Filtercake Cleanup Techniques for Openhole Water Injectors with Sand Control: Lessons from Laboratory Experiments and Recommendations for Field Practices

Abstract

Abstract Many water injection wells in sand control environments are being completed as open holes because of the higher injectivities attainable with open-hole completions. The sand control techniques used in these wells varies from standalone screens or slotted liners (including expandable screens) to gravel packing. In field practice, the drilling fluids used for injectors have also varied from water-based (either sized CaCO3/Polymer or sized-salt/polymer) fluids to oil-based systems. Although a cake cleanup followed by a production period is typically desirable to maximize injectivity, often this is not feasible either due to limited storage capacity on the rig or requirement for artificial lift due to low reservoir pressure. These limitations therefore necessitate direct injection after the completion is installed, which is not trivial as a complete and uniform filtercake removal, including drill solids as well as the bridging agents and polymers, is essential to ensure uniform injection profile in addition to maximizing injectivity index. Although exceeding the fracturing pressure can establish injectivity through bypassing of filtercake damage, this is typically not desirable from a sweep efficiency standpoint. In this paper, we present details of a series of experiments conducted on core samples using both water-based and oil-based reservoir drilling fluid systems and various cleanup techniques involving displacements and soaks in standalone screen and gravel pack environments. It is shown that with the properly selected and designed cleanup treatments, uniform and high injectivities without producing the well is achievable in long open holes. The results from the experiments are discussed in detail, along with the lessons learned and recommendations for field practice.