Depositional model and petroleum significance of the Cretaceous Yageliemu Formation in Xinhe area on the southern slope of Kuqa Depression, Tarim Basin

Abstract

In recent years, drilling in Xinhe area on the southern slope of Kuqa Depression, Tarim Basin revealed that the Cretaceous Yageliemu Formation has active hydrocarbon display and high exploration potential in the field of stratigraphic-lithologic traps, which is an important direction for the next strategic breakthrough. Based on the core, well logs, drill cuttings and 3D seismic data, this paper integrated the analytical methods of core facies, electrofacies, wavelet transform, "impression method" paleogeomorphic restoring, seismic facies, seismic attributes, and coherence cube slicing to study the depositional system of the Cretaceous Yageliemu Formation in Xinhe area under the sequence stratigraphic and paleogeomorphic controls. The study shows that there are two types of paleogeomorphology developed in Xinhe area: (ⅰ) western multi-stage slope breaks, and (ⅱ) eastern thrust cliff paleogeomorphology. The Cretaceous Yageliemu Formation can be classified as a third-order sequence SQ1, which includes the lowstand systems tract (LST), transgressive systems tract (TST) and highstand systems tract (HST), corresponding to the three-phase seismic reflections of this formation overlying the western slope, respectively. The LST slope fans and HST fan deltas of the Yageliemu Formation were deposited above the western multi-stage slope breaks, and TST-HST subaqueous nearshore fans were deposited below the eastern thrust cliff, with erosional valleys on the cliff serving as the feeder channels and providing sources for the subaqueous fans. In situ mature hydrocarbon source rocks of the Triassic Karamay Formation are developed in Xinhe area, which is the migration direction of oil and gas far away from hydrocarbon source, indicating excellent source rocks and reservoir forming conditions. The stratigraphic-lithologic traps of the LST slope fan and TST-HST subaqueous nearshore fan located in the northern part of the thrust cliff are lying on the Triassic source rocks and have great exploration potential, which can serve as the main targets for the next subtle oil and gas exploration in this area.

Keywords

• sequence
• impression method
• slope fan
• thrust cliff
• subaqueous nearshore fan
• southern slope of kuqa depression
• tarim basin