December GM: Optimizing Stage Lengths by Leveraging Fracture Interference

Optimizing Stage Lengths by Leveraging Fracture Interference:

Objectives/Scope: This paper covers a case study in the Denver-Julesburg (DJ) Basin that reveals stage lengths can be dynamically varied when wells are tightly spaced to optimize pad drainage and completion cost in homogeneous rock strata. Alternating stage designs in offset wells can support increased stage lengths up to 6x standard (exceeding 1,000 ft) and still treat and produce as uniformly as smaller stages, due to the cooperative effect of the overlapping fracture network created by neighboring infill wells. These findings were corroborated by fiber optic data acquired during frac (cross-well strain) and post-flowback production monitoring and interference testing. We also observed Formations within damage zones altered from faults can affect drainage results.

Methods, Procedures, Process: Differing stage lengths (X, 2X, 3X and 6X) were trialed in three wells in a six well section.  Fiber optic diagnostics were acquired during frac for cross-well strain evaluation and 60 days post-flowback for production monitoring and interference testing. Locations and extent of fracture interactions were observed during the fracturing process, and later compared to the production and interference testing results after flowback.

Results, Observations, Conclusions: The post-completion diagnostics corroborated the during frac cross-well strain data. Interference testing reveals communication as well as unique geological features in the areas identified by the cross-well strain data. There is little if any difference in cross-well strain or production behavior of standard-length X stages offset by X stage lengths and X offset by 2X or 3X stage lengths. Performance of the 3X and 6X stages is nearly identical to the X stage lengths, in both production and interference from a uniformity and production volume.

Novel/Additive Information: When wells are known to interfere or communicate, completion designs can be modified dynamically to work with overlapping stage designs, optimizing completion costs without sacrificing treatment uniformity nor production. Stage lengths of offset wells, depending on the play and geologic structure, may be dramatically larger than previously thought when offset against smaller stages, while still allowing for sufficient reservoir access and drainage, leading to reduced pad development time.

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BIO:

Evan Rodgers

Production Engineer at Chevron Rockies (former Reservoir Engineer at PDC Energy).

Evan Rodgers is a Petroleum Engineer from the Colorado School of Mines, class of 2012, currently working as a Production Engineer for Chevron in their Rockies business unit within the DJ basin. He has held additional roles outside of Chevron within Reservoir and Completions engineering in various basins including the Utica Shale, Piceance, and DJ basin. He has been a part of both exploration and developmental teams along with projects varying from single well de-liquification to basin-wide reservoir delineation. His interest gravitates towards acknowledging how much we do not fully understand, especially around the technical aspects we think we do. He uses this approach to set his mindset while designing, analyzing, or proposing a field experiment.