Numerical Study of Cuttings Transport of Nanoparticle-Based Drilling Fluid

Cuttings transportation from the drill bit, through the annulus, to the surface is one of the most important functions performed by drilling fluid. The prediction of drilling fluid's performance to transport cuttings in the annulus is very complex task due to the presence of numerous parameters. Nanoparticles (NPs) have been recently introduced into drilling fluid to engineer its properties and enhance its performance. Nevertheless, the lifting capacity has not been sufficiently investigated. The understanding of the influence and the mechanisms responsible for the improvement in cuttings transport process can further advance the application of NPs for drilling fluids. Computational fluid dynamics (CFD) is widely used as a numerical technique in handling complex multiphase flow problems in different operational conditions. The present work has taken the advantages of CFD to computationally analyze the influence of NPs and the effects of various parameters such as drilling fluids rheology, flow rate, pipe rotation, cuttings density, shape, concentration, and drilling fluids-cuttings particle coupling regimes on the cuttings transport in a vertical wellbore. The CFD simulation is carried out by using transient solver of ANSYS-FLUENT commercial code. The dense discrete phase model is used to overcome the main shortcomings of previous Eulerian based approaches. Good agreement has been achieved between the simulation and the published experimental results. It showed that the fluid viscosity and cuttings transport process can be significantly enhanced by adding nanomaterials to the fluid, and the process is highly influenced by cuttings characteristics such as in situ concentration, shape, and density

The leakage current components as a diagnostic tool to estimate contamination level on high voltage insulators

The current paper presents an alternative and innovative technique to predict the severity of pollution of high voltage insulator using a higher harmonics component with up to the 7th component of leakage current. The leakage current was measured using a current transformer and a shunt resistor. Next, laboratory tests were conducted on glass and porcelain insulators with artificial pollution under salt-fog pollution state which is further represented by three levels, namely light, medium, and high contamination. In this case, the formulation of a new severity of harmonic index refers to a ratio of the sum of 5th and 7th to the 3rd harmonic component. More importantly, the new index managed to provide more accurate results when used as a diagnostic tool for the levels of pollution, compared to the ratio of the total harmonic distortion (THD) to the number of odd harmonics components (n) as the boundaries. In this case, the insulators were found to be in a clean and normal condition when the K(5+7)/3 value was greater than 3%. Contrastingly, the insulators were in an extreme condition when the K(5+7)/3 was lower than 3%. Nevertheless, there is a high probability of a flashover in glass and porcelain insulators if the K(5+7)/3 value is less than 2%. The present study shows the possibility of utilizing the value of strange harmonics up to the 7th component of leakage current as the parameter for the monitoring of leakage current in overhead insulators in the presence of contamination. Overall, it can be concluded that the 3rd, 5th, and 7th harmonics details extracted from the leakage current act as a good indicator for the level of contamination

Gallbladder adenocarcinoma with human chorionic gonadotropin: a case report and review of literature

<p>Abstract</p> <p>Background</p> <p>The case of adenocarcinoma with human chorionic gonadtropin (HCG), primary in the male gallbladder, is extremely rare. A Medline search has shown only a few similar cases reported.</p> <p>Methods</p> <p>We herein describe a case of primary gallbladder adenocarcinoma associated by ectopic HCG positive tumor cells in a 79-year-old male.</p> <p>Results</p> <p>Pathological examination showed a mixture of moderately and poorly differentiated adenocarcinoma with ectopic HCG and placental alkaline phosphatase (PlAP) in tumor cells, though the increase of serum or urinary HCG secretion was not confirmed. The literatures were also reviewed.</p> <p>Conclusions</p> <p>A case of gallbladder cancer with ectopic HCG production is quite rare in the literature, though many similar cases in other site, especially in GI tract, are reported. Embryological consideration suggests the increased frequency of similar cases more than being thought now.</p

Diagenesis and epidiagenesis of rocks associated with unconformities

Imperial Users onl

Microfabricated chemical reactors for gas-phase catalytic reactions and micrototal analytical systems for environmental monitoring

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Development of new methods of computation and prediction of thermal comfort in production areas of garment tailoring enterprises with respect to thermophysical properties of packages of garments

Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Cost-effective 2.5 gb/s bidirectional WDM pon using single optical source at the central office

Nowadays, the bandwidth demand of the telecommunication network is growing rapidly due to the increasing number of technology-intelligent users. Optical broadband access networks have emerged to address two issues: (1) channel capacity sharing fairly to the customers, and (2) adequate capacity assignment according to service requirements. The wavelength division multiplexing passive optical network (WDM PON) is a promising solution to provide high data rate, excellent scalability, good protocol transparency and easy upgradability. In this paper, a cost-effective bidirectional WDM PON is proposed to provide symmetrical 2.5 Gb/s by using just single optical laser diode (LD) at the central office (CO). The optical frequency upconversion (OFU) technique is used to implement the proposed network. At the optical network unit (ONU), the reflective semiconductor optical amplifier (RSOA) reuses and amplifies the downlink wavelength to modulate the upstream data. The bit error rate (BER) performance and eye diagrams of the designed system are investigated

Tropical temperature and humidity modeling for free space optical link

Free Space Optics (FSO) or optical wireless systems provide high data rate solution for broadband communication applications. FSO links are highly weather-dependent because different weather conditions significantly affect the link availability. In order to determine the best operational limit of an FSO link with respect to temperature and humidity, the effect of temperature and humidity on FSO network is studied in this work. Two new equations are proposed to model the effect of temperature and humidity on an FSO link operating at 850 nm in tropical climate. The first equation is developed to model the relationship between the humidity and temperature for tropical regions, while the second equation models the FSO link attenuation in terms of tropical temperature. In conclusion, it is suggested that FSO links can be operated with a normal variation of temperature and humidity in a tropical country to achieve near carrier class availability