Assuring Critical Coiled Tubing Re-Entry Operations of Old Wells with Integrity Issues by the Application of the Well Intervention Guide, Provides Execution to Safeguard the Life and Environment

Abstract

This paper presents the critical aspects taken into account during the planning process of a Coiled Tubing re-entry of an old abandoned well with substandard modified wellhead, a section of 2-7/8″ tubing stuck into the surface cement plug, hazardous atmosphere readings, integrity issues exhibiting sustained casing pressure, wellbore fluids migration on surface, presence of formation faults connecting over pressured formations and background of a well control event requiring 21.1 ppg fluid during the completion stage. Due to the complexity of the Coiled Tubing intervention and information uncertainty, the planning strategy was divided in three stages: First, an initial inspection to determine the integrity status of the wellhead and accessories on the surface, then a second stage to ensure and correct the integrity of the wellhead and the last stage to carry out the intervention on coiled tubing. For the last stage the IDA-G-001 Well Intervention Guide process was followed to fulfil a strict operational discipline including several peer reviews by technical authorities to safeguard the life and environment. The well interventions team planned a critical Plug and Abandonment P&A intervention in a restricted access location; the need for more information was a challenge. The field group accomplished the challenge of milling out with Coiled tubing, the 7″ casing cement plug, and 2-7/8″ tubing with expected well pressure below the cement plug with the proper simulations, bases of design and risk assessments. Acquiring more information about the well's integrity by running electric logs was crucial for adequately designing the abandonment that fulfills the government regulations and industry standards. Consequence analysis and multidisciplinary detailed risk assessment were essential for identify contingency plans during the planning. The pre-operational QA Check list was verified for all the services involved in the abandonment, to mitigate the risk of equipment failure, and this contributed to execute the intervention according to the planing. The two first stages of wellhead inspection and subsequent integrity assurance allowed the intervention with no wellbore fluids that could contaminate the surface. The application of the corporate Guide for the Planning and Execution of Special Interventions, (Well Intervention Guide WIG), is a detailed process that, through an initial risk assessment, determines the complexity of the planning and safe execution of high-risk interventions and is a powerful tool when critical operations such as the intervention of old wells with lack of information and integrity are required.