Abstract

The scales precipitated on the electric submersible pump (ESP) will lead to trapped heat, lower the motor's cooling capacity, decrease the pump lifetime, and finally pump failure. Removal of oil field scales commonly requires low pH acid that can cause corrosion, hydrogen sulfide evolution, ferric and ferrous hydroxide precipitation, iron sulfide as a by-product, and/or sulfur precipitation. Scales typically occur in the near wellbore, tubing, downhole pumps, and surface equipment. A mineral deposition is widespread with a change in pressure, temperature, pH, and incompatible mixing between injected seawater and formation water.

This paper presents a new scale dissolver that is non-corrosive and has a high scale dissolution performance for barium sulfate scales. The study explains a series of comprehensive experimental lab tests such as X-ray diffraction (XRD), X-ray fluorescence (XRF), brine compositional analysis, fluid compatibility and stability, solubility test, precipitation tendency for the dissolved solids, and corrosion test to evaluate and simulate the field application of the new dissolver using two field scale types that mainly contain barium sulfate (BaSo4) scales.

The obtained successful results indicated that the novel dissolver had a great dissolution efficiency for two real barium scale samples as the results showed that the dissolution rate recorded 91.3 and 78.4 % at 90 °C for samples 1 and 2 respectively. The novel dissolver showed a very low precipitation tendency for the scale dissolved solids (1.9 and 3.2 % for samples 1 and 2 respectively). Without any additives of corrosion inhibitors, the corrosion rate was 0.00376 lb/ft2 at 1000 psi and 50 °C for 6 hours.

The obtained successful results will help to dissolve the barium sulfate scales, maintain the ESP performance, increase the lifetime, and save extra cost for the pump operational problems due to scale precipitations.

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