Volumetric Requirements for Foam and Mist Drilling Operations

Foam is widely used in fractured reservoirs. However, few studies on the flow characteristics of foam fluid in fractures have been presented, and the flow mechanism of foam in complex fracture networks remains unclear. In this study, a variety of fracture models are used to systematically evaluate the flow characteristics of foam in fractures. First, based on the variable-thickness fracture and parallel fracture models, the variations in foam flow resistance and velocity are explored. Then, the foam flow path and sweep efficiency are evaluated with complex fracture network models. The results show that the foam flow resistance increases with increasing foam quality. At a higher foam quality (90%–92%), the pressure drop peaks and then decreases sharply as the foam quality increases. When the foam quality ranges from 50% to 90%, the foam volume increases with increasing foam quality, and the bubbles have larger diameters in thicker fractures. When foam flows in parallel fractures with different thicknesses, it preferentially flows in thick fractures (100 μm), and gas trapping occurs in the thin fractures. When the foam flows in a complex fracture network, the pressure drop increases with increasing foam quality and flow rate, and the foam quality corresponding to the maximum pressure drop is independent of the flow rate. In the vertical intersecting fracture network model, the range of flowing foam is the most extensive when the foam quality is 80%–90%. In the irregular fracture network model, when the foam quality reaches 92%, the volumetric sweep efficiency reaches a maximum of 86.97%. These findings reflect that it is necessary to consider fractures when foam flows in fractured/vuggy reservoirs and that reasonable predictions can be made with experimental results.

Foam flow in vertical gas wells under liquid loading: Critical velocity and pressure drop prediction

Compared to conventional (incompressible) drilling fluids, relatively little is known about the hydraulic and rheological properties of foamed drilling fluids. The complex flow mechanisms involved in compressible drilling fluid circulation make determination of the optimum combination of liquid and gas injection rates very difficult. Modelling of foam rheology is the key issue in hydraulic design, in order to predict the bottom-hole pressure accurately, and to optimize the different controllable variables for effective cutting transport performance. The University of Tulsa's low-pressure ambient temperature flow loop has been recently modified to accommodate foam flow. The flow loop permits foam flow through 0.0508 m (2 in.), 0.0762 m (3 in.), 0.1016 m (4 in.) diameter pipes, and a 0.2032 m (8 in.) by 0.1143 m (41/2 in.) annular section. Preliminary experiments have been conducted, in which pressure losses were measured for different foam qualities. Measured parameters were gas/liquid flow rates, pressure, differential pressure loss, and temperature. Statistical analysis was carried out to see the degree of fit provided by Bingham plastic, power law, and yield power law models for the generalized foam flow curve data. A comparative study was conducted to investigate the predictive ability of the available foam hydraulic models. Models presented by Beyer et al. (1972), Blauer et al. (1974), Reidenbach et al. (1986), Sanghani and Ikoku (1983), Gardiner et al. (1988) and Valko and Economides (1992) were used to estimate the frictional pressure losses during the flow of foam in horizontal pipes. Comparison of the model predictions with experimental pressure loss values show that model predictions of frictional pressure losses can be different from the actual values by 2 to 250 %. Introduction In the 1970s, high quality foams were developed into a viable fracturing stimulation tool for oil and gas wells(1). Since then, foam rheology has been the subject of numerous investigations, in an effort to design better proppant transport medium. Lord(2) presented one of the first comprehensive mathematical treatments of foam flow behaviour. He used the real gas law and mass balance considerations to develop an equation of state for foam with solids. Later, Spoerker et al.(3) modified Lord's solution and presented a new two-phase flow equation. They used a virial equation(4) instead of the real gas equation of state. They also solved the differential mechanical energy equation to obtain an explicit expresion for pressure loss prediction during foam flow. Reidenbach et al.(5) presented empirical correlations to calculate the rheological properties of N2 and CO2 foam fracturing fluids. Harris(6–9) conducted some excellent studies on the rheology and fluid loss properties of fracturing fluids. Harris and Reidenbach(10) also studied the effect of temperature on the rheology of foam fracturing fluids. Foam has been used as a drilling fluid in many drilling operations, and the results from various field cases are well documented in the literature(11–23).

