Abstract

The North Concho Bluff Field produces from the upper Guadalupian tidal-flat sandstone play of the Queen Formation. Recently, the waterflood production from the field had decreased to where it was barely generating a positive cash-flow. A reservoir simulation model was constructed in an attempt to improve earnings by identifying areas of oil potentially bypassed during waterflooding. The spatial coverage of modern well log and core data within the field, however was inadequate for the simulator study in describing the reservoir. A better method of describing the reservoir heterogeneity was needed.

A 3-D seismic volume, having a uniform density distribution of data, was interpreted across the field. The reservoir interval consisting of four clastic cycles, encased by evaporites produces a classic trough-over-peak seismic response. Seismic attribute mapping of a portion of the seismic volume was used to better define the reservoir characteristics within the inter-well region. Final seismic-guided average porosity and average permeability grid files were used as inputs into a single layer reservoir model. History matching using these grids was accomplished with only minor adjustments to the model, as compared to using well data alone. The model identified an additional potential recoverable reserve target in excess of 2 MMBO.

A limited drilling program was initiated to verify the model, resulting in better than predicted production. Using seismic-guided reservoir properties improved the reservoir description for the simulator, allowing for a strategic drilling plan to be developed. The method presented advances the application of seismic-guided reservoir properties from reservoir description to operational reservoir management. Through strategic drilling, the North Concho Bluff Field had gone from a stage of potential divestiture to adding significant cash-flow from a ‘depleted’ reservoir.