Refrac Candidate Selection, Execution and Performance Evaluation

INSTRUCTOR: Robert 'Bob' Barba
DISCIPLINE: Engineering, Unconventional Reservoirs
CEUS: 1.6


WHO SHOULD ATTEND: Engineers, managers, and geoscientists concerned that their reservoirs may not be completed using the best possible techniques.

COURSE DESCRIPTION: Participants will learn a methodology that first accurately characterizes the reservoir properties to evaluate the effectiveness of the original hydraulic fracture treatment with production data. This enables a determination of the cause of poor production performance; as a function of a poorly designed or executed completion, or poor quality reservoir rock. If the remaining volumetric reserves are adequate, techniques are presented to effectively access these reserves with refracturing treatment(s).



  • Is poor production performance due to the frac or the reservoir?
  • What will a lateral produce as a function of the landing zone?
  • What are the “best practices” for fracs and refracs?
  • What information and analyses are required to answer these questions?



  • Discussion of the current state of the refrac industry
  • Review of basic log analysis techniques
  • Log quality control, calibration, and normalization steps
  • Recovery factor and effective frac length model data requirements
  • Net pay model calibration using log, core, DFIT, well test, and production data
  • Permeability, rock properties and reservoir pressure model calibration to field data
  • Integration of rock properties, permeability, and reservoir pressure models
  • production decline curve analysis issues
  • recovery factor exercises for unconventional reservoirs
  • effective frac length exercises for conventional reservoirs
  • historical best practices for improving frac performance
  • Review of refrac project results
  • Mechanical issues with refrac design and execution
  • Review of local examples and discussion


Mechanical aspects of refrac execution are emphasized to ensure that the maximum stimulated volume possible is obtained. The methodology utilizes basic openhole wireline logs, core data, pre-frac pump-in test data, and production data to predict production performance as a function of frac performance. This information can then be used to determine what refrac practices are resulting in the highest recovery factors. Diagnostic techniques such as production logs, microseismic, tracers, decline curve analysis, and post frac production analysis are discussed to supplement the performance analysis.

For initial completions the methodology can provide an estimate of future hydrocarbon recovery with different landing zone options to maximize results from each lateral and determine the optimum number of stacked laterals for an area. For refracture treatments a key deliverable is candidate selection and the ability to “forward model” refrac results prior to the treatment. Case studies are presented from previous “best practices” studies in both oil and gas reservoirs to reinforce the concepts.

The course includes a comprehensive review of “best practices” from previous evaluations of over 4000 producing zones in past field studies to guide the optimization process for future or existing well completions. Participants will receive a comprehensive log analysis spreadsheet that includes calculation of all inputs required to develop calibrated permeability and stress profiles in ASCII format to load directly into a 3D hydraulic fracture simulator. Additional spreadsheet routines are provided to estimate volumetric reserves from petrophysical data, estimated ultimate recovery from production decline data, and economic analysis of expected production declines.

Upon completion participants will be well equipped to utilize service company and in-house log analysis resource to develop well performance models specific to their reservoirs. Class participants are encouraged to provide local examples for discussion of model implementation and possible “best practices” for their areas of activity.