Change In Effective Permeability Research Articles

Effective permeability changes during hydrate production

The effective permeability impacted hydrate production severely. But its changes during hydrate production are studied few, due to no stable pressure and temperature for permeability measurement. Herein, this condition was achieved by the intermittent depressurization. The effective permeability of hydrate-bearing samples was measured. The feasibility of this method was analyzed by hydrate dissociation and saturation. Afterwards, the measured and predicted effective permeability were compared and further analyzed from hydrate distribution, preferential flow path, and fresh hydrates. The results showed that hydrate dissociation of 1.24%–2.22% did not impact measurements. Hydrate distribution, preferential flow path, and fresh hydrates were found to have a larger effect on the random changes of the effective permeability during hydrate production in comparison of hydrate saturation and pore habits. The stronger heterogeneity of hydrate distribution caused the greater randomness that the effective permeability difference was 0.346 D-0.4 D at the close hydrate saturations. Under this situation, the fixed preferential flow path was possible to form and stabilized effective permeability at 0.563 D-0.569 D. In the sample with a weaker heterogeneous hydrate distribution, the more apparent randomness was increased by fresh hydrate saturation of 1.66%–5.08%. This work may be beneficial to understand gas-water flow capacity in real settings.

Effect of hydrate distribution on effective permeability of hydrate-bearing sediments

Hydrate distribution influences the gas-water flow capacity and thus hydrate production in the hydrate-bearing sediments. The effective permeability is a key parameter to evaluate hydrate production capacity. However, few laboratory studies are focused on the effect of hydrate distribution on the effective permeability in the hydrate-bearing sediments. Thus, the water-phase effective permeability of nine hydrate-bearing samples prepared in a large-scaled pressure vessel under the excess-water setting was measured. The changes of pressure drop, temperature, and the electrical resistance during the measurements were analyzed. The measured and predicted effective permeability were compared. Afterwards, the heterogeneity of hydrate distribution was represented by the net increase of the electrical resistance (NIR) and its variation coefficient (VNIR) to define its effect on the effective permeability. The results showed that water flow channel change for the fresh hydrates caused the averaged pressure drop difference of 39.73 kPa in the repeated measurements. Hydrate dissociation for water flow impacted permeability measurements little. Moreover, the heterogeneous hydrate distribution, instead of hydrate saturation and pore habits, was found to cause a large deviation between the measured and predicted effective permeability. In the sample with hydrate saturation of 3.92%–8.01%, hydrates were mainly distributed at some local position. The corresponding effective permeability had a larger randomness because of the severer heterogeneity. Besides, as hydrate saturation was less than 19.46%, heterogeneity degree changes were opposite to the effective permeability changes. Instead, hydrate distribution impacted the effective permeability little. This work is beneficial to understand the physical properties of the hydrate-bearing sediments.

Compression-induced dynamic change in effective permeability of hydrate-bearing sediments during hydrate dissociation by depressurization

Methane hydrate, a form of clean energy also called flammable ice, has drawn global interest as an alternative energy resource of traditional fossil energy. The effective permeability of formation is a key factor to determine the gas production rate, which is controlled by not only hydrate saturation but also the porosity changes of the host sediment. A decrease in pore pressure leads to an increase in the effective stress and the collapse of the bonded structure made by the hydrate resulting in the volume contraction and permeability reduction. On the other hand, the pore pressure drop induces hydrate dissociation, which increases the porosity and permeability. In this study, we conducted a series of experiments to measure the effective permeability of hydrate-bearing sediments with different hydrate saturation. The experiment results show that the effective permeability of specimens is 30 Darcy without hydrate under 1 MPa effective stress. It decreases with the increasing of hydrate saturation from 0 to 0.396 or effective stress from 1 to 9 MPa. The relationship between void ratio, hydrate saturation and effective permeability is derived. Combining the confined compaction analysis, we proposed a simple formula to estimate the change in effective permeability of hydrate-bearing sediments during hydrate dissociation by depressurization. The formula is embedded the thermal-hydraulic model to predict the gas production under the effective stress. The amount of gas production reaches the maximum value of 1.45 × 10−3 m3 at 50 min and 4.82 × 10−3 m3 at 95 min with soil compaction from experiment, the fitting degree of numerical simulation are 0.997 and 0.998 when hydrate saturation equals 10% and 30%, respectively. This study could evaluate the compression-induced dynamic change in effective permeability and predict the gas/water production under the effect of effective stress during hydrate dissociation by depressurization.

