How to Apply the Flow Velocity as a Design Criteria in RPM Treatments

Abstract

AbstractThe effect of water control using Relative Permeability Modification (RPM) depends strongly on the well's flow rate. This is because the permeability reduction decreases as the flow velocity increases. This will affect the amount of volume as well as the properties of the injected RPM fluid. This paper discusses how the velocity dependent permeability reduction can be accounted for in the job design. The approach is to introduce a velocity dependent permeability reduction and to solve the Darcy law for Non-Newtonian flow.Core flood experiments report permeability reduction as residual resistance factors (RRFw and RRFo). In scaling up to field situations the reduction in productivity is a better measure. Designing an RPM treatment to a fixed reduction in water productivity demonstrated that low volume - high permeability reduction is better than larger volumes with lower permeability reduction. In high productive wells there may be situations where certain RPM systems fail to reduce the water productivity adequately. By including pressure constraints on the injection of the RPM fluid, the planned pumping schedule is derived.The criteria for increased oil production are reported as a balance between the increased drawdown, based on the water-cut reduction and improved lift, and the reduction in oil productivity. The critical oil productivity depends on the water productivity, initial water-cut, density difference between the water and the hydrocarbon phase, and depth (TVD). It is clearly demonstrated that the potential for increased oil production increases by increasing the ratio between the oil and the water productivity reduction (M). In addition, M increases as RRFw increases and the volume decreases.The time to restore the productivity from the oil zone, the clean up time, can be understood based on the fractional flow theory. In theory, the clean up time can be derived from relative permeability curves or the saturation profiles during the oil back production. Also the clean up time was reduced by the use of low volume - high water permeability reduction.