Foam is gaining increasing applications in both drilling and cementing. Typical applications include drilling operations in naturally fractured formations and depleted or patially depleted reservoirs. The unique pressure profile created by foam makes it an ideal drilling fluid in many areas where a narrow operating window exsits between pore pressure and fracture pressure. While rotary drilling is the most widely used drilling technique, there has been no study on foam drilling with drill pipe rotation. This study was undertaken to identify the effect of pipe rotation on pressure losses and velocity profiles of foam flow in both concentric and eccentric annuli. The effects of pressure, foam quality and pipe eccentricity were also investigated. For the first time, pipe rotation effects on foam flow were experimentally studied on a flow loop consisting of a pipe viscometer and an annular test section. Pipe rotary speeds were varied from 0 to 400 RPM with foam qualities ranging from 60% to 90% at different flow rates. Computational Fluid Dynamics simulations were performed to compare with experimental results. A flow-through rotational viscometer was used to investigate foam rheology at higher pressures and verifiy the results of the pipe viscometer. Results show that pipe rotation increases pressure drop by more than 30% for low quality (below 70%) foams in a concentric annulus. It has no noticeable effects on medium quality (70%-80%) foams, and slightly decreases pressure drop for high quality foams. In an eccentric annulus, pipe rotation clearly shifts the maximum axial velocity core along the pipe rotation direction. When there is a cuttings bed, however, the velocity core shifts to a direction that is opposite to the pipe rotation direction, which has a tremendous impact on hole cleaning. Unlike incompressible fluids, the absolute pressure also affects foam rheology and pressure drop for a given quality foam. The results of this study are particularly useful for drilling and cementing design calculations for underbalanced and managed pressure drilling operations.

Many marginal gas wells cannot sustain production without artificial lift. For deep gas wells, one of the most feasible techniques is to use foam lift — inject surfactant in the well and create stable foam to lift the liquid to the surface. Unfortunately, no correlation is available to calculate the pressure drop under foam flow conditions. Conventional pressure drop prediction models are unable to correctly predict the pressure drop under these conditions. In this paper, a new model is developed to predict the pressure drop under foam flow conditions. By using a simple drift flux model and using some of the available literature data on foam, a foam pressure drop model was developed, and compared with 570 data points collected from many gas wells. The match between the model and the actual observations is reasonable. The model can be further improved if additional data on the foam quality, stability and the ability to entrain liquids becomes available.

Validation of CTF pressure drop and void predictions for the NUPEC BWR database

This report summarizes the work done to validate the droplet entrainment and de-entrainment models as well as two-phase closure models in the CTF code by comparison with experimental data obtained at Riso National Laboratory. The Riso data included a series of over 250 steam/water experiments that were performed in both tube and annulus geometries over a range of various pressures and outlet qualities. Experimental conditions were set so that the majority of cases were in the annular/mist ow regime. Measurements included liquid lm ow rate, droplet ow rate, lm thickness, and two-phase pressure drop. CTF was used to model 180 of the tubular geometry cases, matching experimental geometry, outlet pressure, and outlet ow quality to experimental values. CTF results were compared to the experimental data at the outlet of the test section in terms of vapor and entrained liquid ow fractions, pressure drop per unit length, and liquid lm thickness. The entire process of generating CTF input decks, running cases, extracting data, and generating comparison plots was scripted using Python and Matplotlib for a completely automated validation process. All test cases and scripting tools have been committed to the COBRA-TF master repository and selected cases have been added to the continuous testing system to serve as regression tests. The dierences between the CTF- and experimentally-calculated ow fraction values were con- sistent with previous calculations by Wurtz, who applied the same entrainment correlation to the same data. It has been found that CTF's entrainment/de-entrainment predictive capability in the annular/mist ow regime for this particular facility is comparable to the licensed industry code, COBRAG. While lm and droplet predictions are generally good, it has been found that accuracy is diminished at lower ow qualities. This nding is consistent with the noted deciencies in the Wurtz entrainment model employed by CTF. The CTF predicted two-phase pressure drop in the annular/mist ow regime has been found to be highly inaccurate, exhibiting a clear bias with respect to the experimental data. This inaccuracy led to an investigation that revealed deciencies in the implementation of the annular/mist interfacial friction model, which should be investigated further in the future. Looking to published COBRAG results for this same facility reveal it exhibits no bias with regard to experimental pressure drop results. In addition to the problems with pressure drop prediction, the lm thickness was also signicantly under-predicted by CTF compared to both experimental data and Wurtz's analytical calculations. Film thickness is calculated using a simple geometric relationship and lm void fraction in CTF, which is dependent on slip ratio and interfacial friction. It is possible that the issues aecting the pressure drop and lm void prediction are related.

