The appraisal of deep tight gas reservoirs can be technically and economically challenging, with success dependent on applying the most efficient completion technology. Inevitably, this includes designing well completions that encompass the deployment of multiple hydraulic fracturing treatments. There is a tendency in the completion design phase to under-assess the number and variety of interventions that a well could undergo during its evaluation. Subsequently, the development and application of the appropriate well intervention strategy is crucial in maximizing the well potential and reservoir understanding. The deliverable of any tight gas appraisal program is to increase the level of confidence in continuing to pursue the resource opportunity by demonstrating stable and sustainable gas inflow flow rates.
Recent drilling success targeting deep frontier gas reservoirs, such as the Amin located in the central part of Oman, have resulted in the need to evolve the well intervention process to include several new (for the region) technologies. These included the deployment of abrasive perforating to facilitate the initial formation breakdown operations, milling out the shoe track for a hydraulic fracturing treatment in an openhole setting, restoring full wellbore access by milling out multiple frac plugs, and temporary installation of a velocity string to eliminate liquid loading issues. Historically, many of these individual processes have been attempted or deployed with varying levels of success, but this is the first time that they have been integrated into a well strategy.
This paper summarizes the process of selecting the best options for well intervention operations in low-permeability gas reservoirs. The integrated work design consideration and results of these completion techniques will be presented along with the key learnings derived from the process.