Unraveling the Myths Associated with Selecting Standalone Screens and a New Methodology for Sand-Control Applications

摘要

Many completion engineers use laboratory sand-retention testing as a tool to select a screen for standalone sand-control applications, some focusing on prepack and others on slurry testing. Those who use slurry tests for screen selection typically do so based on the conventional wisdom that slurry testing is more challenging; thus, it represents the worst-case scenario for sand production. Furthermore, the general belief in the industry has been that metal-mesh screens with a "pore structure" are better for sand retention compared with wire-wrap screens (WWS) of slot geometry, although they are more prone to "plugging." These are just a few of the many myths that exist in screen selection for standalone screen (SAS) applications. Recent papers on modeling of sand retention by screens of various geometries, and supported by laboratory experiments, provided the tools for predicting sand production in both prepack and slurry conditions, as well as allowing for a systematic performance comparison of various screens using the entire particle-size distribution (PSD) of formation sands (Chanpura, Fidan et al. 2011; Chanpura, Mondal et al. 2012; Mondal, Sharma, Chanpura et al. 2011; Mondal, Sharma, Hodge et al. 2011). In this paper, we discuss and challenge many myths in screen selection for SAS applications and substantiate our findings with modeling and experimental data. The conditions under which a slurry or a prepack test would be more conservative are identified, highlighting the mechanisms of sand retention (size exclusion or bridging dominated). We demonstrate the current thinking that prepack tests are always more conservative from a sand production standpoint is incorrect. We also show that the concept that metal-mesh screens are always superior for sand retention than WWS is incorrect, highlighting the factors that affect sand production through various screens (open flow area (OFA), wire thickness, fraction of bridging-size particles in the formation sand etc.). Finally, a methodology for screen selection in SAS applications is proposed.