Improving Scale Inhibitor Squeeze Design for Naturally Fractured Reservoirs

Abstract

Scale Inhibitor (SI) squeeze treatments continue to be an important method for delivering chemical to the production system. However, while SI squeeze treatments in unfractured reservoirs can generally be readily simulated in matrix flow models, designing such treatments for application in fractured reservoirs is less routine, and resulting field treatment lifetimes can be disappointing. One reason for this is that the flow process and transport mechanisms by which the inhibitors are retained in fractured formations differs considerably from simple matrix flow. In this paper we expand upon previously published work examining the impact of squeeze treatment design on the outcome of a SI squeeze treatment for a fractured well using a novel fractured well squeeze model.In previous papers, we highlighted the importance of diffusion-controlled transport of SI in low permeability tight matrix fractured reservoirs where little matrix flow is possible. In this paper, we report continuing developments of the fracture squeeze model and demonstrate how differences between advection and diffusion-controlled inhibitor transport can significantly alter the predicted squeeze treatment lifetimes, and suggest appropriate treatment design modifications to improve SI squeeze treatments in such fractured reservoirs. This paper will demonstrate that such differences in transport mechanisms directly impacts the distribution of scale inhibitor within the near-wellbore region during the treatment phase. In fractured systems, this SI distribution is affected both by the extent of propagation of injection fluid through the fracture network and rate of diffusion into the surrounding matrix rock. This work examines the influence of factors such as injection rate, soak time, inhibitor diffusivity and retention/release properties on the matrix material.By adjusting injection parameters such as injection rate and soak time in the treatment design, a more desirable distribution of scale inhibitor can be obtained, resulting in improved predicted treatment lifetimes. Thus, using the fracture squeeze model to provide a fuller simulation of the inhibitor transport, retention and release mechanism active in a fractured reservoir, we highlight potential placement issues for such reservoirs and demonstrate methods to improve squeeze design for fractured wells.