Sequence stratigraphic architectures and sand-body distribution models of the Pinghu Formation in the Pingbei slope belt of the Xihu Depression

Abstract

Objective The Pingbei slope belt is one of the key zones for the exploration of lithologic reservoirs in the Xihu Depression. However, the exploration process was inhibited by issues of small thickness and significant lateral variation of sand-bodies. Therefore, research on the tectonic-sedimentary response, including the stratigraphic development patterns, deposition center evolution, and sand-body distribution mechanisms in different tectonic units, is urgently needed. Methods Integrating the newly obtained well drilling, well logging, and high-resolution 3D seismic data, a high-precision sequence stratigraphic framework was established and the third-order sequences and systems tracts were analysed in the Pinghu Formation of the Pingbei slope belt. Results Based on differences in palaeogeomorphology and fault systems, the tectonic-sedimentary units of the Pingbei slope zone were classified. Differences in fault styles, stratigraphic contact relationships, and sedimentary filling patterns under different sequence stratigraphic architectures were analysed in various tectonic units. Additionally, the controlling factors and models of sand-body distribution in various sequence stratigraphic architectures were discussed. Conclusion This study revealed that the Pingbei slope zone can be divided into four types of sequence stratigraphic architectures: steep fault slope, opposite fault step, reversal step fault, and forward step fault. The sequence stratigraphic architectures that were controlled by factors of sediment supply, fault activity, palaeogeomorphic, and base-level cycles generated four sand-body distribution models. Research on the differences in sequence configurations and sand-body distribution models in different tectonic units is important for promoting the exploration of lithological reservoirs in the Pingbei slope belt of the Xihu Depression.

Keywords

• pingbei slope belt
• pinghu formation
• sequence stratigraphic architecture
• sand-body distribution model