An experimental approach to the descaling of production tubing using high pressure flat fan nozzles

Abstract

The mechanical approach of utilizing high-pressure water for scale removal has gained wider acceptance by multinationals despite facing poor downhole performance challenges (cavitation) that need abrasion compensation (sand) with side effect of jeopardizing the integrity of the well completions. The replacement of sand with sterling beads was excellent with good post descaling well completion integrity at the expense of environmental complexity. While the recent single nozzle, solid free aerated jetting descaling technique was characterized with poor scale coverage and high descaling time. This investigation presents the novel technique of scale removal utilizing multiple high-pressure flat fan nozzles at different distances, nozzle configurations and injection pressure to remove soft scale sample made of paraffin. The scale shaped in two different patterns of hollow and solid signifying different growth stages of paraffin in production tubing. The results at 25 mm stand-off distances showed that the scale removal was within the range of 0.8 to 42.8 g (for hollow shape scale) and 0.3 to 5.2 g (for solid shape scale) at 4.8 MPa with different nozzle configurations. Increasing the injection pressure to 6 MPa removed more scale within the range of 1.1 to 93.7 g (for hollow shape scale) and 0.7 to 7.3 g (for solid shape scale). Moreover, at 10 MPa injection pressure the scale removal was within the range of 1.1 to 253.8 g (for hollow shape scale) and 1.1 to 103.7 g (for solid shape scale). This result will provide a practical approach to the removal of organic scales at varying descaling conditions of injection pressure, standoff distance and nozzle configurations. Key words: Scale removal, multiple nozzles, high-pressure water spray, flat-fan nozzle.