Abstract: Shale gas is enriched in deep reservoirs in Luzhou area in southern Sichuan Basin, where the organic matter-rich marine shale in submember 1 of Member 1 of Katian Wufeng Formation and Aeronian Longmaxi Formation is the main shale gas producing layer; it is of great significance to clarify the depositional environment evolution in this area and its controlling role in organic matter enrichment for describing the accumulation mechanism of shale oil. Using the drilling, logging and well logging data, as well as the test data of major, trace and rare earth elements, this paper systematically analyzes the sequence stratigraphy and depositional environment evolution of Katian-Aeronian black shale in southern Sichuan, and establishes a state model of organic matter-enriched paleo-ocean in southern Sichuan. Based on the lithology, typical sedimentary structure, electrical properties of rock and element composition, five maximum flooding surfaces were identified from Katian stage to Aeronian stage; according to the ice age, maximum flooding surface, lithological change and graptolite belt constraint, eight fourth order sequences were divided. Under the constraint of sequence stratigraphic framework, the evolution of paleo-oxygenation facies and paleo-productivity were restored, and the substituted coefficient for identifying the paleo-oxygenation facies and paleo-productivity of high-quality shale was also established. As the shale deposited in Katian Wufeng Formation is controlled by strong stagnant water in the restricted platform, the high productivity supply at the surface is of positive significance for the development of organic matter-rich shale. Since the Rhuddanian stage, ice sheet melting during the ice age has resulted in large-scale transgressions, as well as sea level rise, thus forming a strong reducing environment with water stratification; as a result, the organic matter-rich shale is developed in the lower part of Longmaxi Formation. In the Aeronian stage, continuous marine regression continued, low sea level, sufficient terrestrial source injection, fast deposition rate and redox conditions were not conductive to the preservation of organic matters. However, the paleo-productivity was high in this stage, so that black shale with rich carbon in the upper part and high clay mineral content was formed during the short-termed transgression.

Key words: Sichuan Basin, Kadian-Aeronian, deep-water shale, sequence stratigraphy, sedimentary evolution model

摘要： 四川盆地南部泸州地区深层页岩气富集，凯迪阶五峰组—埃隆阶龙马溪组一段一亚段的富有机质海相页岩是该区页岩气主力产层，明确其沉积环境演化及对有机质富集的控制作用对深化页岩气成藏机理研究具有重要意义。综合利用钻井、录井、测井资料和主量、微量及稀土元素测试数据，系统分析川南地区凯迪阶—埃隆阶黑色页岩的层序地层和沉积环境演化，建立了川南地区有机质富集的古海洋状态模式。基于岩性、典型沉积构造、岩石电性及元素组成，在凯迪阶—埃隆阶识别出5个最大海泛面；综合冰期、最大海泛面、岩性变化及笔石带约束，划分出8个四级层序。在层序地层格架约束下，恢复了古氧相与古生产力演化特征，建立了用于判别优质页岩的古氧相、古生产力的替代系数。凯迪阶五峰组页岩沉积受局限台地的强滞留水体控制，表层高生产力供给对富有机质页岩的发育具有积极意义；鲁丹期开始，冰期冰盖消融造成大规模海侵，海平面上升形成水体分层的强还原环境，沉积龙马溪组下部的富有机质页岩；埃隆期持续海退，海平面较低，陆源注入充足、沉积速率快、氧化还原条件均不利于有机质的保存，但该时期古生产力高，在短期海侵阶段形成龙马溪组上部的富碳、高黏土矿物含量的黑色页岩。

关键词: 四川盆地, 凯迪期—埃隆期, 深水页岩, 层序地层, 沉积演化模式