Water Blocking Research Articles

The Use of the Super Absorbent Polymer as Water Blocker in Concrete Structures

Adding super absorbent polymer to the concrete mix improves the performance of the concrete in its both stages; fresh concrete and hardened concrete. The super absorbent polymer has the ability to absorb relatively large amount of water and convert it into gel at the same time the volume increases proportionally. The new modified concrete has the ability to retain water in the form of gel which helps in the internal curing process of the concrete at its early stages and helps in blocking the water flow through voids and cracks in the mass of the concrete at its later stages. This study focuses on the ability of concrete to block the water flow through the concrete cracks. Several samples were prepared with different amount of super absorbent polymer added to the concrete mix expressed in percentage with respect to the weight of cement. Several cylindrical samples were prepared, but three different samples will be presented in this study. The samples were intentionally broken into two pieces. The two pieces are then put together forming artificially induced cracks in the samples. These samples were subjected to water pressure; falling head and constant head. The water flow through the induced crack in the sample is measured. The effect of the super absorbent polymer on the water flow is monitored and compared with the control samples, which is the sample prepared with no admixtures. The water tightness leading to complete water blockage is studied. The short term effect as well as the long term effect of the super absorbent polymer on the concrete water tightness is also studied. Several amounts of the super absorbent polymer expressed in terms of percentages of the cement weight are used in order to shed the light on the water tightness property of concrete. The increase of the amount of the super absorbent polymer in the concrete mix improves the internal curing properties of the concrete at the same generate more voids in the mass of the concrete which in turn reduces the strength of the concrete. Optimum amount of the superabsorbent polymer should be considered if the focus is the concrete strength. Also, the increase in the amount of the superabsorbent polymer in the concrete improves the water tightness of the concrete, which makes the concrete capable of blocking the water flow through the concrete cracks. There are several advantages of adding the super absorbent polymer to the concrete mix, including improving the concrete plasticity and workability at the same time improving the concrete mix stability and pump-ability.

Influence of clod size and water content on gas permeability of a compacted loess

The northwestern region of China is mainly semi-arid to arid and loess is ubiquitous. This natural resource has considerable potential to be transformed into earthen final covers for local landfills, but first its suitability must be ascertained through extensive tests. In this study, a device was developed to measure the gas permeability of unsaturated compacted loess specimens. Experiments were carried out to investigate the influence of clod size, compaction water content, and post-compaction water content on the gas permeability of the compacted loess. To maintain an identical soil structure, the post-compaction water content was changed using the osmotic technique. It was found that the compaction water content and resultant soil clod size exerted a combined effect on the gas permeability such that, at low water contents, the gas permeability remained fairly constant, but at high water contents the clods became relatively large, and the effect of the clod size dominated the water blockage effect from increasing water content. For specimens with identical soil structure, the gas permeability decreased with the increasing post-compaction degree of saturation at an accelerated rate. A power function is proposed to predict the relationship between the gas permeability normalized by the porosity function of the Kozeny–Carmen model and the post-compaction degree of saturation. Analysis of the experimental data indicates that the parameters for the power function still depend on the porosity of the compacted loess, particularly at high degrees of saturation.

Real-time visualization of oxygen partial pressures in straight channels of running polymer electrolyte fuel cell with water plugging

Visualization inside polymer electrolyte fuel cells (PEFCs) for elucidating the reaction distributions is expected to improve the performance, durability, and stability. An oxygen-sensitive film of a luminescent porphyrin was used to visualize the oxygen partial pressures in five straight gas-flow channels of a running PEFC with liquid-water blockages formed at the end of the channels. The blockage greatly lowered and unstabilized the cell voltage. The oxygen partial pressure decreased nearly to 0 kPa in the blocked channel. With a water blockage in a channel, the oxygen partial pressures in the adjacent channels were lowered due to an extra demand of oxygen consumption. When the number of the blocked channels increased, the oxygen partial pressure in the unblocked channels became much lowered. When the water blockages disappeared, the oxygen partial pressures quickly returned to the values before plugging. The influence of the cross flows of air through the gas diffusion layers in straight channels was much smaller than that in serpentine flow channels.

