Sedimentary Characteristics and Petroleum Geological Significance of the Chang6 Gravity Flow in the Southwest Ordos Basin
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摘要: 鄂尔多斯盆地南部延长组长6油层组中发现大量块状无层理砂岩,属陡坡带处堆积的三角洲前缘沉积物沿斜坡滑塌形成的重力流沉积。综合岩芯、露头、测井及分析化验资料,认为延长组发育滑塌岩、液化沉积物流、砂质碎屑流和经典浊流等多种类型的重力流,不同类型重力流沉积特征差异明显;其中地形坡度、物源供给和一定的触发机制是形成长6重力流沉积的基本条件;在流动过程中由于水的混入和沉积物卸载,重力流沉积物发生浓度变化和流态转换,形成滑塌岩-砂质碎屑流、砂质碎屑流-浊流、浊流等不同组合类型;重力流砂岩延伸至半深湖-深湖相泥岩中,与长7烃源岩侧向连通,形成有利的成藏组合,是研究区延长组重要的勘探目标区。Abstract: There are a large number of massive sandstones in the Chang6 oil reservoir, Southwest Ordos Basin, which are gravity flows from sediments slumping along the slope in a delta front. We determined that there are different kinds of gravity flows, such as slumps, liquefied sediment flows, sandy debris flows, and turbidites, in the Yanchang Formation based on cores, outcrops, logging, and testing data. The slope, sediment supply, and trigger mechanism are the basic formation in the Chang6 gravity flow. Concentration and flow state change due to water maxing and sediment unloading during the flow process and form different kinds of combinations, such as slumps-sandy debris flow, sandy debris flow-turbidite, and turbidite. The gravity flow sandstone extends in the semi-deep lake and deep lake mudstone lateral connection with source rock in the Chang7 oil reservoir and develops favorable reservoir forming assemblages, which are the most important target zone of the Yanchang Formation in the study area.
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图 2 长6油层组滑塌岩、液化沉积物流沉积特征
(a)HH106井,2 138.2 m,变形层理粉砂岩相;(b)HH9井,1 937.2 m,脉状层理粉砂岩相;(c)HH106井,2 230.4 m,透镜层理细砂岩相,顶部见小型交错层理;(d)ZT3井,2 051.5 m,变形层理粉砂岩相,见砂岩透镜体;(e)HH3井,2 248.9 m,浅灰色泥岩,包卷层理;(f)HH106井,2 238.4 m,浅灰色泥岩,搅浑构造;(g)HH9井,1 936.5 m,浅灰色泥岩,微断层;(h)HH66井,1 907.4 m,变形层理粉砂岩相,角砾状泥岩撕裂屑;(i)HH3井,2 250.14 m,浅灰色泥岩,底部具粉砂质团块;(j)HH3井,2 251.02 m,浅灰色泥岩,含粉砂质条带;(k)HH5井,2 212.36 m,浅灰色粉砂岩,泄水构造;(l)HH9井,1 950.6 m,浅灰色泥岩,含粉砂质斑块
Figure 2. Sedimentary characteristics of fluidized sediment and turbidite flows
图 3 长6油层组碎屑流、浊流沉积特征
(a)HH3井,2 250.2 m,块状层理砂岩相,顶部具水平层理;(b)HH66井,1 912.4 m,块状层理砂岩相,底部具扁平状泥砾,定向排列;(c)HH9井,1 935.79 m,块状层理砂岩相,底部具扁平状泥砾;(d)HH7井,2 404.22 m,平行层理粉砂岩相,板条状泥岩撕裂屑定向排列;(e)HH81井,1 981.0 m,平行层理粉砂岩相,底部具剪切面,与下伏泥岩突变接触;(f)HH65井,2 129.5 m,粒序层理砂岩相,底部见次棱角状砾石;(g)HH106井,2 080.5 m,波状层理粉砂岩相;(h)HH78井,2 247 m,平行层理粉砂岩,见微波状构造;(i)HH65井,2 054 m,深灰色泥岩相,底面见槽模构造;(j)HH81井,1 992.5 m,深灰色泥岩相,底面见沟模构造;(k)HH66井,2 054 m,浅灰色泥岩相,槽模构造;(l)HH106井,2 226.3 m,变形层理粉砂岩相,球枕状构造
Figure 3. Sedimentary characteristics of sandy and muddy debris flows in the Chang6 oil reservoir
图 7 研究区HH76~HH5井长6沉积相连井剖面图(剖面位置见图 6)
Figure 7. Sedimentary facies cross-section of wells HH76-HH5 from the Chang6 reservoir in the study area
图 9 鄂尔多斯盆地南部延长组长6油藏剖面图(剖面位置见图 6)
Figure 9. Reservoir profile of the Chang6 reservoir in the southern Ordos Basin
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