Drill Cuttings Re-Injection Well Design and Completion: Best Practices and Lessons Learned

摘要

As part of the well drilling and completion process a significant amount of waste streams including drill cuttings, discarded mud, completion brine, oily drains, and residual pits volume are generated. These waste streams must be properly handled, treated and disposed of in a most environmentally friendly and compliant manner. Drill cuttings sub-surface injection, or Cuttings Re-injection technology is one of the major widely used drilling waste management techniques in most global E&P areas and represents a process of degrading drill cuttings, mixing into slurry and injecting into the subsurface via pumping at pressure exceeding the formation's fracturing pressure gradient. As any subsurface operation the Cuttings Re-injection has its own inherited risks and complexities which must be proactively addressed via comprehensive front-end design to minimize those risks and potential eventualities. These risks and complexities are predominantly applicable to injection wells - a core asset in the injection system and key to the success of the entire drilling campaign. Industry literature cites general guidelines for a safe cuttings injection well design and completion practices; however, this paper addresses and discusses different options, compares pros and cons and shares some best practices and lessons learned from large-scale injection projects. Topic included are: optimum tubing and casing design, solids settling and wellbore displacement efficiency in deviated wells, tubing erosion assessment and field observations, cement bond resistance to pressure-temperature cycles supported by surveillance results and perforation. This paper was developed based on challenging experiences in a broad practice as a cuttings re-injection international service provider and intends to complement previously published general guidelines with practical examples.