Completion Damage

Abstract

Summary Formation damage has received significant attention over many years as one of the primary reasons for well productivity impairment, to the detriment of completion damage. The objective of this paper is to redress this imbalance and to focus on the significant contribution that completion damage has on well productivity. Formation damage is a reduction in inflow performance because of damage to the near wellbore, while completion damage is an increased pressure drop affecting the lower completion (e.g., plugging of sand screens and frac-packs). A completion damage classification system is presented for the first time that relates this damage type to the typical lower completion designs used by Equinor throughout well lifetime. In addition, a review of some of the fluid qualification tests involving completion damage either directly or indirectly has been performed to assess how representative these are. Computational fluid dynamics (CFD) was identified as a useful tool to assess how representative testing was. Fluid compatibility. CFD was used to determine the displacement efficiency from drilling to completion fluid in a candidate well, and hence the mixing ratio of drilling fluid to completion fluid to be used in compatibility tests. Furthermore, CFD simulations provided an indication of the likely shear rates occurring during displacement that were later used in the testing. Fluid stability. To determine the influence of sag on fluid displacement efficiency, CFD was used to model the worst-case situation where all the weighting agents came out of suspension. Using the displacement efficiency and shear rates obtained, a new dynamic completion damage test was devised to determine the potential for screen plugging as this is the most common lower completion used by Equinor. This test uses the same equipment as coreflooding except that the plug is removed, and a screen is inserted. Finally, an overview will be presented with recommendations of how Equinor’s approach to completion damage has changed because of this study, with an increased focus on achieving a better balance in the evaluation of formation and completion damage prior to the drilling and completion of wells.