Page 192 - Pipeline Pigging Technology

Gellypig technology for pipeline conversion

cal difficulties common to extremely cold weather. However, there were no
real problems associated with the actual movement of the pig train once it
was loaded into the pipeline, and no appreciable delays in the job. All frac.
tanks were equipped with propane heaters to help reduce freezing problems.

RESULTS

Samples of the gels and degreaser were taken from each of the gellypig
trains and analyzed for debris loading (i.e. the number of Ib of debris
contained in Igal of gel). Testing was performed at the DS division laboratory
in Houston.
A plot of debris loading vs cumulative train length was constructed for
each gellypig train (see Figs 4 and 5). The total amount of debris removed can
be estimated from the area beneath this curve. Typically, for a line to be
considered relatively clean, the trend is for decreasing debris loading (to a
very low value), in the final portion of debris removal gel, or a very low debris
loading for the entire length of the train. Generally, values of 0.1 to 0.21b/gal
or less, in the final "slug" of debris gel, have been considered an acceptable
level of cleanliness for this type of service.
The total estimate of debris removed with all gellypig trains was 28,9181b,
using a total of 55,000gal of debris removal gel, 24,000gal of separator gel, and
40,000gal of degreaser. The Phase 1 and 2 gellypig trains removed approxi-
mately 20,4431b and 84751b of material, respectively. The curves in Figs 4 and
5 both showed very good results, in that large amounts of debris were
removed early in the pig train, and the amount of debris in the final portions
of the debris gels were very low. The decreasing trend in Phase 2 (Fig.5) was
excellent, with the debris loading values continually decreasing to an ex-
tremely low final value (0.00581b/gal or less!). The final debris loading values
in Phase 2 were not as obvious as Phase 1, since there were some increasing
trends toward the end of the train, but overall the final values were very low
(0.03851b/gal or less!). The gels also exhibited a change in colour (from black
to light grey), which generally indicates a decrease in suspended debris. Phase
2 gels were particularly obvious in their colour change.
The degreaser performed very well in both phases, removing more
residual crude oil and debris than the laboratory analysis would have indi-
cated, for the actual contact times and volumes used. The final hydrotest
water was tested for oil and grease, and suspended particles, and was well
within the limitations imposed (i.e. 20ppm and lOOppm or less, for oil and
grease, and suspended particles, respectively); therefore, the final hydrotest

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