Subject: Topock diesel pigging strategy
From: [email-masked]
To: [email-masked]
Cc: [email-masked], [email-masked], [email-masked], [email-masked]
Date: Fri, 11 Jun 1999 01:59:00 -0700 (PDT)

After the Topock line has been cleaned and placed back in service, I 
recommend immediate flushing with diesel.
The existing Selexol tank and injection system can be used for this purpose. 
HYSIM simulations verify the existing high pressure injection pump is a good 
fit for the quantity of diesel to be added on a continuous basis, 
(approximately 1 B/D).  Inject  1 or 2 barrels of diesel in front of each pig 
to begin with.  I would buy diesel No. 2 because it has a wider boiling point 
range than No. 1.  The diesel should be analyzed for PCB content  before we 
purchase /inject.

The above guideline should be adjusted based on the actual volume of liquids 
seen at the meter station filter separator.  If you can keep a small but 
continuous amount of free liquids at this separator , the gas will be 
saturated with heavy hydrocarbons which will dilute and flush PG&E's 
downstream system.

1 to 2 Barrel per day of diesel injected into 200 MMSCF/D has a major effect 
on the C7+ concentration  in the gas stream and on the hydrocarbon dew point. 
Most of the hydrocarbons in diesel  are naturally ocurring to some extent in 
natural gas. The carbon number for diesel ranges from about C10 to C 20 with 
a corresponding boiling point of 350 oF to 650 oF.  It is anticipated that 
some of the heavier hydrocarbons in the C18 to C20 range will  drop out along 
with compressor oil carryover to substantially increase the amount of liquid 
PG&E sees in their downstream drips.  The net effect of this is a substantial 
reduction of the PCB concentration.  I would expect that after 30 to 60 days 
of continuous injection the PCB contaminant level should drop by an order of 
magnitude.

The reason I would not inject Selexol after the pipeline has been cleaned is 
because you would  leave a finite quantity of Selexol coating the pipeline 
which could  then absorb and concentrate any potential PCB contaminant in the 
gas and potentially  recontaminate downstream equipment.

I will be on vacation from June 19 to June 26.  If you have any questions 
please call.