Solid Tubular Expansion in Horizontal Wells

Abstract

Abstract The 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. Introduction Extrusion, stretching back to last century, is an important manufacturing process which is used in the production of a wide range of products. The process, known as solid expandable tubular (SET) technology, has recently found an increasing interest in the petroleum industry. SET technology is a down-hole process consisting of expanding the diameter of the tubular by pushing or pulling a mandrel through it. It aims at reducing the incurred and operational costs in many well engineering applications. The increased demand in deep, directional, horizontal, and extended-reach drilling continuously creates demand for more use of expandable tubular. Research work in SET [1–3] started to provide solutions for many problems such as zonal isolation, deep drilling, conservation of hole sizes, etc. There is no doubt that the most significant benefit of SET is its "enabling" capacity. Currently, certain critical wells cannot be drilled to their objectives without using SET technology. One example is the drilling of ultra-deepwater wells, water depth of over 5,000-ft, where all available casing strings are used, yet the drilling environment requires more casing points than there are casing sizes. Further interest in SET is becoming more specific in addressing factors such as reduction of power required to achieve certain expansion percentage, effect of friction and weight during expansion, minimization of surplus deformation, optimization of mandrel shape, mandrel speed, pipe size and grade, etc. Knowledge of post expansion tubular properties is required for accurate service rating of the tubular products under evaluation. In 1998, Shell E&P and Grant Prideco made a breakthrough in developing expandable threaded connections making the technology practical for oilfield applications [4]. With the visions to improve production in Shell Petroleum Development Company Nigeria by 20% in the short term coupled with the thrust to reduce environmental impact, most new wells favor utilizing expandable tubular technology. Over 150 wells were identified for this technology in the medium term with 3 wells selected as quick wins for the deployment of SET in 2001 [5]. However, in order to minimize the impact of oil exploitation to the environment such as reduced land uptake, efficient and effective waste management, etc., only horizontal sidetracks were favored. Similar successful application of transforming conventional wells in mature basins to big bore producers using SET is reported in Malaysia [6]. Dupal et al. [7] reviewed the evolutionary steps taken to date toward the realization of true mono-diameter technology and discussed the installations that had served as milestones. Brass et al. [8] have reported the most recent successful application of using solid expandable tubular to shut off the water producing zones. SET with seals was used at various wells to isolate water producing fractures.