Refrac Candidate Selection, Execution and Performance Evaluation for Conventional and Unconventional Reservoirs
INSTRUCTOR: Robert 'Bob' Barba
DISCIPLINE: Engineering, Unconventional Reservoirs
COURSE LENGTH (DAYS): 2 Days
ATTEND AN UPCOMING CLASS:
WHO SHOULD ATTEND: Engineers, managers, and geoscientists who want to maximize the probability of success and minimize surprises from a refrac program in unconventional or conventional reservoirs. Particular emphasis is placed on managing primary (parent) - infill (child) frac interactions within a drilling spacing unit to avoid EUR losses and to maximize the number of wellbores within the DSU. Refracs have been shown to be the most cost-effective method to maximize recovery within a DSU in both the primary and infill wells. “Best Practices” are presented to maximize productivity at the minimum cost possible from the primary and infill wells.
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 economic techniques are presented to effectively access these reserves with refracturing treatment(s). “Best practices” presented include recovery factor analysis, perforation cluster optimization using Extreme Limited Entry constrained by critical rate, and the use of expandable tubulars to minimize refrac costs. Innovative techniques such as single perforation hole clusters are discussed to more accurately gauge cluster efficiency. Treatments are designed to both maximize productivity from “new rock” and recharge the existing fracture system to prevent infill well EUR losses.
STUDENTS ARE REQUIRED TO PROVIDE A LAPTOP WITH MICROSOFT EXCEL AND ADOBE READER INSTALLED.
- What makes a good refrac candidate in conventional and unconventional reservoirs?
- Is the poor performance of the candidate due to the initial frac or the reservoir?
- What is the optimum refrac strategy for primary wells to avoid infill well EUR losses?
- What will a refracced well produce?
- What are the “best practices” for refracs in conventional and unconventional reservoirs?
- What information and analyses are required to answer these questions?
In addition to identifying the best refrac candidates the 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.