Hydraulic fractures are often believed to provide durable, highly conductive channels that remain effective during decades of production. Traditional well test analyses often yield non-unique solutions, with poor ability to distinguish whether steep decline curves should be attributed to insufficient reservoir quality or declining fracture effectiveness. However, there is a growing body of evidence demonstrating that fractures lose effectiveness over time, apparently due to a number of mechanisms.
This paper will:
Examine evidence that fractures fail to provide durable, effective conductivity throughout the created extent
Tabulate suspected mechanisms causing loss of fracture effectiveness
Summarize best practices currently used to address these concerns
Comment on other needed data collection, research and development and efforts to introduce best practices
This study has identified a number of field examples which convincingly indicate that fractures have failed to sustain a conductive channel over time, including:
Wells interconnected during a fracturing treatment, which fail to sustain interference during production
Production results highly sensitive to lateral depth, indicating fractures fail to drain reserves from thick pay sections
Infill drilling through a microseismic swarm without evidence of pressure depletion
Adjacent wells improved or unaffected by offset well " bashing"
Field studies examining the performance of alternate frac designs, convincingly demonstrating the initial treatment was not optimized
Lack of agreement between " perm while pumping" and " perm after closure"
Restimulation results which compare the durability of initial completion strategies
This paper explores a previously underappreciated concept. The results indicate that greater focus should be placed on fracture effectiveness, instead of initial fracture length or extent. The cited field results are encouraging, and suggest that best practices are emerging which can improve fracture effectiveness and durability.