Increase In Differential Pressure Research Articles

Pore Pressure Disturbance Induced by Multistage Hydraulic Fracturing in Shale Gas: Modelling and Field Application

Currently, there is no proper method to predict the pore pressure disturbance caused by multistage fracturing in shale gas, which has challenged drilling engineering in practice, especially for the infilling well drilling within/near the fractured zones. A numerical modelling method of pore pressure redistribution around the multistage fractured horizontal wellbore was put forward based on the theory of fluid transportation in porous media. The fracture network of each stage was represented by an elliptical zone with high permeability. Five stages of fracturing were modelled simultaneously to consider the interactions among fractures. The effects of formation permeability, fracturing fluid viscosity, and pressure within the fractures on the pore pressure disturbance were numerically investigated. Modelling results indicated that the pore pressure disturbance zone expands as the permeability and/or the differential pressure increases, while it decreases when the viscosity of the fracturing fluid increases. The pore pressure disturbance level becomes weaker from the fracture tip to the far field along the main-fracture propagation direction. The pore pressure disturbance contours obviously have larger slopes with the variation of permeability than those of the differential pressure. The distances between the pore pressure disturbance contours are smaller at lower permeability and higher viscosity. The modelling results of the updated pore pressure distribution are of great importance for safe drilling. A case study of three wells within one platform showed that the modelling method could provide a reliable estimation of the pore pressure disturbance area caused by multistage fracturing.

An improved visual investigation on gas–water flow characteristics and trapped gas formation mechanism of fracture–cavity carbonate gas reservoir

Water encroachment is a serious problem for developing an edge and bottom water reservoirs. The fracture–cavity gas reservoir has various reservoir media and strong heterogeneity, leading to the complex gas–water flow mechanism and trapped gas formation during water encroachment. Presently, no systematic study on the gas–water flow characteristics and trapped gas formation mechanism exists, especially through visual experiment. In this paper, the creation and testing of three types of visualization micromodels were described based on the CT scan images and microelectronic photolithography techniques. Subsequently, a 2D visual experiment was conducted initially to investigate the gas–water flow characteristics and the trapped gas formation mechanism intuitively. Then, ImageJ gray analysis method was utilized to study the distribution of trapped gas, saturation, and gas recovery quantitatively. Finally, several development suggestions were presented for different types of reservoirs based on the quantitative characterization results. Experimental results showed that the flow characteristics of fracture-, cavity-, and fracture–cavity-type micromodels are different during water encroachment, resulting from the large difference of microstructures. The trapped gas formed at dead ends or blind corners, circumfluence, and cutoff phenomenon, can be commonly found in three types of micromodels. However, the trapped gas formed at H-shaped channels, dumbbell-shaped channels, and microfractures are specific to certain micromodels. The main factors that influence the trapped gas formation are capillary force, hydrodynamic force, Jamin effect (the additional resistance effect of the bubble when it traverses narrow pores), and pore–throat connectivity. Quantitative results reflect that approximately 76% of the trapped gas in the cavity-type micromodel is formed by circumfluence and cutoff phenomenon, whereas approximately 67% of the trapped gas in the other two micromodels is formed at network of microfractures, dead ends, and blind corners. In addition, the ultimate gas recovery of cavity-type reservoirs increases while the displacement differential pressure increases; by contrast, the ultimate gas recovery of fracture- and fracture–cavity-type micromodels increases initially and then decreases with the increase in displacement differential pressure. The visual investigation presented not only improves our intuitive understanding of the gas–water flow mechanism in fracture–cavity carbonate reservoirs but also provides a novel image analysis method for quantitative characterization of visual experiments.

Comparing Biofouling Development in Membrane Fouling Simulators and Spiral-Wound Reverse Osmosis Elements Using River Water and Municipal Wastewater

Membrane fouling simulators (MFS) are flat cell units to simulate the biofouling development of spiral-wound reverse osmosis (RO) elements. MFS units and two RO testing systems were operated in parallel, using different water types. Differences in differential pressure increase and fouling distribution between the two pilot plants were evaluated. Several RO elements and MFS units were operated with the same conditions to assess the reliability of the testing systems. In a second study, the performance of different feed spacer types assembled in full-scale RO elements was compared to the same feed spacer types assembled in the MFS unit. These studies showed that the relative biofouling impact in the MFS units was equivalent to the performance of the RO elements. Additionally, the results from the second study provide indications that a prototype 28 mil feed spacer (28 T1) may provide more significant additional biofouling resistance than any of the other spacers evaluated.

