东营凹陷沙三中亚段三角洲前缘滑塌型重力流岩相类型及其分布特征

以东营凹陷沙三中亚段三角洲前缘滑塌型重力流砂体为研究对象,利用三维地震、钻井岩心、测录井和分析测试等资料,开展三角洲前缘滑塌型重力流砂体岩相和岩相组合类型划分及分布特征研究。根据泥质含量和沉积构造,划分出13种岩相类型,其中块状层理砂岩相在研究区最为发育。以泥岩、冲刷面或岩相转化面为界,划分出20种岩相组合类型,分为5大类,分别是保留原始沉积构造的岩相组合、变形构造发育的岩相组合、块状层理和碎屑发育的岩相组合、下部碎屑流和上部浊流沉积的岩相组合,以及不完整鲍马序列的岩相组合,反映重力驱动事件中的滑动、滑塌、碎屑流、碎屑流-浊流、浊流沉积作用。根据不同类型重力流的垂向组合和典型剖面岩相分布特征,认为从盆地斜坡到盆地平原,重力流呈现滑动-滑塌-碎屑流-浊流演化特征,滑塌近端主要发育滑动作用岩相组合和滑塌作用岩相组合,滑塌中部主要发育碎屑流岩相组合和碎屑流与浊流过渡转化岩相组合,滑塌远端主要发育浊流作用岩相组合。

Delta front gravity flow deposits in the middle submember of the third member of the Shahejie Formation in the Dongying depression:Lithofacies and lithofacies association types and their distribution

Exemplified by the delta front deep-water gravity flow deposits in the middle submember of the third member of the Shahejie Formation in the Dongying depression, the emphasis in the present paper is placed on the classification and distribution of the lithofacies and lithofacies association types according to 3-D seismic data, core data, well logs and analytical results. The deep-water gravity flow deposits are divided into 13 lithofacies types according to mud contents and sedimentary structures, and 20 lithofacies association types which are involved into five categories, i. e., the lithofacies associations (1) with primary sedimentary structures;(2) with synsedimentary deformational structures;(3)with the massive beddings and abundant clasts;(4)with the lower debris flow deposits and upper turbidity current deposits, and (5)with imcomplete Bouma sequences. Judged from the lithofacies and lithofacies associations types and distribution of delta front gravity flow deposits types, there are gradations of slide-slump-debris flow-turbidity current from the slope to the deep-water plain. The slide-and slump-dominated lithofacies and lithofacies association types are observed in the proximal part;the debris flow-and mixed debris flow-turbidity current dominated lithofacies associations appear in the central part, and turbidity current-dominated lithofacies associations are common in the distal part. The redivision of lithofacies and lithofacies associations types may be helpful to the prediction of the gravity flow sandstones and future petroleum exploration in the study area.