Structural Patterns of Thrust-Related Folds of Deepwater Fold and Thrust Belts in NW Borneo

Tang Wu; Zhao Zhigang; Xie Xiaojun; Liu Shixiang; Wang Yibo; Song Shuang; Wang Long; Guo Jia; Sun Rui

Abstract：The structure and characteristics of deepwater fold and thrust belts (DFTBs) can change with time and thus affect the exploration and development of deepwater oil and gas,while the research on this aspect is relatively weak in the DFTBs of NW Borneo.Based on the combination method of seismic and geology,this paper determines the structural patterns of thrustrelated folds,discusses the formation process and controlling factors,establishes the accumulation model of thrust-related folds in the study area.The results show that four types of structural patterns of thrust-related folds develop in the DFTBs of NW Borneo,namely,hidden type,crest faulted type,slump type and buried type,and on the planar the above four type thrustrelated folds successively distribute from sea to land.The amplitude of anticline fold of hidden type is relatively low,with no obvious seafloor expression,mainly forming in the foremost of DFTBs.The crest faulted type is characterized by the development of faults in the crest of anticline,with apparent seafloor relief.The crest of slump type anticline is influenced by the normal faults,with flanks associated with slides and slumps.The buried type anticlines mainly develop close to the shelf margin,buried by a thick sedimentary overburden,with no prominent seafloor expression.Four type thrust-related folds structures stage,with hidden type,crest faulted type,slump type and buried type anticline,successively developed.At the same time,if viewed along the strike of the DFTBs,there are significant variations in the geometry of laterally corresponding thrust-related folds under the same compression,controlled by the topography,differential sediment input and the development of subsurface gas hydrates.Under this special tectonic background,a unique fault-controlled accumulation model forms in the study area,with favorable exploration potential.