scholarly journals Effect Study of Aperture Distribution on the Capillary Pressure-Saturation Relation for the Single Fracture

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Yuan Wang ◽  
Chenglong Wu ◽  
Yuntian Zhou
Keyword(s):  
Capillary Pressure ◽  
Effect Study ◽  
Single Fracture ◽  
Saturation Curve ◽  
Static Displacement ◽  
Statistical Parameters ◽  
Dual Connectivity ◽  
Fluid Saturation ◽  
The Difference ◽  
Aperture Distribution

A systematic numerical method was presented to investigate the effect of aperture distribution on the relation of capillary pressure versus fluid saturation (P-S relation) for a single fracture. The fracture was conceptualized as a two-dimensional lattice-grid model and its aperture field was described by a probability distribution. Based on the invasion percolation theory, a program was developed to simulate the quasi-static displacement. The simulation was verified validly by comparisons of the experimental results. The effects of the statistical parameters were further quantified. The results show that the largest local aperture on the fracture boundary determines the AEV. The larger mean decreases the variation coefficient, which causes the more uniform aperture field, smoother air invasion front, and steeper capillary pressure-saturation curve (CPSC). The larger standard deviation increases not only the range but also the contrast degree of the apertures, thus providing a nondeterministic rule in the P-S relation. The larger correlation length causes a more homogeneous aperture field and a dual connectivity of the fracture. The increase of the difference and contrast degree between the small and large apertures results in dual-aperture fields. The dual-aperture field and dual connectivity of the fracture both contribute to the bimodal characteristic of the CPSC.

Capillary pressure, osmotic pressure and bubble contact areas in foams

Soft Matter ◽  
2021 ◽  
Author(s):  
Reinhard Höhler ◽  
Jordan Seknagi ◽  
Andrew Kraynik
Keyword(s):  
Osmotic Pressure ◽  
Capillary Pressure ◽  
Continuous Phase ◽  
Dispersed Phase ◽  
Average Pressure ◽  
Contact Areas ◽  
The Difference

The capillary pressure of foams and emulsions is the difference between the average pressure in the dispersed phase and the pressure in the continuous phase.

Capillary Equilibrium in Porous Materials

1965 ◽  
Vol 5 (01) ◽  
pp. 15-24 ◽  
Author(s):  
Norman R. Morrow ◽  
Colin C. Harris
Keyword(s):  
Mass Transfer ◽  
Fluid Flow ◽  
Porous Materials ◽  
Capillary Pressure ◽  
Chemical Engineering ◽  
Fluid Distribution ◽  
Bulk Fluid ◽  
Fluid Saturation ◽  
Capillary Pressure Curves ◽  
The Relationship

Abstract The experimental points which describe capillary pressure curves are determined at apparent equilibria which are observed after hydrodynamic flow has ceased. For most systems, the time required to obtain equalization of pressure throughout the discontinuous part of a phase is prohibitive. To permit experimental points to be described as equilibria, a model of capillary behavior is proposed where mass transfer is restricted to bulk fluid flow. Model capillary pressure curves follow if the path described by such points is independent of the rate at which the saturation was changed to attain a capillary pressure point. A modified suction potential technique is used to study cyclic relationships between capillary pressure and moisture content for a porous mass. The time taken to complete an experiment was greatly reduced by using small samples. Introduction Capillary retention of liquid by porous materials has been investigated in the fields of hydrology, soil science, oil reservoir engineering, chemical engineering, soil mechanics, textiles, paper making and building materials. In studies of the immiscible displacement of one fluid by another within a porous bed, drainage columns and suction potential techniques have been used to obtain relationships between pressure deficiency and saturation (Fig. 1). Except where there is no hysteresis of contact angle and the solid is of simple geometry, such as a tube of uniform cross section, there is hysteresis in the relationship between capillary pressure and saturation. The relationship which has received most attention is displacement of fluid from an initially saturated bed (Fig. 1, Curve Ro), the final condition being an irreducible minimum fluid saturation Swr. Imbibition (Fig. 1, Curve A), further desaturation (Fig. 1, Curve R), and intermediate scanning curves have been studied to a lesser but increasing extent. This paper first considers the nature of the experimental points tracing the capillary pressure curves with respect to the modes and rates of mass transfer which are operative during the course of measurement. There are clear indications that the experimental points which describe these curves are obtained at apparent equilibria which are observed when viscous fluid flow has ceased; and any further changes in the fluid distribution are the result of much slower mass transfer processes, such as diffusion. Unless stated otherwise, this discussion applies to a stable packing of equal, smooth, hydrophilic spheres supported by a suction plate with water as the wetting phase and air as the nonwetting phase. SPEJ P. 15ˆ

scholarly journals Research on the relationship between postoperative D-dimer clearance and trauma infection complications in patients with different degrees of fracture

2020 ◽  
Author(s):  
Hai-Mei Ma ◽  
Yong-wei Pan ◽  
Lianxu Chen
Keyword(s):  
Orthopedic Surgery ◽  
Clearance Rate ◽  
Correlation Equation ◽  
Severe Trauma ◽  
P Value ◽  
Single Fracture ◽  
Traumatic Fracture ◽  
The Difference ◽  
Thrombotic Diseases ◽  
D Dimer

