A Review of 25 Coiled Tubing Well Interventions: Customized Solutions for Bolivian Sub-Andean Basin.

Abstract

Abstract Fields in the Bolivian Sub-Andean Basin are remote, difficult to access locations. The producing zones include the country’s most challenging wells with depths of 26,000 ft. with high pressure, high temperature, high gas cut, cross flow, dog leg severity, well access restrictions, etc. A review of 25 well interventions (WI) delivered to extend the life of those wells is covered, including nitrogen lift, acid wash, milling, shifting sleeves, setting packers, stimulation, Velocity Strings (VS), and fishing. In order to overcome logistic issues related to wells in remote locations, there were several opportunities to reduce mobilization and operational times without risking HSE or SQ, starting with using skid-based Nitrogen Generation Units (NGU), splitting the Coiled Tubing (CT) string into two sections (then joining the sections at location), and so on. Laboratory tests were performed to analyze the solids recovery of the well in order to choose the correct acid treatment. CT strings were designed to enable pumping at rates 1-2 bpm, without exceeding yield limits, and to reach extended depths. Lessons learned and best practices, including diagnostic design and customized delivery of operations, compiled in this paper refer to:Logistic improvements for transportationRunning 5,000 m velocity string (VS) jobs with large 2 7/8-in. strings in live well conditionsManaging the corrosion generated by the oxygen associated with the NGU to avoid the formation of a plug inside the CT string during the N2 jobsRunning CT strings in a gas environment with no or minimum buoyancy effect and high well head pressure to reduce the risk of collapseIssues with shifting sleeves. Evaluating the ability of a mechanical shifting tool with low nominal diameter to close large diameter sliding sleevesRunning CT jobs while the well is in production to the processing plant For well/reservoir conditions that include challenging access to locations, the versatility of customized intervention solutions is a differentiator in today’s industry. The state-of-the-art technology presented in this paper covering 25+ well interventions offers a unique compilation of lessons learned and methodologies. This paper presents a guide for planning and solving cost-effective well interventions in fields with similar issues. These methods provide operators with customized solutions to increase the value of their assets with collaborative teamwork.