Geological characteristics and exploration practice of deep carbonate buried hills in Nanpu Sag, Bohai Bay Basin

Abstract

The deep carbonate buried hills are widely distributed in the Nanpu Sag of Bohai Bay Basin. They have experienced multiple stages of tectonic movement and show a tectonic pattern of alternating sub-sags and uplifts. Exploration discoveries have been achieved in multiple structural belts and layers. In recent years, with the deepening of exploration, many exploratory wells deployed on the slope belt and the downdip area were failed, and the exploration of deep buried hills has stagnated. To clarify the potential and exploration direction of buried hills, on the basis of improvement of seismic data, starting from the three major accumulation elements of hydrocarbon supply window and supply mode, high-quality reservoir type and trap type, the re-evaluation of accumulation conditions and the re-understanding of main controlling factors of accumulation were carried out. The deep Paleozoic carbonate buried hills in the Nanpu Sag develop multiple sets of reservoir-caprock assemblages, [JP] with good physical properties, high-quality source rocks, and favorable hydrocarbon accumulation conditions. Oil and gas enrichment is controlled by multiple factors such as hydrocarbon supply mode, window, type of trap and reservoir, and there are various types of oil and gas reservoirs. The hydrocarbon supply window controls the formation of hydrocarbon accumulation, the type of trap determines the type of oil and gas reservoir, and the dominant reservoirs formed by fault fracture-supergenic karst and fracture-burial karst generated by multi-stage karstification control the enrichment and high yield. The comprehensive evaluation of the accumulation conditions shows that the slope area and the trough area of the Nanpu No. 1 and No. 2 structural belts as well as the inner Cambrian buried hills of the Nanpu No. 2 and Nanpu No. 3 structural belts are important directions for the next exploration. Through the integrated application of geological research and exploration technology, several favorable[JP] exploration targets have been classified and evaluated. Overall breakthroughs have been made in the exploration of carbonate buried hills in the Nanpu Sag, and good exploration results have been achieved.

Keywords

• carbonate buried hill
• characteristics of hydrocarbon accumulation
• exploration direction
• nanpu sag
• bohai bay basin