Controlling effect of strike-slip faults on Ediacaran Dengying Formation microbial mound-shoal complex reservoir,Penglai Gas Field,SW China

Abstract

The mound-shoal complex (MSC) is an effective reservoir for the accumulation of solid minerals and hydrocarbons within carbonate strata. Previous studies have emphasised the alteration effect of diagenetic fluids (including seawater and atmospheric freshwater) on MSC, leaving a gap in understanding how strike-slip fault control MSC reservoir. To fill this gap, a multi-scale fracture identification technique, based on frequency separation, is used to extract information about fractures at various scales in this study. Based on the restoration of sedimentary geomorphology, waveform classification techniques are used to characterise the distribution of the MSC in Ediacaran Dengying 2nd Member. The results indicate that platform-margin strike-slip faults control the migration of the platform margin and, thus controlling the large-scale MSC distribution. Strike-slip faults within the platform can cause surface deformation, leading to topographic variations that create new high-energy zones favourable for the growth of MSC, thereby facilitating MSC-building. The platform-margin strike-slip fault during the end of Ediacaran not only provided topographic conditions for the formation of the MSC, but also promoted the alteration of the MSC by atmospheric fresh water. Later-activated strike-slip faults provided migration pathways for hydrothermal minerals, which hindered the preservation of the reservoir quality in the MSC. The findings of this study are valuable for future exploration of MSC reservoir, as they will enhance the understanding of the controlling factors for MSC reservoir.