Liquid transport during gas flow transients applied to liquid loading in long vertical pipes

2015 ◽  
Vol 68 ◽  
pp. 652-662 ◽  
Author(s):  
Paulo J. Waltrich ◽  
Gioia Falcone ◽  
Jader R. Barbosa
Keyword(s):  
Gas Flow ◽  
Liquid Loading ◽  
Liquid Transport ◽  
Flow Transients

Simulation of the Performance of the Venturi Scrubber for an Advanced Reactor Containment Venting Conditions

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Goel Paridhi ◽  
K. Nayak Arun
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Gas Flow ◽  
Pressure Profile ◽  
Absorption Efficiency ◽  
Severe Accident ◽  
Mitigation Measures ◽  
Liquid Loading ◽  
Venturi Scrubber ◽  
Iodine Absorption

Abstract Post Fukushima, nuclear plants are being retrofitted with severe accident mitigation measures. For attaining depressurization of the containment and mitigate the consequences of the release of the radioactivity to the environment during a severe accident condition, filtered containment venting systems (FCVS) are proposed to be installed in existing reactors and being designed for advanced reactors. The design of FCVS is particular to the reactor type. The FVCS configuration considered in this paper comprises of a manifold of venturi scrubber enclosed in a scrubber tank along with metal fiber filter and demister for an advanced Indian reactor. This study focuses on the assessment of the design of the venturi scrubber for the reactor conditions at which venting is carried out through a numerical model. The numerical model is first validated with experiments performed for prototypic conditions. The predicted pressure drop and the iodine absorption efficiency were found to be in good match with the experimental measurements. Subsequently, the model is implemented for predicting the hydrodynamics, i.e., pressure drop, droplet sizes and distribution, and iodine absorption for prototypic conditions. The hydrodynamics, i.e., pressure profile in the venturi scrubber showed a decrease in the converging section and in the throat section. The diverging section showed decrease in recovery of pressure with the decrease in gas flow because of the increased liquid loading to the scrubber. The iodine absorption efficiency showed a value of 92% for high gas velocity which decreased to 68% for the lowest gas flow rate.

The Effect of Surfactants on Vertical Air/Water Flow for Prevention of Liquid Loading

SPE Journal ◽  
2016 ◽  
Vol 21 (02) ◽  
pp. 488-500 ◽  
Author(s):  
A. T. van Nimwegen ◽  
L. M. Portela ◽  
R. A. Henkes
Keyword(s):  
Surface Tension ◽  
Pressure Gradient ◽  
Water Flow ◽  
Annular Flow ◽  
Surfactant Concentration ◽  
Gas Flow ◽  
Liquid Loading ◽  
Dynamic Surface ◽  
Flow Rates ◽  
Churn Flow

Summary From field experience in the gas industry, it is known that injecting surfactants at the bottom of a gas well can prevent liquid loading. To better understand how the selection of the surfactant influences the deliquification performance, laboratory experiments of air/water flow at atmospheric conditions were performed, in which two different surfactants (a pure surfactant, sodium dodecyl sulfate, and a commercial surfactant blend) were added to the water. In the experiments, a high-speed camera was used to visualize the flow, and pressure-gradient measurements were performed. Both surfactants increase the pressure gradient at high gas-flow rates and decrease the pressure gradient at low gas-flow rates. The minimum in the pressure gradient moves to lower gas-flow rates with increasing surfactant concentration. This is related to the transition between annular flow and churn flow, which is shifted to lower gas-flow rates because of the formation of an almost stagnant foam substrate at the wall of the pipe. At high surfactant concentration, it appears that the churn flow regime is no longer present at all and that there is a direct transition from annular flow to slug flow. The results also show that the critical micelle concentration, the equilibrium surface tension, the dynamic surface tension, and the surface elasticity are poor predictors of the effect of the surfactant on the flow.

Investigation of Back Pressure Effects on Transient Gas Flow Through Porous Media via Laboratory Experiments and Numerical Simulation

2014 ◽  
Author(s):  
Xiaolei Liu ◽  
Akkharachai Limpasurat ◽  
Gioia Falcone ◽  
Catalin Teodoriu
Keyword(s):  
Steady State ◽  
Gas Flow ◽  
Laboratory Experiments ◽  
Transient Flow ◽  
Pressure Profile ◽  
Back Pressure ◽  
Pressure Effects ◽  
Gas Wells ◽  
Liquid Loading ◽  
Final Steady State

