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Increasing Cement-Sheath Integrity To Reduce Gas Migration in the Marcellus Shale Play

This study examines the effects of drilling, completion, and production operations and their associated cyclic stresses on a cement sheath. The operations performed after cement placement can damage cement-sheath integrity and the bond with the casing or formation, resulting in loss of zonal isolation and in sustained casing pressure, often requiring remediation and reducing productivity.

Introduction

The study reported here is a derivative of a long-term investigation aimed at improving zonal isolation for horizontal wells drilled in the Marcellus shale. The impetus for this long-term study is to optimize drilling and completion practices to reduce cost, improve zonal isolation, and improve well-success rate.

One of the initial actions of the study was assessment of well performance in the Marcellus play. Interestingly, the well-success rate was much lower in the intermediate string than in either the production casing or the surface casing. This observation was unexpected. The intermediate casings of Marcellus wells were set in straight hole at relatively shallow depth. Mixing and placement procedures were implemented similarly on all of these intermediate-casing cement jobs. Sufficient spacer volume, large excess cement volume, and cementing to surface ensured optimal drilling-fluid displacement. With no weak zones creating the risk of lost circulation and with normal drilling fluid and cement densities, adequate displacement rates, and routine use of gas-flow-control cement systems, the loss of zonal isolation in the intermediate/surface annulus did not point to a short-term zonal-isolation issue. Rather, the potential flow path more likely resulted after the cement had set.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 168650, “Cement-Sheath Durability: Increasing Cement-Sheath Integrity To Reduce Gas Migration in the Marcellus Shale Play,” by Jessica McDaniel, SPE, and Larry Watters, SPE, CSI Technologies, and Arash Shadravan, Texas A&M University, prepared for the 2014 SPE Hydraulic Fracturing Technology Conference, The Woodlands, Texas, USA, 4–6 February. The paper has not been peer reviewed.
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Increasing Cement-Sheath Integrity To Reduce Gas Migration in the Marcellus Shale Play

01 May 2015

Volume: 67 | Issue: 5

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