A large-scale simulation of aerosol nucleation and growth in a turbulent mixing layer is performed and analyzed with the aim of elucidating the key processes involved. A cold gaseous stream is mixed with a hot stream of vapor, nanometer sized droplets nucleate as the vapor becomes supersaturated, and subsequently grow as more vapor condenses on their surface. All length and time scales of fluid motion and mixing are resolved and the quadrature method of moments is used to describe the dynamics of the condensing, non-inertial droplets. The results show that a region of high nucleation rate is located near the cold, dry stream, while particles undergo intense growth via condensation on the hot, humid vapor side. Supersaturation and residence times are such that number densities are low and neither coagulation nor vapor scavenging due to condensation are significant. The difference in Schmidt numbers of aerosol particles (approximated as infinity) and temperature and vapor (near unity) causes a drift of the aerosol particles in scalar space and contributes to a large scatter in the conditional statistics of aerosol quantities. The spatial distribution of the aerosol reveals high volume fraction on the hot side of the mixing layer. This distribution is due to drift against the mean and is related to turbulent mixing, which displaces particles from the nucleation region (cold side) into the growth region (hot side). Such a mechanism is absent in laminar flows and is a distinct feature of turbulent condensing aerosols.

To understand and quantify casing wear during drilling operations, an experimental setup with real drill pipe joints (DPJ) and casings was designed and used to carry out wear tests, simulating various operating conditions and environments. P110 steel casing samples were tested under dry and wet conditions. Actual field oil- and water-based fluids were utilized to lubricate the contact area at two different side loads (1000 N and 1400 N) and DPJ speeds (115 and 207 rpm). The results show that for the same testing conditions, the casing wear volume and wear factor under water-based lubrication were more than twice those obtained under oil-based fluid testing. As expected, the wear volume and wear factor were highest under dry conditions. Moreover, it was noticed that, as the normal load was increased at a constant rotational speed (rpm), the wear factor increased. On the other hand, raising the rotational speed at the same applied load reduced the casing wear factor, due to the observed absence of adhesive wear and possible localized softening effects at higher speeds. SEM analyses of the worn areas showed that under dry conditions, the main wear mechanisms were abrasion and delamination. However, both adhesive wear and abrasive wear mechanisms were observed under oil-based lubrication. The energy dispersive spectroscopy (EDS) analysis of the worn surface revealed that at higher loads and speeds, a heavy transfer of particles from the oil-based lubricant took place. On the other hand, some contaminants of the water-based lubricant were observed on the worn surfaces.

The increasing complexities of wellbore geometry imply an increasing potential of damage resulting from downhole casing wear. The present method of using old wear factors results in unreliable predictions. The main objective of the present work is to develop new casing wear factors for drillpipes and casings to improve the accuracy of wear prediction. The paper focuses on design, manufacturing, control and measurements of important parameters contributing to casing wear as well as wear volume evaluation. A new casing wear testing facility is designed and built by repurposing and automating an old lathe machine. Real drillpipes with tool joints and casing sections made of different materials are used. The lathe spindle controls the mandrill rotational speed on which the DP is tightly mounted. The versatile casing section holder is fixed on a sliding system comprising a dynamometer and a step-motor with a microcontroller allowing for the control and measurement of the side loadings and lateral displacements. A slurry fluid pump system is designed to feed water-based or oil-based muds at the contact surfaces. The as-received drillpipes and casing materials were analyzed by microscope and optical emission spectrometry (OES) to determine their microstructure and chemical composition. The hardness of both casing and DP materials was also measured. The lathe main spindle was able to provide stable rotating speeds varying from 100 to 1000 rpm. Though the irregular tool joint hard-facing surface was machined to allow for better control of the side loadings, the measured radial load shows variations of +/− 15%. The designed pumping system was able to provide a continuous stream of water-based and oil-based mud, at the contact surface, during testing. The wear depth is measured both directly using a 3D optical profilometer and indirectly by the lateral sliding displacement, thus allowing for the establishment of a calibration curve that can be used for in-situ measurement of the wear depth and wear volume evaluation. The initial set of tests has shown that the designed system is performing satisfactorily. More tests are being performed to confirm the robustness of the design.

Casing wear in directional drilling is inevitable and may result in catastrophic failure of the casing column. It is thus essential to understand its mechanisms and quantify its extent by estimating the casing wear factor. In this research, actual field casing samples, drilling pipe joints and muds were considered. An in-house built testing facility was used to test several L-80 casing samples by considering three rotational speeds of the drill pipe joint (DP-TJ) (207, 154 and 115 rpm) and three side loads (1000 N, 1200 N and 1400 N). The influence of the water- and oil-based muds on the wear volume, factor and mechanisms were investigated.
The results revealed that under water-based mud (WBM) lubrication casing wear volume and wear factors were more than twice that of oil-based mud (OBM) lubrication. Moreover, it was observed that as the side load increased under both OBM and WBM lubrication at a constant rpm, both wear volume and wear factor increased. However, increasing the rotational speed to 1400 rpm while maintaining the side load constant decreased the wear factor, owing to the localized softening effect caused by the high heat generated at the contact area and the possible hydrodynamic lubrication regime at higher speeds.
The analysis of the digital microscopic images taken at the wear region shows that the main abrasive mechanism was dominant in the case of OBM lubrication. On the other hand, both abrasive and adhesive wear mechanisms were present under WBM lubrication.

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