| dc.description.abstract | This thesis focuses on the application of polyelectrolyte complexes (PECs) to oil well cements. Cementing is a critical step in the process of any current drilling and completion program. The hardened cement sheath provides protection and support for the casing string while creating the necessary low permeability barrier to contain underground fluids. Unfortunately, despite advancements in technology and regulation, cement barrier failures still occur and carry with them potentially serious consequences. Leaking fluids lead to irreversible environmental contamination and possible life-threatening blowouts.
Engineers face difficult challenges when designing cement slurries. Competing matters of rheology, fluid loss, gelation, and sedimentation, to name a few, must thoughtfully be considered before formulating the ideal slurry. Polymers are regularly employed to solve these issues but often carry unwanted side-effects. Despite all of the research performed on polymers in oil well cements, little has been done regarding the technology of PECs.
PECs have been highly regarded in the medical industry for their effectiveness in targeted drug delivery systems. They have also made their way to the oil and gas industry for use in hydraulic fracturing and enhanced oil recovery (EOR) processes. The intent of this thesis is to demonstrate that properly designed particles can be utilized in oil well cements to achieve optimum fluid loss control while maintaining acceptable rheology and stability.
The PECs discussed herein were created using polyethyleneimine, carboxymethyl hydroxyethyl cellulose, and polyacrylic acid – common cement additives. They were characterized using high performance liquid chromatography, dynamic light scattering, and total nitrogen analyses. Then, they were added at varying concentrations to cement slurries and studied for fluid loss control, rheology, stability, density, and mixture thickening time. One such combination has demonstrated an excellent fluid loss control of just 38mL/30min. at 40°C even with low concentrations of the primary fluid loss additive. This PEC/slurry mixture has also proven to have ideal rheology and stability as compared to control samples. | en |
