Nanoparticles for Oil Well Drilling Fluids and Cement

Abstract

Drilling fluids and oil well cement are essential elements of the drilling process and well construction. Drilling fluids play a crucial role in the drilling process, ensuring the safety and efficiency of well construction. Continuous monitoring and adjustment of drilling fluids are required to optimize the drilling process and solve potential problems. The job of drilling fluids is to perform several important functions, such as carrying cutting from the bottom of the hole to the surface, providing cooling and lubrication to the drill bit, maintaining hydrostatic pressure to prevent the inflow of formation fluids, stabilizing the wellbore, and creating filter cake on the wellbore wall to control fluid loss. To perform these functions, the properties of drilling fluids, such as viscosity, density, yield stress, gel strength, and filtration, are important. The typical formulation of drilling fluids is based on water and oil. Typically, drilling fluids contain additives such as clay minerals, weighting agents, polymers, and various other additives. Factors such as well conditions, environmental considerations, and formation characteristics dictate the selection of appropriate drilling fluids. Conventional water-based and oilbased drilling fluids encounter certain challenges, such as fluid loss, formation damage, stuck pipe, differential sticking, or even wellbore collapse. Maintaining proper wellbore stability requires appropriate drilling fluid formulation. Oil well cementing involves the placement of cement slurry into the annular space between the wellbore wall and casing to achieve zonal isolation, well integrity, and structural support. Conventional oil well cement can encounter various issues that can impact the well integrity, short-term and long-term performance. These include fluid loss, improper placement and setting, strength development, and formation of micro annuli, among others. Addressing these issues requires the use of specialized additives and advanced formulations tailored for specific well conditions. In addition to the above shortcoming, conventional oil well cement contributes to significant CO2 emissions. Therefore, researchers are looking into possible alternative materials. Geopolymer is one of the alternatives to conventional cement. It is a cementitious material typically produced by combining aluminosilicate sources with the hardener solution. While geopolymer can offer several advantages, it has shortcomings that need to be addressed, such as workability, low tensile strength, long-term durability & performance, and limited industry adoptions. Nanoparticles (NPs) have gained immense attention for their potential application in drilling fluids, oil well cement, and geopolymer. The emergence of NPs is due to their ability to improve the performance of these materials. Notably, NPs are extensively researched as a multifunctional additive in these materials. However, to maximize the benefits and ensure safe and effective application in these materials, the optimal selection of NPs, dosage, and compatibility with other additives present in these materials still needs consideration. Therefore, the current work focuses on applying various NPs in these materials. This thesis is based on four publications and unpublished work. The first section of this work deals with the application of different NPs (with respect to shape, size, surface charge, and surface functionality) on water-based drilling fluids (Papers I, IV, and unpublished work). The work investigated the performance of NPs based on iron oxide nanoparticles (IONPs), carbon nanotubes, and silica NPs on bentonite and potassium chloride (KCl) water-based drilling fluids. The results indicate that NPs can influence the properties of water-based drilling fluids. For instance, IONPs and nanotubes presence in the bentonite drilling fluids increases the gel strength and yield stress of the fluid. However, surface modification of IONPs with silica and polymer controls the gel-forming ability of the fluid and reduces gel strength. Moreover, silica NPs reduce bentonite drilling fluid’s gel strength and yield stress. In addition, all types of NPs in the bentonite drilling fluids promote the shear thinning behavior by reducing the excessive gel formation at low shear rates. Adding NPs to the bentonite drilling fluids significantly reduces the friction values, and low concentration of IONPs and nanotubes in the drilling fluids show better performance than high concentration. Surface modified silica NPs however provide a higher reduction in friction values. Fluid loss results suggest that NPs provide better reduction for bentonite-based fluids; NPs filled the pores in the filter cake and control the fluid flow. Microscale analysis of filter cake confirmed this behavior. In case of KCl drilling fluids, adding IONPs and nanotubes reduces the gel strength values of the fluid. While surface modification of IONPs with Si and silica NPs improves the gel strength of KCl fluids. Moreover, the yield stress of KCl fluids increased by adding silica NPs. Furthermore, NPs in KCl drilling fluids reduce friction values. While in case of KCl-based fluids, there was no significant reduction in fluid loss owing to the no-uniform distribution of NPs. Also, NPs adsorbed in the cake structure without filling the pores. The second section includes the impact of hydrophobic IONPs on oilbased drilling fluids (Paper II). This work investigates the ability of IONPs to influence yield stress, HPHT fluid loss, mechanical friction, and barite sagging. The results suggested that NPs can increase the yield stress of oil-based drilling fluids at high temperature. Moreover, barite sagging, mechanical friction, and fluid loss were reduced by adding NPs to the drilling fluids. Also, drilling fluids with NPs produced a thin filter cake owing to the reduced permeability of the filter cake. The third part of the thesis (paper III and unpublished work) focuses on applying aluminum oxide and carbon nanotubes to the fluid state and mechanical properties of cement and geopolymer materials. Additionally, the impact of NPs on the morphology and mineralogy of materials is tested. NPs in the cement and geopolymer slurry increase the viscosity of the slurries, as NPs control the segregation of materials by providing better cohesion. Fluid loss results for cement show that NPs delay the gelation of cement at high pressure and temperature and increase the fluid loss values. While for geopolymer, nanotubes show a significant reduction in fluid loss. NPs delays the pumpability of cement and geopolymer slurries at high temperature and pressure. Furthermore, NPs increase the compressive strength of cement and geopolymer, especially after 28 days. While only nanotubes provide improvement in the tensile strength of cement. In case of geopolymer, NPs improve the tensile strength significantly until 7 days. However, after 28 days, only nanotubes show improvement in tensile strength. Microstructure and mineralogy analysis reveal that NPs are present throughout the structure of cement and geopolymer.