Investigating dynamic evolution of pore structures during long term water flooding via in-situ CT scanning: A case study of the Beibu-Gulf Basin in the South China Sea

Abstract

Long term water flooding (LTWF) can alter the micro-porous structure of oil reservoirs, thereby affecting the water flooding efficiency. Based on the core samples collected from the Beibu-Gulf Basin in the South China Sea, the online in situ CT scanning and digital rock techniques were adopted to elucidate the impacts of long-term water flooding on microscopic pore structures. Dynamic prediction models of pore radius, throat radius, porosity and permeability changing with the volume of injected water were established. The results show that in reservoirs with permeabilities ranging from medium to high, the average pore and throat radii increase after water flooding, resulting in better pore connectivity and more regular pore shape. For low permeability reservoirs, the overall permeability and average throat radius decrease ascribe to the blockage of smaller throats by migrating tiny particles. The average pore radius, throat radius and pore shape factor of the core samples satisfy exponential relationships with the volume of injected water.