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Water and Gas Injection Methods |
RF — Rogaland Research, Box 2503 Ullandhaug, N-4004 Stavanger, Norway
Creation of in situ foam barriers to gas flow is a potential way to improve production from wells which suffer gas breakthrough and give high gas-oil ratios. In this paper, new results on gas blockage by foamed liquid hydrocarbons are reported. These foams are applicable in the foam-block process because they can be injected as low-viscous, low-density surfactant solutions which may allow deep penetration near the gas/oil contact. Foam barriers of large radial extent may be created as oil production is resumed by reservoir gas coning through the treated zone.
It is shown by experiments in a sector model that a hydrocarbon foam of lower density than the reservoir oil, when injected at a low rate to allow gravity segregation, will place itself near the gas-oil contact and, upon production start-up, create an effective barrier to reduce the effect of gas coning. Gas coning in the absence and the presence of foams is investigated and compared.
Effective gas blockage is demonstrated for the first time with hydrocarbon foams at low pressure and at reservoir pressure and temperature. Foam performance is studied in water-wet model porous media at varying temperature and surfactant concentration. Experiments with and without wetting water present show the same performance. A given foamer formulation produced poorer gas-blocking performance in reservoir-condition tests than in low pressure tests. This was found to be related to the loss of solution viscosity as a result of gas dissolving at high pressure. By blending the kerosene solvent with a viscous hydrocarbon liquid such that the viscosity of the high pressure system was matched to that of the low pressure system at the respective foaming conditions, the gas-blocking ability of the high pressure foam was restored to match that of the low pressure system.