Imbibition and Water Blockage In Unconventional Reservoirs: Well-Management Implications During Flowback and Early Production

Summary Driven by field logistics in an unconventional setting, a well may undergo weeks to months of shut-in after hydraulic-fracture stimulation. In unconventional reservoirs, field experiences indicate that such shut-in episodes may improve well productivity significantly while reducing water production. Multiphase-flow mechanisms were found to explain this behavior. Aided by laboratory relative permeability and capillary pressure data, and their dependency on stress in a shale-gas reservoir, the flow-simulation model was able to reproduce the suspected water-blocking behavior. Results demonstrate that a well-resting period improves early productivity and reduces water production. The results also indicate that minimizing water invasion in the formation is crucial to avoid significant water blockage.

Experimental Investigation and Numerical Determination of Custom Gas Diffusion Layers to Understand Water Transports in PEMFC

Water management is an important impact to determine the polymer electrolyte membrane fuel cell (PEMFC) performance. In particular for fuel cell system operation at high humidity conditions and current densities, the proper water management requires good understanding of water transport in the different components of the cell. The gas diffusion layer (GDL) is one of the vital components of PEMFCs that has a variety of functions significant for their overall performance and durability. The GDL is usually a dual-layer carbon based porous substrate and tropically treated with polytetrafluoroethylene (PTFE) to make it hydrophobic in order to avoid liquid water blockage of its internal pores and keep them available for reactant gas transport to the adjacent catalyst layer [1]. When the gas phase is saturated with water vapor, water condensation takes place and resulting liquid water starts to fill the open pores of the GDL and covers the catalyst particles, rendering them electrochemically inactive [2]. The maximum current density is limited by oxygen concentration at the cathode catalyst surface [3]. This value represents the oxygen transport limitation through the GDL. The mass transfer through the GDL may indeed be rate limiting at high current densities when the GDL is saturated with water [4].In this study, the different designs of GDL with the introduction of two micro porous layers were investigated on PEMFC performance through characterization of their materials and structures as shown in Fig. 1. This new design of GDLs has been modified from standard AvCarb GDLs by adding two micro porous layers. Each set has been treated with two different methods in order to provide two different value of diffusivity. Polarization curves were collected at different designs of GDL as shown in Fig. 2. Further, the internal fuel cell resistance was measured by high frequency resistance (HFR) technique at 1000 Hz. Pore size distribution (PSD) data of the different GDLs were reported and analyzed. It is well known that tortuosity (τ) and porosity (ε) are two important parameters to relate free-stream properties with the actual mass transport in GDL [5]. The relationship of tortuosity (τ) and porosity (ε) was measured as the MacMullin number.In addition to these experiments, we present a computational fluid dynamic (CFD) analysis of the PEMFC operation with provided GDL characterization information, specifically the MacMullin number and PSD to compare with experiment data. The CFD prediction of current density distribution and gas/water transports in PEMFC will be used to understand the effect of these new designs of GDL. Acknowledgement This project is supported by the Department of Energy Contract Grant# DE-EE0000471 References M.V. Williams, et al., J Electrochem Soc, 151 (2004) A1173-A1180.U. Pasaogullar,i et al., J Electrochem Soc, 151 (2004) A399-A406.A.A. Kulikovsky, Electrochem Commun, 4 (2002) 845-852.J.T. Gostick, et al., J Power Sources, 173 (2007) 277-290.M.J. Martinez et al., J Electrochem Soc, 156 (2009) B80-B85.

