Pump-Down Diagnostics for Plug-and-Perf Treatments

Abstract

Abstract This paper introduces pump-down diagnostics, an economical process in which cement sheath integrity, perforation cluster spacing and frac plug integrity can be assessed for every frac stage, potentially leading to improvements in stimulation, completion, cementing and drilling practices. It is based on analyzing wellbore pressure responses occurring at key segments of the wireline pump-down and perforating operation and correlating the results among multiple frac stages and wells in a field or play. A special requirement is that the frac ball (ball check) is inserted in the frac plug and pumped to seat prior to performing perforating operations. A complementary benefit of this process is that selectively establishing injectivity in the most distant perforation cluster can be used to establish inhibited HCl acid (wireline acid) coverage across all perforation intervals for uniform reduction in near-wellbore tortuosity. Reviews of pump-down diagnostics field cases from several unconventional plays provide the following insights. 1.) pump-down diagnostics are time efficient and economical, requiring about 15 minutes per frac stage, 2.) evaluating communication to the previous frac stage can serve as a key performance indicator for treatment control or cement sheath integrity, 3.) pump-down diagnostic results can be more reliable than cement bond log evaluation, 4.) stage isolation characteristics can be strongly affected by cluster spacing.