Title:

Tracer Testing at Soultz-Sous-ForÍts (France) Using Na-Benzoate, 1,5 and 2,7-Napthalene Disulfonate

Authors:

SANJUAN Bernard, ROSE Peter, FOUCHER Jean-Claude, BRACH Michel, BRAIBANT Gilles

Key Words:

tracer testing, NA-BENZOATE, 1,5, 2,7-NAPHTHALENE DISULFONATE, SOULTZ-SOUS-FOR TS

Geo Location:

Soultz-sous-Forets, France

Conference:

Stanford Geothermal Workshop

Year:

2004

Session:

HOT DRY ROCK

Language:

English

File Size:

265KB

View File:

Abstract:

A hydraulic stimulation was conducted in well
GPK-2, at Soultz-sous-ForÍts (France), in July 2000,
one year after its deepening from a depth of 3,500 m
to 5,100 m. During this operation, two organic tracers
(Na-benzoate and 1,5-naphthalene disulfonate) were
continuously injected at a controlled concentration of
about 2 mg/l into GPK-2 with around 26,800 m 3 of
fresh water. The chemical composition of this water
is very different from that of the geothermal brine
(NaCl fluid with a TDS close to 100 g/l). Four short-term
production tests were carried out between
December 2000 and April 2002. The fluid produced
from GPK-2 was geochemically monitored during
these tests. This paper presents the main results of
that fluid monitoring. Comparison with natural
tracers such as chloride indicated that the organic
tracers were remarkably stable during more than 2
years at around 200?C. At each production test, the
mass proportions of injected fresh water and
geothermal brine could be estimated; the recovered
fresh water could also be calculated (less than 7%
relative to the total volume of fresh water injected
into GPK-2). It was observed that the injected fresh
water was internally replaced by the geothermal brine
in the reservoir. The mean flow rate of the
geothermal brine circulation could be estimated at
1-1.2 m 3 /h. Between January and March 2003, and
during another operation of hydraulic stimulation, a
third tracer (2,7-naphthalene disulfonate) was
injected into GPK-2 at a controlled concentration of
about 3 mg/l, with about 24,000 m 3 of fresh water.
The detection of 1,5-nds, almost 3 years after its
injection into GPK-2, and that of 2,7-nds in the fluid
discharged from GPK-3, have shown that the recently
drilled GPK-3 well (depth of 5,100 m) is directly
connected to GPK-2.


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