The formation of silver nanoparticles (AgNPs) via reduction of silver ions (Ag(+)) in the presence of humic acids (HAs) under various environmentally relevant conditions is described. HAs tested originated from the Suwannee River (SUW), and included samples of three sedimentary HAs (SHAs), and five soils obtained across the state of Florida. The time required to form AgNPs varied depending upon the type and concentration of HA, as well as temperature. SUW and all three SHAs reduced Ag(+) at 22 °C. However, none of the soil HAs formed absorbance-detectable AgNPs at room temperature when allowed to react for a period of 25 days, at which time experiments were halted. The appearance of the characteristic surface plasmon resonance (SPR) of AgNPs was observed by ultraviolet-visible spectroscopy in as few as 2-4 days at 22 °C for SHAs and SUW. An elevated temperature of 90 °C resulted in the accelerated appearance of the SPR within 90 min for SUW and all SHAs. The formation of AgNPs at 90 °C was usually complete within 3 h. Transmission electron microscopy and atomic force microscopy images showed that the AgNPs formed were typically spherical and had a broad size distribution. Dynamic light scattering also revealed polydisperse particle size distributions. HAs appeared to colloidally stabilize AgNPs based on lack of any significant change in the spectral characteristics over a period of two months. The results suggest the potential for direct formation of AgNPs under environmental conditions from Ag(+) sources, implying that not all AgNPs observed in natural waters today may be of anthropogenic origin.

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The use of lubricants is commonplace when drilling with water-based drilling fluids. They are less frequently applied when drilling with non-aqueous fluids, as the oil-based drilling fluid is thought to impart a high lubricity. With increased reach of the wells, lubricants are also applied in non-aqueous fluids (NAF) to reduce torque and drag at high angle, for extended reach and horizontal wells to improve drilling efficiency. However, the performance of these lubricants in NAF at extended periods of elevated temperature at downhole conditions is often inconsistent, thought to be hampered by ineffective metal binding and hydrolytic instability of the lubricant molecule. This requires frequent re-dosing and therefore higher cost to maintain performance. In order to identify a better-performing lubricant, it was necessary to better understand the fundamentals of lubrication in a drilling fluid. For example, what portion of the well contributes most to torque and drag? What is the frictional regime that dominates the lubricity between a drill pipe and its contact points? Looking at theoretical analysis and modeling, it was found that the horizontal portion is dominated by the boundary and mixed layer friction regime, which is a combination of surface forces and fluid viscosity. Additionally, understanding of tribology from other industrial applications was employed to better design a molecule that can deliver optimum lubricity in a NAF. This new understanding led to identifying an optimized lubricant for NAF. A lubricant derived from a plant-based raw material was specifically designed to be chemically and thermally stable, binding strongly to metal surfaces, and providing a tenacious film that reduces metal-to-metal friction factors during drilling, casing run and other completion operations. The identified lubricant was tested for compatibility with NAF, including effects on rheology, elastomers, and formation damage potential. Coefficients of friction and fluid rheology comparisons and research-related field trials are presented. The results show significant (20%) reduction in the coefficient of friction after treatment, especially after hot-rolling, indicating thermal and oxidative stability of the product.

A new technique of delivering long-lasting treatment for damaging well conditions, such as scales, corrosion, or organic deposits, has been achieved using a novel technology. This new technology involves a viscoelastic, biopolymer-hydrogel as the matrix to incorporate and transport chemicals into the formation. When placed in the fracture length, the porous matrix controls the release of the treatment agent over a long period of time. The system is environmentally safe and cost-effective, and designed to be pumped with stimulation fluids during proppant transport. This technology has proven to provide a more efficient delivery, placement, and long-term protection compared to other existing technologies, where maximum loading of the product is somewhat restricted. Solid and liquid chemicals can be embedded within this viscoelastic biodegradable polymer-scaffold and placed in the formation during well stimulation without requiring any additional mechanical tools or equipment. The polymeric material is inert in nature and remains unchanged at varied range of pH, temperature, pressure and other wellbore conditions. This crush-resistant matrix can withstand high amount of closure stress and extends the effective treatment life of the inhibition process without causing any adverse effect to the proppant-pack conductivity. Additionally, unlike other existing technologies where the liquid treatment agents are surface-adsorbed resulting in large initial release of the products during placement, this new technology enables the chemicals to be embedded inside the hydrogel. Consequently the release of chemicals is significantly slower resulting in longer lasting well treatment. The development and efficacy of several products for scale, paraffin, asphaltene, and downhole corrosion control using this new delivery method have been studied in detail. These systems are compatible with all types of stimulation and completion fluids and their additives, and found to be effective in a wide range of downhole conditions. This technology not only provides operational simplicity but also reduces costly well interventions for the operators especially in deepwater or remote locations for long period of time. This paper discusses some of the applications of this new technology and also updates on the recent field trials offshore.