Novel, Thermally Stable Fluid-Loss Pill Performs Better Than Guar-Based Gels

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 165096, ’Performance and Formation-Damage Assessment of a Novel, Thermally Stable Solids-Free Fluid-Loss Gel,’ by Pubudu Gamage, Jay P. Deville, SPE, and Bill Shumway, SPE, Halliburton, prepared for the 2013 SPE European Formation Damage Conference and Exhibition, Noordwijk, The Netherlands, 5-7 June. The paper has not been peer reviewed. A novel solids-free fluid-loss pill for higher-temperature reservoirs has been formulated. This pill can be used effectively in reservoirs with temperatures up to 350°F. Static thermal aging at 320°F demonstrated no noticeable loss of gel strength for at least 20 days. With regard to thermal stability and fluid loss, the synthetic-polymer-based gel outperforms guar-/borate-based gels tested under similar conditions. Introduction High downhole temperatures put a strain not only on equipment but also on the complex chemistry of drilling muds, drill-in fluids, and viscous pills. Some conventional materials, such as polysaccharide gums and sodium tetraborate crosslinking agents, are demonstrably unstable or simply rendered useless under high thermal loads for extended periods. This paper describes the development of a material for one such challenge—replacement of biopolymer-based gels for high-temperature applications. Research produced a novel, workable aqueous monovalent brine-based gel derived from a synthetic water-soluble polymer. The gel, which can be used for a variety of downhole applications including well kills, perforations, and other fluid-loss applications, is thermally stable and can be applied at temperatures up to 350°F, conditions where both polysaccharides and borate crosslinking begin to fail. The gel was specifically developed to be used in a 320°F gas reservoir. Gas regained permeability was used to assess any formation-damage issues of the gel in downhole applications. However, leakage of brine into the core during the hold-off period alters the water saturation of the core, adding complication in the regained permeability experiments because of water blockage. Experimental Section Gel Formulation. Gel was formulated with a high-density brine solution of a synthetic water-soluble polymer and a metal-based crosslinker. Further additives include pH buffers to lower the pH to an appropriate range for crosslinking to occur (pH of 4 to 5) and thermal stabilizers to mitigate gel decomposition by radical reactions and other processes. Concentration of polymer, the polymer/crosslinker ratio, and the pH of the formulation were tuned carefully to provide optimized gelling and fluid-loss properties. The formulations presented in this paper were based on 10.0-lbm/gal brine prepared by diluting stock 12.5-lbm/gal NaBr brine with water.

Simulation of Gel Filter-Cake Formation, Gel Cleanup, and Post-Fracture Well Performance in Hydraulically Fractured Gas Wells

SummaryPolymer and gel damage is a major issue in the cleanup of hydraulically fractured gas wells. This paper addresses the issue by using a gas/water flow model that simulates fracture propagation with gel filter cake-formation as mechanical trapping of polymer molecules on the fracture face and filtrate transport into the adjacent matrix. The model accounts for polymer as a chemical component. This approach is different than treating polymer as a highly viscous gel phase, which is the common method in most literature. In this model, the gel filter-cake thickness is calculated on the basis of experimental data. For leakoff, the model allows only the sheared polymer molecules, which are the major cause of formation permeability reduction, to cross the fracture face into the formation and adsorb on the matrix. Other features of the model include water blockage, non-Newtonian flow, non-Darcy flow, and proppant and reservoir compaction.

Dynamic Nonequilibrium of Water Flow in Porous Media: A Review

This review provides an overview on various phenomena, hypothesized causes, and modeling approaches that describe “dynamic nonequilibrium” (DNE) of water flow in soils. Dynamic nonequilibrium is characterized from observations on the macroscale by an apparent flow-rate dependence of hydraulic properties or by local nonequilibrium between water content and pressure head under monotonic imbibition or drainage histories, i.e., not affected by traditional hysteresis. The literature indicates that key processes causing DNE are pore-scale phenomena such as relaxation of air–water-interface distributions, limited air-phase permeability, dynamic contact angles, and time-dependent wettability changes. Furthermore, entrapment of water and pore water blockage, air-entry effects, and temperature effects might be involved. These processes act at different pressure head regions and on different time scales, which makes effective modeling of the combined phenomena challenging. On larger scales, heterogeneity of soil properties can contribute to DNE observations. We conclude that there is an urgent need for precision measurements that are designed to quantify dynamic effects.

