Use Of Water Base Spacer With Thixotropic Cement Solves Varied Cementing Problems

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Thixotropic cements are cement slurries which are thin when mixed and pumped, gel rapidly when pumping stops, and become fluid if pumping is resumed within a short time. They have pumping is resumed within a short time. They have found wide application in the solution of many difficult cementing problems since they are self-supporting and have expansion properties. Until recently it had not been possible to control water loss of these systems due to their incompatibility with commonly used water loss control additives. A new approach to this problem has resulted in reduced water loss from the thixotropic cement slurry by means of a water base spacer being run ahead. The water loss of the water base spacer is designed to allow use of the thixotropic cement slurry in these conditions where water loss control is needed or desired. This paper describes thixotropic cements, their uses, and techniques of application. Development of the water base spacer and its effect on thixotropic systems is also described. Comparative results show how improved well production can be achieved with use of the spacer and production can be achieved with use of the spacer and thixotropic cements. Introduction During the Past few years, a number of factors have been studied both in the laboratory and field application to improve the primary cement job. Some of the factors: pipe movement, position of pipe, use of a water loss controlled cement slurry, use of a spacer to separate mud and cement, and use of a cement slurry that exhibits expansive characteristics after setting. The use of a thixotropic cement has found use in most all areas because of its unique properties. properties. The application of all the aforementioned factors have not been possible because the commonly used water loss control additives destroy the thixotropic properties of the desired cement slurry. Research efforts to date have not allowed the development of an adequate water loss control additive, therefore the possibility of using a spacer with excellent water loss control ahead of cement slurry was studied. The filter cake laid down must not only be adequate to control water loss of cement slurry, it must have properties that are applicable to a well designed properties that are applicable to a well designed spacer system. Some of these are:Compatible with both the drilling fluid and the cement system.Low water loss.