A fully coupled thermo-hydro-mechanical model with ice-water phase change for liquid nitrogen injection simulation

Cryogenic liquid nitrogen (LN2) fracturing or treatment in nearly impermeable reservoirs has attracted widespread attention due to its strong thermal shock and frost heave effects. We derive a fully coupled thermo-hydro-mechanical (THM) model considering the ice-water phase change to simulate the process of LN2 injection into shale gas reservoirs. The novel model accommodates the following dominant phenomena: (1) LN2 driving unfrozen water flow in porous media; (2) pore water freezing into ice below the freezing temperature; (3) fully coupled thermo-poroelastic effect incorporating frost heave pressure; (4) effective fluid permeability associated with unfrozen water content and phase saturation; (5) temperature and pressure-dependent fluid thermodynamic properties. The proposed model is verified against a classical thermo-poroelastic model and a coupled THM model for freezing rocks. Simulation results show that LN2 injection into water-bearing shale reservoirs will result in ultra-high injection pressure. A high injection rate is beneficial for the fracture initiation, but it is detrimental from phase solidification. Reducing the injection rate is not conducive to the subsequent penetration of LN2 into the reservoir. The evolution of effective permeability, as well as phase saturation, can be reasonably captured during LN2 injection. The comparative advantages between fluid infiltration and temperature propagation are different at high and low injection rates, which leads to significant differences in phase saturation and effective permeability changes. The multiple mechanisms, including pore pressure, frost heave pressure, and thermal stress that induce rock damage, can be efficiently revealed. At relatively low temperatures, the deformation of the reservoir at high and low injection rates is dominated by high-pressure expansion and cryogenic contraction, respectively. The research results can provide some insights for cryogenic non-aqueous fracturing.

Enhanced oral bioavailability of linagliptin by the influence of gallic acid and ellagic acid in male Wistar albino rats: involvement of p-glycoprotein inhibition.

Background Linagliptin is an antidiabetic drug used for the treatment of type-2 diabetes. The oral bioavailability of linagliptin is low (29.5%) due to its first pass metabolism in the intestine and liver. Gallic acid and ellagic acid are natural polyphenols which are widely distributed in fruits and medicinal plants. Gallic acid and ellagic acid have been reported to inhibit p-glycoprotein (p-gp) and enhance the bioavailability of p-gp substrate drugs. Hence, the purpose of the study was to evaluate the effect of gallic acid and ellagic acid on intestinal transport and bioavailability of linagliptin, a p-gp substrate in diabetic rats. Methods The intestinal transport of linagliptin was assessed by conducting an in situ single-pass intestinal perfusion study. The oral pharmacokinetics was evaluated by conducting oral bioavailability study in diabetic rats. Results After pretreatment with gallic acid and ellagic acid, no significant change in effective permeability of linagliptin was observed at the ileum part of the rat intestine. A significant improvement in the peak serum concentration (Cmax) and area under the serum concentration time profile (AUC), AUMC, AUCtotal and decrease in clearance were observed in rats pretreated with gallic acid and ellagic acid. Conclusions This study demonstrates that gallic acid and ellagic acids increase the bioavailability of oral linagliptin in rats due to the inhibition of p-gp. These animal data need to be confirmed in a clinical setting to determine whether linagliptin dosing should be adjusted when given concomitantly with these phytochemicals or gallic acid/ellagic acid-containing dietary supplements.

