The Art of Disintegration – Ten Years in Review of Disintegrable Metals and Downhole Tools

Abstract

Disintegrable metal (DM) has proven its market value since the first set of disintegrable frac balls were successfully employed in a shale well in Bakken field about 10 years ago. The DM material technology and tools have changed the downhole tool operation landscape with unprecedented efficiency, reliability, by reducing the operational complexity or simplifying tool installation or actuation procedures. This paper reviews the advancement of DM materials technology, arts to engineer and control the disintegrating performance, various DM downhole tools, and the field operation case studies over the last 10 years. Review of the art of disintegration of disintegrable metals is based literature surveys and author’s own research and development results. Disintegrable metals currently available on the market could be classified into two different metallic systems based on their base metal chemistry: magnesium based disintegrable metal and aluminum-based disintegrable metal. Both systems are light weight, strong as steel and completely disintegrable in typical downhole environments. The paper will review the material design, microstructure, and properties of the two metallic systems, then discuss how to match material properties with requirement of downhole disintegrable tools, and finally share field operation cases. Most of DM materials have micro-galvanic cells built into their microstructures and disintegrate through galvanic corrosion when contacting with wellbore fluid. Key variables affecting the rate of disintegration include material composition, well temperature, tool surface area exposure to a fluid, fluid type, concentration and agitation conditions. The review reveals that it is critical to select the correct DM material to match the application environment for a successful field application of disintegrable tool. In today’s multi-stage hydraulic fracturing market, DM tools would be the preferred technology of choice when DM material selection and tool design and performance match properly to the needs of hytraulic fracture operation of a well. The thermodynamics and kinetics that control the disintegration performance of DM tools, or the art of disintegration, will be reviewed and shared with the readers. The profound arts and engineering of DM materials and field case studies shared by this paper would shed light on how to make sound selection of DM materials, design optimal DM tools for a defined well or field application, develop the best field operation procedures, and execute a MD application efficiently.