Deepwater Casing String Deployment for Elimination of Rat Hole Section: Retractable Shoe Joint

Abstract

This paper describes the development of a deepwater casing shoe which ensures subsea casing strings designed to land in a wellhead can be run to full wellbore depth with no rat hole. The problem with excess rat hole occurs when drilling and holecleaning operations enlarge a normally-gauged hole or the unsupported, uncemented portion of the wellbore collapses and leaves an over-gauged hole. Such hole conditions are conducive to compromised primary cementing operations, poor zonal isolation, and can lead to stuck logging or other downhole tools in the subsequent interval.This shoe allows the rat hole section to be completely covered with casing while simultaneously landing the subsea casing hanger in the wellhead. This technology represents a paradigm shift in primary cementing practice; allowing cement to be placed at wellbore TD without a rat hole. This is especially true in deviated and/or horizontal wellbores, where zonal isolation is critical to well-life expectancy and production.