Abstract

This paper outlines a multi-year project to evaluate, test, qualify, and trial "unlimited" frac sleeve completion systems that were readily available in the market for use in ConocoPhillips global operations. This effort is to replace legacy, conventional and limited, graduated ball drop sliding sleeve systems. In addition, the "unlimited" systems were viewed as a potential new disruptive technology to the Plug and Perf (PnP) process when cluster/sleeve/perforation spacing is at, or greater than, one joint of tubing.

A series of dynamic surface flow loop tests that mimic downhole loads and conditions, utilizing several hundred feet of completion assembly to replicate target sleeve spacing, as well as different sleeves/stage configuration options were setup along with high horsepower frac/pump down trucks to determine if the "unlimited" sleeve systems functioned (open or stay closed) per design and perform as advertised. Darts or collets were pumped at recommended pump down rates through a single sleeve or multiple sleeves to confirm the sleeve systems functioned successfully. High frequency data was recorded using listening devices, accelerometers, cameras, and pressure gauges to effectively evaluate the systems.

Not all systems performed as advertised or were able to replicate Vendor benchtop "qualifications". Some systems failed to ever work, other systems went through various modifications after yard testing uncovered learnings which ultimately yielded success, and some systems tested worked per design.

Impact loads and "wear and tear" proved detrimental to some systems and components as the darts/collets travelled through upper sleeves to the deepest sleeves. Dissolution time vs dart/collet durability continues to be a difficult tradeoff for material selection due to the variability in downhole conditions and stimulation fluids. Biasing forces in the mechanical systems posed issues passing through upper completion components when the dart passed in a compressed state. The geometry of the activation dart introduces new challenges for ensuring successful deployment, especially in subsea and stimulation vessel applications.

In the field trials, various data sources measured during stimulation operations led to the initial interpretation that "unlimited" sleeve systems were functioning downhole as designed, however, further diagnostics indicated the sleeves appeared to not open. Measured data sets were inconclusive at times, leading to confusion over actual operability. Dynamic surface flow loop testing was designed and performed to qualify each of the systems under a more rigorous set of field conditions. This dynamic surface testing and subsequent additional downhole imaging ultimately confirmed whether the sleeves had opened or closed. This paper will give guidance on how to assess the field diagnostics, determine sleeve opening results, and robustly qualify frac sleeve systems.

This content is only available via PDF.
You can access this article if you purchase or spend a download.