Evaluating Reservoir Communication in a Naturally Fractured Reservoir: An Integrated Surveillance Case Study Using Tracers, Dynamic Modelling and Flow Diagnostics

This paper presents an integrated study aimed at evaluating reservoir communication in a naturally fractured system. The key objective is to determine the extent to which natural fractures influence reservoir performance and flow connectivity in the initial seven years of production and injection. The study applies a combination of tracer diagnostics, dynamic modelling, and reservoir surveillance to assess whether the system initially behaves in a fracture-dominated or matrix-dominated manner, and to support development decisions to maximize recovery. A multi-disciplinary workflow was deployed early in the field's development, integrating image logs, tracer diagnostics, dynamic reservoir modelling, pressure transient analysis and injection surveillance. Tracers tracked inter-well communication and breakthrough timing, while Residence Time Distribution model clarified matrix versus fracture flow. Dynamic modelling with streamline simulation, calibrated using early production and pressure data, helped assess reservoir response. Flow diagnostics such as rate analysis and Hall plots characterized flow regimes and injection response. Integrating these datasets enabled cross-verification of reservoir behaviour in a naturally fractured setting, enhancing confidence in connectivity interpretation and performance prediction. All three techniques consistently indicated that the reservoir is matrix-dominated, despite the presence of conductive and resistive natural fractures. Tracer results showed well-behaved, delayed, and predictable breakthrough, suggesting limited fracture connectivity or channelling. Dynamic reservoir simulation results matched historical performance only when matrix properties were the primary control on flow. Flow diagnostics further confirmed matrix-dominated response, with pressure transient and rate data lacking typical fracture flow signatures such as rapid pressure propagation or bilinear flow. Tracer residence time and breakthrough were found to be controlled by well spacing, injection rate and uptime, with no signs of unexpected or rapid water cut typically associated with natural fractures. Hall plots indicate most injectors encountered resistance to flow, which is contrary to expectations for a fractured reservoir with enhanced permeability. These findings demonstrate that while natural fractures exist and contribute to heterogeneity, they do not adversely affect sweep efficiency, pressure support, or early production performance. The reservoir exhibits stable communication and controllable injection response, supporting field development through conventional matrix-driven strategies. The consistency of interpretation across tracers, reservoir modelling, and diagnostic methods adds robustness to the conclusion and suggests a nondetrimental influence of natural fractures on initial well placement, spacing, and waterflood design decisions. However, with continued production and injection, influence of natural fractures is expected to play a role as the dynamic conditions change within the reservoir. This study provides a greenfield example where an integrated diagnostic approach demonstrates initial matrix-dominated behaviour in a fractured carbonate reservoir. It challenges the assumption that fractures inherently complicate reservoir management. Influence of natural fractures can be delayed and better managed by avoiding aggressive operating conditions such as high offtake rates and injection close to fracture pressure. The methodology and insights presented offer a transferable knowledge for similar fields where fracture influence is uncertain, helping operators to make data-driven decisions on reservoir connectivity and development planning.