Characteristics and formation mechanism of stratified deformation of Lower Paleozoic faults in Gaojiapu area, eastern Ordos Basin

Abstract

In recent years, exploration breakthroughs have been successively achieved in the strata deeper than the fifth member of the Lower Ordovician Majiagou Formation in the Ordos Basin, revealing its tremendous exploration potential. With the deployment of high-precision 3D seismic data and the deepening of oil and gas exploration, the control exerted by faults on the gas reservoirs in the deeper layers of the fifth member has become increasingly prominent. Based on high-precision 3D seismic data, this study systematically characterized the geometric features of faults in the Gaojiabao area, dissected typical fault structural patterns, established fault formation and evolution models, and, in conjunction with drilling and testing data, discussed the control of faults on the differential enrichment of gas reservoirs in the deeper layers of the Majiagou Formation. The study yielded the following insights: Faults in the Lower Paleozoic of the Gaojiabao area in the Ordos Basin exhibit distinct stratified deformation characteristics, with the two sets of gypsum-salt rocks in the third and fifth members being major contributors to fault stratification. The Lower Paleozoic in the Gaojiabao area mainly develops strike-slip faults with compressional and torsional properties and thrust faults. Through studying the structural morphology and fault patterns of the Gaojiabao area, it is inferred that the Yanshan tectonic movement was the most significant phase of reformation affecting the faults formed during the Caledonian tectonic movement. The coupling of the structural uplift period with the oil-gas charging period in the Gaojiabao area means that faults play multiple roles, including improving reservoirs, connecting source rocks, and controlling traps.

Keywords

• yanshanian age
• caledonian age
• fault stratification
• ordovician
• gaojiapu area
• ordos basin