In this work, the C14‐16alpha olefin sulphonate (AOS) surfactant, octylphenol ethoxylate (TX‐100), and methyl bis[Ethyl(Tallowate)]‐2‐hydroxyethyl ammonium methyl sulphate (VT‐90) surfactant were selected as representatives of anionic, nonionic, and cationic surfactant to stabilize foam. The effects of surfactant concentration and gas/liquid injection rates on foam performance were examined by performing a series of oil‐free foam flow tests by injecting CO2and a foaming surfactant simultaneously into sandpacks. Foam flooding was conducted as a tertiary enhanced oil recovery (EOR) method after conventional water flooding and surfactant flooding. Furthermore, a new method was proposed to determine the residual oil saturation. The foam stability in the presence and absence of heavy oil was studied by a comparative evaluation of the mobility reduction factor (FMR) in both cases. The foam fractional flow modelling by Dholkawala and Sarma[36]was modified based on experimental results obtained in this study. The range of the ratio of two important model parameters (Cg/Cc) at various foam qualities was determined and could be used for large‐scale predictions. The results showed that during the oil‐free foam displacement experiments higher foam apparent viscosities () were attained at lower gas flow rates and the maximum was attained at a total gas and liquid injection rate of 0.25 cm3/min with a gas fractional flow ratio of 0.8 for the foam in the absence of oil. The presence of oil reduced the foam mobility reduction factors (FMR) to different degrees withFMR‐without oil/FMR‐with oilranging from 4.25–13.69, indicating that the oil had a detrimental effect on the foam texture. The foam flooding successfully produced an additional 8.1–21.52 % of OOIP, which can be attributed to the combined effect of increasing the pressure gradient and oil transporting mechanisms.

Although rotary drilling is being used in most wells, the impact of drillpipe rotation on hole cleaning during foam drilling has not been investigated. There has been no single predictive tool developed to address pipe rotation effects on foam drilling. This paper presents the first study of cuttings transport using foam with pipe rotation under simulated downhole conditions. A field-scale, high pressure high temperature wellbore simulator with a 73-ft long, 5.76″ by 3.5″ eccentric annular test section was used to investigate the effects of pipe rotation, foam quality and velocity, downhole pressure and temperature on cuttings transport and pressure losses in a horizontal wellbore. Experiments were conducted with backpressures from 100 to 400 psi and temperatures from 80 to 160 degrees F. Pipe rotary speeds were varied from 0 to 120 RPM with foam qualities ranging from 60% to 90% and foam velocities from 2 to 5 ft/s. It was found that pipe rotation not only significantly decreases cuttings concentration in a horizontal annulus but also results in a considerable reduction in frictional pressure loss. The reduction in cuttings concentration is up to 40% at a medium foam velocity (3 ft/s) when pipe is rotated up to 120 RPM. The decrease in frictional pressure loss is up to 50% at a medium foam velocity and is more than 60% at a low velocity. Using a higher foam velocity or quality also improves hole cleaning, however, pressure losses are significantly increased. A mechanistic model and an associated computer simulator were developed for practical design and field applications. It can be used to predict cuttings concentration, bed height and pressure drop during horizontal foam drilling with various pipe rotary speeds, eccentricities, foam qualities and velocities under different pressure and temperature conditions. Comparisons between model predictions and experimental results show that the difference is less than 15% in most of the cases.

