Structural characteristics and hydrocarbon exploration prospect of the Laoshan uplift in the South Yellow Sea Basin

Meso-Paleozoic marine deposits widely occur on the Laoshan uplift of the South Yellow Sea Basin. As a new field and layer for oil and gas exploration, it shall be the future targets for strategic discovery of oil and gas and the breakthrough point of exploration understandings. Based on the detailed seismic interpretation results and exploration progress made in recent years, the uplift is divided into two parts, the Qingfeng deformation zone in the north and the Gaoshi stable zone in the south. The Qingfeng deformation zone is a cover-detachment overthrust nappe system characterized by NE trending thrust faults, while the Gaoshi stability zone a weak deformation and stable zone. NW trending synclinal faults are developed in small scale. The fault system of the Laoshan uplift can be subdivided into three groups, NE, NW and nearly EW in trending, and the boundary fault is a reverse fault nearly in EW direction. The deformation of marine structural layer is strong in the north and west and weak in the south and the east, strong in the upper and weak in the lower. The Laoshan fault-uplift area was formed by Indosinian-Early Yanshanian compressional thrust and late Yanshanian-Early Himalayan weak tension/tension torsion, and four structural styles of compressional, tensional, strike-slip and inversional are recognized. Through the analysis of their forming process, it is revealed that the Laoshan uplift is an old uplift formed in Caledonian period. It was a stable platform in Hercynian. In the Indosinian period, the northern foreland basin was probably a foreuplift flexural belt, formed on an anticline with increasing amplitude. The early Yanshanian fault anticline was a reformed fault anticline. The uplifting was basically stopped in middle Yanshanian stage. The uplifting and denudation happened in late Yanshanian-early Himalayan period, and local residual depressions developed. The overall subsidence began in late Himalayan. Combined with the analysis of oil and gas geological conditions, it is considered that the Gaoshi stable zone in the south of the Laoshan uplift is a favorable region for Marine oil and gas exploration, and the lower structural layer from Sinian to Silurian is weak in deformation and transformation. It should be also a favorable layer for oil and gas exploration.