Development of the Strasshof Tief Sour-Gas Field Including Acid-Gas Injection Into Adjacent Producing Sour-Gas Reservoirs

Abstract

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. Three injection scenarios are contemplated: 200, 400, and 800×103 std m3/d (6.4, 12.8, and 25.6 MMcf/D). The applied acid-gas composition is carbon dioxide (CO2) (80%), hydrogen sulfide (H2S) (16%), nitrogen (N2) (3%), and methane (CH4 or C1) (1%). 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.