| Post-rift magma is widely distributed in Jiaojiang Sag, East China Sea Basin. However, the type, spatial
distribution and formation period of magmatism have not been systematically studied, which seriously limits the oil and gas
exploration and deployment in the basin. Based on the newly acquired high-precision 3D seismic data, drilling data，this
paper identifies and finely describes the magma in the post-rift period, and determines the development regulation of
magmatism and the control effects on oil and gas accumulation in Jiaojiang Sag. The results show that the volcanic rocks
are mainly distributed in the central and eastern parts of Jiaojiang Sag, with overflow facies as the main type. They are
developed along the T 20 interface and up and down, but more developed along the T 20 interface. There are three types of
occurrences of magma intrusion, including saucer, sill, and dike, with saucer being the main occurrence. The emplacement
of magma intrusions in the Jiaojiang Sag mainly include three stages: before the Wenzhou stage (>43 Ma), during the
Pinghu-Huagang stage (43-23.3 Ma)，during and after Longjing stage (<23.3 Ma), and the Pinghu-Huagang stage is the
most important period for magma intrusion. The distribution of magma intrusion channels in the study area are related to the
northwest striking basement hidden faults, but separated from the Cenozoic faults and have no symbiotic relationship
between them. It is traditionally suggested that the magmatism in the post-rift stage may cause damage or alteration to early
oil and gas reservoirs, therefore, when selecting potential targets, efforts should be made to avoid the influence of magmatic
activity as much as possible. On the other hand, magma intrusion has formed a large number of forced anticlines, and their
formation time is later than the peak period of oil and gas generation, which belongs to a good potential trap type.
Therefore, these forced anticlines in the magma-rich activity area within Jiaojiang Sag are still worth exploring. |
