Experimental Investigation of Factors Influencing Remaining Oil Distribution under Water Flooding in a 2-D Visualized Cross-Section Model

Abstract

About 70% of the remaining oil remains underground after water flooding, and there is a need to better understand the formation and distribution of this remaining macroscopic oil to enhance oil recovery. In this study, three types of visual plate models were devised with different packing sequences: homogeneous (J), high-permeability layer on top (F), and low-permeability layer on top (Z). Based on these models, several visual flooding experiments were conducted to study the water flooding physics and the remaining oil distribution pattern of an offshore thick heavy oil reservoir under the impact of formation heterogeneity, packing sequence, model length, and permeability contrast during water flooding. These displacements were monitored photographically, and the effluent production profiles were recorded. The results showed that layer permeability and gravitational segregation play an important role during the water flooding process in layered porous media. Experimental results based on the model with different lengths show that the breakthrough oil recovery decreases with the increase of well spacing. Finally, a correction was made to the gravity number by introducing a scaling factor that characterized the formation heterogeneity and packing sequence in thick formation, compared to a known gravity number; the modified gravity number showed a better correlation with breakthrough oil recovery of water and polymer flooding. The research results provide effective guidance for the remaining oil distribution and injection and production parameter optimization in actual reservoirs.

Laboratory Evaluation on the Water Flooding Characteristics in Bottom Water Reservoir Containing Interbeds

“…An interbed is defined as a low permeability sublayer or an impervious stringer in a reservoir bed, such as sedimentogenic muddy intercalation, boulder clay, or diagenetic calcareous layer. In a bottom water drive reservoir, the low-permeability interbeds can prevent the injection water from flooding below the interbed where remaining oil can accumulate or decrease the flooding efficiency of the oil sheet above the interbeds due to their isolation effect. − The distribution of interbeds’ feature can curb the occurrence of coning water effectively, which has a great influence on bottom water drive reservoir. , Therefore, it is of great scientific and engineering significance to systematically study the water flooding characteristics in the bottom water–oil reservoir containing interbeds. Wu et al investigated the mechanism of improved oil recovery by nitrogen foam flooding in bottom water reservoirs and revealed that the seepage resistance of foam in the water layer is much greater than that in the oil layer, effectively increasing the displacement strength of the oil layer.…”