Validation of a new phenomenological “jump-and-channel” model for the wet pressure drop of oil mist filters

The “wet pressure drop” of oil mist filters (i.e. the increase in differential pressure of the air flow due to loading of the filter with liquid) is presented as a function of two mechanisms by which coalesced oil is transported through the filter. These mechanisms operate in separate regions of the filter and make separate (and separately measurable) contributions to the overall wet pressure drop. This new concept, which was first formulated qualitatively in a phenomenological model by Kampa et al. (2014), leads to semi-quantitative predictions regarding the dependence of pressure drop Δp and saturation S on filter operating conditions, filter properties and liquid properties. These predictions are first formulated and then validated for a range of wettable and non-wettable filter media in combination with 4 mineral oils of different viscosity. The key findings, summarized below, are consistent with the model and apply to both wettable and non-wettable media.Oil transport across media interfaces (i.e. transitions between regions of different porosity and/or wettability) was associated with a relatively sharp increase in pressure drop ∆p and oil saturation S over a very thin layer of the filter (a “∆p jump”). The magnitude of this ∆p jump was determined by the media properties. It correlated well with the respective static break-through pressures for oil or air, but did not depend on the oil viscosity and loading rate of the filter (at constant air velocity). Oil transport through channel regions of the filter (i.e. the regions connecting interfaces) was associated with a linear increase in ∆p with channel length and liquid throughput. The corresponding saturation level S was relatively flat throughout the channel region and lower than at an interface. (Both quantities are media dependent, of course.) An increase in oil viscosity μ (at constant oil throughput) led to different responses depending on filter wettability.

Experimental characterization of novel microdiffuser elements

Micropumps can play a significant role in thermal management applications, as a component of microfluidic cooling systems. For next-generation high density optical communication systems, in particular, heat flux levels are sufficiently high to require a microfluidic circuit for cooling. Valveless piezoelectrically-actuated micropumps are a particularly promising technology to be deployed for this application. These pumps exploit the asymmetric flow behaviour of microdiffusers to achieve net flow. They feature no rotating or contacting parts, which make them intrinsically reliable in comparison to micropumps with active valves. In this paper, two novel microdiffuser elements are reported and characterized. The micropumps were fabricated using a 3D Printer. Each single diffuser had a length of 1800 pm and a depth of 400 pm. An experimental characterization was conducted in which the flow rate and differential pressure were measured as a function of operating frequency. In comparison with standard diffuser, both elements showed an increase in differential pressure in the range of 40 – 280 %, but only one of the elements exhibited an improved flow rate, of about 85 %.

Quantitative evaluation of fouling resistance of PVDF/PMMA-g-PEO polymer blend membranes for membrane bioreactor

Fouling resistance of various kinds of membrane materials including blends of poly(vinylidene difluoride) (PVDF) and copolymer of methyl methacrylate (MMA) and poly(ethylene glycol) methyl ether methacrylate (PVDF/PMMA-g-PEO) was quantitatively evaluated by measuring the amount of model fouling compounds adsorbed on the surface of membrane materials using a surface plasmon resonance (SPR) sensor. The order of the amount of adsorption in the adsorption tests negatively correlated with hydrophilicities of membrane materials. PVDF/PMMA-g-PEO demonstrated superior fouling resistance comparing to pure PVDF and other materials. Pure PVDF and PVDF/PMMA-g-PEO membranes with different length of PEO side chains were fabricated in non-solvent induced phase separation (NIPS) method. Membrane structure and surface composition were analyzed with scanning electron microscopy (SEM) and X-ray photoelectoron spectroscopy (XPS) respectively. Moreover, short-term and long-term activated sludge filtration experiments were conducted. The rate of increase of differential pressure during filtration process correlated with the amount of adsorbed BSA in the adsorption tests.

