Flowing Material Balance (FMB) and Rate Transient Analysis (RTA) have evolved as well and reservoir performance evaluation techniques which make use of the large amount of pressure data from permanent downhole gauge (PDHG). Meaningful analysis requires the pressure and production data to be continuous but often there are operational breaks in the data making analysis quite difficult. Case histories of FMB and RTA that use augmented non-continuous pressure data from PDHG as basis for modelling well and reservoir performance to deal with this gap are presented in this paper. The proposed method involves derivation of continuous pressure trend by splicing and merging depth-converted tubing head pressure data with non-continuous PDHG pressure data in the intervals where the later are discontinuous with appropriate quality checking to ensure no hump or sink at the transitions as well as consistency in trend. Any remaining gaps are then handled by interpolation of offset points. The augmented non-continuous PDHG data is then applied in FMB and RTA to estimate connected GIIP and remaining recoverable resources following an acceptable analytical or numerical history matching. A workflow to enable application of the process is documented in this paper. Results from the case histories are comparable with previously published 3D static and dynamic models. The results could be influenced by the noise level in the data but this could be managed with appropriate de-noising method like wavelength filtration which was used in this case study. This approach offers the maximum use of PDHG pressure data in reservoir surveillance not just as a real time monitoring technique but additionally as enabler in predicting life cycle performance of a reservoir in the absence of, or complimentary to 3D dynamic simulation model or other methods in the industry. It is simpler and less resource consuming performance-based approach than 3D dynamic simulation.