Summary
Slop mud, created by water contamination of invert drilling fluids during
displacement and cleaning activities, has been successfully treated at source
to recover the drilling-fluid phase and water phase. This method included
treating the slop mud with a biodegradable demulsifier. The recovered drilling
fluid can be reconditioned to acceptable properties for reuse or can be sent
for disposal. The recovered/separated slop water phase is contaminated with
hydrocarbons and cannot be discharged in an offshore environment unless it
meets the discharge criteria of < 30 mg/L of oil in water. Thus, it becomes
imperative for the operator to treat the water at source, reduce the enormous
expenses associated with transportation/disposal, and embark upon a potentially
significant environmental issue. This was achieved by development of an on-site
treatment process including filtration, ozonation, and phase separation.
A synthetic-based drilling fluid contaminated with water was separated with
a biodegradable demulsifier. The addition of the surfactant resulted in phase
separation (i.e., separated drilling-fluid and water phases). As tested by the
approved International Organization for Standardization (ISO) method, the
separated water phase was found to have oil-in-water content of 4,000 mg/L,
which is unacceptable for discharge. The separated water then was treated with
ozone. The ozone-treated water was allowed to separate in two phases (i.e.,
clarified water phase and organic rich phase). The oil-in-water content of the
clarified ozone-treated water phase was found to be 30 mg/L, thus reducing the
oil-in-water content by 99%.
This paper will present the demulsification methodology, chemistry of
ozonolysis, and results obtained to meet or exceed the oil-in-water discharge
limits of 30 mg/L. The environmental and economic impact of the process will be
discussed.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
19 February 2009
- Meeting paper published:
20 April 2009
- Manuscript approved:
15 April 2009
- Published online:
22 December 2009
- Version of record:
11 March 2010
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