南海盆地宝岛-松涛凹陷低位体系域时空组合特征及其与油气赋存关系

南海盆地宝岛-松涛凹陷低位体系域发育的多期次性受盆地演化的阶段性控制。在不同演化阶段。低位体系域的内部构成及其空间组合特征不同。在裂陷早期的陆相和海陆过渡相沉积背景下，低位体系域主要由冲积扇、扇三角洲构成，多呈孤立式分布。在裂陷晚期生长断层背景下，以盆底扇和斜坡扇为主，呈断控悬挂式。在坳陷期。低位体系域的沉积体呈相互依存式。在末端陡倾缓坡背景下，发育低位楔状复合体，以三角洲、低位楔、滑塌扇、斜坡扇、盆底扇等组合为特征。在似被动大陆边缘背景中，盆底扇、斜坡扇和前积楔均发育。这些低位沉积体位于有利的生储盖组合之中．可以形成岩性圈闭、地层-岩性及构造-岩性等复合型圈闭，具有广阔的勘探开发前景。图7表1参9

The spatial assemblage characteristics of the lowstand system tract and their occurrence with oil and gas, Baodao-Songtao Sag, South China Sea Basin

The inner-architecture of lowstand system tract (LST) of the Baodao-Songtao Sag in the South China Sea Basin was defined by the evolutionary phases of the basin. Accompanied by the evolutionary phases and deposited in the geological settings of the basin, the inner-architecture of LST and the spatial assemblage characteristics are diversified. During rifting, specifically in the nonmarine and epeiric settings, the lowstand sedimentary systems such as alluvial fans or fan deltas were distributed in a scattered and isolated way. In the growth fault setting, the fault-controlled suspension characterizes the distribution of the lowstand sedimentary systems. The slope fans and basin floor fans were well developed. During sagging, the lowstand sedimentary systems are co-existensive. Specifically, in the low slope or ramp with steep end, lowstand wedges were well developed. The spatial assemblage is characterized by delta-lowstand wedge, incised valley-slump fanlowstand fan and slump fan-slope fan-basin floor fan. In the quasi-passive continental margin setting, the spatial assemblage is characterized by basin floor fan-slope fan-lowstand wedge, which were all well developed. Due to their existence in a key position within the petroleum system, the aforementioned lowstand sedimentary systems may be developed into lithologic traps, lithologic-stratigraphic and lithologic-structural traps and constituted primary targets for hydrocarbon exploration and development.