A 3-D simulation model of a Rotliegend gas field was made to describe the fluid behavior in the reservoir under strong water drive. The model was supported by a detailed geological model giving the lateral distribution of the porosity, horizontal permeability and the flow characteristics of the reservoir rock. The vertical effective permeability was coupled to the horizontal permeability by means of a statistical probability technique.
The model was matched satisfactorily with the decline of the average field pressure and with the detectable water movement in the field (including water breakthrough in one of the producing wells). The adjustments to the matching parameters were endorsed by the geological research. The geological model thus provided a base for an adequate and relatively simple modeling procedure.
The simulation model indicates that the gas-water contact in major parts of the field is at present located at a higher level than is supported by field observations. The presence of fluviatile shaly members plays an important role in the water movement in the field. It is believed that field observations on the water movement may to some extent be masked by the presence of major shale breaks in the eolian units in the vicinity of the wells.
The simulation model was used successfully to predict fluid movement in the reservoir.