paleogeography Characteristics of Ordovician Wulalike Formation in the western margin of Ordos Basin
- Received Date:
2024-05-06
- Available Online:
2024-10-09
Abstract: [Objective] The western part of the Ordos Basin was located in the Qilian Sea area in the Middle-Late Ordovician Wulalike period, where a thick layer of black marine shale was developed. In recent years, many exploration wells in the Ordos Basin have produced industrial oil and gas flow from the Wulalike Formation, which demonstrates a good potential for exploration and development of marine shale oil and gas. The study of the Ordovician paleogeography in the western part of the basin is conducive to clarifying the distribution of hydrocarbon source rocks and reservoirs, as well as the next exploration direction of marine shale gas. [Methods] Through a large amount of field outcrops, drilling cores, rock thin sections, and elemental geochemistry data, this paper comprehensively studies the petrological characteristics, sedimentary facies types, and sedimentary evolution of the Wulalike Formation. [Results] The results show that: (1) Wulalike formation includes various types of rocks such as siliceous shale, calcareous shale, clay shale, mixed shale, and granular limestone, among which laminated siliceous shale was identified as the most favorable lithofacies for shale gas exploration; (2) Based on the analysis of sedimentary facies, five sedimentary facies types were identified from west to east: basin facies, broad sea shelf facies, slope facies, and carbonate platform facies; (3) During the Wulalike period, the western part of the Ordos Basin experienced multiple transgressive-regressive processes, with the water gradually becoming shallower and the sedimentary environment transitioning from deep water to shallow water. [Conclusion] In conclusion, a carbonate platform margin sedimentary model of the Wulalike period in the western Ordos Basin was established, and it was proposed that the broad sea shelf, slope, and granular shoal are favorable exploration facies for natural gas in the next step.
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