Thermally Insulated Tubing Application to Prevent Annular Pressure Buildup in Brazil Offshore Fields

Abstract

Abstract Heat transfer issues in offshore wells construction and maintenance are increasing in last years. New production development scenarios are bringing challenges related to flow assurance, well construction and maintenance. Insulation projects are being considered to enable the oil and gas production. This paper presents the studies carried out in two projects of thermal insulation using VIT (Vacuum Insulated Tubing) technology and its structural and thermal evaluation using commercial software for numerical simulation. The present work aimed to evaluate VIT application in a production string to reduce APB (Annular Pressure Build-up) effects. This event happens when production flow is heating any well confined annulus causing its fluid expansion and increasing pressure inside it. In this way, annular pressure build up can lead casing collapse or burst even, in an exteme condition, production string damage. All these effects combined could lead to unacceptable well losses. VIT is uded to avoid APB effects. However, a VIT string isn’t be able to provide a smiliar collapse and burst resistance than a usual same dimension tubing string. So VIT will dominate the string installation and production constraints due its back pressure lacking. In this way production string performance evaluation is a key issue on VIT design, length and technical specification. In order to evaluate the performance of the production string designed for two Petrobras projects, several numeric simulations were performed to evaluate loads and strains on intermediate casing and production string during its installation and well production, including the APB events. In addition, the length of pipes with insulation needed to mitigate the effect of AFE was defined and a sensitivity analysis performed to define the value of the minimum apparent thermal conductivity, which would allow operation without risk to well integrity.