Study on crustal thickness and the prediction of prolific depressions: the Bohai Basin as an example

Abstract

The deep crustal structure is closely related to oil and gas reserves. Predicting the oil and gas enrichment of depressions based on the Moho depth and crustal thickness is a promising research topic with significant implications for guiding exploration in petroliferous basins. In this study, seismic data were used as a constraint on the use of satellite gravity anomaly inversion to obtain the distribution of Moho depth and crustal thickness in the Bohai Basin. Stretching factors were calculated to analyze the differential distribution of deep crustal structural activity. Four indicators, including the minimum Moho depth, minimum crustal thickness, sum of Moho stretching factors, and sum of crustal stretching factors, were selected. Principal component analysis was applied to reduce the dimensionality of the multi-indicator system and obtain an oil and gas enrichment score for quantitative prediction of favorable prolific depressions. The deviation between the inverted Moho depth and seismic constraints was small; thus, the data effectively reflect the variations in the characteristics of each depression. The analysis revealed significant statistical features related to the minimum Moho depth/crustal thickness and the sum of Moho/crustal stretching factors associated with prolific depressions. Based on the oil and gas enrichment score, the depressions were classified into four categories related to their different deep crustal structural characteristics. Highly active Class I, Class II, and Class III depressions are predicted to be favorable prolific depressions. This study expands the research on quantitatively predicting favorable prolific depressions in the Bohai Basin using the deep crustal structure and can contribute to reducing production costs and improving exploration efficiency in future explorations.