Reservoir permeability is an integral parameter in the prediction of gas well and reservoir performance which is critical in operating a business built on gas deliverability. In the absence of dynamic performance data; core calibrated log permeability is typically used to estimate well deliverability. Historically actual permeability derived via pressure transient analysis indicated the need for further upscaling to the core calibrated log permeability. Two new permeability transforms are proposed for the bp Trinidad and Tobago LLC fields in the Columbus basin in Trinidad. This provides the ability to incorporate upscaling heterogeneities that would not be represented at a core or log scale.

The updated transforms replace a single legacy transform which is no longer applicable since the underlying log calculated permeability method has undergone a refresh and the pressure transient analysis database has also been revised. The updated pressure transient derived permeability-thickness encompassed forty-plus wells from across the basin and was utilized in tuning well models to replicate actual performance and hence provide assurance against forecasted gas rate deliverability.

The transforms have been developed for conventional sands in the Basin and are regional. Since they have been deployed, they have been blind tested with additional pressure transient analysis tests that have so far proven their robustness. This updated transform has proven to be a valuable tool to the business as wells have been designed as primarily big-bore high rate wells with the aim of delivering gas to market with minimal well count.

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