Summary
OMV operates two producing sour-gas reservoirs in lower Austria: the
Reyersdorfer dolomite (shallow reservoir) and the Schoenkirchen Uebertief
dolomite (deep reservoir). A new, separate reservoir called the
Perchtoldsdorfer dolomite (Strasshof Tief field) has been discovered, and
options for how its acid gas can be handled are being investigated. The two
currently producing reservoirs deliver to a gas plant with a 30-tonne/d sulfur
plant. The sulfur plant is too small to accommodate the additional production.
OMV has evaluated acid-gas injection as an alternative to a new, larger sulfur
plant. Acid gas could be injected into either the Reyersdorfer dolomite or the
Schoenkirchen Uebertief dolomite. In either case, injection would be occurring
concurrently with production.
The intent of this project was to determine at a scoping level if sufficient
injectivity and storativity are available in either the Reyersdorfer dolomite
or the Schoenkirchen Uebertief dolomite. Compositional modeling and the
prognosis of the breakthrough time at the producing wells were carried out to
determine the contamination risk to existing production.
The simulation work included generating compositional numerical-simulation
forecasts of production-rate/composition forecasts under concurrent
injection/production scenarios; modeling in-situ miscibility and
gravity-separation effects of acid gas; and evaluating risk scenarios for
existing production to determine the optimal solution.
Introduction
OMV's recent discovery of the Strasshof Tief reservoir prompted a review of
whether acid-gas injection could be a viable alternative to a new or expanded
sulfur plant. The issues were whether to inject into the Reyersdorfer or
Schoenkirchen Uebertief reservoirs ( Figs. 1a through 1c and Fig. 2 ), how
injection would affect the existing recoveries, when breakthrough would occur,
and whether there would be sufficient injectivity and storativity in both
reservoirs. A complicating factor in the analysis is that the size of the
Strasshof Tief is unknown at this time (testing was scheduled for 2006). The
composition of the Strasshof gas is also unknown, but it was estimated on the
basis of Modular Formation Dynamic Tester (MDT)* samples from the
Perchtoldsdorfer dolomite and the known composition of the adjacent sour-gas
reservoirs in the dolomite rock.
Our review of the problem was broken into two phases. The initial phase was
a brief analytical review to estimate the injectivity and storativity of each
reservoir and to assess which reservoir was clearly more suitable. In the
second phase, the selected reservoir was simulated to determine breakthrough
times and whether there was an impact on recovery. Because of the accelerated
schedule of this project, where initial simulation results were necessary to
initiate discussions with regulatory agencies and obtain approvals so that 2006
development plans could proceed, it was agreed that geological models would be
built for both reservoirs immediately so that the simulation could proceed when
a decision was made after the initial review.
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
22 February 2006
- Meeting paper published:
12 June 2006
- Revised manuscript received:
19 January 2007
- Manuscript approved:
3 February 2007
- Version of record:
20 October 2007
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