Mitigating Risks From Waste Subsurface Injection Through Accurate Downhole Pressure Measurement, Analysis, and Fracture Monitoring

Abstract

AbstractEnhanced environmental awareness and controls for new offshore and onshore field developments has increased the requirement for effective management of cuttings and associated drilling waste. Subsurface injection of these wastes has proven to be an environmentally sound alternative for waste management.This paper describes the results of injection monitoring and in-depth fracture diagnostics pressure analysis for injection assurance in a dedicated waste injection well located offshore in the southern Caspian Sea. The benefits and value generated from real-time downhole pressure measurements recorded during subsurface waste injection and decline periods provided an insight into waste domain monitoring and obligatory waste management quality assurance. Precise interpretation and thorough evaluation of non-standard pressure signatures registered during regular injections provided critical information to reveal sub-surface injection pressure anomalies, potential impact on injection assurance and effectively mitigate associated potential risks.Early in the project, fracture re-orientation into the horizontal plane as a result of injection wells being located in a tectonically active environment and on the flank of a compressional anticline with higher horizontal stresses, resulted in additional challenges for the injection assurance. This prompted the immediate need for close and continuous pressure monitoring and analysis. Detailed analysis of the downhole and surface pressure response coupled with regular collaboration of the operational team and subsurface geo-mechanics experts has contributed to the successful delivery of a waste management program. It is via an integrated team that has made the challenges and success of this project feasible.This paper also includes the risks identified throughout the injection project as well as lessons learned from the experience. Downhole pressure measurements coupled with real-time injection monitoring provided the quality assurance required to meet zero discharge objectives in a tectonically active offshore environmental with complex in-situ conditions.To date, more than 200,000 bbl of drilling waste have been safely disposed of in this well using subsurface injection.