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.

Tying Stage Architecture to Wolfcamp Performance Through Stacked Diagnostics

Abstract

While post-frac erosion and Fracture Driven Interactions (FDI) can be good indicators of a successful frac, getting long-term performance data has mainly been limited to full wellbores of a single design and waiting months for the results. The Permian Asset team was debating the impact of stage architecture on production. Did different designs come on strong, but then fall off over time? Could a doubling of flow area from the standard design lead to a doubling of performance? An experiment was designed to answer these questions with a toolbox of emerging production diagnostics. By combining these latest techniques with some geologic characterization from in-bit accelerometer data, performance of a particular design can be examined on a single wellbore, saving time and money. Three different stage architecture designs were alternated along a Wolfcamp wellbore. These designs were selected to look at the impact of cluster and stage spacing and perforation orientation. A novel methodology for oil tracers (AB testing) was deployed in the test well. Oil tracers that had previously underwent calibration testing for an affinity for each other and the reservoir were pumped during frac. A unique oil tracer was pumped per design. Additionally, an oil tracer was pumped in stages along a greenfield portion of the lateral and another in brownfield stages next to a parent well.  A carbon fiber rod was run to get an initial look at production allocation by cluster, stage, and design type, allowing a comparison to oil tracers at that snapshot in time. 

Depletion analysis was calculated by stage along the entirety of the lateral. Depletion values ranged from 0 up to 500 psi. Despite lateral variability, when averaged by design type, the depletion values were within the margin of error. The oil tracer is showing that an extended stage length 0 degree phased stage (300’ Top Shots) is the top performer versus an extended stage length 90-270 deg phased design (300’ 90/270) and a design with half the stage length and cluster spacing to double the flow area (150’ Top Shots). Initially, the greenfield portion of the lateral (3600’ in the toe) was outperforming the next 3600’ of lateral adjacent to a parent well, but this trend reversed over time. The carbon fiber rod provided a cluster level analysis with the majority of the clusters contributing to the overall production. There is a heel bias associated with the well that is in directional agreement with the greenfield and brownfield tracers at the time of deployment. The rod has the most production attributed to the 150’ Top Shot design, followed by the 300’ Top Shots, with the 300’ 90/270 design coming in last. There is a discrepancy between the top design with the oil tracer and fiber rod data. This could be a normalization issue or a water allocation problem. Continued work is needed in this space to find the root cause. Overall, the stacked diagnostics provided actionable insights on completion designs that can inform future deployments.    

 Speaker Bio

Jessica is a Senior Completions Engineer for the Ovintiv Chief Completions Team. Her focus is on optimizing job size and perf design through modeling and integrated diagnostics. Prior to Ovintiv, she was a Senior Reservoir Engineer focusing on field studies and data analytics in the DJ Basin at Great Western Petroleum. Previously, she worked for WPX Energy as a Senior Completions Engineer in the Williston Basin, where Jessica was one of the lead engineers for a completion and spacing optimization program.  As a Completion and Production Engineer at Schlumberger, she worked a variety of technical projects, including the design, execution and evaluation of hydraulic fracturing treatments, rate transient analysis, production history matching and microseismic monitoring and evaluation.  She received her M.S. in Petroleum Engineering and B.S in Environmental Engineering from the Colorado School of Mines.

Education

M.S. Petroleum Engineering, Colorado School of Mines, December 2006

B.S. Engineering, Environmental Specialty, Colorado School of Mines, May 2004

Professional Affiliations

Colorado School of Mines Women’s Basketball Team: Fall 2000 – Spring 2004 

Society of Women Engineers since 2002

American Association of Petroleum Geologists since 2005

Society of Petroleum Engineers since 2006

Wyoming Geologic Association since 2017

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