Venturi-Assisted Debris Cleanout Through Coiled Tubing to Enable Successful Fishing Operations in a North Kuwait HPHT Well

Abstract

During an E-line conveyed perforation operation using a coiled tubing (CT) unit in a North Kuwait well, the perforating gun became unintentionally detached from the CT string after firing, leaving a fish in the wellbore. Multiple fishing attempts using conventional tools failed to achieve a positive latch. Repeated Lead Impression Block (LIB) runs showed irregular and unclear impressions, indicating debris accumulation and an obstructed fish top. Conventional circulation-based cleanout attempts were ineffective, highlighting the limitation of traditional methods in restoring access to the true fish top and necessitating an innovative cleanout solution. To address debris accumulation around the fish top, a specially engineered Venturi junk basket (VJB) was deployed as part of the bottomhole assembly through a conventional CT string. The tool utilizes the Venturi effect, where fluid acceleration through an internal restriction generates a localized low-pressure zone, creating hydraulic suction to actively entrain debris. This marked the deployment of this technology in Kuwait using a standard CT string without concentric CT. Multiple controlled cleanout runs were conducted while circulating fluid to activate the suction mechanism and progressively remove debris from the fish vicinity. Initial Venturi basket runs recovered significant quantities of metallic shavings and solid debris at surface, confirming effective debris removal. Subsequent runs continued until the basket returned clean, indicating sufficient cleanout around the fish top. A follow-up LIB run then produced a clear and well-defined impression, confirming unobstructed contact with the true fish top. Based on this assessment, an overshot fishing tool was deployed and successfully engaged and retrieved the fish without further complications, validating that debris obstruction was the primary cause of earlier multiple fishing failures. This application demonstrated the effectiveness of a Venturi-assisted debris cleanout approach over conventional methods, particularly in scenarios where debris obscures reliable LIB interpretation. The successful use of a VJB through conventional CT eliminated the need for more complex interventions while significantly improving fishing success. Following this operation, the technique was adopted as a benchmark solution for similar fishing challenges in Kuwait, enhancing operational efficiency and reliability in debris-obstructed fishing scenarios. The paper can serve as a technical guideline for addressing comparable challenges across other fields.