Construction of 3D well pattern for barrier water injection in offshore reservoirs with gas cap

The offshore reservoirs with gas cap and narrow oil ring are parallel to the fluid interface, and to deploy horizontal well in these reservoirs can achieve good effects in avoiding gas and controlling water, however, However, in the middle and late development stages, these reservoirs still face the difficulties in intensified gas channeling, decreased liquid volume, and urgent adjustment of development methods. By using the method of reservoir numerical simulation, for the testing well group, the comparison of different schemes referring different water injection well types, different horizontal well layout directions, and different horizontal well layout locations was performed, and the construction test of the 3D well pattern for barrier water injection was completed. The testing results show that the development effect of the parallel 3D injection-production well pattern with horizontal wells deviated from central axis and 40 m away from the phase I wells was the best, and the recovery rate was increased by 7.8 percent compared with natural energy development. According to the results of well pattern optimization, 3D physical simulation experiment was carried out, with an ultimate recovery rate of 43.1%, which was 8.9 percent higher than the recovery rate of 34.2% simulated by natural energy development. The physical simulation experiments confirmed the effectiveness of the barrier water injection and quantified the development effect of the barrier water injection. In the next step, it is planned to adjust the development mode in a pattern of well group test and gradual promotion, trying to provide a basis for the studying barrier water injection schemes in similar oilfields.