Abstract

Classic well performance interpretations based on core, log, and completion/stimulation styles often is inadequate to define the range of exhibited fractured well behavior Comprehensive stratigraphic and structural interpretation may not confirm an assessment. Initial comfort from better than expected fractured well performance is seldom critically questioned. Interestingly this enhanced early performance may accelerate performance deterioration. When performance deteriorates unexpectedly serious consideration is given to what can be done about those natural fractures?

Several example reservoirs, both in and beyond the Powder River Basin, yield case studies of reservoir flow character and the contrasting influence of varying rock pore character relative to varying fracture and fracture network connectivity and ease of cross-system flow. Contrast between Cretaceous and Pennsylvanian age formations is illustrated.

The focus of the paper is on insights gained through cost-effective, passive observation of dynamic reservoirs. Idle wells can indeed be used to monitor ongoing reservoir operations and gather useful information about reservoir interconnectivity and compartmentalization vs. flow channels.

Contrasting examples illustrate results dominated by well-to-well interference, reservoir dominance of observed well pressure, and well dominance of observed reservoir trends. Long term monitoring of both static and dynamic wells in an active reservoir system provides unique insights for reservoir flow characterization and simulator validation. Reservoir simulation binds performance and pressure data into a constrained solution that can dramatically enhance flow precision of classic interpretations with findings more directly applicable than those of 4D seismic methods being developed to assess reservoir dynamics.