Discontinuities in effective permeability due to fracture percolation

Motivated by a triaxial coreflood experiment with a sample of Utica shale where an abrupt jump in permeability was observed, possibly due to the creation of a percolating fracture network through the sample, we perform numerical simulations based on the experiment to characterize how the effective permeability of otherwise low-permeability porous media depends on fracture formation, connectivity, and the contrast between the fracture and matrix permeabilities. While a change in effective permeability due to fracture formation is expected, the dependence of its magnitude upon the contrast between the matrix permeability and fracture permeability and the fracture network structure is poorly characterized. We use two different high-fidelity fracture network models to characterize how effective permeability changes as percolation occurs. The first is a dynamic two-dimensional fracture propagation model designed to mimic the laboratory settings of the experiment. The second is a static three-dimensional discrete fracture network (DFN) model, whose fracture and network statistics are based on the fractured sample of Utica shale. Once the network connects the inflow and outflow boundaries, the effective permeability increases non-linearly with network density. In most networks considered, a jump in the effective permeability was observed when the embedded fracture network percolated. We characterize how the magnitude of the jump, should it occur, depends on the contrast between the fracture and matrix permeabilities. For small contrasts between the matrix and fracture permeabilities the change is insignificant. However, for larger contrasts, there is a substantial jump whose magnitude depends non-linearly on the difference between matrix and fracture permeabilities. A power-law relationship between the size of the jump and the difference between the matrix and fracture permeabilities is observed. The presented results underscore the importance of fracture network topology on the upscaled properties of the porous medium in which it is embedded.

Water Blocks in Tight Formations: The Role of Matrix/Fracture Interaction in Hydrocarbon-Permeability Reduction and Its Implications in the Use of Enhanced Oil Recovery Techniques

Summary Hydraulic fracturing is used to obtain economical rates from tight and unconventional formations by increasing the surface area of the reservoir within the flowing distance to a high-conductivity pathway. However, a significant fraction of the fracturing fluid is never recovered, and thus may reduce the hydrocarbon permeability near the fracture. Here, we experimentally mimic the water-invasion process during fracturing, and measure the effective permeability changes in a low-permeability core. Measurements of water flowback and effective permeability as a function of interfacial tension (IFT), flow rate, and shut-in time suggest that water is being held at the fracture face because of the capillary discontinuity (i.e., when the water leaves the matrix and enters a space with minimal capillary pressure). This effect arises from the capillary interaction between the matrix and the fracture, and is akin to the capillary end effect in coreflood experiments. The results show that this effect, although only a laboratory experimental artifact for conventional reservoirs, can be a significant source of effective hydrocarbon-permeability reduction by fracturing-fluid invasion into the formation in unconventional and tight reservoirs.

Rate-transient analysis of an undersaturated CBM reservoir in Australia: Accounting for effective permeability changes above and below desorption pressure

Rate-transient analysis (RTA) of coalbed methane (CBM) wells is an on-going reservoir engineering challenge because of the dynamic nature of coal reservoirs. During their lifetime, producing CBM wells completed in initially undersaturated reservoirs (flowing above desorption pressure) experience a change from single-phase water to two-phase (gas + water) production as desorption pressure is reached, and the production characteristics of these wells are affected by a multitude of dynamic CBM reservoir properties. Amongst the most important dynamic properties influencing production is absolute permeability of the natural fracture (cleat) network.Prolific coalbed methane wells in the Fairview Field, central Queensland, eastern Australia, exhibit stress-dependent permeability changes during early dewatering, followed by strong desorption-dependent permeability effects below desorption pressure. These effects, combined with the switch from single-phase to two-phase flow at desorption pressure, make quantitative production data analysis for reservoir properties (e.g. permeability and original gas-in-place) particularly challenging.In this study, a combination of flowing material balance (FMB) equations for gas and water, modified for dynamic changes in effective permeability, and analytical simulation is used to analyze a Fairview Field CBM well completed in coals of the Bandanna Formation using the cavitation technique. The subject well exhibits strong permeability changes for the first several years after desorption pressure is reached, after which permeability changes appear to occur more gradually. Single-phase water production data above desorption pressure is analyzed using an FMB method modified for stress-dependent permeability; gas production data below desorption pressure is analyzed using an FMB method modified to account for relative permeability and desorption-dependent permeability. Because of uncertainty in below-desorption pressure FMB model inputs, the FMB equations and analytical simulation are linked. This approach allows for a consistent, if not unique, analysis.The RTA approach outlined herein provides a reasonable starting point for more rigorous numerical simulation, which in turn can be used for reserves forecasting and development planning. Because of the multitude of reservoir properties (several of the key properties being dynamic) affecting the production characteristics of CBM wells such as those in the Fairview Field, it is important to advance RTA methods to constrain numerical model inputs.

