Scratch test for strength and toughness of oil well cement with nanoclay as an additive

The mechanical properties are determined to measure the sustainability and long-lasting behavior of cement slurry under wellbore conditions. Different measurement methods were adopted in the past to study the mechanical behavior of a cement slurry. The most commonly used methods applied in oil and gas sector are cement crushing and acoustic velocities measurements. Both techniques have some limitations and additional techniques are warranted. Scratch test technique is commonly used for characterization of mechanical properties of metals, coatings and other materials. Advances in scratch testing of materials has resulted in its application to cohesive material such as rocks and cement. Recently, scratch test has been successfully applied for the strength evaluation of oil well cement. In this paper, we present the results of scratch tests carried out on oil well cement using type G cement and the specimens modified using nanoclay as an additive. The compressive strength test results from scratch test was compared to the macro level testing of cement cores loaded in compression up to failure. The dynamic elastic parameters of cement mix, elastic modulus and Poisson's ratio, were also determined using the scratch test. The scratch test based strength measurement technique will serve as a very handy tool for drilling and geomechanics engineers to study the mechanical properties of the cement slurry aged under different wellbore conditions with high level of certainty.