A Comparative Study on WAS, SWAS, and Solvent-Soak Scenarios Applied to Heavy-Oil Reservoirs Using Five-Spot Glass Micromodels

Summary In this work, a series of solvent- and water-injection scenarios were conducted on horizontal five-spot glass micromodels that were saturated initially with heavy oil. Sandstone and limestone rock look-alike and network patterns with different pore structures were used in the experiments. The results show that the ultimate oil recovery of a water-alternating-solvent (WAS) scheme was greater than that of a simultaneously water-alternating-solvent (SWAS) scheme, and the efficiency of a solvent-soak scheme also offers a greater recovery. Likewise, the WAS scheme resulted in greater oil recovery when compared with continuous solvent injection (CSI), with the same amount of solvent consumption. Furthermore, some pore-scale phenomena, such as viscous fingering, diffusion of solvents into heavy oil, and localized entrapment of oil and solvent because of heterogeneity and/or water blockage, are also illustrated. The results of this work can be helpful for better understanding and verification of flow transport and pore-scale events during different solvent-based-injection scenarios in heavy-oil reservoirs.

Variable Pore Connectivity Model Linking Gas Diffusivity and Air‐Phase Tortuosity to Soil Matric Potential

Soil‐gas diffusivity (Dp/Do) and its dependency on soil matric potential (ψ) is important when taking regulative measures (based on accurate predictions) for climate gas emissions and also risk‐mitigating measures (based on upper‐limit predictions) of gaseous‐phase contaminant emissions. Useful information on soil functional pore structure, e.g., pore network tortuosity and connectivity, can also be revealed from Dp/Do–ψ relations. Based on Dp/Do measurements in a wide range of soil types across geographically remote vadose zone profiles, this study analyzed pore connectivity for the development of a variable pore connectivity factor, X, as a function of soil matric potential, expressed as pF (=log |−ψ|), for pF values ranging from 1.0 to 3.5. The new model takes the form of X = X* (F/F*)A with F = 1 + pF−1, where X* is the pore network tortuosity at reference F (F*) and A is a model parameter that accounts for water blockage. The X–pF relation can be linked to drained pore size to explain the lower probability of the larger but far fewer air‐filled pores at lower pF effectively interconnecting and promoting gas diffusion. The model with X* = 2 and A = 0.5 proved promising for generalizing Dp/Do predictions across soils of wide geographic contrast and yielded results comparable to those from widely used predictive models. The X–pF model additionally proved valuable for differentiating between soils (providing a unique soil structural fingerprint for each soil layer) and also between the inter‐ and intraaggregate pore regions of aggregated soils. We further suggest that the new model with parameter values of X* = 1.7 and A = 0 may be used for upper limit Dp/Do predictions in risk assessments of, e.g., fluxes of toxic volatile organics from soil to indoor air at polluted soil sites.

Linking Particle and Pore Size Distribution Parameters to Soil Gas Transport Properties

Accurate estimation of soil gas diffusivity (Dp/Do, the ratio of gas diffusion coefficients in soil and free air) and air permeability (ka) from basic texture and pore characteristics will be highly valuable for modeling soil gas transport and emission and their field‐scale variations. From the topsoil of two Danish arable fields representing two natural clay gradients, Dp/Do and ka were measured at soil water matric potentials between −1 and −100 kPa on undisturbed soil cores. The Rosin–Rammler particle size distribution parameters α and β (characteristic particle size and degree of sorting, respectively) and the Campbell water retention parameter b were used to characterize particle and pore size distributions, respectively. Campbell b yielded a wide interval (4.6–26.2) and was highly correlated with α, β, and volumetric clay content. Both Dp/Do and ka followed simple power‐law functions (PLFs) of air‐filled porosity (εa). The PLF tortuosity–connectivity factors (X*) for Dp/Do and ka were both highly correlated with all basic soil characteristics, in the order of volumetric clay content = Campbell b > gravimetric clay content > α > β. The PLF water blockage factors (H) for Dp/Do and ka were also well (but relatively more weakly) correlated with the basic soil characteristics, again with the best correlations to volumetric clay content and b. As a first attempt at developing a simple Dp/Do model useful at the field scale, we extended the classical Buckingham Dp/Do model (εa2) by a scaling factor based on volumetric clay content. The scaled Buckingham model provided accurate predictions of Dp(εa)/Do across both natural clay gradients.

