Simulation on the Water Controlling Performance of RPM in Hydraulic Fracturing of Low Permeability Reservoirs

Abstract

AbstractHydraulic fracturing is the most effective method for improving hydrocarbon production in low or ultra-low permeability oil reservoirs, but the majority of selected wells for fracture stimulation are considered "risky" because of significant water cut increase after stimulation. Relative Permeability Modifiers (RPM) have proven to be an effective method to enhance oil recovery, especially under linear flow conditions achieved after fracturing. However, RPM treatments are not always effective. At present, the evaluation of water controlling performance of RPM is mainly based on the core flow test in lab and the actual water product after RPM treatment and the results can not provide the effective support for the RPM treatments in hydraulic fracturing, especially for low or ultra-low permeability reservoir.In this paper, the interrelations between the water controlling performance of RPM and the main parameters in hydraulic fracturing such as the properties of reservoir matrix, fracture and fluid (reservoir fluid and treatment fluid) etc, were studied using a model. The model is a radial, isothermal, two-phase, multi-component and single layer mathematical model, in which the threshold pressure gradient is considered. Through simulation, we can conclude that the most influential factors in the treatment response, i.e. the water cut reduction, are the combination of polymer adsorption type (kinetic or equilibrium) with method of application of the resistance factors (threshold or variable), resistance factor ratio, reservoir fluid properties, fracture properties and reservoir layout. On the other hand, the polymer solution rheology is not an important factor regarding the treatment response. Hence, the factors that affect the polymer solution viscosity such as shear stress, reservoir salinity and pH are of some importance with respect to drawdown, but they do not have a major influence on the response outcomes in terms of oil recovery.