Improve cement bond logs, maximize zonal isolation, and manage nonaqueous fluid (NAF) mobility to limit detrimental effects of mud channeling.
Poor cement bond logs across production zones in some offshore wells induced compromises in subsequent perforating and multistage stimulation operations. Conventional cementing technology was leaving channels of oil-based drilling fluid (OBM) in long (1,200-m) horizontal segments even when following cementing best practices for mud removal, centralization, and casing movement.
As an initial step to improve the NAF removal and water-wetting of downhole surfaces, the operator used CemPRIME engineered chemistry spacer, which improved bond logs but still left channels where casing standoff is not optimal. Furthermore, the centralizer distribution was increased from an average of one per two joints to one per joint, but the result remained less than optimal.
CemFIT Shield system improves zonal isolation in wells drilled with NAF, especially in a long horizontal well where limited casing standoff or inability to move casing impeded complete mud removal.
After extensive laboratory testing and blend characterization, Well A was cemented using CemFIT Shield system. Bond logs verified the high quality of the cement sheath across all of the production zones, a marked improvement as compared with a neighboring well cemented conventionally. The result enabled well perforation to proceed as designed, without compromises to accommodate the detrimental effects of channeling on subsequent multistage stimulation operations.
To improve zonal isolation in long horizontal offshore wells drilled with nonaqueous fluid (NAF), an operator in West Africa used CemFIT Shield mud-sealing cement system, achieving significantly better bond logs as compared with nearby wells cemented using conventional slurry at the same density.