Enhanced oral bioavailability of metoprolol with gallic acid and ellagic acid in male Wistar rats: involvement of CYP2D6 inhibition.

Cytochrome P450-2D6 (CYP2D6), a member of the CYP450 mixed function oxidase system, is an important CYP isoform with regard to herbal-drug interactions and is responsible for the metabolism of nearly 25% of drugs. Until now, studies on the effects of various phytochemicals on CYP2D6 activity in vivo have been very rare. Gallic acid and ellagic acid are natural polyphenols which are widely distributed in fruits and medicinal plants. In the present study, the effects of gallic acid and ellagic acid pretreatment on intestinal transport and oral bioavailability of metoprolol were investigated. The intestinal transport of metoprolol was assessed by conducting an in situ single pass intestinal perfusion (SPIP) study. The bioavailability study was conducted to evaluate the pharmacokinetic parameters of orally administered metoprolol in rats. After pretreatment with gallic acid and ellagic acid, no significant change in effective permeability of metoprolol was observed at the ileum part of rat intestine. A significant improvement in the peak plasma concentration (Cmax) and area under the serum concentration-time profile (AUC) and decrease in clearance were observed in rats pretreated with gallic acid and ellagic acid. Gallic acid and ellagic acid significantly enhanced the oral bioavailability of metoprolol by inhibiting CYP2D6-mediated metabolism in the rat liver. Hence, adverse herbal-drug interactions may result with concomitant ingestion of gallic acid and ellagic acid supplements and drugs that are CYP2D6 substrates. The clinical assessment of these interactions should be further investigated in human volunteers.

Fracture opening or self-sealing: Critical residence time as a unifying parameter for cement–CO2–brine interactions

Understanding long-term property evolution of cement fractures is essential for assessing well integrity during geological carbon sequestration (GCS). Cement fractures represent preferential leakage pathways in abandoned wells upon exposure to CO2-rich fluid. Contrasting self-sealing and fracture opening behavior have been observed while a unifying framework is still missing. Here we developed a process-based reactive transport model that explicitly simulates flow and multi-component reactive transport in fractured cement by reproducing experimental observation of sharp flow rate reduction during exposure to carbonated water. The simulation shows similar reaction network as in diffusion-controlled systems without flow. That is, the CO2-rich water accelerates the portlandite dissolution, releasing calcium that further reacted with carbonate to form calcite. The calibrated model was used for CO2-flooding numerical experiments in 250 cement fractures with varying initial hydraulic aperture (b) and residence time (τ) defined as the ratio of fracture volume over flow rate. A long τ leads to slow replenishment of carbonated water, calcite precipitation, and self-sealing. The opposite occurs when τ is small with short fracture and fast flow rates. Simulation results indicate a critical residence time τc – the minimum τ required for self-sealing – divides the conditions that trigger the opening and self-sealing behavior. The τc value depends on the initial aperture size through τc=9.8×10−4×b2+0.254×b. Among the 250 numerical experiments, significant changes in effective permeability – self-healing or opening – typically occur within hours to a day, thus providing supporting argument for the extrapolation of short-term laboratory observation (hours to months) to long-term prediction at relevant GCS time scales (years to hundreds of years).

