The real story of cement expansion

Abstract

One of the most serious problems encountered when cementing casing in a well is the failure of the cement casing and cement formation bond. The failure of the cement bonding is a major problem from the standpoint of allowing migration of fluids from one zone to another. Also, poor bonding can result in large losses of reservoir fluids, premature reservoir depletion, and unsatisfactory stimulation operations. With these factors in mind, it has long been recognized that superior cementing operations could be achieved if expansion could be induced in oil well cements. Expansion currently is induced in oil well cements by two methods, addition of salts (salt cements), or addition of an expanding component (chemically compensated cement). The purpose of this paper is to compare the expansion characteristics of these types of cements. Additional characteristics such as pumping time, compressive strength, and bonding are also compared.