Better controls during well drilling and cementing operation are critical to ensure safety during construction and the entire service life of the wells. For a successful cementing operation determine the setting of cement in place length of cement supporting the casing and performance of the cement after hardening. At present there are no technologies available to monitor the cementing operations without using buried sensors that could weaken the cement sheath.In this study, smart cement with 0.38 water-to-cement ratio was modified with Iron nanoparticles (NanoFe) to have better sensing properties, so that its behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated the smart cement behavior with and without NanoFe in order to identify the most reliable sensing properties that can also be relatively easily monitored. Tests were performed on the smart cement from the time of mixing to hardened state behavior. During the initial setting the electrical resistivity changed with time based on the amount of NanoFe used to modify smart oil well cement. A new quantification concept has been developed to characterize cement curing based on electrical resistivity changes in the first 24 hours of curing. When cement was modified with 0.1 percent of conductive filer (CF), the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the rheological and setting properties of the cement. For the smart cement the resistivity change at peak stress was about 2000 times higher than the change in the compressive strain after 28 days of curing.The shear thinning behavior of the smart cement slurries with and without NanoFe at two different temperatures (25°C and 85°C) have been quantified using the new hyperbolic model and compared with another constitutive model with three material parameters, Vocadlo model. The results showed that the hyperbolic model predicated the shear thinning relationship between the shear stress and shear strain rate of the NanoFe modified smart cement slurries very well. Also the hyperbolic model has a maximum shear stress limit were as the other model did not have a limit on the maximum shear stress. Based on the hyperbolic model the maximum shear stresses produced by the 0 percent, 0.5 percent, and 1 percent of NanoFe at temperature of 25°C were 175 Pa, 224 Pa, and 298 Pa, respectively. The maximum shear stresses produced by the 0 percent, 0.5 percent, and 1 percent of NanoFe at temperature of 85°C were 349 Pa, 377 Pa and 465 Pa respectively. Additional of 1 percent NanoFe reduced the initial resistivity of the smart cement by 16 percent. In a 24-hour period the maximum change in the electrical resistivity (RI 24 hr) for the smart cement without NanoFe was 333 percent. The RI 24hr for the smart cement with NanoFe increased with the amount of NanoFe. Addition of 1 percent NanoFe increased the compressive strength of the smart cement by 26 percent and 42 percent after 1 day and 28 days of curin...

Maintaining the density hierarchy for wellbore fluids has been a routine while achieving a proper rheological hierarchy for mud, spacer and cement could have been compromised due to tedious testing and sometimes limitations in the field. Establishing appropriate rheological and friction pressure hierarchy prevent fluids (mud-spacer-cement slurry) intermixing especially in deviated and horizontal wells. The objective of this paper is to present a spacer rheological properties model along with a new micro-emulsion spacer formulation which improves well integrity. This water-based spacer system, with densities ranging from 8.5 to 16 ppg, was modeled to temperatures up to 325°F and provided proper suspension properties, confirming stability at bottomhole circulating elevated temperatures. In addition, ccompatibility of this spacer package with various synthetic based muds, oil based muds and cement slurries, designed for Gulf of Mexico, the US land, North Sea and the Middle East, plays a significant role in achieving great displacement efficiency, wellbore clean up, long term effective zonal isolation and sustainable hydrocarbon production. It is not always possible to accomplish the turbulent flow. Therefore, a rheological model was developed to accomplish the ideal viscosity hierarchy by optimizing the spacer formulation design. Optimum rheological hierarchy occurs where the viscosity profile of a spacer system is higher than the viscosity profile of drilling fluid and lower than the cement slurry. Model's predictions have been validated by one atmospheric and two industry-known HPHT rheometers. The model predictions show that the rheological profiles of the spacer fluid, for all the main standard shear rates, are between the mud and cement profiles. Data obtained from field case histories show the improvements and added values such as ideal fluid compatibility, better displacement efficiency, friction pressure hierarchy and effective zonal isolation,

For a successful cementing operation, it is critical to determine the flowing of cement slurry between the casing and formation, depth of the circulation losses and fluid loss, setting of cement in place and performance of the cement after hardening. Recent case studies on cementing failures have clearly identified some of these issues that resulted in various types of delays in the cementing operations. At present there is no technology available to monitor cementing operations in real time from the time of placement through the borehole service life. Also, there is no reliable method to determine the length of the competent cement supporting the casing. In this study well cement was modified to have better sensing properties, smart cement, so that its behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated well cement behavior with and without modifications in order to identify the most reliable sensing properties that can also be relatively easily monitored. During the initial setting the electrical resistivity changed with time based on the type and amount of additives used in the cement. During curing initial resistivity reduced by about 10 percent to reach a minimum resistance, and maximum change in resistance within the first 24 hours of curing varied from 50 to 300 percent depending on the additive. A new quantification concept has been developed to characterize cement curing based on electrical resistivity changes in the in the first 24 hours. When cement was modified with less than 0.1 percent of conductive additives, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the cement rheological and setting properties. For modified smart cement the resistivity change at peak stress was about 400 times higher than the change in the strain.

The benefits of a new class of a multifunctional cement additive and the performance of the resulting cementing systems are evaluated in comparison to conventional slurry designs used for cementing wells in the Northeastern U.S. Cement testing procedures, lab test results, logistical and operational aspects, economical and ecological balances, chemical footprints of slurry designs are presented and discussed. The tested multifunctional additive can fully replace at least 4 different additives (extender, suspending agent, free fluid, fluid loss, and gas control additive) to achieve the desired performances and so simplify cement slurry designs. The multifunctional additive in this study also exhibits delayed hydration, which facilitates surface mixing and generates desired high viscosity over time, minimizing settling issues in horizontal wells during placement. The innovative cement design concept using a multifunctional additive reduce the number and loadings of chemical additives required to adjust the performance of cement slurries, thereby improving economics, reducing the chemical footprint, and simplifying logistics and operations.