Prediction of pressure drop with steady state pneumatic conveying of solids in horizontal pipes

Water management remains a critical challenge in proton exchange membrane (PEM) fuel cells, particularly concerning flooding under high-current density and prolonged operation. Dynamic water distribution directly affects gas phase transport, encompassing convection within gas channels (GCs) and diffusion through porous electrodes. The fluctuation of pressure drop has been highlighted in previous studies [1-3], which is more frequent when compared with that when only single-phase flow in the channel is considered. A reasonable cathode channel pressure drop can benefit fuel cell performance [1] and energy efficiency [4]. Although pressure drop correlations have been conducted experimentally and numerically [5], the pressure drop prediction still needs to be improved, for example, involving the liquid transport from gas diffusion layers (GDLs) [6]. In this study, two-phase flow simulations in an assembled GC and fibrous GDL are conducted by the volume of fluid method in OpenFOAM. To utilize the fibrous GDL structures to mimic the natural breakthrough water, different GDLs are stochastically reconstructed using straight- and curved- cylinders (regarded as carbon fibers) and keeping the same bulk porosity and fiber diameter, as shown in Figure 1. The GC pressure drop is studied in local and total regions in different scenarios, e.g, different GDL structures (see Figure 1(c)), different surface wettability, and different air flow rates. Preliminary results show that the pressure drop does not exhibit a direct correlation with the liquid amount present in the GC, suggesting a multifaceted relationship that extends beyond mere liquid content, as shown in Figure 2. Therefore, it is imperative to explore additional factors that may influence this critical parameter. Figure 3 displays the spatial and temporal distribution of pressure and water cross-section area of 23 cross-section along the GC length direction in 13.5 ms in Case A and B. The breakthrough types in the GDL/GC interface and drainage flow types in GCs are found to relate more to the pressure drop. In future work, we aim to explore all the above scenarios to gain deeper insights into their impact on pressure drop behavior and ultimately enhance our understanding of the complex interactions governing two-phase flow in PEM fuel cell systems.References Li, P. Pei, Z. Wu, H. Xu, D. Chen and S. Huang, Applied Energy, 190, 713 (2017). Liu, L. Guo, R. Zhang, L. Chen and W.-Q. Tao, Applied Energy, 302, 117625 (2021). Zhang, S. Liu, Z. Wang, R. Li and Q. Zhang, International Journal of Hydrogen Energy, 47, 17713 (2022). S. Ijaodola, Z. El- Hassan, E. Ogungbemi, F. N. Khatib, T. Wilberforce, J. Thompson and A. G. Olabi, Energy, 179, 246 (2019). Li, H. Zhou, C. Li, Z. Liu, P. Zhang and C. Lu, Experimental Thermal and Fluid Science, 155, 111198 (2024). Mortazavi and K. Tajiri, Renewable and Sustainable Energy Reviews, 45, 296 (2015). Figure 1

HEPA filter are installed to remove radioactive aerosol in the ventilation system of the fuel cycle facility. In the fire accident, the pressure drop of the filter increases with time due to a large amount of particle. The collapsing the filter might be caused by high pressure across the filter. The prediction of pressure drop is important to contribute on safety confirmation. The study measuring the pressure drop of the filter under the condition of combusted PMMA and PC have been conducted. In this study, numerical analysis of pressure drop and lifespan of HEPA filter under the fire accident condition was conducted. The effects of soot distributions on the pressure drop were investigated. The pressure drop was calculated by the plane filter model. The model takes into the account the fiber distribution. The main characteristics of HEPA filter for fuel cycle facility and soot distribution under the condition of combusted PMMA and PC were applied to initial condition. The pressure drop under the soot distribution of PMMA was higher than PC, because the smaller particles were deposited to entail the higher pressure drop.

MP-PIC simulation of blood cell movement through a LAD with high stenosis

Foam flow in low-permeability Berea Sandstone cores: a laboratory investigation

Prediction of nanofluid heat transfer characteristic and pressure drop in helical coil via artificial neural networks