Cold water-flooding in a heterogeneous high-pour-point oil reservoir using computerized tomography scanning: characteristics of flow channel and trapped oil distribution

Abstract There are relatively few studies that consider the influence of reservoir heterogeneity on reservoir wax deposition. This study conducts a computerized tomography scan to study the flow channels, heavy component retention, displacement efficiency, and trapped oil distribution in a high-pour point oil reservoir with a positive sedimentary rhythm under various water injection temperatures. This study greatly improves the understanding of the wax deposition influences on the flow channel. Three displacement models are proposed: water-flooding breakthrough model (49.5 °C), approximate-equilibrium piston-like displacement model (54.5 °C / 59.5 °C), and non-equilibrium piston-like displacement model (64.5 °C). When the injection temperature is lower than the wax appearance temperature (59.5 °C), an elliptical wax deposition is formed at the inlet, the most serious deposition is in the middle-permeability layer. A wax deposition barrier is formed away from the inlet, and constrains the downward movement trend of the water injected above. Therefore, the moderate wax precipitation will improve the oil recovery from the top low-permeability layer. However, the heterogeneity in the spaces and strength of the barrier result in the oil recovery from the 100 mD layer at 59.5 °C begin higher than that at 54.5 °C; moreover, at 59.5 °C, the recovery at the inlet is better than that at the outlet. The vortex phenomenon increases the oil recovery from wax deposition area in the bottom layer at the inlet. The heavy component retention is significant, and the oil recovery decreases with decreasing injection temperature. After flooding, the formation mechanisms of the trapped oil include wax deposition, weak water washing, and reservoir sedimentary rhythms. The research results provide initial insights for the evaluation of cold damage.