AbtractHeat 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.
Global increase in energy demand and the lack of opportunities onshore or in shallow waters are driving production of hydrocarbons towards deep and ultra deep-water basins, where reservoirs are usually formed by weak and unconsolidated sandstones that require sand control methods to prevent damage in surface and subsurface equipments. Guidelines to select sand control systems are primarily based on sand exclusion, seeking to optimize balance between oil rate and fines production. Another aspect, often overlooked, is collapse strength of the system formed by the sand control equipment and the formation itself, subjected to mechanical loadings that change during life of the well. This contribution presents a method to evaluate collapse strength of sand control systems taking into account mechanical interaction between the formation and sand control screens. Elastoplastic models are used to represent granular materials. The most usual sand control system was studied: gravel pack with premium screens. A model to describe contact between granular materials (gravel and formation) and soil-pipe interaction is proposed. Results demonstrate that perforated base pipes used in premium screens may be oversized for applications under regular operating conditions. Introduction From the 80s the offshore world oil production surpassed the 25% of the total volume produced and became a new frontier in the search of non-renewable energy sources. Since then, the continuous increase of oil demand and the high oil prices allowed for the development of basins in more challenging scenarios. In the last years, most part of oil and gas reserves which have been discovered are found in deep and ultra deep water in Gulf of México (GoM), Brazil, West of Africa and Austrália in a complex environment comprising turbiditic reservoir, non-consolidated sandstones, reative shales, low fracture gradient and high porosity and permeability reservoirs. These are a great challenge to the development explotation projects (Bianco, 2007). In this scenario, it is mandatory to develop alternatives to sand control to build high rate wells, and the Open Hole Horizontal Gravel Packing (OHHGP) constitutes one of the most used techniques for solid control in horizontal wells. In Brazil more than 200 wells have been built by means of this technique, and it is one of the main alternatives used by Petrobras for offshore well completion. During the sand control design and selection, the aim is to obtain an optimal relation between the oil rate and the solid production in terms of the formation granulometry. However, the loading imposed on sand control system by formation has not been considered in the OHHGP design.
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