Spe 81001

SPE 81001 Design of High Toughness Cement for Effective Long Lasting Well Isolations
Walter Morris, Marcelo A. Criado, SPE, Jorge Robles, SPE and Gustavo Bianchi / San Antonio - Pride Int. Neuquen, Argentina.
Copyright 2003, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the SPE Latin American and Caribbean Petroleum Engineering Conference held in Port-of-Spain,Trinidad, West Indies, 27–30 April 2003. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflectany position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permissionto reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836 U.S.A., fax 01-972-952-9435.

Abstract During the well service life the cement isolation is exposed to extreme conditionsthat can cause its premature failure. Certain well completion operation as perforating and hydraulic fracturing, the changes in temperature and pressure during secondary recovery or the mechanical stress originated by formation displacements may cause severe damage to the cement isolation. The mechanical properties (compressive and tensile strength, toughness, Young modulus and Poisson ratio) ofdifferent cements were evaluated in order to establish their best service performance. Typical slurry designs were tested focusing the attention on the effect of certain additives such as latex, fibers and other polymers used as fluid loss control or dispersants. The cement mechanical properties were determined according to ASTM and API standard test methods. The cement toughness was evaluatedfollowing the API RP 43 standard for testing well perforators. The experimental results show that the mechanical properties of cement are strongly dependant on the particular additives used when preparing the slurry. Even when cement with no admixtures presents high compressive strength it also shows a fragile behavior with limited strain and low toughness. The use of latex improves the cement elasticbehavior although it does not better its impact resistance. On the other hand, the addition of polymer fibers improves the cement toughness and its elastic behavior. As it was demonstrated by well testing profiles run before and after perforating, the addition of fibers improves the cement performance when exposed to the different events that may damage the isolation during the well service life.Introduction There are many factors that should be considered when designing slurry for well cementing operations. Some of the most critical ones are temperature, density, rheology, filtration and resistance, among others. A wide variety of additives have been developed to ensure successful cementing operations. API RP-10B presents a number of laboratory procedures to evaluate and predict theslurry performance at specific service conditions. Several physical properties such as the slurry rheology, fluid loss control and thickening time are used to characterize the slurry short-term performance. On the other hand, less attention is placed on the hydrated cement medium and long-term properties and how they can affect the well isolations mechanical and durable performance. During the...