Comparing Wireline Formation Tester Derived Productivity Index to Drill Stem Test

Abstract Drill stem test (DST) derived average effective permeability and productivity is our industry's accepted standard but DST expenses are not always justified especially in development wells. Although zonal contribution could be measured by production logging survey but this requires an additional well intervention operation and most likely interruption of production as well. Zonal productivity modeled correctly in a well is of immense value for reservoir management. In exploration well, accurate productivity index prior to DST is invaluable for operational planning, while in development well accurate productivity index is crucial for completion design. If dynamic data is not available, zonal productivity had been estimated based on permeability derived from petrophysical log data. Single probe open-hole wireline formation tester (OH-WFT) pretest mobility is often used to calibrate log data estimated permeability. However, OH-WFT pretest almost always measure the invaded or drilling induced damaged zone and is at a scale much smaller than DST derived average permeability. Interval Pressure Transient Test using wireline formation tester estimate permeability further away from invaded or drilling induced damaged zone provides a more accurate permeability measurement. Multi-probe or Single-probe WFT is an attractive option when borehole condition does not allow wireline formation tester with straddle packer (WFT-PA) operation. For Single-probe WFT data, permeability anisotropy has to be assumed while permeability anisotropy can be calculated from Multi-probe or Packer-probe pressure data. WFT estimated permeability from pressure transient analysis allows zonal productivity to be calculated, utilizing also pressure, temperature, fluid data, zonal thickness, completed interval and formation dip data. Log data modeled zonal productivity from static data had resulted in off-forecast compared to actual well performance. In this paper, multi-probe and packer-probe wireline formation tester permeability test is used to derive zonal productivity. This productivity estimate is compared to actual DST productivity index.