Laboratory Scale Flow Loop Research Articles

Modeling wax deposition in pipes: Developing a closure relationship for improving the prediction accuracy

Wax deposition remains one of the most challenging flow assurance issues faced by the oil and gas industry. The first cases of paraffin deposition problems in pipelines started to draw attention more than 50 years ago. However, no unequivocal model for its prediction has yet been proposed and accepted. The most used models for paraffin phenomenon prediction usually return over or under-predictions up to 100% in relative errors. Accurate prediction of this phenomenon will lead to proper flowline sizing, insulation requirements, pigging strategies, chemical treatments, etc. With the recent improvements in mechanistic understanding of wax deposition mechanisms based on in-situ microscopic visualization, it became clear that precipitated wax crystals occur within the boundary layer. Therefore, more than one mechanism governs the deposition process. These observations are the core for proposing a new estimation model that accounts for wax crystal precipitation. The model determines the concentration of precipitated crystals of wax through a material balance involving the soluble amount of wax in the system, the degree of supersaturation, and the precipitation rate constant (kp). Deposition data obtained from a laboratory-scale flow loop was used to validate the proposed model, resulting in great improvement in the relative errors between estimated and measured values for deposit thickness and wax fraction. Comparatively, the SD (Santos-Daraboina) Model resulted in predictions with relative errors as low as 12.8% against experimental data, while the FMT model, in some cases, resulted in overpredictions up to 299%.

Pressure transmission in yield stress fluids - An experimental analysis

The current work presents an experimental investigation of the pressurization of a yield stress fluid contained in a closed pipeline under isothermal conditions. The tests were performed in a laboratory-scale flow loop placed inside a thermally controlled chamber. Sensors located along the pipeline measured fluid pressure and temperature. Differently from Newtonian fluids, experiments conducted with a viscoplastic fluid showed that the pressure imposed at one end of a closed pipeline was not fully transmitted to the other end, supporting prior mathematical model results. The results also revealed that the final pressure distribution was dependent not only on the fluid yield stress but also on the shear history the fluid underwent during pressurization and on the ratio between the pressure wave inertia and viscous dissipation. A comparison of the fluid yield stress obtained from rheometric measurements with the shear stress at the pipeline wall showed that they were of the same order of magnitude and that the higher the pressure wave inertia-viscous dissipation ratio the higher was the discrepancy between them.

Validation of wax deposition models with recent laboratory scale flow loop experimental data

Experimental data at various conditions are important for improving wax deposition prediction and upscaling efforts. This study consolidates several single-phase wax deposition data acquired in recent years and validates several wax deposition models for a comprehensive range of experimental conditions. The film mass transfer (FMT), equilibrium (EM), Matzain (1999), and Venkatesan (2004) models were tested against 70 experimental data points (19 sets of initial operating conditions), obtained with four different oils and flow loop facilities. Uncertainty propagation analysis was performed to estimate reasonable ranges of error in the prediction that may be caused by fluid properties or standard correlations instead of the model formulation itself. The FMT model regularly over-predicts the deposition rate, which is consistent with previous theoretical, experimental, and visualization studies. It is observed that EM does not necessarily serves as the lower bound of deposition rate, suggesting that some form of flux reduction effects may exist. Sherwood number analysis was performed to validate conclusions from FMT and EM model assessment. A fix set of shear coefficient values in Venketasan's model is not sufficient to achieve acceptable accuracy in general, indicating that the shear coefficients are likely to be oil and flow conditions dependent. Matzain's model delivers relatively superior performance on deposit wax mass and flux predictions among the four models, although it is still unable to predict aging mechanistically and the deposition trends as a whole. In conclusion, more mechanistically rigorous wax deposition models and experimental data are still needed.

Investigation of inhibitors efficacy in wax deposition mitigation using a laboratory scale flow loop

Statistically reliable wax inhibition experimental data was obtained by utilizing the newly built laboratory scale flow loop. The comb‐shaped inhibitors are found more effective in decreasing the thickness compared to the linear inhibitor under the same conditions. Moreover, this becomes more predominant as the chain length of inhibitors increases. Interestingly, even though all the inhibitors decreased the deposit thickness, the wax content increased significantly. Besides, the longer chain length (PI‐B) of the inhibitor results in a higher wax content. Since the combination of growth and aging influenced by the presence of inhibitor significantly, paraffin inhibition efficiency (PIE) based on the wax mass was proposed to quantitatively assess the inhibitors. Based on the PIE, PI‐B, and PI‐C have more inhibition efficiency than PI‐A. Therefore, when selecting wax inhibitor, one should be aware about the strength of the deposit gel in addition to the reduction of the deposit mass. © 2016 American Institute of Chemical EngineersAIChE J, 62: 4131–4139, 2016

A Wireless Sensor Network-Based Infrastructure for Real-Time and Online Pipeline Inspection

The aim of this paper is to present a secure wireless sensor network-based infrastructure for fast and accurate detection of eventual leaks that might occur in multiphase pipelines (i.e., pipelines which carry simultaneously more than one fluid). The system is scalable to monitor long distances of pipelines. It consists of a newly designed low-cost pipeline set which is composed of an inner pipe that carries the multiphase fluid, surrounded by a second outer pipe that holds the leak detection unit. This latest comprises an air-ultrasonic sensor which continuously senses the presence of the leak. The location of the leak is determined by a bidirectional microphone. Both these sensors are interfaced to a wireless sensor module which performs control, signal processing, and transmission tasks. Hence, the second contribution of this paper is to provide a new secure and reliable communication protocol that takes into consideration the nature of the network in terms of packets patterns and hardware constraints of the communicating nodes. Online tests in a laboratory scale flow loop indicate that the system is capable to accurately determine the location of the leak and its rate (in 1/min) in fast response time for different scenarios of leaks.

