Drilling waste generated during development of oil and gas offshore and onshore fields are required to be disposed of in a responsible and environmentally friendly manner. The remoteness of such environments, coupled with the ever-tightening environmental regulations and then green operation initiatives of operators, can create significant economical, logistical and regulatory challenges. The subsurface drilling cuttings reinjection becomes the preferred option allowing oil and gas operators to achieve zero discharge which can meet the most stringent environmental standards. To prevent all possible injection issues that were experienced earlier in the industry globally (early 1990's), a novel "design, execute, evaluate approach was introduced, this enables us to deliver reliable, single sourced start to finish solutions Subsurface drilling waste injection has been and continues to be used on several offshore projects where many millions of barrels of waste have been injected in a single well. This has been achieved through the engineering approach "design, execute, evaluate". The design study assesses the subsurface strata and identifies suitable injection zones, with a focus on waste containment assurance. The execution and evaluation phase begins with an initial injectivity test to calibrate all the reinjection modelling completed so far, we then implement real time injections surveillance including advanced pressure analysis as a risk control tool. The key focus is to analyze, identify, and recommend necessary adjustments during injections to prevent injection failure. The studied cases have been operated successfully since their start to date. No injectivity issues have been experienced during drilling waste fluids injections. Several on-time interventions have been made to proactively prevent the well becoming plugged and maintaining surface injection pressures within normal ranges. Recent advances of Real-time data streaming have made big step change improvement in the data delivery process, monitoring pressure analysis. It creates a direct link between the wellsite and worldwide multidisciplinary technical expertise and provides visualization capability at anytime and anywhere to all personnel involved in the project. This step change in monitoring drilling cuttings reinjection operations provides truly "Acquisition to Answer" integrated solution, mitigates the injection risks and enhances the intrinsic value of drilling cuttings reinjection on offshore development projects. This paper shares the experience and the success of subsurface drilling cuttings reinjection where wastes are injected for final and responsible disposal. The offshore field cases are presented to illustrate the value of the recent technological advances along with best practice guidelines and recommendations for safe and economical disposal of drilling waste fluids to achieve true zero discharge results.

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.

Management of drilling wastes presents major challenges during drilling operations in environmentally protected areas. An Abu Dhabi offshore field development project selected cuttings reinjection (CRI) services as an appropriate solution for waste management. Although CRI is a proven technology in the region, fracturing injection always inherits its own containment-related risks. To prevent all possible failures that were experienced earlier in the industry globally, a novel real-time monitoring and analysis of fracturing injections data was introduced. A comprehensive front-end engineering design (FEED) study was performed to evaluate the feasibility of CRI techniques by selecting a suitable injection formation and designing a CRI-dedicated well, surface facilities, slurry testing, and appropriate operations execution plan. The CRI well was drilled and completed to accommodate waste volumes. An assurance program based on industry best practices was used to support zero solids settling, fracture, or perforation plugging. To achieve on-time intervention, the first real-time CRI data transfer through a satellite-based network to a support center staffed by global experts in Abu Dhabi was deployed to analyze fracture injection and shut-in pressure responses for early identification of possible risks and to map the fracture waste domain. The project has been operated successfully since its inception with more than 300,000 bbl of drilled cuttings and drilling waste fluids injected since July 2016. No injectivity issues were experienced during drilling waste fluids injection. Several on-time interventions had been made to prevent well plugging and to maintain surface injection pressures within normal ranges. Real-time data streaming has made a step-change improvement in the data delivery process, monitoring, and fracture pressure analysis. It creates a direct link between the wellsite and worldwide multidisciplinary technical expertise centralized in Abu Dhabi and provides visualization capability at any time and to any where to all personnel involved in the project. This step change in monitoring CRI operations provides an acquisition-to-answer" integrated solution, mitigates the injection risks, and enhances the intrinsic value of CRI services. The paper shares the experience of implementing the novel real-time CRI subsurface injection assurance program dedicated for cuttings reinjection operations. Real-time support from multidisciplinary experts provides live injection monitoring and fracture waste domain mapping for highly complex and risk-prone subsurface injection environments with stringent regulations

Cuttings reinjection (CRI) project at OFFSHORE ABU DHABI field achieved successful operation with three million barrels injected to date with zero subsurface failures setting up an environmentally friendly and cost-effective waste management success story that complies with zero discharge requirements. The project exceeded initial expectations by accommodating non-aqueous drilling waste from jack-up drilling rigs in addition to artificial islands own rigs. Subsurface assurance and engineering workflows proved to be effective in ensuring subsurface containment of drilling waste in challenging environment while ensuring efficiency of operation to meet demanding drilling schedules. Injection schedules and procedures were based on results of thorough subsurface FEED study and global best practices. Slurry fluid quality requirements were verified thru extensive laboratory tests. Throughout injection operation downhole pressure and temperature of the injection well was vigilantly monitored and analyzed along with well temperature survey and periodic fracture modeling updates of the fracture waste domain to ensure seamless fracturing of formation and containment of waste domain within selected formation. More than 3 million barrels of drill cuttings and associated drilling waste have been safely and successfully disposed of into a single injection zone of two cuttings reinjection wells over five years of project operation to date. No downtime was experienced and no impact to drilling schedule was induced demonstrating high capability of technology when designed and executed in right way. Results of actual injections showed accuracy and robustness of the engineering workflow implemented from Job design, planning and execution The paper presents unique and knowledge-based steps that contributed to success of project and set high bar for region for the drilling waste management.