The Permian basin-scale unconformity in the northern truncation zone of Shawan sag of Junggar Basin develops between the Shangwuerhe Formation and the underlying strata

exhibiting an erosional unconformity contact. The Fengcheng Formation

Xiazijie Formation

and Xiawuerhe Formation exhibit good hydrocarbon shows in this region. Recently

a new breakthrough has been made in exploration of Well TT1 in the lowstand system tract conglomerate reservoirs of the Shangwuerhe Formation. To further summarize the Permian hydrocarbon accumulation regularities in Shawan sag

a systematic study on reservoir characteristics

sedimentary facies

and controlling factors was conducted

leading to the following conclusions. (1)The angular unconformity at the bottom of the Shangwuerhe Formation in Shawan sag controls oil and gas enrichment. The Shangwuerhe Formation possesses favorable conditions for large-scale accumulation and serves as the main target for large-scale cost-efficient exploration. (2)The Zhongguai fan provenance is abundant and the scale is large

with the development of effective reservoirs at its distal end. In the Shangwuerhe Formation retrogradational fan delta depositional system

the thin sandstone layer from the Member 2 of Shangwuerhe Formation and the sandstone body from the Member zero of Shangwuerhe Formation constitute the main reservoir bodies. (3)A Permian accumulation model characterized with "unconformity-controlled migration

anticline-controlled enrichment

and overpressure sealing" was established in the northern truncation zone of Shawan sag. The oil-over-gas distribution pattern is the result of the dynamic coupling between petroleum migration and overpressure sealing systems. The discovery of the lowstand system tract conglomerate oil reservoirs in the Shangwuerhe Formation of Well TT1 not only marks a new exploration idea of "prospecting sandstone beneath mud"

but also provides valuable insights for expanding exploration fields and optimizing exploration strategies in Shawan sag.