Utilization of Surfactant-Stabilized Foam for Enhanced Oil Recovery by Adding Nanoparticles

Nitrogen foam flooding is a promising technique for enhanced oil recovery, but instability of the foam limits its application. In this article, partially hydrophobic modified SiO2 nanoparticles with an anionic surfactant, sodium dodecyl sulfate (SDS), were used together to increase foam stability. Micromodel flooding and sandpack flooding were adopted to assess the stability and effect on enhanced oil recovery of the SiO2 stabilized foam (SiO2/SDS foam). The experimental data showed that the foam stability was decreased with an increase in temperature, while the foam volume was increased first and then decreased. SiO2/SDS foam showed better temperature tolerance than the SDS foam (foam stabilized by SDS) due to the adsorption of nanoparticles on the surface of the bubble. Almost all of the bubbles maintained spherical or ellipsoidal shape with prolonged time due to the enhanced surface dilational viscoelasticity, which was different from that of SDS foam. According to the micromodel flooding results, SiO2/SDS foam displaced more oil than brine flooding, SDS solution flooding, or SDS foam flooding. As the foam stability was enhanced, gas mobility and channeling were controlled effectively. In addition, more oil on the pore wall and in the dead-end pores was displaced out because of the higher viscoelasticity of the SiO2/SDS foam. The sandpack flooding results showed that the increase of differential pressure and profile control effect was a proportional function of the SiO2 concentration in SiO2/SDS foam. The test with a higher SiO2 concentration resulted in a higher oil recovery when SiO2 concentration was less than 1.5 wt %.

Numerical Simulation for Gas-Liquid Two-Phase Flow along the Borehole after Air Cutting

When gas kick Occurs during drilling, because of pressure, temperature, coefficient of gas compressibility and other parameters changing continuously, gas will slip along the borehole and also accompany expansion some extent, and bottom hole differential pressure increases, resulting in the amount of invasion gas increasing continuously until blowout. The procedure of gas kick till blowout in the borehole is transient gas-liquid two-phase flow, studying on The development of gas-liquid two-phase flow parameters variation characteristics and bottom hole pressure variation characteristics plays an significant role to understand blowout occurrence and development characteristics. This paper using methane-mud as the circulating medium simulates the procedure of gas kick till blowout near the bottom under the condition which is almost the onsite drilling process, Analyzing the flow pattern, bottom hole pressure variation characteristics, and velocity distribution under the different stages of gas kick, different influx, and obtained an initial understanding.

수평력을 받는 Plastic type PCV 밸브 내부 유동 가시화

PCV(Positive Crankcase Ventilation) system is designed to remove blowby gas. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates various operating conditions of an automotive engine. As this valve plays a crucial role, the demand in its design is high owing to the small size and high velocity. For this reason, a numerical investigation was carried out to understand both the spool dynamic motion and internal fluid flow characteristics. As a result, the spool dynamic characteristics(i.e. displacement, velocity, acting force), increase in direct proportion to the magnitude of the pressure difference and indicate periodic oscillating motions. Moreover, the velocity at the orifice region decreases according to the increase in differential pressure due to energy loss caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in front of the spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement.

포집량에 따른 p-DPF의 정화효율 및 BPT 특성에 관한 실험적 연구

The number of vehicles applied diesel engine are rapidly rising for fuel economy. Accompanying this trend, application of an after-treatment system is strictly required as a result of reinforced emission regulation. The Diesel Particulate Filter (DPF) system is considered as the most efficiency method to reduce particulate matter (PM) by car makers but also in retrofit market. In recently, various kinds of partial flow DPF are widely used for proper filtration performance and reducing of pressure drop but it is difficult to define the characteristics of these filters because the filtration mechanism is obscure according to the status of these systems. In this paper we investigated the characteristics of cell open type DPF according to the status of filter especially, PM loading. The PM loading mass in the p-DPF are predicted from increase of differential pressure of DPF and the trend of filtration efficiency so that we can measure filtration efficiency and Balance Point Temperature (BPT) of this p-DPF according to PM loading.

