对川北地区大安寨段沉积环境及找油意义的认识

COGNITION ON THE SEDIMENTARY ENVIRONMENT OF DA’ANZHAI MEMBER, NORTH SICHUAN, AND ITS SIGNIFICANCE IN OIL EXPLORATION

王当奇

Wang Dangqi

地质矿产部西南石油地质局

The 1st Headquarters for Petroleum Prospecting and Exploration, Ministry of Geology and Minerals

川北地区湖相大安寨段的岩相工作始於1979年5月石龙场构造川30井大安寨段上部钻喷工业性油气流。尔后,为了探索区内控油因素,预测新油气田,指导勘探布署,对岩相的研究逐步深入。自1980年3月到1981年12月,在近两年的时间内,对区内与邻区(包括川中、川西北)计54口钻井的地质资料,周边一些露头剖面的地层、岩相与油气进行了研究。本文就是在此基础上,以推理性的思维方法阐述了作者对川北地区大安寨段的沉积环境及控油(气)的观点。试图激发同行研究者发表不同解释,将川北地区的勘探工作向“准”的方向更推进一步。

The lacustrine Da'anzhai member of Northern Sichuan can be subdivided into two different sedimentary facies areas, To the north of Yonghe (Jiulong shan)-Fuyangba, there is the Baitianba facies area; and to the south of it, there is the Ziliujing facies area. The later, from the bottom tothe top, can be divided into three different sedimentary layers. The lower layer is of transgression sediments. It is mainly a suite of interbedding shell limestones and shales with equal thickness. The middle layer was deposited when the lake area reached its climax. It is mainly a suite of black shales intercalated with more or less argillaceous shell limestones. The upper layer is of regression sediments. It is mainly a suite of shell limestones intercalated with argillacous shales. The lacustrine Da'anzhai member of northern Sichuan consists of from north to south a series of beach, shallow water lacustrine, moderately-deep water lacustrine, deep water lacustrine sediments. The first surrounds the second, the second surrounds the third and etc., forming half ring-shaped belts or ring-shaped belts. The inner zone of the shallow water zone, which was adjacent to the moderately-deep water-deep water zones, always emerged above the wave base and received a shell deposit of high energy beach. The shell beach is a good reservoir for oil and gas, and lithological and/or structural-stratigraphic oil and gas pools were formed there. Therefore the objective for oil search in Da'anzhai member of northern Sichuan, should be a good geologic body with proper porosity and permeability in the inner shallow water zone around the moderately-deep water and deep water zones (oil-generating depression). This means the shallow water shell beach deserves to lay emphasis.

https://doi.org/10.11781/sysydz198303170