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Using Shale as a Barrier Simplifies Well Abandonment

The complete paper presents the results of an investigation into the creep behavior of North Sea shales and their ability to form effective annular barriers. The large-scale laboratory results show that Lark-Horda shales will form competent low-permeability annular barriers when left uncemented, as confirmed using pressure-pulse-decay measurements. Experimental conditions were found to influence the rate of barrier formation. Higher effective stress, higher temperature, and beneficial manipulation of annular fluid chemistry all have a significant effect.

Introduction

An alternative to traditional plug-and-abandonment techniques presented itself more than a decade ago, with observations that formations such as mobile salts and shales could creep into uncemented annular spaces and form competent annular barriers that could be identified on sonic and ultrasonic bond logs and verified using pressure testing. Shale particularly has the necessary characteristics that several guidelines require of a good barrier, being largely impermeable, nonshrinking, ductile, and resistant to chemicals and substances, all of which help provide long-term integrity.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 199654, “Simplifying Well Abandonments Using Shale as a Barrier,” by Eric van Oort, SPE, and Maria Juenger, The University of Texas at Austin, and Munir Aldin, SPE, Metarock Laboratories, et al., prepared for the 2020 IADC/SPE International Drilling Conference and Exhibition, Galveston, Texas, 3–5 March. The paper has not been peer reviewed.
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Using Shale as a Barrier Simplifies Well Abandonment

01 January 2021

Volume: 73 | Issue: 1

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