Ultrahigh-Sensitivity Mediator-Free Biosensor Based on a Microfabricated Microwave Resonator for the Detection of Micromolar Glucose Concentrations

This paper presents a miniaturized microwave-resonator-based ultrahigh sensitivity mediator-free biosensor for determining the level of glucose in deionized-water glucose solutions and human sera using integrated passive device technology on a gallium–arsenide substrate. The proposed glucose biosensor, which consists of cross-coupled stepped-impedance resonators (SIRs), strongly concentrates electromagnetic energy between the coupling regions at a central frequency of 6.53 GHz. The changes in effective permeability $(\mu_{\rm eff})$ and permittivity $(\varepsilon_{\rm eff})$ , which correlate with the variations in the glucose concentration, effectively change the equivalent series inductance and shunt capacitance of the biosensor resonator. This concept was used for the first time to develop an ultrahigh-sensitivity biosensor based on a low $-$ Q microwave resonator. The length of each SIR was meandered width wise, and a meandered-line stub-load was embedded inside the SIR to utilize the equivalent high series inductance and shunt capacitance, respectively. The newly designed present biosensor, which linearly detected glucose level within a wide range of concentration, exhibited an ultrahigh sensitivity (978.7 ${\hbox{MHz/mgmL}}^{-1}$ for sera) at least 4.918 times higher than that of previously reported microwave-resonator-based glucose biosensors, a lower detection limit of 0.01928 $\mu{\hbox{M}}$ , and a rapid detection time of less than 5 s. Supported by S-parameter-based effective-medium-parameter analysis and a sensitivity enhancement principle, the detection accuracy of the proposed biosensor was increased using its glucose-level-dependent spreading of propagation constant $(\gamma)$ and self-resonances of impedance $(Z)$ .

Design and Full Characterization of Planar Active Magnetic RF Metamaterials

Applications of metamaterials have been limited by parasitic resistive losses. We present the design and measurement of split ring resonators with embedded active field effect transistor circuits comprising a magnetic metamaterial. We show that the imaginary part of the effective permeability changes sign within the bandwidth of the negative differential resistance region, creating a stable gain medium. We present experimental reflection and transmission measurements showing a sign change in the permeability loss term and two applications of such a metamaterial. use as a mu-negative near field parasitic element for small magnetic antennas and as an amplifying material in free space. We show the active metamaterial can provide property enhancement compared with related passive structures in both applications, providing a path to overcoming parasitic loss in previously demonstrated metamaterial structures.

Magnetic resonance measurements of flow-path enhancement during supercritical CO2 injection in sandstone and carbonate rock cores

Sandstone and carbonate core samples were challenged with a two-phase supercritical CO2 and brine mixture to investigate the effects of chemical processes on the physical properties of these rocks during injection of CO2. The experiments were monitored in real-time for pressure, temperature, and volumetric rate discharge. Pore geometry and connectivity were characterized before and after each experimental challenge using magnetic resonance (MR) imaging and two-dimensional MR relaxation correlations. Quartz arenite sandstone cores were largely unaffected by the challenge with no measurable change in effective permeability at moderate and high temperatures (~50 °C and ~95 °C) or brine concentrations (~1 g/L and ~10 g/L). In contrast, a carbonate core sample showed evidence of significant dissolution leading to a six-fold increase in effective permeability. MR images and relaxation measurements revealed a marked increase in the volume and connectivity of pre-existing pore networks in the carbonate core. We infer that the increase in permeability in the carbonate core was enhanced by focused dissolution in the existing pore and fracture networks that enhanced fast-flow paths through the core.

Reactive Transport Modeling of Interactions between Acid Gas (CO2 + H2S) and Pozzolan-Amended Wellbore Cement under Geologic Carbon Sequestration Conditions

