Case Study 06
Reducing Oil and Suspended Solids in Produced Water
Challenge
An oilfield operator required a more effective treatment solution for produced water containing high concentrations of oil and suspended solids.
The treatment facility was designed for a water throughput of 54,000 barrels per day. However, the actual feed fluctuated significantly and could contain more than 10,000 ppm of total petroleum hydrocarbons (TPH) and up to 1,800 ppm of total suspended solids (TSS).
The operator reported off-specification discharge with average concentrations of approximately 20,000 ppm TPH and 1,500 ppm TSS, compared with discharge requirements of 40 ppm TPH and 150 ppm TSS.
Fine, oil-wet solids smaller than 2 μm contributed to a stable oil-in-water emulsion. Conventional coagulants and flocculants alone did not provide the required treatment performance.
Solution
We developed a customized chemical treatment program to destabilize the oil-in-water emulsion and improve the separation of oil, water, and suspended solids.
Customized Surfactant Treatment
A specially formulated weighted polymeric surfactant was developed to modify the wettability of dispersed solids and destabilize the stable oil-in-water emulsion. It also promoted the settling of fine suspended particles.
Coagulation
A coagulant was introduced to aggregate the destabilized suspended solids, supporting the separation of contaminants from the water phase.
Flocculation and Solids Separation
A flocculant strengthened the aggregates into larger flocs, which could then be handled by the facility’s solids management system. The combined chemical program was implemented at the treatment plant to improve separation performance under variable feed conditions.
Results
The customized chemical program consistently reduced both TPH and TSS by more than 95% and brought the treated water back within the specified discharge limits.
The solution also expanded the operating envelope of the treatment equipment, allowing it to handle off-specification inlet TPH levels reported as 500% above the original design basis and TSS levels up to 1,000% above the design basis. Permanent infrastructure was being installed for continuous application.
TPH REDUCTION
>95%
Feed up to 10,000 ppm; limit 40 ppm
TSS REDUCTION
>95%
Feed up to 1,800 ppm; limit 150 ppm
TPH ABOVE DESIGN BASIS
500%
Handled during the trial
TSS ABOVE DESIGN BASIS
1,000%
Handled during the trial