Biodiesel Impact on Engine Lubricant Dilution During Active Regeneration of Aftertreatment Systems

Experiments were conducted with ultra low sulfur diesel (ULSD) and 20% biodiesel blends (B20) to compare lube oil dilution levels and lubricant properties for systems using late in-cylinder fuel injection for aftertreatment regeneration. Lube oil dilution was measured by gas chromatography (GC) following ASTM method D3524 to measure diesel content, by Fourier transform infrared (FTIR) spectrometry following a modified ASTM method D7371 to measure biodiesel content, and by a newly developed back-flush GC method that simultaneously measures both diesel and biodiesel. Heavy-duty (HD) engine testing was conducted on a 2008 6.7L Cummins ISB equipped with a diesel oxidation catalyst (DOC) and diesel particle filter (DPF). Stage one of engine testing consisted of 10 consecutive repeats of a forced DPF regeneration event. This continuous operation with late in-cylinder fuel injection served as a method to accelerate lube-oil dilution. Stage two consisted of 16 hours of normal engine operation over a transient test cycle, which created an opportunity for any accumulated fuel in the oil sump to evaporate. Light duty (LD) vehicle testing was conducted on a 2010 VW Jetta equipped with DOC, DPF and a NOx storage catalyst (NSC). Vehicle testing comprised approximately 4,000 miles of operation on a mileage-accumulation dynamometermore » (MAD) using the U.S. Environmental Protection Agency's Highway Fuel Economy Cycle because of the relatively low engine oil and exhaust temperatures, and high DPF regeneration frequency of this cycle relative to other cycles examined. Comparison of the lube oil dilution analysis methods suggests that D3524 does not measure dilution by biodiesel. The new back-flush GC method provided analysis for both diesel and biodiesel, in a shorter time and with lower detection limit. Thus all lube oil dilution results in this paper are based on this method. Analysis of the HD lube-oil samples showed only 1.5% to 1.6% fuel dilution for both fuels during continuous operation under DPF regeneration events. During the second stage of HD testing, the ULSD lube-oil dilution levels fell from 1.5% to 0.8%, while for B20, lube-oil dilution levels fell from 1.6% to 1.0%, but the fuel in the oil was 36% biodiesel. For the LD vehicle tests, the frequency of DPF regeneration events was observed to be the same for both ULSD and B20. No significant difference between the two fuels' estimated soot loading was detected by the engine control unit (ECU), although a 23% slower rate of increase in differential pressure across DPF was observed with B20. It appears that the ECU estimated soot loading is based on the engine map, not taking advantage of the lower engine-out particulate matter from the use of biodiesel. After 4,000 miles of LD vehicle operation with ULSD, fuel dilution in the lube-oil samples showed total dilution levels of 4.1% diesel. After 4,000 miles of operation with B20, total fuel in oil dilution levels were 6.7% consisting of 3.6% diesel fuel and 3.1% biodiesel. Extrapolation to the 10,000-mile oil drain interval with B20 suggests that the total fuel content in the oil could reach 12%, compared to 5% for operation on ULSD. Analysis of the oil samples also included measurement of total acid number, total base number, viscosity, soot, metals and wear scar; however, little difference in these parameters was noted.« less

Pressure effects on the joint elastic-electrical properties of reservoir sandstones

We conducted a laboratory study of the joint elastic-electrical properties of sixty-three brine-saturated sandstone samples to assess the likely impact of differential pressure (confining minus pore fluid pressures) in the range 8–60 MPa on the joint interpretation of marine seismic and controlled-source electromagnetic survey data. The samples showed a wide range of petrophysical properties representative of most sandstone reservoirs. We found that a regression equation comprising both a constant and an exponential part gave a good fit to the pressure dependence of all five measured geophysical parameters (ultrasonic P- and S-wave velocity, attenuation and electrical resistivity). Electrical resistivity was more pressure-sensitive in clay-rich sandstones with higher concentrations of low aspect ratio pores and micropores than in clean sandstones. Attenuation was more pressure-sensitive in clean sandstones with large open pores (macropores) than in clay-rich sandstones. Pore shape did not show any influence on the pressure sensitivity of elastic velocity. As differential pressure increases, the effect of the low aspect ratio pores and micropores on electrical resistivity becomes stronger than the effect of the macropores on attenuation. Further analysis of correlations among the five parameters as a function of pressure revealed potentially diagnostic relationships for geopressure prediction in reservoir sandstones.