The Effects of Fish Cages on Ambient Currents

Experiments were carried out to measure forces on and wake characteristics downstream from fish cages. Cylinders made from metal mesh with porosities of 0%, 30%, 60%, 75%, 82%, and 90% were tested in a towing tank. The drag force was measured with strain gauges, and the flow field downstream from the models was analyzed using particle image velocimetry. The Reynolds numbers ranged from 1000–20,000 based on the model diameter and 15–300 based on the diameter of the strings of the mesh as an independent obstacle. High porosities (here, 82% and 90%) lead to low water blockage and allow a substantial amount of water to flow through the model. The data indicate that the wake characteristics change toward the wake characteristics of a solid cylinder at a porosity just below 75%. The drag force is highly dependent on the porosity for high porosities of a cylinder.

Compaction and rotovation effects on soil pore characteristics of a loamy sand soil with contrasting organic matter content

AbstractThe high input of mechanical energy in common agricultural practice can negatively affect soil structure. The impact of compaction (P) and rotovation (R) on soil pore characteristics was compared with those in soil from untreated reference (U) plots of a loamy sand soil receiving for 14 yr, either only mineral fertilizer (MF) or, in addition, animal manure (OF). Undisturbed soil cores were taken from two separate fields in consecutive years at an identical stage in the crop rotation. We measured soil organic carbon (OC), soil microbial biomass carbon (BC), and hot‐water extractable carbon (Chot). Water retention, air permeability and gas diffusivity were determined at −100 hPa in both years and for a range of water potentials in one of the years. The continued addition of animal manure had increased OC, BC, and Chot compared with the soil receiving only mineral fertilizer. Soil under treatment OF had larger porosity than that from treatment MF. Treatment P eliminated this difference and significantly reduced the volume of macropores. This interaction between soil organic matter content and mechanical impact was also reflected in the gas diffusion data. Specific air permeability was mainly influenced by mechanical treatment. Modelling the diffusion data normalized to the inter‐aggregate pore space showed no significant treatment effects on pore‐connectivity, although there was a tendency of more water blockage in soil under treatment MF. More studies are needed to confirm this interpretation. Our studies indicate that organic manure increases soil porosity, but compaction reduces the related gas exchange effects to the level of compacted soils receiving mineral fertilizer.

Effects of dry bulk density and particle size fraction on gas transport parameters in variably saturated landfill cover soil

Landfill sites are emerging in climate change scenarios as a significant source of greenhouse gases. The compacted final soil cover at landfill sites plays a vital role for the emission, fate and transport of landfill gases. This study investigated the effects of dry bulk density, ρ b , and particle size fraction on the main soil–gas transport parameters – soil–gas diffusivity ( D p / D o , ratio of gas diffusion coefficients in soil and free air) and air permeability ( k a ) – under variably-saturated moisture conditions. Soil samples were prepared by three different compaction methods (Standard and Modified Proctor compaction, and hand compaction) with resulting ρ b values ranging from 1.40 to 2.10 g cm −3. Results showed that D p and k a values for the ‘+gravel’ fraction (<35 mm) became larger than for the ‘−gravel’ fraction (<2 mm) under variably-saturated conditions for a given soil–air content ( ε), likely due to enhanced gas diffusion and advection through less tortuous, large-pore networks. The effect of dry bulk density on D p and k a was most pronounced for the ‘+gravel’ fraction. Normalized ratios were introduced for all soil–gas parameters: (i) for gas diffusivity D p / D f , the ratio of measured D p to D p in total porosity ( f), (ii) for air permeability k a / k a ,pF4.1, the ratio of measured k a to k a at 1235 kPa matric potential (=pF 4.1), and (iii) for soil–air content, the ratio of soil–air content ( ε) to total porosity ( f) (air saturation). Based on the normalized parameters, predictive power-law models for D p ( ε/ f) and k a ( ε/ f) models were developed based on a single parameter (water blockage factor M for D p and P for k a ). The water blockage factors, M and P, were found to be linearly correlated to ρ b values, and the effects of dry bulk density on D p and k a for both ‘+gravel’ and ‘−gravel’ fractions were well accounted for by the new models.

