Summary Increasing consumption of fossil fuels and environmental concern has led to increased use of compressed natural gas (CNG) in the transportation sector. Keeping in view limited resources of CNG, biogas is advised as potential fuel to provide continuous supply of CNG in the form of bio‐CNG. Various technologies, that is, physical and chemical absorption (using water and amine solutions, respectively, for the absorption of carbon dioxide), pressure swing adsorption, membrane separation, and cryogenic separation, are available for purifying biogas and thus upgrading it, to bio‐CNG with about 95% methane. Among these, water scrubbing and pressure swing adsorption are the best technologies with respect to various aspects including cost; however, suitability of a technology is decided by various factors including size/quantity of biogas generation, targeted quality of biogas, site of application, and economics of process. Copyright © 2017 John Wiley & Sons, Ltd.

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Production of high-octane gasoline is important to improve upon the performance and hence economics of oil companies worldwide.

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Flow through annulus is frequent in drilling and work-over operations. Annular flow is also utilized in some fracturing treatments. In all these applications, Newtonian and non-Newtonian fluids are widely used. Therefore the knowledge of annular flow performance of these fluids becomes important for planning and design of well-bore hydraulics. Existing knowledge about the behavior of non-Newtonian fluids in annulus is very limited due to their complex behaviour. A range of correlations is available in the literature for both Newtonian and non-Newtonian fluids in laminar and turbulent flow regime. Selection of the appropriate correlation for the desired fluid and flow regime is very important for the accurate determination of friction losses. Experimental and simulation study has been undertaken to investigate the flow behavior and friction pressure losses of Newtonian and non-Newtonian fluids in concentric annuli. Computational Fluid Dynamics (CFD) has been used along with limited experimentation on a field-scale set up to validate the simulation results. The fluids investigated are water and frequently used concentrations of guar and Xanthan fluids. CFD simulations have been performed for different annular dimensions in flow range encompassing both the laminar and turbulent flow regimes. The annular dimensions used in the simulations cover the range used in the industry. The frictional losses of non-Newtonian fluids exhibiting drag-reducing characteristics have been investigated through experiments. Based on the comparison with simulation results recom¬mendations are made to use the appropriate correlations for Newtonian and non-Newtonian fluids in the laminar and turbulent flow regime.Improved correlations are proposed to determine frictional losses of non-Newtonian fluids exhibiting drag-reducing characteristics. These correlations are based on experimental data gathered for a wide range of concentrations of guar and Xanthan fluids. The recommendations made along with the correlations presented in this study will greatly improve the accuracy of determining friction pressure losses in concentric annuli. Introduction Flow of Newtonian and non-Newtonian fluids through annulus has received considerable attention in the past. The flow of Newtonian fluids in annulus has been studied extensively in fluid mechanics literature. On the other hand, knowledge of annular flow of non-Newtonian fluids is limited due to the complex nature of these fluids. Understanding annular flow of fluids with different rheological properties is important, as accurate knowledge of flow performance of different fluids is critical in the planning and design of the hydraulics program of a well. Significant pressure losses can occur in the constrained space, which necessitates their accurate estimation. The knowledge of rheological data and methods of predicting pressure losses are the key points to calculate proper pump rates and avoid any obstacle in the normal operation of oil production. Determination of friction pressures is useful in calculating horsepower requirements, bottomhole treating pressure, and maximum wellhead pressure. Accurate knowledge of friction losses is also important from economic point of view. Optimizing the friction pressure loss calculations through the well bore annulus allows making an appropriate evaluation of the well-bore hydraulics, which is essential to reduce the problems and avoid high costs of operation.

Coiled tubing is widely used in the petroleum industry to pump fluids in the well bore at high rates. The friction pressure losses occurring in the tubing at these high rates are an issue of immense concern to the industry. Most of this friction loss can be attributed to the section of the tubing reeled on the spool during the treatment. The dimension of the reel used in the treatment governs the degree of curvature of the tubing and in turn the corresponding pressure drop. These pressure losses apart from increasing the cost of the treatment due to increased energy requirements also reduce the life of the tubular used. Experimental and simulation study has been undertaken to determine friction pressure loss in 1 1/2 and 2 3/8-in. coiled tubings using water and 35 lb/Mgal guar as test fluids. Computational Fluid Dynamics software FLUENT has been used to generate simulations that have been validated with limited experimentation using a field-scale test setup. Previous experiments used limited flow rates and few curvature ratios due to high field-scale experimentation costs. But using CFD simulations friction pressure loss data have been gathered for a range of curvature ratios and flow rates that are comparable to the ones used in the field. Results obtained have been used to determine the effect of curvature ratio on friction pressure losses while pumping Newtonian and non-Newtonian fluids in 1 1/2-in. and 2 3/8-in. tubing. Introduction Coiled Tubing (CT) units are being used in a multitude of applications in the industrial arena. This technology due to its versatility has found a range of applications in the petroleum industry including drilling, cementing, cleaning sand from a well bore, acidizing, scale removal and formation fracturing to name a few. Most of these applications involve pumping fluids through these coiled tubing units at very high rates. The frictional pressure losses occurring across the tubing length impose economic concerns and limit the flow rates that can be achieved while using this technique. Since fluid transport through coiled tubing has gained popularity in numerous engineering applications, including the petroleum industry, an accurate calculation of the frictional pressure loss in such tubing is of extreme importance. Accurate estimation of frictional pressure loss plays a crucial role in determining the horsepower requirements for pumping fluids through coiled tubing. Furthermore, friction pressure loss calculations are very important in the design of any hydraulic fracturing treatments using coiled tubing and estimating bottomhole treating pressure, and maximum wellhead pressure. The coiled part of the tubing during a fracturing operation exhibits significantly higher losses as compared to the straight section. Higher frictional losses in coiled geometries are generally caused by increased secondary flow effects that dominate the flow pattern in turbulent flow regime. Even small increase in friction pressure gradients can become critical due to the large lengths of tubing involved in fracturing operation. Some critical factors in the accurate determination of magnitude of friction losses occurring across the tubing lengths are fluid type, tubing length, tubing diameter and tubing curvature. Various experimental approaches have investigated the effect of tubing size1,4. The effect of using different fluid has also been studied for common fracturing fluids10. But these studies have been limited to the straight conduit. On the other hand, the flow behavior of commonly used fluids in coiled tubing, which takes into account the effects of curvature, has scarcely been reported in the literature.

In the present work, a novel cross-linked polymer was synthesized though the anionic polymerization of cyanoacrylate with moisture as an initiator, methylene-bis-acrylamide as a cross-linker, and linseed oil as a spacer. Two layers of the synthesized polymer was coated over polyacrylamide for its homogenous impregnation in Class-G cement slurry for the synthesis of cement core. Fourier Transformation Infrared spectroscopy and X-Ray diffraction spectrum of the synthesized polymer and cement core were obtained to investigate the presence of different functional groups and phases. Moreover, the morphologies of the dual-encapsulated polyacrylamide was observed through scanning electron microscopy. Furthermore, the water-absorption capacity of the synthesized dual-encapsulated polyacrylamide in normal and saline conditions were tested. A cement core impregnated with 16% of dosage of dual-encapsulated polyacrylamide possesses an effective self-healing capability during the water-flow test. Moreover, the maximum linear expansion of the cement core was observed to be 26%. Thus, the impregnation of dual-encapsulated polyacrylamide in cement slurry can exhibit a superior self-healing behavior upon water absorption in an oil well.