More-Effective Plug-and-Abandonment Cementing Technique

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 148640, ’Novel Approach to More-Effective Plug-and-Abandonment Cementing Techniques,’ by Thomas E. Ferg, Hans-Jacob Lund, and Dan Mueller, ConocoPhillips; Morten Myhre, Arne Larsen, and Patrick Andersen, SPE, HydraWell Intervention; Gunnar Lende, SPE, Halliburton; Charlie Hudson, SPE, M-I Swaco; and Cato Prestegaard, SPE, and David Field, Halliburton, prepared for the 2011 SPE Arctic and Extreme Environments Conference & Exhibition, Moscow, 18-20 October. The paper has not been peer reviewed. The effectiveness of a permanent abandonment plug is measured by its ability to bridge the wellbore cross section, both vertically and horizontally, including all annuli, with a plugging medium that can withstand the harsh environment to which it is exposed (Fig. 1). A new method is presented that creates a permanent abandonment plug by use of a system that perforates uncemented casing, washes the annular space, and then mechanically places the cement across the wellbore cross section in a single run. Introduction Traditional methods of creating an annulus barrier in uncemented casing require removal of a section of casing by milling, cleaning the created open hole to remove swarf (i.e., metal filings or shavings produced by a cutting tool) and other debris, underreaming the section to expose new formation, and then setting a balanced cement plug. These operations can be time consuming and difficult to execute safely and effectively. Fluids for use in section milling must have sufficient weight to keep the open hole stable and sufficient viscosity to suspend and transport swarf and debris to surface. The required fluid-viscosity profile for milling operations can generate equivalent circulating densities that exceed the fracture gradient of the exposed open hole, leading to losses while circulating, swabbing and well-control problems, poor hole cleaning, and packing off of the bottomhole assembly (BHA). The problems occur because not all swarf and skimmed casing remnants can be cleared from the wellbore. Swarf and casing debris can become strung out along the wellbore, lodging in the annular and ram blowout-preventer equipment, seriously effecting function. At the surface, handling equipment must be positioned and installed within the return flowline beyond the bell nipple and in front of the shakers to separate and capture the generated metal returns from the active mud system. An example of metal brought to surface during milling operations is shown in Fig. 2.