Abstract
The identification and interpretation of buried strike-slip faults are of great significance int the search for structural traps in oil and gas exploration. However, it is difficult to identify and interpret buried strike-slip faults from seismic profiles and variance slicing, because they may be clear at depth but vague in the shallow. This study proposes a 3D stress body attribute taking into consideration formation deformation and lithologic variation to identify buried strike-slip faults. Taking into account thin plate theory and the generalized Hooke's law, a relationship between stress field, formation deformation and lithologic variation is established. Structural curvature body is used to represent the formation deformation, which is obtained by scanning of the body dip angle and second-order derivation of the wave number domain, while Poisson's ratio and Young's modulus volumes are employed to reflect the spatial lithologic variation, which are calculated by the multivariate linear fitting method or prestack inversion. This technique is applied to the secondary structural interpretation of JinZhou 25-1 oilfield in LiaoDong Bay depression of BoHai Bay Basin. Compared with the 2000 ms variance slice, it can be seen clearly that there is a significant stress concentration zone in the location of LiaoXi buried strike-slip fault from the 3D stress body attribute slice, which is consistent with a sudden change in strata observed on the profile. The LiaoXi buried strike-slip fault has been identified and interpreted. Many structural traps greater than 20km2 have been found along its course. Among them, W structure was drilled in 2016 and about 4.5 million tons of oil was found. This suggests that the spatial distribution of buried strike-slip faults associated with tectonics can be effectively identified through the strength property of the stress field, which is greatly superior to the conventional variance-related methods. It verifies the ability of this technique in the identification and interpretation of strike-slip faults in the entire Bohai Bay Basin and thus its potentially critical role in guiding secondary seismic interpretation.
Determining the main strand of the Eskişehir strike-slip fault zone using subsidiary structures and seismicity: a hypothesis tested by seismic reflection studies