Fracture driven interactions (FDIs) within a drilling spacing unit (DSU) have been a topic of increasing concern to organic shale operators. Failure to protect primary wells from infill well FDIs can result in up to 40% EUR losses in infill wells on both sides of the primary well from asymmetric fractures. Adverse FDIs between wells in a DSU can be largely eliminated with a combination of primary well refracs and infill well zipper fracs. The keynote address at the April 2019 SPE FDI conference from a major operator that had done both preloads and refracs suggested that refracs were substantially more effective than anything other than huge preloads in preventing these significant EUR losses.
Historically, refrac operations in horizontal organic shale wells have had unpredictable production results, with the industry moving toward mechanical isolation following an often-painful history with “pump and pray” chemical or ball sealer type diversion over the entire lateral. While results from mechanical isolation have been much more consistent than diverter-only isolation, there is now a discussion on the most cost efficient mechanical isolation method to use. The two most common isolation techniques are cemented conventional casing and expandable liners. The main advantage of the cemented casing is lower upfront costs. The main advantage of the expandable liner is a larger diameter that allows for 20% to 25% higher pump rates. With the combination of XLE and expandable liners the higher rates translate directly into longer stage lengths while still maximizing cluster efficiency. XLE is preferred over intra-stage diversion since diversion can result in incomplete recharging of the depleted clusters if it is employed too early. The resulting lower stage count reduces the overall stimulation cost well below the incremental initial cost of the expandable liner.
SPE 195962 presented at the 2019 ATCE, Robert Barba, Integrated Energy Services, Inc, Mark Villarreal, Enventure Global Technology, Inc.
Mr. Barba received the SPE Regional Formation Evaluation Award for the Southwest North America region (Permian Basin) in May of 2018. He served as a Distinguished Lecturer for the SPE on the optimization of completion designs using petrophysical and reservoir engineering inputs. Mr. Barba is a recognized industry expert on refracturing mechanics and practices, delivering the keynote address at a major refracturing conference for the SPE in January 2016. He has pioneered techniques to evaluate well performance in organic shales using production data and routine well log data, developing a methodology to estimate organic shale EURs from triple combo log data calibrated to production data. Mr. Barba currently teaches a refracturing optimization industry short course, an organic shale petrophysical and performance analysis course, and a basic open hole log analysis course. He has a BS from the US Naval Academy and an MBA from the Warrington School of Business at the University of Florida.