American Oil and Gas Reporter - October 2020 - 50

pages 46-53_Layout 1 10/13/2020 2:23 PM Page 50

FracFocus: Monitoring Insights
tration within the sample. Each blob in
the chromatogram was screened using a
proprietary algorithm for a combination
of peak shape, peak volume and repeatability standards. Quantitative blobs that
passed the screening standards were
aligned and zone-specific diagnostic ratios
were identified using a pattern recognition
algorithm.
Figure 2 demonstrates that clear geochemical distinctions were observed
among each of the formations across the
2,240-foot interval. Hundreds of geochemical profiles were established for
each of the formations from cutting and
oil samples. These profiles served as the
baseline for the production allocation
work that followed. The black box denotes
duplicate analysis ran for the 10,240foot sample to demonstrate the significance
of the vertical geochemical differences
observed among the formations.
Produced oil samples from the hori-

zontal wells were collected at the wellhead
and shipped to the lab for GCXGC measurement. The collected geochemical fingerprint information from produced oils
was processed and aligned with the cutting
baseline samples. More than 2,000 compounds were found in the oil samples in
various categories, including alkanes,
alkenes, cycloalkanes, alkyl-benzenes,
aromatic and saturated biomarkers. The
crude oils are composed of those naturally
occurring compounds that can be used
as natural tracers providing hints to reveal
subsurface reservoir performance.
Figure 3 is a geochemical ratio crossplot of produced oil samples clustered
by wells. The GCXGC chromatogram of
the illustrated blobs is at upper right.
The results indicated the four wells were
draining from different reservoir rock
volumes or vertical zones, although there
was some overlapping that caused higher
similarity between wells 1 and 2 versus

NRG Safe is dedicated to safety in the oil and gas
industry. Our solar powered LED safety markers
are the preferred option when electricity is not
available on your location. These markers also aid
in darkened roadway illumination, lane delineation
and as a wrong way driver deterrent to create a
safer environment on high-traf昀c roads.

No Batteries
10 + Year Life
No Wires
Grid Independent
100% Waterproof
Multiple Color Options
3 Year Warranty

YHYS

YHDD

405.558.1295 * www.nrgsafe.com * sales@nrgsafe.com
50 THE AMERICAN OIL & GAS REPORTER

wells 3 and 4. Many compounds have
been identified, and the diagnostic ratio
it shows is not unique, in that it is one of
hundreds of geochemical ratios that effectively distinguishes oils from different
wells/formations. The robustness of the
geochemical information was reflected
by the fact that the clustering was observed
in all the oil samples collected for nine
months.
Production Allocation
There were noticeable geochemical
signature changes in oils collected at different times from the same well. Correlating
these geochemical variations in the oil
samples to the baseline cuttings samples
quantitatively using a regression model
revealed how the contribution from each
formation changed through time, leading
to observed geochemical variations.
Quantitative production allocation
showed that Well 1's drainage was largely

http://www.nrgsafe.com

American Oil and Gas Reporter - October 2020

Table of Contents for the Digital Edition of American Oil and Gas Reporter - October 2020