Lab and pilot scale investigations on membrane fouling during the ultrafiltration of surface water

In the combined laboratory and pilot plant investigation powder activated carbon dosing and inline coagulation were investigated for surface water from river Spree. The aim was to understand the fouling behaviour of this raw water and to understand and to identify strategies to minimize the irreversible fouling in this application. Trials with activated carbon showed significant differences in the adsorption of biopolymers on different types of carbon. Whereas the TOC removal was in the same range for both types the coarse carbon type showed very small removal of biopolymers. The effect of different types of coagulants, dosage and pH was investigated in a laboratory filtration set up. Samples were investigated by LC-OCD measurements for fractionation of DOC for raw water, flocculated water and permeate. The removal of biopolymers was possible with iron and alumina salts, however the alumina salts tend to remove humic acids as well and this results in a higher overall DOC removal. In the pilot plant the inline coagulation was investigated under actual site conditions. Whereas the results for the effect of coagulation and DOC removal were confirmed it turned out that aluminium coagulants give a significantly higher increase in differential pressure. The use of ferric coagulants at slightly acidic pH was thus identified as a robust method to achieve a stable performance of the ultrafiltration system at this site.

Fabric filter bag investigation following field testing of sorbent injection for mercury control at TXU's Big Brown Station

Field testing of mercury control sorbent injection options with a TOXECON™ configuration has been completed at TXU's Big Brown Station. Mercury control results at Big Brown were promising and have been previously reported. However, the high air-to-cloth ratio of operations at this unit results in significant differential pressure, and thus there was little operating margin before differential pressure limits were encountered, especially at high loads. This limited the use of sorbent injection as the added material contributes to the overall differential pressure. After field testing, the residual differential pressure across the test fabric filter module had increased relative to baseline conditions to the point that the plant performed a filter change of the test module several months ahead of schedule. An investigation was conducted on pre- and posttest filter samples from the test module and a parallel nontest module to examine the effect of activated carbon injection. Analysis of the samples indicates an increase in residual dust embedded in the filters which appears to explain the low fabric permeabilities. The long-term increase in differential pressure did not appear to be associated with activated carbon injection, but instead was due to a gradual buildup of embedded material on the filters that was not cleaned away by the pulse cleaning system. The injected activated carbon appeared to behave like additional fly ash in terms of baghouse differential pressure but did not appear to accelerate the buildup of residual material.

Differential Pressure in Membrane Channel Caused by Foulant Capture onto Spacers

Feed spacers in spiral-wound reverse osmosis membrane modules are highly susceptible to deposition or attachment of suspended particulates and organic matters in the feed stream. This type of fouling can cause a significant pressure drop along the membrane channel (differential pressure) without much effect on the average permeate flux. In practical applications, membrane cleaning is often triggered when the differential pressure in a membrane channel exceeds a threshold value. A mathematical model was developed to simulate the development of differential pressure in the feed channel resulting from foulant capture by the feed spacers. Simulations were carried out to investigate and demonstrate the effect of various parameters on differential pressures in the membrane channel. Differential pressures observed in a two-stage reverse osmosis water reclamation plant were simulated with the model, and the results showed that the model could adequately describe the increase of differential pressure with operating time in the reverse osmosis plant.

Biostability characterization in a full‐scale hybrid NF/RO treatment system

The objective of this study was to quantify the assimilable organic carbon (AOC) in processing water at several stages of a full‐scale nanofiltration (NF) water treatment plant. The NF membrane plant investigated was a 45,400‐m3/d (12‐mgd) water‐softening facility in Plantation, Fla. The average AOC concentration of raw feedwater was estimated at 158 μg/L acetate‐C. After pretreatment (acid and antiscalant addition), AOC levels increased by 12.7% (p‐value = 0.055), suggesting that pretreatment chemicals used to control scaling may enhance bacterial growth potential on the membrane surface. The results also demonstrated that the membrane system was capable of effectively removing 63.4% of AOC and showed a decrease in membrane productivity over time (declined linearly at a rate of approximately 1.2 times 10‐4 L/m2/h ÷ kPa [4.9 times 10‐4 gfd ÷ psi] per d). This decrease could be attributed to biofouling, as observed by a steady increase in differential pressure during operation, and to natural organic matter fouling, as shown by the composition of the organic matter in the feedwater (54.9% hydrophobic and 18.1% hydrophilic neutral compounds).

