Underbalanced Jetting in CSG play

Abstract

Historically, openhole barefoot completions used in conjunction with cavitation and surging or underreaming techniques, have proven to be an effective way to stimulate coal seam gas wells to increase effective permeability. (Logan et al, 1989). However, despite having a positive impact on production, the unpredictable time required to cavitate and surge the wells can be substantial, sometimes requiring up to 4 weeks to execute required scope. This time consuming technique leaves the operator vulnerable, working in an unstable borehole where fishing operations are common and the outcome of delivering scope is not guaranteed. The main challenges of accurately predicting cost to keep the projects economical, continuing to produce coal fines during cavitating and surging, and continual sloughing are some major drawbacks. The other alternative on the market is underreaming, which has its own limitation in relation to the maximum possible enlargement of the borehole or more specifically, the size of the underreamer that can be utilized. Faced with these limitations, there was a significant need for an innovative way to stimulate wells to increase production while minimizing costs. This paper introduces the ingenious use of a newly designed jetting tool, with specialized nozzles, to enlarge a borehole size using a combination of air and mist. This case study conducts a lookback on design parameters, cost, and safety improvements introduced by this new technology.