Flow rate effect on two-phase relative permeability in Iranian carbonate rocks

Abstract

The effect of flow rate on relative permeability curves has been investigated in very tight Iranian carbonate rocks. Core samples were prepared from outcrop of Asmari formation. Asmari formation represents huge oil carbonate reservoirs in Iran. This formation belongs to Oligocene-Miocene period and is mainly limestone. The dynamic displacement experiments were performed at three different flow rates. In all experiments, we injected both water to displace oil and oil to displace water and relative permeability curves were generated with the Jones and Roszelle method for both water-flooding and oil-flooding experiments. We found a critical rate in which we could not obtain any relative permeability curves above this rate. This critical rate represents the limit of injectivity capacity of each core sample. We observed that in the water-flooding process, water relative permeability curves and its end points were not affected by flow rate. However, it was detected that the oil relative permeability decreases at lower flow rates. This variation vanishes at the central saturation points. During oil-flooding experiments, we also observed the same no rate effect in water relative permeability curve but in the oil relative permeability curves, although it was seen the flow rate effect, it was not found any meaningful trend in the curves and its end-point saturations. We found hysteresis effect in both water and oil relative permeability curves. At higher flow rates, the effect of this phenomenon increases in water relative permeability curves while the hysteresis effect decreases in the oil relative permeability curves. Copyright 2007, Society of Petroleum Engineers.