25th International Meeting on Organic Geochemistry IMOG 2011

P-345
Oil Fingerprinting associated with Well Temperature Profiles as
an Alternative Production Logging Tool
Alain Noyau, Dominique Andre, Jan Mersmann, Francois Dabat
TOTAL Centre Scientifique & Technique, Pau, France (corresponding author:alain.noyau@total.com)
To monitor reservoir production when wells produce
multiple zones it is necessary to allocate the
production of each formation. The most commonly
used technique is the PLT (Production Logging Tool)
acquisition using various sensors such as spinner,
densimeter, pressure and temperature, the last one,
being rarely used or only for qualitative data until
recently.
However PLT interpretation is occasionally unreliable
or even unachieved.
Reservoir geochemistry based on statistical
processing on molecular fingerprints of oils or
condensates using Gas Chromatography (GC)
techniques has been successfully applied for decades
as a PLT alternative tool for production allocation.
Contamination-free DST reference samples with
clearly different signatures are usually needed for
production split calculations.
The goal of this paper is to demonstrate that
allocation can also be successfully done using a
combination of:
- Molecular fingerprinting of oils from downhole
samples containing OBM contaminants used as
references (end-members).
- A quantitative interpretation of PLT temperature
sensor tool string and pressure data.
In this particular case study a classical PLT was run.
However due to high formation temperature and
consequent electronic failure, spinner data acquisition
was not possible but a temperature data interpretation
was performed to estimate production influx at each
layer. In addition, geochemical analysis by fingerprints
of the oil samples taken at surface during the test and
downhole acquisitions was carried out. These
analyses validated the flow profiles per interval
resulting from the temperature log matching (see
illustration).
Excellent split concordance is obtained between
allocation by geochemistry (25-75%) and using
temperature flow profiles (24-74%) for the PLT2
sample. It provided confidence to calculate the
allocation of the PLT3 (18-82%) using only
geochemical fingerprinting in absence of a reliable
temperature data. Moreover cross flow was identified
for the PLT1 since there was discrepancy between
the geochemical and the temperature results.
In the past, when spinner failed, a new PLT run was
often performed leading to additional cost and lost
time of production.
Oil fingerprinting in tandem with well temperature
profiles can be two complementary operational tools
with strong impact in the deep offshore context for
reservoir monitoring purposes when traditional PLT
acquisition is challenging and costly.
476