The implementation of acid gas cosequestration requires investigation of the potential for acid gas leakage along existing wellbores at sequestration sites. In this study, the interaction between pozzolan-amended wellbore cement (35 vol % pozzolan/65 vol % cement, hereafter referred to as 35:65 sample) and acid gas (e.g., a mixture of CO2 and H2S) was simulated using the reactive transport code CrunchFlow. The model was applied to describe, interpret, and extrapolate scanning electron microscopy-backscattered electron (SEM-BSE) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) results on pozzolan-amended cement samples exposed to a 1 wt % NaCl solution saturated with an acid gas mixture of 21 mol % H2S and 79 mol % CO2 under the temperature of 50 °C and pressure of 150 bar. Simulation outputs included calcite volume percentage, total Ca and S weight percentages in the solid phase, porosity, and effective permeability from the surface to the interior of pozzolan-amended wellbore cement. The model reproduced the observed calcite zone formed in the brine-cement interface region of the sample after 2.5 days of exposure. The model also predicted that the calcite layer became dense (calcite vol % in the layer reached 55%) after 90 days of exposure, consistent with the experimental observation. C–S–H was the primary Ca2+ source to form the calcite layer, followed by C3S and Ca(OH)2. The main observed products of reaction between the 35:65 sample and H2S were pyrite and ettringite. Pyrite was primarily formed within 0.5 mm from the brine-cement interface; ettringite mainly formed within 1 mm from the interface. The model simulated these reactions that only the interface region (up to 2 mm distance from the surface) of the 35:65 sample became porous after 30 years of exposure. However, this narrow porous region could still serve as a migration pathway for acid gas, which was indicated by the increase in effective parallel permeability values determined from the simulation results. Those results show consistency with results of neat cement samples exposed under similar conditions. An increase in H2S content (in the range of 0 mol % to 40 mol %) results in more dissolution of Ca-bearing minerals in cement and more precipitation of calcite. Overall, this study indicates that an increase of porosity and permeability of pozzolan-amended wellbore cement at the cement interface with brine saturated with CO2 and H2S can cause significant changes in effective permeability of the cement.

Rate-transient analysis of 2-phase (gas + water) CBM wells

In recent work, the authors (Clarkson et al., 2008, 2007; Jordan et al., 2006) demonstrated how modern production data analysis (PDA) methods, such as flowing material balance (FMB) and production type-curves, may be adapted to account for the unique reservoir characteristics of coalbed methane (CBM) reservoirs through the appropriate use of material balance and time transforms. Reservoir characteristics related to storage and fluid flow that were addressed included: adsorbed and free-gas storage; single-phase flow of water above desorption pressure (undersaturated coals); 2-phase flow of gas and water below desorption pressure (saturated coals); non-static absolute permeability during depletion; and multi-layer behavior. Example (field) applications of the new PDA methods were limited to vertical wells that were either openhole completed, or slightly stimulated with hydraulic fracturing methods.In this work, new workflows and analytical approaches are provided for analyzing vertical, hydraulically-fractured and horizontal CBM wells. The analysis and methodology for 2-phase flow reservoirs is complex, requiring modifications to account for desorption and changes in effective permeability. The proposed workflow for 2-phase CBM wells includes the transformation of the well production and flowing pressure data into dimensionless type-curve and straight line (ex. flowing material balance) coordinates using certain outputs (krg, pR) from the simulator used in turn to history-match the production data. Transient straight-line (pressure-transient analysis analog) techniques are applied for the first time to 2-phase CBM well production data. The type-curve and straight-line matches to actual production data are then used to retrieve reservoir properties (e.g. absolute permeability) and stimulation conditions (e.g. skin), which in turn are compared to reservoir simulation input as a consistency check. Both simulated and field cases are analyzed to illustrate the new procedures and analytical techniques.The primary contribution of the current work is the application of modern production analysis methods to 2-phase CBM reservoirs. These methods have been modified for CBM reservoir behavior and combined with analytical (or numerical) modeling to extract quantitative reservoir information from CBM reservoirs which exhibit a wide-range in production characteristics, and are completed in a variety of styles. The modifications proposed in this work to enable the use of single-phase flow techniques must be regarded as practical approximations. The methods rely heavily on late-time data because of the poor quality of water production and flowing pressure data that typically exists. The methods are expected to be used as a pre-cursor to or in parallel with field reservoir simulation, to assist with CBM development decisions.

