Rapid determination of complex oil well cement properties using mathematical models

Abstract

The chemistry of oil-well cement is very complex. As a result of incompatibility of some simultaneously added chemical combinations to obtain better cement workability, undesirable interactions reflect on the properties of the cement slurry. Experimental investigation of these properties is lengthy and depends on accuracy. In this work, the compatibility between lignosulfonate as a retarder R and NSF polycondensates as dispersants D is studied. Furthermore, optimum dosages are proposed based on the zeta potential technique at ambient conditions. The results show that the optimum dosage for (R2 + D1) is 0.2% by weight of cement. Moreover, the obtained results are supported by adsorption isotherms. The competitive adsorption is attributed to the differences in anionic charge densities between the additives and is postulated to take place on C₃A hydrates. The effect of the proposed additive dosages is studied on cement hydration. The obtained dosages show a good setting time (21 h) at a water-to-cement ratio of 0.4 and under ambient conditions. Furthermore, due to complex interactions with cement hydrates, mathematical models are proposed that are able to validate experimental results of surface properties and hydration processes.