When developing a transient numerical reservoir simulator, it is important to consider the back pressure effects that waves propagating from one end of the porous medium will have on the temporal distribution of pore fluid pressure within the medium itself. Such waves can be triggered by changing boundary conditions at the interface between reservoir and wellbore. An example is given by the transient reservoir response following pressure fluctuations at the wellbore boundary for gas wells suffering from liquid loading. Laboratory experiments were performed using a modified Hassler cell to mimic the effect of varying downhole pressure on gas flow in the near-wellbore region of a reservoir. Gauges were attached along a sandstone core to monitor the pressure profile. The results of the experiments are shown in this paper. A numerical code for modelling transient flow in the near-wellbore region was run to mimic the experiments. The comparisons of simulations and laboratory test results are presented here, for the initial and final steady-state flowing conditions, and where the inlet pressure was maintained constant while initiating a transient pressure build up at the core outlet. The concept of the U-shaped pressure profile along the near-wellbore region of a reservoir under transient flow conditions, originally proposed by Zhang et al. [1], was experimentally and numerically reproduced for single-phase gas flow. This is due to a combination of inertia and compressibility effects, leading to the reservoir response not being instantaneous. The results suggest that, in two phase gas-liquid conditions, liquid re-injection could occur during liquid loading in gas wells. From the experimental results, the U-shaped curves were more obvious and of longer duration in the case of greater outlet pressure. The transition from the initial to the final steady state condition occurred rapidly in all the cases shown here, with the U-shaped pressure profile appearing only over a relatively short time (at the small scale and low pressures tested in this study).

A 3D Numerical Investigation on Droplets Distribution in a Wave-Plate Separator

2013 ◽  
Vol 842 ◽  
pp. 522-529
Author(s):  
Yong Lei Qu ◽  
Shi Bu ◽  
Bo Wan
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Geometrical Model ◽  
Turbulent Dispersion ◽  
Liquid Loading ◽  
Wave Plate ◽  
Gas Liquid Flow ◽  
Set Up ◽  
Plate Separator

The gas-liquid flow in a wave-plate separator is extremely complex due to its three-dimensional characteristic. Numerical simulation accomplished by former investigators using two-dimensional model may be appropriate for the iteration of pressure drop, but they were far from accurate in prediction of removal efficiency. To fill the gap, a three dimensional geometrical model of wave-plate separator is set up in this paper, RNG k-ε model is employed to compute the gas phase flow field, and the droplet trajectories were predicted applying the Lagrangian method. The turbulent dispersion of droplets were simulated by discrete random walk model. Using the assumption of a constant liquid loading of gas flow, simulation were accomplished for six different inlet velocities and two different droplet sizes. The influence pattern of gravity together with gas velocity on droplets distribution and the overall removal efficiencies were obtained.

Unstable Well Behaviour in Gas Well Liquid Loading

2017 ◽  
Author(s):  
S. P. C. Belfroid ◽  
A. van Wijhe
Keyword(s):  
Pressure Drop ◽  
Mass Flow ◽  
Gas Flow ◽  
Gas Production ◽  
Liquid Loading ◽  
Lower Velocity ◽  
Reservoir Characteristics ◽  
Stability Point ◽  
Production Wells ◽  
The Stability

Liquid loading is the mechanism that is associated with increased liquid hold-up and liquid back flow at lower gas flow rates in gas production wells. In laboratory, most liquid loading experiments are performed at fixed gas and liquid rates (mass flow controlled). In the field, the well behavior is a coupled well-reservoir system in which the reservoir results in a pressure or mass flow controlled inflow, depending on the reservoir characteristics. In this paper results are presented which have been performed with a pressure controlled vessel attached to a vertical pipe. The pressure drop between the vessel was varied to represent reservoir characteristics from tight to prolific. The goal of the experiments was to evaluate the relation and the time ‘trajectory’ between the minimum in the pressure drop curve and the actual flooding point. From these experiments it was concluded that the stability is determined by the overall pressure drop curve. That is the pressure drop from vessel to separator and not the tubing pressure drop curve. This stability point can be at a higher or lower velocity than the actual loading/flooding point and therefore, loading is not the cause of the production decrease. That also means stable production is possible below the flooding point in slugging conditions. In future, the distinction between stable flow and loading/flooding must be made more strict.

