Abstract:

Based on the detailed interpretation of three-dimensional seismic data, horizontal coherent slices and seismic lines of
different directions were used to analyze the development features of transpressional structural belt in the south of Liaozhong sub-sag.
Combined with the stratum development and stress field, the genesis and evolution of transpressional structural belt was studied and its
control of hydrocarbon accumulation was discussed. The result shows that the origin and evolution of transpressional structural belt are
controlled by the NNE trending Liaozhong 1 Fault and the Central Strike-slip Fault. These two faults mainly show both extensional and
strike-slip features, and occur as a“S”-shaped left-stepped arrangement on the plane. Extensional subsidence during Early Paleogene
and the compressive stress derived from strike-slip fault of Late Paleogene are the main controlling factors of the origin and evolution of
transpressional structural belt in the Liaozhong sub-sag. Extensional subsidence of Ek-Es3 in the Paleogene in the south of Liaozhong
sub-sag and tectonic transformation at the end of Es3 led to the formation of transpressional structural belt. At the end of Paleogene(Ed),
Liaozhong 1 Fault and the Central Strike-slip Fault showed strong dextral strike-slip. During the dextral shear, the left-stepped
arrangement and the“S”shape of central strike-slip fault generated regional compressional stress. After this, the tectonic compression of
Dongying movement at the end of Paleogene and Bohai movement at the end of Neogene reshaped its pattern continuously.Transpressional structural belt showed a convexed top and a concaved bottom, and the strata of the Dongying Group and the Neogene
System became bent to form upward arches. Transpressional structural belt is a favorable area for hydrocarbon accumulation and the
Central Strike-slip fault as the main plugging fault is tightly closed and it is beneficial to lateral sealing at the stress-increasing part of the
"S"-shaped bend, which is an advantageous factor for the formation of large-medium size oil and gas reservoirs.

Key words: transpressional structural belt, strike-slip fault, derivative stress, hydrocarbon accumulation, the south of Liaozhong sub-sag