Chord length distributions measurements during crystallization and agglomeration of gas hydrate in a water-in-oil emulsion: Simulation and experimentation

The formation of gas hydrates from water-in-oil emulsion was investigated on two different flow loops: a laboratory scale flow loop (Archimede flow loop: 30 m long, and 1 cm diameter, St-Etienne School of Mines) and a pilot scale flow loop (Lyre flow loop: 150 m long, 5 cm diameter, IFP Solaize). Both flow loops are equipped with a focused beam reflectance measurement (FBRM) probe for in situ particle size analysis. These FBRM probes were used to monitor chord length distribution (CLD) during the crystallization process of water-in-oil emulsions into gas hydrate slurries. When water droplets crystallize into hydrate particles, an agglomeration phenomenon is evidenced by pressure drop measurements. This agglomeration phenomenon is also detected by the FBRM probe and is highlighted by a sharp change in the mean chord length and a spread of the CLD to larger chord length. In order to better interpret the chord length distribution measurements, a modelling work has been made. This paper gives a description of the algorithm used for building 3D fractal aggregates and simulating CLD measurements on them. Aggregates are constructed from a monodisperse spherical particle. The influence of different parameters (fractal dimension, number of particles in the aggregate, diameter of primary particles) on the simulated CLD is also discussed. Some comparisons between experimental and simulated CLD are finally used to describe the physical properties of aggregates during an experiment.

An Accurate Machine for Real-Time Two-Phase Flowmetering in a Laboratory-Scale Flow Loop

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A new flow measurement system for real-time flow computation of a two-phase flow in an oil field is described. The system utilizes an array of ultrasound sensors together with capacitance and conductance sensors to accurately interpret the fluid composition in the whole water-cut range. The flow rate is determined using venturi and differential pressure techniques. A dedicated hierarchical neural network algorithm that relies on the various physical properties of the fluid was implemented and tested in a laboratory-scale flow loop. Experimental results demonstrated that real-time classification within a <formula formulatype="inline"><tex Notation="TeX">$\pm$</tex></formula>5% relative error in volumetric flow regardless of the flow regime or the fluid composition can be achieved. This is an improvement over traditional systems, where weak accuracy is usually obtained either within the 40%–60% water-cut range or in the case of a high water cut. </para>

Friction pressure correlations for turbulent flow of drag reducing polymer solutions in straight and coiled tubing

Accurate determination of friction pressure losses of dilute drag reducing polymer solutions remains to be a challenge in many practical applications. These include a wide variety of hydraulic operations performed on a daily basis in the oil and gas industry. Most drilling, completions, and stimulation jobs require pumping fluids at high flow rates, which in turn generates high frictional pressure losses, enhanced by the use of small diameter tubing or coiled tubing. Curvature in this latter is believed to generate secondary flows and thus extra flow resistance. Therefore, good drag reduction characteristics of fluids are desirable. In this study, energy dissipation by eddies in turbulent flow of viscoelastic fluids is assumed to be the mechanism causing drag reduction. Various concentrations of Nalco ASP-700 and Nalco ASP-820 dilute polymer solutions are tested at ambient temperature in laboratory-scale and full-scale flow loops installed with straight and coiled tubing sections exhibiting different values of diameter, curvature ratio and pipe roughness. In addition, flow tests are conducted at 100 °F and 130 °F using the laboratory-scale flow loop. Effects of concentration, temperature, curvature ratio, and pipe roughness on drag reduction are discussed in light of Fanning friction factor versus solvent Reynolds number plots. Results show that drag reduction in coiled tubing is lower than in straight tubing. As curvature ratio increases, drag reduction decreases. The effect of increasing temperature is to decrease drag reduction in straight tubing and increase it in coiled tubing. In turn, the effect of increasing pipe roughness is to slightly decrease drag reduction in straight tubing up to a certain Reynolds number value and then it starts to increase. For coiled tubing, the effect of increasing pipe roughness is to decrease drag reduction. In this study, generalized correlations for the prediction of drag reduction in dilute polymer solutions flowing in straight and coiled tubing are developed on the basis of the energy dissipation of eddies in turbulent flow field and a shear rate dependent relaxation time. In addition, correlations are validated using experimental data for a low concentration guar fluid flowing through full-scale flow loop.

Fused Chemical Reactions. 3. Controlled Release of a Catalyst To Control the Temperature Profile in Tubular Reactors

The feasibility of an exothermic fused chemical reaction (FCR) system to control the temperature profile inside a tubular reactor is demonstrated in a 300-m laboratory-scale flow loop. The exotherm...