Cementing Displacement Practices: Application in the Field

Abstract

ABSTRACT The majority of remedial cementing operations and cementing related problem costs are the result of annular gas leakage or zonal communication in the cemented annulus after primary cementing. The most important factor in successful primary cementing, next to the physical properties of the cement, is good mud removal by the cement slurry. All or at least a very high percentage of the drilling fluid must be displaced by the cement in order to obtain a hydraulic seal in the annulus. Good mud removal is achieved through high displacement rates. There have been many laboratory investigations conducted using full scale models to determine those factors which contribute to high displacement efficiencies. Some of these factors include annular velocity, hole conditioning time, casing movement, preflush fluids, drilling fluid condition, mechanical aids and the condition of the wellbore. In actual field conditions it is often very difficult to implement all of these "good practices". In order to try to optimize cementing operations, a study of these practices and the implication to the field operations was conducted. An extensive cementing operations database was developed to relate the historical problems to actual operational practices. Combining this historical data with field testing programs, an effort was made to determine the significance of various displacement parameters. The field tests indicated that one of the most important factors affecting the displacement efficiency is annular velocity. As a result, a practical cement placement program has been developed which incorporates the results of the field and laboratory tests. Since implementation of this program, a decrease in primary cementing failures and remedial cementations has resulted.