Offshore cementing poses many challenges across the world as drilling oper ations move towards deep-water and ultra -deep-water. As a new initiative of continuous improvement, a deep-water cementing peer review process was started early 2011. To this date, th is team has reviewed more than 12 00 deep-water cementing jobs in more than 30 countries worldwide.

As cement changes from liquid slurry to solid, its load-bearing response, strength and permeability characteristics are expected to change with time. Consequently the ability of any cement to withstand changes in wellbore pressure and temperature will be determined, in part, by the changes in elastic properties, failure criteria and permeability that occur over time. An experimental study of time evolution of mechanical and flow properties of Class G neat cement is presented in this study. The objectives of this intra-laboratory test program were to answer the following questions: How rapidly do the mechanical and flow properties evolve over time? Can changes in microtexture be observed and correlated to those properties?What are the optimal times required to observe time-independent responses?What is happening to the water in the cement and does it correlate with the time evolution observed in mechanical properties and permeability? Measurements of liquid permeability, static and dynamic elastic properties, compressive and tensile strengths, pore size distribution and microtexture and fabric photography were recorded over a 10 day interval. The time evolution of mechanical and flow properties for 15.8 pound per gallon Class G cement and their relationships with water content are presented throughout the paper. Permeability is shown to dramatically decrease and equilibrate over the first 24-32 hours, while the mechanical properties continued to increase over a longer time period. The changes in mechanical/flow properties were strongly correlated to the decrease in water content and the shifting of pore size to smaller distribution functions. Complete stabilization of static elastic properties was not observed after 10 days, implying that, for certain cement formulations, these properties may need to cure for longer than industry standard times. From tests results, 96 hour cure times may be insufficient to characterize certain mechanical properties of wellbore cements. This study also sets a base standard for comparison with more complex cement chemistry's that are currently (and in the future) being used in oil-field operations. The authors also concluded that the use of NMR measurements of pore size and, in turn, water content correlate very well with conventionally used methods. Motivation for this study is based on limited data available on the simultaneous response of all critical wellbore cement properties from the very early stages of hydration to long-term set.

In this study, a field well was installed and cemented using the smart cement mixture with enhanced piezoresistive properties. The field well was designed, built, and used to demonstrate the concept of real time monitoring of the flow of drilling mud and smart cement and hardening of the cement in place. The well was installed in soft swelling clay soils to investigate the sensitivity of the smart oil well cement. A new method has been developed to measure the electrical resistivity of the materials using the two probe method. Using the new concept, it has been proven that the resistivity dominated the behavior of drilling fluid and smart cement. LCR meters (measures the inductance (L), capacitance (C) and resistance (R)) were used at 300 kHz frequency to measure the changes in resistance. The well instrumentation was outside the casing with 120 probes, 18 strain gages and 9 thermocouples. The strain gages and thermocouples were used to compare the sensitivity of these instruments to the two probe resistance measure in-situ in the cement. The electric probes used to measure the resistance were placed vertically at 15 levels and each level had eight horizontal probes.Change in the resistance of hardening cement was continuously monitored since the installation of the field well for over 100 days. Also, a method to predict the changes in electrical resistance of the hardening cement outside the casing (Electrical Resistance Model -ERM) with time has been developed. The ERM predicted the changes in the electrical resistances of the hardening cement outside the cemented casing very well. In addition, the pressure testing showed the piezoresistive response of the hardened smart cement and a piezoresistive model has been developed to predict the pressure in the casing from the change in resistivity in the smart cement.

Extreme well conditions, especially higher temperatures, are becoming more commonplace. This in turn requires improvements to our wellbore fluids. This study focuses on the development of a new spacer system designed especially for those wells exhibiting extremely high temperatures. A critical characteristic of this spacer is that the surface rheology must not be overly excessive as to maintain a pumpable fluid; however, the downhole rheology must not diminish due to thermal thinning or degradation of the gelling agent so the spacer remains stable. To ensure the spacer suitably meets these requirements, both ambient and elevated temperature rheologies are analyzed and reported. The stability of the spacer related to settling of solid particulates is examined by conducting dynamic settling tests at 300°F and above. In this study, spacer compositions and densities were adjusted to examine effects on rheology and stability of the solids within the system at elevated temperatures. Results show that conventional spacer systems are not adequate at elevated temperatures especially above 300°F. The newly developed spacer system shows much improved results from dynamic settling tests even up to 400°F. Also, the surface rheology of the new spacer system is not significantly different from that of the conventional system. The innovative spacer system within this paper was shown to add significant value to extreme cementing operations. In addition, by comparing the results between these two testing methods, the dynamic settling test should be considered as an alternate procedure for testing the stability of spacers under high temperature conditions.