Innovative Remedial Cementing Solution Provides Annular Isolation in Duyong B -4, Petronas Carigali

摘要

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, conventional or microf ine cement slurry will dehydrate and bridge off before it can achieve its objectives. This paper describes the use of 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 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 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 the well conditions. Results showed excellent penetration in narrow gaps, optimum fluid-loss control, and low rheology, both at surface and downhole conditions.