Production Data Analysis of Coalbed-Methane Wells

SummaryRecent advances in production data analysis (PDA) techniques have greatly assisted engineers in extracting meaningful reservoir and stimulation information from well-production and flowing-pressure data. Application of these techniques to coalbed-methane (CBM) reservoirs requires the unique coal storage and transport properties to be accounted for. In recent work, the authors [ex. Clarkson et al. (2007a) and Jordan et al. (2006)] and others [ex. Gerami et al. (2007)] have demonstrated how new techniques such as the flowing material balance (FMB) and production type curves may be adapted to account for CBM storage mechanisms (i.e., adsorption), but, to date, the focus has been on relatively simple CBM reservoir behavior such as single-phase (gas) reservoirs with static effective permeability.The major contribution of the current work is the adaptation of modern PDA techniques (by use of modified material balance time/pseudotime and pseudopressure definitions) to analyze producing wells completed in CBM reservoirs exhibiting several possible flow characteristics: single-phase flow of gas in dry CBM reservoirs, single-phase flow of water (in undersaturated reservoirs), and two-phase (gas and water) flow (in saturated reservoirs). The latter reservoir type commonly exhibits effective permeability changes during depletion (because of relative and/or absolute permeability changes) and changing gas composition caused by relative adsorption effects, both of which have been accounted for in the current work. Specifically, the FMB technique is modified to include several complex CBM reservoir characteristics, and production type curves are applied to some scenarios. Although dry-CBM-well analysis was covered previously [ex. Clarkson et al. (2007a)], we will also discuss FMB development in these reservoirs for completeness.Several synthetic and field examples are given to demonstrate how FMB, type-curve analysis, and analytical simulation can be used in parallel to provide a particularly useful data-analysis toolset and workflow. These techniques were used successfully to extract quantitative reservoir information from single- and two-phase CBM-simulated and field-production pressure data. The PDA techniques developed for two-phase CBM require further evaluation, however.

Microstructural change upon annealing FeZrB alloys with different boron contents

To clarify the reason for the change in effective permeability with increasing boron content before and after crystallization, we investigated the microstructure of Fe 93− x Zr 7B x ( x = 2, 4, 6, 8) alloys annealed for 1 h in the temperature range 350–600 °C, using transmission electron microscope. In low boron alloys ( x = 2, 4), the amorphous phase showed indications of a typical interconnected pattern, exhibiting a spinodal-type decomposition. After crystallization, it changed to a mainly single b.c.c. structure with a homogeneous grain size distribution of about 20 nm, and the effective permeability had a high value of around 19000. In high boron alloys ( x = 6, 8), the microstructure after crystallization showed an inhomogeneous grain size distribution, and a low effective permeability. These results may be the result of the different phase separation pattern in the amorphous state.

Patterns of Effective Permeability of Leaf Cuticles to Acids.

Plants in the field are frequently exposed to anthropogenic acid precipitation with pH values of 4 and below. For the acid to directly affect leaf tissues, it must pass through the leaf cuticle, but little is known about the permeability of cuticles to protons, or about the effect of different anions on this permeability. We investigated the movement of protons through isolated astomatous leaf cuticles of grapefruit (Citrus X paradisi Macfady.), rough lemon (Citrus limon [L.] Burm. fils cv Ponderosa), and pear (Pyrus communis L.) using hydrochloric, sulfuric, and nitric acids. Cuticles were enzymically isolated from leaves and placed in a diffusion apparatus with pH 4 acid on the morphological outer surface of the cuticle and degassed distilled water on the inner surface. Changes in pH of the solution on the inner surface were used to determine rates of effective permeability of the cuticles to the protons of these acids. Most cuticles exhibited an initial low permeability, lasting hours to days, then after a short transition displayed a significantly higher permeability, which persisted until equilibrium was approached. The change in effective permeability appears to be reversible. Effective permeabilities were higher for sulfuric acid than for the others. A model of the movement of protons through the cuticle is presented, proposing that dissociated acid groups in channels within the cutin are first protonated by the acid, accounting for the low initial effective permeability; then protons pass freely through the channels, resulting in a higher effective permeability.

