Standardized Qualification Process Improves Swell-Packer Performance

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 230518, “Improving Swell-Packer Performance Through Standardized Qualification Process, ” by Manabu Nozaki, SPE, Jesse J. Constantine, and Nola R. Zwarich, SPE, ConocoPhillips, et al. The paper has not been peer-reviewed. _ Swell packers have been used for decades as openhole zonal isolation for conformance control or stimulation treatments. API 19OH dictates how to qualify swell packers and perform differential pressure testing once they are fully set. Currently, no standard exists for predicting swelling performance. This would increase the success rate of casing or liner runs and time predictions for achieving zonal isolation. The authors present the results of their investigations into the potential of a standard testing method to improve swelling performance, including validation of repeatability, using a field case. Field Observations In this study, water-actuated swell-packer performance was reviewed after swell packers retrieved from a failed liner run revealed that swelling speeds featured significant variance. Zonal-isolation effectiveness during hydraulic fracturing also was evaluated on separate wells using radioactive tracers. These results drove an investigation of the industry’s current qualification process for swell packers in order to understand the gap between predictions and the actual outcomes. Actual Swelling Speed in Well A. In Well A, the reservoir liner with fracturing sleeves and swell packers was retrieved because of a liner-hanger failure. All swell packers were retrieved and each swell packer’s outer diameter (OD) was measured at surface. Three measurements (ends and middle) were made across the 10-ft swell-packer element to obtain the average OD for each swell packer. All the measurements were within +40% error except for one that featured a +100% error. Only three swell packers entered the openhole; some damage was observed on these swell packers. The borehole size was 6. 5 in. , and if the liner run continued, several swell packers could have caused a liner-run issue. The discrepancies from prediction were considerable, and swelling speeds were not consistent. This surprising data led to an investigation of a potential root cause of these prediction errors. In particular, areas of investigation included how swelling-speed prediction and quality control of swell packers are performed by different suppliers. Evaluation of Zonal-Isolation Effectiveness. In eight wells, radioactive tracers were pumped during hydraulic fracturing stimulation and logged after the cleanout job if one was performed. In Well F, nine stimulation stages were chosen to pump radioactive tracers for zonal-isolation evaluation. In total, five zonal-isolation failures were confirmed in Well F. No strong correlation exists between zonal-isolation failure and enlarged hole sections. The success percentage is in general higher than the water swell results from the Anadarko Basin; however, the failure rate measured still is considered unacceptably high. An additional complexity is that all eight wells were designed to create longitudinal fractures for a line-drive waterflood, and the zonal-isolation failure could be induced because the fractures could propagate in the direction of the wellbore. However, it is uncertain how likely hydraulic fracturing-induced zonal isolation occurs because longitudinal fractures perfectly aligned with the wellbore are less likely; a few degrees of off azimuth can reduce the contact length significantly; additionally, the fracture-initiation point is unknown.