Experimental Investigation of Miscible CO2 Flooding

Management of water alternating gas (WAG) injection projects requires making decisions regarding the WAG ratio, half-cycle-slug size, and ultimate solvent slug size. The impact of these decisions affects the capital cost and ultimate incremental oil recovery. Core flooding runs were conducted on 2 and 4 ft core samples. Injection scheme (continuous gas injection [CGI] vs. WAG), WAG ratio, and slug size were investigated. In addition, miscible WAG flooding as a secondary process was investigated and its efficiency was compared to the conventional tertiary miscible gas flooding. Miscible gas flooding at different miscible WAG parameters (WAG ratio and slug size) indicate that 1:2 WAG ratio at 0.2 PV slug size is the best combination yielding the highest recovery and tertiary recovery factors. Miscible WAG flooding as a secondary process indicated a higher ultimate recovery compared to the conventional tertiary WAG flooding. However, a larger amount of gas injection is consumed particularly in the early stages of the injection process. Miscible CGI mode conducted using n-Decane as oleic phase appears to have better performance than miscible WAG injection in term of recovery. When light Arab crude oil was used as oleic phase, higher recovery was obtained for miscible WAG flooding. The reversal trend seen in is believed to be due to the presence of crude oil, which alters the rock wettability toward an oil-wet condition, preventing the water blockage during the WAG process.

Two-Region Extended Archie's Law Model for Soil Air Permeability and Gas Diffusivity

The air permeability (k a ) and soil gas diffusion coefficients (D p ) are controlling factors for gas transport and fate in variably saturated soils. We developed a unified model for k a and D based on the classical Archie's law, extended by: (i) allowing for two-region gas transport behavior for structured soils, with the natural field moisture condition (set at -100 cm H 2 O matric potential [pF 2]) as the reference (spliced) point between the large-pore (drained pore diameter ≥30 μm at pF ≤ 2) and the small-pore (subsequently drained pores 2) regions, and (ii) including a percolation threshold, set as 10% of the total porosity for structureless porous media or 10% of the porosity in the large-pore region for structured soils. The resulting extended Archie's law with reference point (EXAR) models for k a and D were fitted to the measured data. For both structureless and structured porous media, Archie's saturation exponent (n) was higher for D p than for k a , indicating higher water blockage effects on gas diffusion. For structured soils, the saturation exponent for the large-pore region (n 1 ) was lower than for the small-pore region (n 2 ). Generally, n 1 values of ∼1 for k a and 2 for D p and n 2 values of 4/3 for k a and 7/3 for D described the data well. Two reference-point expressions for k a at pF 2 were also developed and tested together with existing models for D at pF 2 against independent data across soil types. The best-performing reference-point models were a k a model based on the classical Kozeny equation and the Moldrup D p model.

The performance of superhydrophobic and superoleophilic carbon nanotube meshes in water–oil filtration

Vertically-aligned multi-walled carbon nanotubes (CNTs) were grown on stainless steel (SS) mesh by thermal chemical vapor deposition with a diffusion barrier of Al 2O 3 film. These three-dimensional porous structures (SS-CNT meshes) were found to be superhydrophobic and superoleophilic. Water advancing contact angles of 145–150° were determined for these SS-CNT meshes in air and oil (gasoline, isooctane). Oil, on the other hand, completely wet the SS-CNT meshes. This combined superhydrophobic and superoleophilic property repelled water while allowed the permeation of oil. Filtration tests demonstrated efficiencies better than 80% of these SS-CNT meshes as the filtration membranes of the water-in-oil emulsions. We have conducted quantitative analysis on the diameters of the oil droplets in both the feed emulsion and the filtrate. Then, we have evaluated the issue of water blockage and possible way to improve the filtration efficiency. Finally, the filtration and blockage mechanisms are proposed.

