Wastewater Disposal Wells Management and Injectivity Remediation Approaches

Abstract Tengizchevroil (TCO) has more than 30 years of experience in industrial (technical, treatment, produced water) wastewater disposal (WWD) into the subsurface Neocomian sandstone reservoir through disposal wells. Malfunction of any component (surface or subsurface) of the WWD system can lead to production curtailment; hence, WWD wells are identified as "critical" wells in the business unit. This paper will cover the subsurface part and demonstrate TCO’s approaches to remediate injectivity of wells, which are being conducted successfully. TCO’s current wastewater disposal system has its own maximum capacity, which is mainly limited by disposal wells, booster and injection pumps, power distribution, pipelines, and tanks. TCO has four main injectivity remediation approaches: backwashing the wells, which is the simplest and most cost-effective option; newly developed chemical treatment by bullheading; coiled tubing clean-out; and perforation/re-perforation of existing and new intervals. Additionally, TCO has efficiently used lessons learned from existing wells and successfully applied them to drill 2 new WWD wells. This paper will demonstrate the injectivity remediation work results in wells after applying four different approaches. Each approach has provided different outcomes. Post-remediation well performance and long-term performance were the main factors considered for analysis and decision-making on further approach selection and application. Until 2023, TCO had been using methods that provided sufficient injection capacity. However, starting in 2023, the demand for capacity increased due to higher wastewater volumes, prompting TCO to improve the technology, which was successfully developed and executed.