Comparative Study of Retarders and Their Effects in Oil Well Cementing

Abstract

The design of cement slurry holds a special place throughout a well cementing. A comprehensive understanding of the parameters of well is vital to guarantee good quality cementing, as well as cement slurry behavior (especially at high temperatures) and implementation of recognized cementing procedures. The knowledge of temperature conditions during cementing is important because bottom-hole circulating temperatures (BHCT) affect thickening time, rheology, set time and compressive strength development of the cement slurry. Getting to know the definite temperature which the cement slurry faces during pumping permits the selection of appropriate cementing material for a particular application. Of the cement additives, the most important are the retarders because their selection is crucial with respect to temperatures. These retarders not only alter the pump-ability of cement slurry, but also affect the strength of cement sheath and flow behavior of the slurry. This work summarizes the behavior of three different retarders at different temperature and pressure conditions. The effects of varying concentration of a (a) modified lignosulfonate based retarder, (b) a saccharide derivative retarder and (c) an organophosphate based retarder are studied for thickening time, compressive strength and rheology. Furthermore a comparative analysis is given which makes it easier to select a retarding admixture for cement slurry at a specific temperature.