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Technical Paper: A Novel Technique for Achieving High-Rate Water Injection at Matrix Rates in Openhole Sand-Control Completions: A Case History from Akpo Field, Nigeria

Society: SPE
Paper Number: 127825
Presentation Date: 2010
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Abstract

Many water injectors in sand control environments are completed as long open holes because of higher injectivities attainable with such completions. Although target rates may often be achieved without any cleanup chemicals in production wells, injection wells require filtercake cleanup if producing the well prior to injection is not feasible or desirable, or if injecting above fracture pressure is not feasible or acceptable.

Most cleanup techniques and chemistries are not effective in producers. As demonstrated through laboratory experiments, achieving consistently high injectivities requires removal of drill solids from the filtercake, through either dissolution or effective displacement techniques. In addition, an effective filtercake removal (including drill solids) in long open holes without inducing high losses into the formation remains a formidable challenge that grows even larger in wells drilled with conventional oil-based muds (OBM), particularly in reactive shale environments.

Authors present a novel technique that addresses these challenges, proven through field application on a standalone screen water injector in Nigeria. The technique involves displacement of OBM with a viscous spacer pill containing a demulsifier, followed by completion brine containing a mutual solvent to weaken the filtercake without attacking the bridging agents, subsequent performance of a high-rate viscous pill displacement to remove the external cake, and finally spotting a water-based self-destructive fluid-loss-control pill to control the losses while pulling the washpipe. Details are given on laboratory testing for designing the displacement stages, field execution, and well performance evaluation.

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