Water shutoff treatments need different approach and chemicals in gas and oil fields due to the inverse mobility ratio. Therefore, the primary aim of the research project was to develop special treating solution, which may form barrier phase against the flow of water by in-situ mixing of the treating fluid with formation water. As a novelty, water sensitive petroleum-based solutions were developed, which are stable until they are contacted with water. The induced phase inversion of such metastable systems restricts the water flow by 80-90% in sandstone cores through evolving extremely high viscosity in the mixing zones. Optimizing the composition of the treating fluid containing environmentally friendly chemicals the method was qualified as matured for field pilot tests. In 2013 and 2014, five pilot tests (one repeated one) were carried out at the largest Hungarian stacked oil and gas field. All wells were operating in a depleted gas-capped oil field after terminating the oil production from the lower zone. Special treatment protocol tailored individually to wells was used and injecting 40-100 m3 treating solution, nitrogen drive served to reach deep penetration in the reservoir. Applying short shut-in time, transient production period was observed, and that was followed by gradual and unexpected improvement of production characteristics. Depending on wells, the water production dropped by 40-60% in certain wells; meanwhile in other cases the water production slightly changed though, but the gas production doubled and tripled. The most stunning observation was that all wells never producing oil earlier started to produce substantial amount of oil. Until now, the accompanying oil production is more than 2500 t (18,000 bbl). The outstanding performance of well treatments can be attributed to water shutoff, reduced skin factor, bottomhole clean-up and mobilization of the residual oil saturation from the lower zones. The field project is successful not only in technical, but also in economic point of view. Evaluation of all data proved that the multifunctional stimulation technology might open new vistas in reservoir conformance control in gas fields.


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