Ribbon Rod - Improvement in Sucker Rod Technology Shows Need to Re-Evaluate Current Artificial Lift Installations
Authors: Foley W.L. , Hensley H.N. 
Published: December 2007

This study describes ribbon rod as a continuous graphite composite material that can be currently used to partially replace a conventional sucker rod string. The physical properties of composite material, such as light weight, high strength, and corrosion resistance, make it beneficial to oil field applications. The manufacturing process, running, and pulling considerations are also discussed. A database of 33 case histories was assembled that demonstrates a range of producing conditions and failure rates for ribbon rod installations. A simplified design spreadsheet has been developed which can be used to quickly optimize a given installation and predict the performance of theoretical installations for producing even 3,000 bbl/day. A list of advantages, limitations, and future developments is also given.

Introduction

Producers have a strong need to reduce both capital and operating costs. Problems such as rod and tubing wear, corrosion, and overloaded pump jacks, drive up capital costs when equipment is replaced. Other factors causing operating costs to escalate are evident, e.g., in a mature water flood, the energy costs per bbl of oil typically increase over time since increasingly larger volumes of fluid must be handled at increasingly higher water cuts. Overall, economic concerns are among the main reasons why operators are willing to take some risk and try new technology. From a service company's point of view, the customer's needs represent a potential market for new products.

Ribbon rod is a product that can potentially address some of the producers needs. The idea behind ribbon rod is to replace 40% or more of a conventional steel sucker rod string with a long slender ribbon of graphite composite material. (see Figure 1). The technology to make composite material was originally developed by the aerospace industry decades before the ribbon rod idea evolved. The major physical properties that make composite material beneficial to both the oil and aerospace industries are that it's typically stronger than steel, resistant to corrosion, and extremely light weight. For example, ribbon rod will typically be only about 30% loaded when lifting 800 bbl/day of fluid from 7,000 ft. The cross sectional area of ribbon rod is about the same as a 5/8 inch diameter rod. To lift the same fluid using steel rods could require running 1 inch and 7/8 inch steel rods in the top half of the string. In this case, the steel rods add about 10,000 lbs more load at polished rod compared to the ribbon rod string and are likely to be over 90% loaded.

However, a big tradeoff is the cost. Ribbon rod costs more per foot than conventional steel sucker rods. In addition, a ribbon rod string requires that some steel rods or sinker bars be run on the bottom in order to keep the tension in the ribbon rod section. Also, some steel rods are required on top in order to connect it to the polished rod. A specialized assembly, as shown in Figure 2, is used to make this connection. This specialized assembly can support a maximum load of only 18,000 lbs and is typically 90% loaded, while the ribbon rod has a maximum working stress of 160,000 psi and is only 30% loaded.

Physical Properties of Ribbon Rod. Table 1 compares a ribbon rod's graphite composite material to materials commonly used by other sucker rods.

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