川东地区三叠系嘉陵江组邻水-丰都台凹的发现及油气勘探意义

地质历史时期的构造-沉积分异作用对大型含油气盆地内碳酸盐岩层系的沉积充填过程及成藏地质条件具有重要影响。通过覆盖全区的二维地震及钻测井资料，对川东地区三叠系嘉陵江组沉积时期隆凹格局及古地理演化进行了精细刻画。研究结果表明: ①从地震剖面、地层及岩性组合等特征上识别出邻水-丰都台凹，其两侧坡度为 1°～2°，且左侧坡度大于右侧坡度；②邻水-丰都台凹与其他古地质单元共同控制了嘉二段沉积时期川东地区的古地理格局及构造-沉积分异特征，嘉二段沉积早-中期，颗粒滩沿邻水-丰都台凹周缘发育，晚期台凹内则大面积发育膏质潟湖沉积；③邻水-丰都台凹及周缘微古地貌控制沉积早期颗粒滩分布，台凹周缘地貌高部位更易形成优质白云岩储层，持续干旱、蒸发环境致使沉积晚期台凹内形成区域盖层沉积；④总体来看，嘉二段具备良好的成藏地质条件，有望成为寻找滩相整装气藏的战略勘探层系，建议将邻水-丰都台凹周缘台内滩相发育带作为川东地区嘉陵江组下步勘探重点区之一。

Discovery of Linshui-Fengdu intra-platform depression of Triassic Jialingjiang Formation in eastern Sichuan Basin and its significance for oil and gas exploration

The tectono-sedimentary differentiation through geologic history has an important influence on the tectonicsedimentary filling processes of the carbonate strata and the geological conditions for hydrocarbon accumulation in large petroliferous basins. Through the high-density 2D seismic data and logging-drilling data covering the whole area，the uplift and sag patterns and paleogeographic evolution of eastern Sichuan Basin during the depositional period of Triassic Jialingjiang Formation were described in detail. The results show that: (1) Linshui-Fengdu intra-platform depression was identified from the characteristics of seismic section，stratigraphic and lithological combination. Its slope is about 1°-2°，and the slope on the left is greater than the slope on the right. (2) LinshuiFengdu intra-platform depression and other paleogeological units jointly controlled the paleogeographic pattern and tectono-sedimentary differentiation during the depositional period of the second member of Triassic Jianglingjiang Formation (T₁ j²). The intra-platform depression controlled the distribution of shoal around it during the early and middle period of T₁ j²，and a large area of gypsum lagoons developed in the intra-platform depression during the late period. (3) The Linshui-Fengdu intra-platform depression，with around micro-paleo-geomorphology， controlled the distribution of grain shoals during the early depositional period，and high-quality dolomite reservoirs were more likely to be formed in the high parts of the peripheral structure. The continuous arid and evaporative environment formed a regional cap layer. (4) In general，the T₁ j² has good reservoir-forming geological conditions and is expected to be a strategic exploration area for searching as shoal-facies monoblock gas reservoirs. It is recommended that the high-energy intra-platform shoal facies development belt around the Linshui-Fengdu intraplatform depression should be the key exploration area of Jialingjiang Formation in eastern Sichuan Basin in the future.