Effect of Surfactant (Foamer) Delivery Location on Horizontal Wells Deliquification

2017 ◽  
Author(s):  
Carolina V. Barreto ◽  
Hamidreza Karami ◽  
Eduardo Pereyra ◽  
Cem Sarica
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Rate ◽  
Gas Flow ◽  
Vertical Section ◽  
Horizontal Wells ◽  
Static Mixer ◽  
Liquid Holdup ◽  
Liquid Loading ◽  
Delivery Location

One of the methods to unload liquid from gas wells is foam-assisted lift. The applied surfactant reduces the liquid surface tension facilitating foam stability, and consequently, reducing mixture density and gas slippage. In this experimental study, a 2-in ID facility consisting of a 64-ft lateral section followed by a 41-ft vertical section is used to determine the optimum surfactant delivery location in horizontal wells. Water and compressed air are the liquid and gas phases, and an anionic surfactant is applied continuously with fixed concentration. Lateral section inclination is varied between ±1°, and four injection points are tested, including one with a static mixer, used as an external source of agitation. Recorded parameters are flow pattern, pressure gradient, liquid holdup, and foam quality. In the lateral section, the highest efficiency is obtained by using a static mixer causing significant drop in liquid holdup and increase in pressure drop due to frictional losses. All other injection points show similar behavior to the air-water case, due to negligible generated foam amid the existing flow pattern agitation. In the vertical section, all injection points show similar and significant drops in liquid holdup and delays in liquid loading onset compared to air-water case, and foam quality decreases as gas flow rate is reduced. Increasing the liquid flow rate causes increases in liquid holdup and pressure drop and shifts liquid loading onset to higher gas flow rates. The experimentally observed liquid loading onset is compared to the predictions of Turner et al. (1969), and a modification is proposed in this correlation to consider the effects of surfactant injection. The number of experimental studies investigating foam effects on liquid loading is limited especially for off-vertical configurations. The results of this study provide an experimental source to optimize foam lift in deviated wells.

Analytical Models for Liquid Loading in Multifractured Horizontal Gas Wells

SPE Journal ◽  
2016 ◽  
Vol 21 (02) ◽  
pp. 471-487 ◽  
Author(s):  
Juntai Shi ◽  
Zheng Sun ◽  
Xiangfang Li
Keyword(s):  
Flow Velocity ◽  
Gas Flow ◽  
Liquid Drop ◽  
Liquid Droplet ◽  
Shape Change ◽  
Analytical Models ◽  
Gas Wells ◽  
Gas Reservoirs ◽  
Liquid Loading ◽  
Gas Flow Velocity

Summary Liquid loading is a key issue in gas reservoirs with horizontal wells and multiple hydraulic fractures, especially for shale-gas reservoirs. Field results show that only 15–30% of the original fracturing fluid is recovered. Most liquid is trapped in the rock matrix near the fracture face and induced fractures. Water flowback from reservoir to wellbore and liquid loading from wellbore to surface are two main factors affecting the recovery of the original fracturing fluid. Significant efforts have been made to understand the effect of liquid loading on well performance, and some models have been proposed to describe the liquid loading. However, these models ignore the effect of liquid-drop size and its shape change with size. The falling liquid is nearly spherical in shape when its diameter is smaller than 2 mm, but when larger than 2 mm, it will change to be a half-hamburger in shape. Hence, ignoring the liquid-drop size and its shape change with size will lead to inaccurate calculations of the critical liquid-loading-flow rate. In this study, we conduct several groups of experiments to examine the liquid-droplet-shape change with liquid-droplet size in a gas-flow wellbore with different inclined angles. Similar to the falling liquid in air, larger liquid droplets are half-hamburger in shape (like the top half of the bun, flat on bottom and round on top). On the basis of this phenomenon, we propose analytical models to describe the critical liquid loading in vertical, slanted, and horizontal wellbores by considering the size and shape of liquid drops. Also, we validate this model by use of field data from the Daniudi gas field, and apply the proposed model to evaluate the liquid-loading problem in the Marcellus shale. Results show that the ratio of the liquid-drop height/width is a strong function of the liquid-drop width. Both the maximum and minimum ratios are determined: The maximum is unity, representing the shape of a sphere; the minimum is 0.3765; and the liquid drop is unstable when the ratio is less than 0.3765. In addition, the liquid drop with the minimum ratio is most easily loaded and produced from the vertical wellbore of gas wells. The key coefficient of B in the model of critical liquid-loading-flow velocity—vg = B[σ(ρl–ρg)/ρg2]0.25—is a function of the width of the liquid drop. The range of B is quantified as from 1.54 to 2.5. In the slanted wellbore of gas wells, the critical liquid-loading gas-flow velocity is related to the angle β, the slant angle, and the width of the liquid droplet. In the horizontal wellbore of gas wells, the critical liquid-loading gas-flow velocity is a function of the width of the liquid droplet. The models proposed in this work can accurately calculate the critical liquid-loading-flow rate for multifractured horizontal gas wells. This study can provide critical insights into the understanding of the liquid flowback and its effect on well productivity in gas reservoirs.

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