磁気ヘッド用磁性材料としての6%Vパーマロイの磁気的および機械的性質

The suitability of a 6%V permalloy for magnetic head materials used in a digital tape recording equipment of an electronic computer was investigated in comparison with high permeability permalloys commonly used, e.g., 4%Mo-5%Cu permalloy and 4%Mo permalloy.Measurements of dc magnetic properties, ac magnetic permeabilities at H=0.4 A/m (frequency range 1-300 kHz) and its stress-sensitivity, e.g., the change in effective permeability caused by application of the compressive stress 1 MPa perpendicular to the sheet surfaces, were carried out for these permalloys 0.1, 0.05 and 0.025 mm in sheet thickness, subjected to various heat treatments. Wear tests were carried out by rubbing the test specimens of these permalloys against a γ-Fe2O3 magnetic tape at the running speed of 3 m/s. The saturation magnetostriction, the electrical resistivity and the mechanical hardness were also measured.Results obtained are summarized as follows:(1) The V permalloy examined has a better ac magnetic permeability at a high frequency range as well as a better dc magnetic properties than the compared alloys, and in particular its magnetic properties at low annealing temperatures below 1173 K are characteristically superior to those of the familiar high permeability permalloys.(2) The stress-sensitivity in the magnetic properties of the V permalloy is much smaller than that of the compared alloys at any examined annealing temperatures and exciting frequencies, so that values of permeabilities under the compressive stress remain very high.(3) Thin oxide films are formed on the contact surface of the V permalloy specimen during rubbing against the γ-Fe2O3 magnetic tape at high speed, and this formation brings about the wear-resistance property superior to that of the compared alloys.(4) The V permalloy has the same degree of mechanical hardness as other technical soft permalloys, and hence has a good workability.(5) From these results, the 6%V permalloy is an excellent and favourable alloy as a magnetic head material.

Pressure Transient Analysis of a Vertically Fractured Well Produced by Solution Gas Drive

Abstract Pressure transient data were investigated in a homogeneous and uniform reservoir containing oil and gas and producing at a constant surface oil rate by solution gas drive by means of a vertically fractured well. The well is assumed to be located at the center of a closed-square drainage area. Gravity effects were not included. To my best knowledge, this is the first study ort the pressure transient behavior of a vertically fractured well producing by solution gas drive. producing by solution gas drive. A recent paper presented a new method for analyzing pressure data in wells producing by solution gas drive. The method incorporates changes in effective permeability and fluid properties (formation volume factor, viscosity, and gas solubility) with pressure by means of a pseudo-pressure function however, it dealt exclusively pseudo-pressure function however, it dealt exclusively with plane radial flow. This paper presents the application of that new technique to vertically fractured wells. Dimensionless groups are used throughout to extend the results to other situations having different permeabilities, spacing, reservoir thickness, porosity, etc, provided the PVT relations and relative-permeability characteristics are identical to those used in this study. The pseudo-pressure function concept used to analyze pseudo-pressure function concept used to analyze drawdown and buildup behavior extends the applicability of the results to a wide range of PVT relations and relative-permeability characteristics. Introduction In recent years, the analysis of pressure data of fractured wells has received considerable attention. However, most of this work is related to single-phase flow. An examination of the literature indicated that no rigorous study has been made regarding the pressure behavior of a vertically fractured well producing by solution gas drive. The first objective of this paper is to discuss the transient floe, behavior of the system described above. The second objective is to demonstrate the applicability of a recent technique for determining absolute formation permeability when two phases (oil and gas) are flowing simultaneously. This technique is based on using a pseudo-pressure function that rigorously incorporates changes in permeability with saturation and fluid properties permeability with saturation and fluid properties with pressure. It will be shown that, by using the procedure suggested here, better estimates of procedure suggested here, better estimates of fracture length also can be obtained. LITERATURE REVIEW General equations of motion describing multiphase flow in porous media are well known and will not be discussed here. A summary of the work in this area as if pertains to well test analysis is presented in Ref. 5. This section briefly reviews only the computation of an integral (henceforth called the pseudo-pressure function), which was used in Ref. pseudo-pressure function), which was used in Ref. 5 to analyze drawdown and buildup. In a recent paper, Fetkovich suggested that if the pseudo-pressure function, m (p), given by: (1) is used, then transient, pseudo-steady-state and steady-state multiphase flow through porous media may be described by simple expressions similar to that for the flow of a slightly compressible fluid. For example, Fetkovich suggested that for transient radial flow one can express the flow rate as (2) where to is the dimensionless time given by (3) In Eq. 2, s' represents the skin effect that, in general, includes the effects of damage in the vicinity of the wellbore, as well as a skin effect caused by the development of a gas saturation. SPEJ P. 369