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SCAVTREAT 7107C Improves Downhole H2S Treatment in Brazilian Pre-Salt Oil Well

Benefits
  • Reduced chemical use by 65% (about 990,000 liters per year)
  • Significant decrease in tank movement reduced shipping logistics costs and improved HS&E profile
  • Efficiency of SCAVTREAT 7107C enabled a lower dose rate, generating substantial cost savings

Background

An offshore oil production platform operated by a major producer in Brazil experienced challenging conditions with the treatment of H2S from a pre-salt well. The H2S, measured at 100 ppmv during routine well tests, was required to be below 15 ppmv in order to maintain the integrity of the downstream pipework and facilities.

To meet these specifications, the incumbent H2S scavenger was applied on a continuous basis at 175 liters / hour (L/h), which corresponded to a dose rate of 1,325 ppm. 

H2S Concentration 100 ppmv
Gross Well Production 3,168 m3/day
Water Salinity (NaCl) 276,375 mg/L

Clariant Oil Services was asked to recommend an alternative high-performing, cost-effective scavenger. The product was also required to have the following specific features:

  • Suitable for subsea deployment through an umbilical
  • Will not cause fouling in the umbilical or process facilities
  • Will not adversely affect oil and water separation

Innovation and Value Delivered

Clariant Oil Services performed extensive laboratory evaluations of scavengers suitable for high salinity produced water applications. SCAVTREAT 7107C was recommended for further evaluation by the operator in a field trial. SCAVTREAT 7107C was injected through an umbilical at an initial flow rate of 90 L/h (682 ppm); the level of H2S in the gas phase subsequently dropped to 9 ppmv. After several optimization steps, the optimum injection flow rate of SCAVTREAT 7107C was determined to be 62 L/h (470 ppm) to maintain the H2S level at 15 ppmv.

SCAVTREAT 7107C removed 2.8 times more H2S than the incumbent, representing a 65% reduction in consumption. Consequently, the number of tank movements decreased, improving the operation’s HS&E profile. Additionally, improvement in scavenger efficiency reduced the dose rate from 1,325 ppm to 470 ppm, generating substantial annual savings.

Lastly, SCAVTREAT 7107C was successfully deployed subsea in the umbilical with no evidence of fouling or incompatibility with the high salinity produced water, and did not cause interference in the oil and water separation units.

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