Improving Water Imbibition and Recovery Performance in Fractured Carbonate Rocks using Biochemical EOR

Carbonate reservoirs are more complex than the conventional sandstone reservoirs. This is because many carbonate reservoirs have a fractured network which results in a varied distribution of porosity and permeability. Oil recovery from such reservoirs is challenging because the injected fluid tends to flow through the fractured formations rather than through the oil-wet matrix. In this research, the concept is to plug the fracture network using biopolymer Xanthan Gum (XG), and then modify the wettability of the carbonate rock towards a water-wet system using a biosurfactant. Scanning Electron Microscopy (SEM) was employed to approve the presence of the biosurfactant RL and biopolymer XG at the rock surface. The results revealed that oil recovery increased by up to 7-9% in the oil-wet fractured carbonate cores using the biopolymer / biosurfactant / water flooding. In the proposed mechanism using the biopolymer flooding, the fractured zone was temporarily plugged (reducing fracture permeability by 18%) which caused an improvement in the water imbibition process.