All Purpose Cement-Mud Spacer

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Society of Petroleum Engineers of AIME Symposium on Formation Damage Control, to be held in Houston, Tx., Jan 29–30, 1976. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract This paper deals with the problem of formation damage generated by high pressure differentials between annulus pressure differentials between annulus and formation during cementing. Specifically, the elimination of viscous cement-mud mixtures by the usage of a water external (oil in water), temperature stable emulsion spacer is presented. presented. Careful attention is given to the preparation of the casing and well bore preparation of the casing and well bore surfaces by the spacer, prior to cementing. Lab and field results clearly show that cement bonds best to a waterwet surface created by the water external spacer. The effect of contamination on fluid loss control of well fluids is presented. Other tests indicate that cement strength is less affected when contaminated with a water external emulsion spacer than when contaminated with oil base fluids. Introduction Mud displacement mechanisms, spacers and problems created by the contamination of cement by drilling muds have been discussed previously in the literature. However, in this paper we take a closer look at spacers from the point of view of formation damage control and cement bonding. Formation damage can be caused by drilling fluids during drilling operations, but further formation damage can occur during cementing operations. The fluids and solids lost from slurries can cause damage by entering the formation and reducing its permeability. The amount of fluid lost from a cement slurry into a formation depends on several factors, including the pressure differentials occuring during pressure differentials occuring during cementing. The higher the pressure differential into the formation, the more fluid will be lost to the formation.