The Effect of PAO Aerosol Challenge on the Differential Pressure of an ePTFE Media ULPA (Experimental) Filter

A new generic ePTFE (expanded polytetrafluoroethylene) media super ULPA filter was subjected to six hours of continual PAO (polyalphaolefin) challenge to determine the effect on the filter differential pressure and delivered air flow. A continuous challenge concentration of 15 to 16 μg/L was introduced upstream of the filter. To limit the effect of the fan curve, air volume was adjusted to maintain the initial value of 500 f3/min ± 5% for the duration of the study. A volume of 500 f3/min is typical for a terminal housing to limit noise generation in a facility and maximize filter life. Over the test period the air volume and differential pressure were taken every 15 minutes. The results showed a 96% increase in differential pressure over the course of study. As a result of this significant increase in differential pressure, it was determined that the ePTFE is not suited for the intended application requiring semiannual certification using an oil-based aerosol challenge.

Filtration von kaltgepresstem Rapsöl aus dezentralen Anlagen

In decentralised oil processing, purification has significant effects on vegetable oil quality. Through sedimentation or filtration, most of the particles are separated from the vegetable oil. Additional use of so-called safety filters with a defined pore width at the end of the oil purification process is specially important. Through this, impurities caused by the over-proportional increase of differential pressure in the safety filter can be avoided and faults in the oil filtration process can be detected. The filtration of cold-pressed rape-seed oil with a chamber filter press and the suitability of various safety filters was investigated.

Modified Biot-Gassmann Theory for Calculating Elastic Velocities for Unconsolidated and Consolidated Sediments*

The classical Biot-Gassmann theory (BGT) generally overestimates shear-wave velocities of water-saturated sediments. To overcome this problem, a new theory is developed based on BGT and on the velocity ratio as a function of G(1−φ)n, where φ is porosity and n and G are constants. Based on laboratory data measured at ultrasonic frequencies, parameters for the new formulation are derived. This new theory is extended to include the effect of differential pressure and consolidation on the velocity ratio by making na function of differential pressure and the rate of porosity reduction with respect to differential pressure. A scale G is introduced to compensate for discrepancies between measured and predicted velocities, mainly caused by the presence of clay in the matrix. As differential pressure increases and the rate of porosity reduction with respect to differential pressure decreases, the exponent n decreases and elastic velocities increase. Because velocity dispersion is not considered, this new formula is optimum for analyzing velocities measured at ultrasonic frequencies or for sediments having low dispersion characteristics such as clean sandstone with high permeability to predict velocities from porosity or from porosity and P-wave velocity and is in good agreement with laboratory and well log data.

Differential Pressure as a Means of Estimating Respirable Dust Mass on Collection Filters

Abstract Researchers have studied various types of respirable dust sampling filters to determine if the differential pressure across them at a constant air flow rate can be used to estimate the accumulated dust mass. Results suggest that glass fiber depth filters that allow the dust particles to penetrate well into the filter material have considerable merit. The correlation between the increase in differential pressure (AP) and dust mass (M) when using 37-mm glass fiber filters is linear, provided they are not loaded with more than approximately 5 mg of dust. Under these conditions, the relationship between differential pressure and dust mass can be described by the equation [°P(cm H2O) = 0.25 M(mg)]. Most of the data fall within ± 25 percent of a best-fit regression line and have a correlation coefficient (R2) of 0.88. These results were obtained using coal dusts from Pittsburgh, Upper Freeport, and Pocahontas seams mixed with various percentages (0 to 100%) of rock dust. The density of these dusts vari...