A Good Solution for Household Based on Fast Waste Water Blockage Detection

Problem statement: The waste pipes from the wash basin are always flow in with several waste form kitchen preparation. Due to time consideration the pipe may comes through blockage and need blockage maintenance. Approach: This study presented an invention for early warning blockage detection for a kitchen waste water drain pipe. The waste water pipe some be connected through vertical pipe runs which are usually embedded in the wall. The Fast Waste Water Blockage Detection (FWABET) is to create early detection of a blocked waste water level at kitchen appliances means for quick action knowing fluid flow passing through detector and indicates sign and alarm. Results: User society and country will be benefited from FWABET such as restaurants, slaughters house, hotels, hospitals, building developers and plumbing contractors. It is the first invention in Malaysia and can be adapt as a part of building services requirements. Conclusion: It is concluded that by apply the FWABET’s, it may reduce the costs and time of blockage waste water blockage drainage maintenance operations.

Phase-Behavior Study of Hydrocarbon/Water/Methanol Mixtures at Reservoir Conditions

Summary This paper presents a study of gas/condensate hydrocarbon mixtures and the effect of water, methanol, and isopropanol on their phase behavior. Only sparse data are available on the phase behavior of hydrocarbon/water/methanol mixtures at the high temperatures typical of these reservoirs. Such data are needed for compositional reservoir simulations of well treatments to optimize the performance of solvent treatments of blocked wells. Constant-composition expansion (CCE) experiments were performed to measure the phase behavior of hydrocarbon/water/methanol mixtures up to 300°F. The effects of temperature, pressure, and water and methanol concentration on the phase behavior were measured. The Peng-Robinson equation of state (EOS) was used to model hydrocarbon/water/methanol mixtures. The binary interaction parameters were tuned to fit the data and were found to show a linear variation with temperature. The binary interaction parameters and temperature-dependent volume-shift parameters are the key parameters to model these complex polar mixtures. Both the classical van der Waals and the Huron-Vidal (Huron and Vidal 1979) mixing rules were used and were found to give good agreement with the data. Phase-behavior experiments performed on hydrocarbon/water/isopropanol mixtures showed that isopropanol decreases the aqueous-phase volume fraction and increases the liquid-hydrocarbon-phase volume fraction compared with the analogous hydrocarbon/water/methanol mixtures. These data are needed to predict the conditions under which methanol/isopropanol treatments can be applied successfully in gas wells to remove water and condensate blockage.

Effect of Particle Size and Soil Compaction on Gas Transport Parameters in Variably Saturated, Sandy Soils

The soil gas diffusion coefficient (Dp) and air permeability (ka) and their dependency on soil air content (ε) control gas diffusion and advection in soils. This study investigated the effects of average particle size (D50) and dry bulk density (ρb) on Dp and ka for six sandy soils under variably saturated conditions. Data showed that particle size markedly affects the effective diameter of the drained pores active in leading gas through the sample at −100 cm H2O of soil water matric potential (calculated from Dp and ka) as well as the average pore diameter at half saturation (calculated from the water retention curve), both exhibiting similar and exponential relationships with D50 Under variably saturated conditions, higher Dp and ka in coarser sand (larger D50) were observed due to rapid gas diffusion and advection through the less tortuous large‐pore networks. In addition, soil compaction (larger ρb) simultaneously caused reduced water blockage effects and a reduction of large‐pore space, resulting in higher Dp(ε) but lower ka(ε). Two recent models for Dp(ε) and ka(ε) were evaluated: the water‐induced linear reduction (WLR) model for Dp, and the reference‐point power law (RPL) model for ka, with reference point ka set at −100 cm H2O. The performance of both models for the sandy soils (particle size range 0.02–0.9 mm) was improved if the pore connectivity–tortuosity factor and water blockage factors were assumed to be functions of D50 and ρb Water blockage factors, N for the WLR Dp(ε) model and M for the RPL ka(ε) model, showed a strong nonlinear relationship (R2 = 0.95) that seems promising for predicting Dp(ε) from the more easily measureable ka(ε).