Gas resources and accumulation model of BZ19-6 Archean buried-hill large-scale gas reservoir in Bozhong Sag, Bohai Bay Basin

Abstract

Traditionally the Bohai Bay Basin is prone to oil rather than gas pooling because it is dominated by lacustrine mudstones. Factors such as the development of young structural faults are not conducive to natural gas accumulation and preservation. Based on the understanding of the dynamics, evolution, and sedimentary filling characteristics of the Bozhong Sag in the Bohai Sea area, a thermal simulation of source rock evolution and gas generation rate was carried out. Under the background of rapid hydrocarbon generation in oil-rich basins, the reservoirs in the secondary gas generation stage have the hydrocarbon generation intensity to form large natural gas reservoirs during deep burial. The regionally distributed thick Paleogene overpressure mudstones not only prevent the loss of natural gas, but also provide the drive for natural gas migration and charging. Research on fluid inclusions shows that the Bozhong Sag has generally experienced the accumulation of early oil and late gas. The BZ19-6 buried hill structure has formed a large-scale high-abundance condensate gas reservoir due to multiple sources of high-intensity gas generation, rapid and strong charging close to the hydrocarbon source, and thick mudstone overpressure sealing. The understanding and successful discovery of the BZ19-6 condensate gas field has broken through the understanding that it is difficult to find large gas fields in oil-rich basins, expanded the field of natural gas exploration, and is important for natural gas exploration in deep buried ancient metamorphic buried hills and active fault zones.

Keywords

• source rock thermal evolution
• sealing conditions
• accumulation model
• bz19-6 gas field
• bozhong sag
• bohai sea