Dynamic Irreducible Water Saturation And Its Determination Method

The irreducible water saturation, the saturation of water when it begins to flow, is not a fixed value in the development process, whose numerical value is related to specific reservoir production conditions. Based on the integration of relative permeability curve and mercury intrusion curve, the author studies the change regularity of the irreducible water saturation under different production conditions (drawdown pressure), and puts forward the concept of dynamic irreducible water saturation and its determination method. Taking west Sulige gas field for application example, the actual drawdown pressure is 13.7 MPa and its dynamic irreducible water saturation is 30%. However, the conventional irreducible water saturation is 38%, which is getting from relative permeability curve. By analyzing the differences between two kinds of irreducible water saturation, the author thinks that the dynamic irreducible water saturation is closer to the actual production condition and it can be used in the correction of relative permeability curve and the study of lower limit of reservoir physical property.