Recently, field engineers have tried to use a new technique using expandable tubular with elastomers to seal the annulus. Ultrasonic down-hole measurements carried out for evaluation of zonal isolation revealed that the tubular expanded to an oval x-section instead of the desired circular x-section at certain locations. This is a phenomenon previously unknown. It is believed to occur due to expansion in irregularly shaped boreholes. The ovalization of expanded tubular was studied to avoid such problems in future. The finite element method was used to predict tubular ovality and compare it to measured values. Results were then used to develop ready-to-use design curves in making decisions for running a completion tool in expanded tubular.
Although more than a decade of work is behind the successful use of Solid Expandable Tubular (SET) in oil and gas industry for a wide range of applications, a thorough review of literature indicates that most of the research and development work is based on finding a fit-for-purpose solution for specific field problems. A significant aspect, which in certain circumstances is not well understood, is the pre and post expansion material and mechanical characterization of SET. Simple analytical and numerical models are developed to estimate the operational parameters like expansion force, length shortening, wall thinning etc., without having an appropriate understanding of material transformation and contact effects, which the tubular experiences during expansion. Although the calculated parameters are not optimum, these have significant effect on SET performance during its operational life in the well. In order to understand the critical mechanical properties and design accordingly, a predictive control of the material characteristics in the deformation process is essential. The current study is based on the comparison of experimental and simulation results of the expansion process for SET. Experimental work done using expandable tubular test-rig and simulation using finite element analysis has been done on 174.625 mm, 177.8 mm and 182.88 mm inner diameter tubular for expansion ratios varying from 12% to 28%. However, only the results of selected tubular are presented. The results clearly indicate that the maximum expansion ratio is severely limited by the post expansion collapse pressure of the tubular. Simple calculations as well as numerical simulation show that the thickness reduction beyond 13% results in considerable reduction in collapse rating. The microscopic study of the tubular material after burst and fracture zone showed regions of overload, shallow dimples and fine microscopic cracks. The elongated dimples intermingled with fine microscopic voids are reminiscent of localized ductile failure. These informations will lead to a better understanding of possible SET failure mechanism during its operational life and comprehensive data to manufacturers and scientists to seek improved material with higher ductility while maintaining strength after expansion. A good progress will result in extending the operational envelope of the tubular and its applications.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe expansion process subjects a solid tubular to large plastic deformations leading to variations in tubular thickness and length, which may result in premature and unexpected failures under normal operations. Simulation work, laboratory tests, and field trials proved the viability of tubular expansion downhole and field engineers have gained enough knowledge in handling this process. However, tubular expansion in open hole of horizontal sections still presents another challenge to researchers and field engineers due to gravity and drag between the seal and the formation. The present work, therefore, presents simulation results of tubular expansion under various field conditions. In this study a typical tubular size of 57.15 mm outer diameter and 6.35 mm wall thickness is used with two different elastomer seals, 5 mm and 7 mm thick placed at equal spacing of 20 cm. It is found that the drawing force increases as the mandrel angle, expansion ratio, and friction coefficient increase. A typical expansion simulation showed that the drawing force required for expansion using a rotating mandrel is 15% less than that of non-rotating mandrel having same configuration. However, tubular thickness reduction is found to increase by 47% for a rotating mandrel as compared to a non-rotating one, which may affect the post-expansion tubular performance. The tubular wall thickness decreases as the mandrel angle, expansion ratio, and friction coefficient increase.
The use of solid expandable tubular technology during the last decade has focused on solving many challenges in well drilling and delivery including zonal isolation, deep drilling, conservation of hole sizes, etc. not only as pioneered solution but also providing cost effective and long lasting solutions. Concurrently, the technology was extended for construction of multilateral in typical wells. The process of horizontal tubular expansion is similar to the vertical expansion of expandable tubular in down-hole environment with the addition of uniformly distributed force due to its weight. The expansion is targeted to increase its diameter such that post expansion characteristics remain within allowable limits. In this study a typical expandable tubular of 57.15 mm outer diameter and 6.35 mm wall thickness was used with two different elastomer seals of 5 and 7 mm thickness placed at equal spacing of 200 mm. The developed stress contours during expansion process clearly showed the high stress areas in the vicinity of expansion region which lies around the mandrel. These high stresses may result in excessive wear of the mandrel. It was also found out that the drawing force increases as the mandrel angle, expansion ratio, and friction coefficient increases. A mandrel angle of 20o requires minimum expansion force and can be considered as an optimum geometrical parameter to lower the power required for expansion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.