(182d) Produced Water Tank Explosion Case Study

Produced
Water Tank Explosion Case Study

J. Kelly Thomas, Ph.D.

Baker Engineering and Risk
Consultants

3330 Oakwell Court, Suite
100

San Antonio, TX  78218-3024

(210) 824-5960

KThomas@BakerRisk.com

Produced water tanks are not typically viewed as posing a
significant explosion risk.  This is
generally a reasonable view on a relative basis if there are other explosion
hazards present in the vicinity that could cause more severe consequences and/or
for which the explosion frequency is higher (i.e., which pose a relatively high
risk).  The consequences of a produced
water tank explosion are normally limited to the immediate vicinity of the
tank, although hazardous debris (e.g., tank roof, tank shell, attached
equipment, etc.) can be thrown a significant distance.  Produced water tank explosions are also
relatively low frequency events. 
Nevertheless, produced water tanks can and do explode.  Depending on the operational parameters
associated with the separator feeding the tank and the volume and frequency of
produced water transfers, the produced water tank vapor space fuel
concentration can exceed the lower flammability limit (LFL) and may normally be
above the upper flammability limit (UFL). 
This is the case even with the separator functioning as-designed and with
no significant condensate carryover.

The work described in this paper was the result of the
investigation of a produced water tank explosion.  The purpose of this paper is to provide the
owners and operators of such tanks with the information required to recognize
and evaluate this hazard.  The
development of the flammable mixture in a tank vapor space is evaluated
parametrically to illustrate the impact of operational parameters (e.g.,
separator pressure, water salinity, water temperature, water transfer rate, product
withdrawal rate, air in-leakage rate).  A
range of potential explosion prevention and mitigation options are identified
that could be utilized for conditions under which a flammable atmosphere may
develop.