Geology and formation mechanism of late Quaternary shallow biogenic gas reservoirs in the Hangzhou Bay area, eastern China
Geology and formation mechanism of late Quaternary shallow biogenic gas reservoirs in the Hangzhou Bay area, eastern China
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DOI：
10.1306/01070403038
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发表时间：
2004-05
期刊：
影响因子：
3.5
通讯作者：
Chun-Ming Lin;L. Gu;Guigen Li;Y. Y. Zhao-Y.;W. Jiang
中科院分区：
文献类型：
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作者：
Chun-Ming Lin;L. Gu;Guigen Li;Y. Y. Zhao-Y.;W. Jiang
浙江北方杭州湾地区晚第四纪浅层生物气藏是近年来发现和开发的一个重要气藏。在最盛冰期，该地区河流强烈切割下伏古河床，形成钱塘江和太湖下切河谷。这些下切的山谷充满了河流沉积物，并在冰后期被海洋沉积物掩埋。下切河谷区晚第四纪地层自下而上由四种沉积相组成：河床相（IV）、洪泛平原相（III）、滨海湾相（II）和河口湾相（I），工业气田均产于下切河谷洪泛平原砂体中。这些尸体埋深3060米（98197英尺），厚3.07.0米（9.823英尺），最大厚度超过10米（33英尺）。它们被不透水的粘土所包围。上覆滨海湾沉积物的快速沉积不仅提供了丰富的气源，而且提供了良好的保存条件。主要烃源岩为洪泛平原相的深灰色粘土和滨海湾相的灰色泥岩。两相沉积物有机碳含量一般大于0.4%。浅层生物气田和深层气田需要截然不同的钻井和完井技术。生物气田的钻完井成本低得多，东部沿海除洪洲湾外的第四系下切河谷和洪泛平原是进一步勘探浅层生物气的有利目标。
Late Quaternary shallow biogenic gas reservoirs have recently been discovered and exploited in the coastal Hangzhou Bay area, northern Zhejiang Province, eastern China. The river in this area strongly incised the underlying old beds during a period of glacial maximum, which resulted in the formation of the Qiantangjiang and the Taihu incised valleys. These incised valleys were filled with fluvial sediments and buried by marine sediments during the postglacial period. Late Quaternary strata of the incised-valley area are composed of four sedimentary facies in ascending order: fluvial floor facies (IV), flood-plain facies (III), sublittoral-marine bay facies (II), and estuarine facies (I).All commercial gas fields occur in flood-plain sand bodies of incised valleys. The bodies are buried 3060 m (98197 ft) deep and are 3.07.0 m (9.823 ft) thick, with a maximum thickness of more than 10 m (33 ft). They are surrounded by impermeable clays. Rapid deposition of overlying sublittoral-marine bay sediments supplied not only abundant gas sources, but also good preservation conditions. The main hydrocarbon sources are dark gray clays of the flood-plain facies and gray muds of the sublittoral-marine bay facies. Sediments of both facies have organic carbon content generally more than 0.4%. Shallow biogenic gas fields and deep gas fields require vastly different drilling and completion techniques. Drilling and completion costs are much lower for the biogenic gas fields.Quaternary incised valleys and flood plains other than Hongzhou Bay in coastal areas of eastern China are promising targets of further exploration for shallow biogenic gas.