3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Investigation of the effects of zinc oxide nanoparticles and synthesized cellulose nanocrystals (CNCs) on emulsion-based drilling fluids(2019) Aka, Tiemele Wilfried AndersonDrilling Mud holds an important role in the drilling process in such a way that it is a determinant key to the success of the operation as well as the money spent throughout the process. Indeed the success and the cost of the operation can be severely impacted by some challenges experienced while drilling such as temperature and pressure conditions which leads to fluid loss, fluid deterioration...As a result there is a need to formulate a fluid with desirable rheological properties to withstand such undesirable parameters. Therefore this work was aimed to improve emulsion drilling fluids (EDFs) based nanoparticles with enhanced properties. Many investigations were performed to find a proper emulsion stability as well as a good drilling fluid performance. The stability of the prepared emulsion drilling fluids was done using surfactant with different concentrations for several days. After several days of preparation, the EDFs containing DTAB as surfactant have showed a better emulsion stabilizer compared to the Triton X-100 ones. In addition an investigation combining both NPs and surfactants confirmed the used of NPs to improve DF and revealed the effective use of ZnO NPs for drilling fluids application and preferentially with DTAB as surfactant. Following that result, the 2nd part of the work was based on the synthesis and characterization of CNCs as NPs to formulate EDF with DTAB as surfactant. The CNCs NPS were successfully obtained via the method of oxidation of microfibrillated cellulose through TEMPO-mediate and after characterization using TEM, spherical NPs with small size varying from 10-50nm were observed. The FANN® Model 35 viscometer served to display the behavior of the shear stress and viscosity of the prepared fluids against variable shear rate at variable NPs and temperature concentration. The rheological and filtration properties were increase with increase in CNCs content from 0.8 to 1.2% of fluid in room temperature and with an increase in temperature.Item Assessment of nano-crystalline cellulose as viscosifying agent and fluid loss modifier for drilling fluid(2017) Molekwa, Ramasela QueenThe success of a drilling operation is significantly dependent on the quality of the drilling fluid used, thus it is important to use drilling fluids that will operate optimally in a given exploration environment in order to maximise recovery. As current Oil and Gas fields are approaching their maturity, there is a need to explore further offshore in deeper waters. Drilling technologists are thus faced with a challenge of sourcing improved methods and technologies for exploration operations, often in very harsh environments. Drilling fluid constitutes about 15% of the drilling cost, and the common challenges experienced during drilling are fluid loss and rheological properties necessary to withstand extreme operating temperature and pressure conditions. This study evaluates the impact of different concentrations of Nano-crystalline cellulose (NCC) as additive for bentonite-water based drilling fluid, to improve the rheological properties and fluid circulation control. TEMPO Oxidation synthesis of NCC yielded spherical NCC of sizes ranging between 40 and 90 nm, supported by strong hydrogen bonding within the NCC structure. Fluid loss measurements were carried out at varying temperatures of 30, 40, 50, 60, 70 °C and pressures of 100, 200, 300, 400 kPa. The increase in NCC concentration in drilling fluid samples from 0.2% to 1.2 wt% NCC resulted in fluid loss reduction ranging from 10.6 to 52.5%. More fluid loss was observed at higher temperatures due to reduced interaction between water absorbed and NCC. Viscosity measurements indicated that higher NCC concentrations improve the thermal stability of the fluid, as observed through increased viscosity of the fluid samples with increasing temperature ranging from 30 to 70˚C. Furthermore, the yield stress was improved at increased NCC concentrations (0.0 to 1.2 wt%) indicating the enhanced ability to suspend and facilitate the removal of drill cuttings and other solids to the surface. There was also better thixotropic behaviour and improved percentage regeneration with increasing NCC concentration from 0.0 – 1.2 w%, allowing NCC based fluid samples to have better flow properties. This confirms that NCC can be used as a potential additive for improvement of drilling fluid properties.