Investigation of the effect of cement mixing energy on cement strength and porosity using NMR and UPV methods

Abstract

Cement is a key element of wellbore integrity. Cement mixing conditions and how cement properties are affected are of great importance but often ignored in the oilwell cement design. The oilfield cement is a complex mixture of water, solids and other additives which are mixed together in order to produce expected properties in a very consistent manner. Evaluating and understanding cement properties becomes essential for the purpose of short- and long-term integrity of the wells. It is known that cement properties may change with downhole conditions such as pressure or temperature, but as shown in this paper, the mixing energy affects the short- and long-term development of cement properties. The major objective of this paper is to investigate the effect of mixing energy and curing time using destructive and non-destructive evaluation methods in order to evaluate their impact on different cement properties. By conducting comprehensive laboratory tests, new correlations have been developed that show the mechanical properties and changes of cement performance. Finally, a relationship between porosity (obtained from NMR) and UCS was generated as a function of mixing energy and shear rate. Furthermore, results of NMR testing and porosity measurements help to evaluate the impact of cement mixing condition on porosity development and pore size distribution.