Summary
Whether a cement-squeeze operation results in an annular seal depends
heavily on how far the cement can penetrate and disperse in the fine channels
of a partially cemented annulus. In many cases, a conventional- or
microfine-cement slurry will dehydrate and bridge off before it can achieve its
objectives (Nelson et al. 1990). This paper describes the use of an engineered,
optimized slurry for a squeeze operation in the Duyong B-4 well, which had a
perforated zone that demonstrated a low rate of seawater injectivity. This
paper also presents the slurry design and properties, execution procedure, and
prejob and post-job log evaluations.
After several years of production, gas bubbles appeared in various locations
throughout the Duyong field. Shallow seismic readings showed gas charging in
several shallow gas layers throughout the Duyong field. Several wells were
investigated as possible contributors to the charging of the shallow sandstone
layers, and Duyong B-4 was selected as a probable contributor. Duyong B-4 is a
gas well that was completed in November 1983 with four producing zones. In
September 2003, this well was selected as a test well to evaluate the cement
quality behind the casing. Both cement-bond logs and ultrasonic-imaging logs
showed gas and fluid channels behind the casing. An optimized cement slurry
(OCS) was engineered and tested in the laboratory under well conditions.
Results showed excellent penetration in narrow gaps, optimum fluid-loss
control, and low rheology, both at surface and downhole conditions.
The slurry was used in the squeeze operation; post-job logs demonstrated the
success of the treatment. The slurry penetrated the narrow gaps without
dehydrating, and good mechanical properties were achieved in short setting
times (Moulin et al. 1997). These properties are especially important in
gas-producing wells, and they met all the objectives set forth by the
client.
Introduction
The Duyong gas field is located offshore, approximately 220 km (136 mi) east
of peninsular Malaysia. The first gas from the field was produced in 1984. The
complex comprises three wellhead platforms (DDP A, DDP-B, and DDP-C), a central
processing platform (CPP), a gas-compression platform (GCP), a flare tripod
(FT), and a living-quarters platform (LQP).
The platforms that make up the main complex—the LQP, CPP, GCP, and DDP-B
platform—are connected by a bridge. The FT is located north of the CPP and is
connected by a bridge to the CPP. DDP-A and DDP-C are remote to the CPP
complex. Each wellhead platform has nine well slots. Four wells were completed
on DDP-A, six wells on DDP-C, and six wells on DDP-B. The fluids from the wells
are piped to the CPP. Separation of gas condensate and produced water,
dehydration of the gas, and metering and disposal of the produced water take
place at the CPP. Gas is then piped to shore through the peninsular Malaysia
gas system.
The Duyong shallow-gas second-mitigation studies indicated that Well B-4 had
fair-to-poor cement bond behind the 9⅝-in. casing. There are no data on the
cement quality behind the 13⅜-in. casing. Furthermore, casing to casing
pressure was observed in the annuli of CCP1 between the 9⅝ and 13⅜-in. casing
and in the annuli of CCP2 between the 13⅜- and 20-in. casing. The observed
pressures are believed to originate from gas channeling behind the
casing(s).
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
8 November 2004
- Revised manuscript received:
21 July 2005
- Manuscript approved:
22 July 2005
- Version of record:
20 March 2006
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