Haddad, Mohamed (ADNOC Offshore) | Rashed Al-Aleeli, Ahmed (ADNOC Offshore) | Toki, Takahiro (ADNOC Offshore) | Pratap Narayan Singh, Rudra (ADNOC Offshore) | Gumarov, Salamat (Schlumberger) | Benelkadi, Said (Schlumberger) | Bianco, Eduardo (Schlumberger) | Mitchel, Craig (Schlumberger) | Burton, Phil (Schlumberger)
Injection of drilling waste into subsurface formations proves to be an environmentally-friendly and cost-effective waste management method that complies with zero discharge requirements. It has now become the technology of choice in offshore Abu Dhabi.
The aim of cuttings reinjection (CRI) is to mitigate risks associated with subsurface waste injection and reduce cuttings processing time and cost. In order to meet these goals, a cuttings reinjection subsurface assurance methodology was developed to improve cuttings processing and continuously monitor drilling waste injection operations.
Preparing for CRI operations required extensive drilling cuttings slurry testing to minimize processing time and develop optimum particle size distribution to reduce cost and increase the injected waste volume. The improvements were accompanied by downhole pressure and temperature monitoring of the injection well, thus facilitating analysis of injection pressures. Fracture containment was verified through a combination of pressure decline analysis, periodic injectivity test, temperature survey, and periodic modelling for fracture waste domain mapping. A backup injection well was used also as an observation well to monitor the pressure signitures in the injection formation.
More than 1 million barrels of drill cuttings and associated drilling waste have been safely and successfully disposed of into a single injection zone of CRI well over three years of operations.
The cuttings reinjection subsurface assurance method optimizes grinded cuttings particle size distribution, detects and identifies potential risks to provide mitigation options to prolong the life of the injector.
The proactive subsurface injection monitoring-assurance program was built into the fit for purpose CRI injection procedure to continually avoid injecting any rejected hard material, improve and update the process as per subsurface injection pressure responses, thus reducing processing time and cost, mitigating injection risks, and extending the injection well life.
This paper presents the unique and technically challenging cuttings slurry properties design and pressure interpretation experience learned in this project; the enhancement of cuttings processing helped increase injection volumes and an in-depth interpretation of fracture behavior which behaved like a risk-prevention tool with mitigation options. Significant enhancement was developed in slurry treatment procedures to avoid injectivity loss and maximize the disposal capacity.