AbstractBackgroundOccurrence of thrombotic disease after orthopedic surgery has always been an important issue affecting the prognosis of patients. In this paper, retrospective analysis was used to analyze the D-dimer clearance rate after different degrees of fractures, suggesting that the D-dimer clearance rate can be used as an index to evaluate thrombotic diseases after orthopedic surgery.Material/MethodsSeventy-five patients with orthopedic surgery were randomly selected from March to June 2017. According to the degrees of fractures and complications, they were divided into SF(single fracture), MF(multiple fracture), FCI(Fracture combined with infection)three groups, 25 in each group.D-dimer results of each case on 1 day, 2 days, 3 days, 4 days, 5 days, and 7 days after orthopedic surgery were recorded and counted.The slope of correlation equation of D-dimer value according to time is the D-dimer clearance rate.ResultsThe D-dimer clearance rate in the SF□JMF □FCI group was −0.0490, −0.0502 and −0.0692□The P value is respectively 0.0049, 0.0061 and 0.0163, the difference is significant.ConclusionsAfter traumatic fracture surgery, whether D-dimer clears at a normal rate is closely related to its outcome. Decreasing D-dimer clearance is related to postoperative infections and thrombotic diseases. D-dimer clearance can be used as an important parameter and observation index for judging the clinical outcome of patients with complications such as severe trauma and infection. At the same time, we can further study the cut-off value of D-dimer clearance.

Investigation of the Factors Influencing the Flowback Ratio in Shale Gas Reservoirs: A Study Based on Experimental Observations and Numerical Simulations

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
Lin Hun ◽  
Zhou Xiang ◽  
Chen Yulong ◽  
Yang Bing ◽  
Song Xixiang ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Capillary Pressure ◽  
Influencing Factors ◽  
Shale Gas ◽  
Water Distribution ◽  
Pressure Curve ◽  
Gas Reservoirs ◽  
Desorption Process ◽  
Fluid Saturation ◽  
Shale Gas Reservoirs

Abstract The flowback behavior of hydraulic fractured horizontal well in shale gas reservoir is relatively different from that of conventional reservoirs. Therefore, it is necessary to investigate the relationship between the potential influencing factors and the flowback behavior in shale gas reservoirs. This study is based on experimental observations and numerical simulations. In the experiments, the flowback process was simulated through a gas displacement experiment, and the cores were scanned simultaneously to obtain the water distribution. Then, the water migration and retention mechanisms were investigated to determine the flowback behavior. For the numerical simulations, a multi-porosity model was established. The mathematical model accounted for the capillary pressure term. By matching the fluid saturation-front curves of the experimental and simulation results, a fitted capillary pressure curve, which reflects the multiple mechanisms controlling flowback, was obtained. Based on the established model and fitted capillary pressure, the flowback behavior and relevant influencing factors of the shale gas were investigated. The results show that the flowback ratio is inversely proportional to the clay content of the shale. A high salinity fracturing fluid or a surfactant solution can increase the flowback ratio. In addition, the injection pressure is proportional to the flowback ratio, while the matrix permeability and the flowback ratio have an inverse relationship. The adsorption–desorption process of gas has no significant effect on the flowback ratio. This study aims to provide a new method for analyzing the flowback performance of shale gas using a combination of experimental and numerical simulation methods.

Simultaneous Interpretation of Three-Phase Relative Permeability and Capillary Pressure for a Tight Carbonate Reservoir From Wireline Formation Testing

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Xiangnan Liu ◽  
Daoyong Yang
Keyword(s):  
Capillary Pressure ◽  
Relative Permeability ◽  
History Matching ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Fluid Saturation ◽  
Three Phase ◽  
Tight Carbonate ◽  
Wet Condition ◽  
Oil Gas

Abstract In this paper, techniques have been developed to interpret three-phase relative permeability and water–oil capillary pressure simultaneously in a tight carbonate reservoir from numerically simulating wireline formation tester (WFT) measurements. A high-resolution cylindrical near-wellbore model is built based on a set of pressures and flow rates collected by dual packer WFT in a tight carbonate reservoir. The grid quality is validated, the effective thickness of the WFT measurements is examined, and the effectiveness of the techniques is confirmed prior to performing history matching for both the measured pressure drawdown and buildup profiles. Water–oil relative permeability, oil–gas relative permeability, and water–oil capillary pressure are interpreted based on power-law functions and under the assumption of a water-wet reservoir and an oil-wet reservoir, respectively. Subsequently, three-phase relative permeability for the oil phase is determined using the modified Stone II model. Both the relative permeability and the capillary pressure of a water–oil system interpreted under an oil-wet condition match well with the measured relative permeability and capillary pressure of a similar reservoir rock type collected from the literature, while the relative permeability of an oil–gas system and the three-phase relative permeability bear a relatively high uncertainty. Not only is the reservoir determined as oil-wet but also the initial oil saturation is found to impose an impact on the interpreted water relative permeability under an oil-wet condition. Changes in water and oil viscosities and mud filtrate invasion depth affect the range of the movable fluid saturation of the interpreted water–oil relative permeabilities.

Good’s theory of cascade processes applied to the statistics of polymer distributions

1962 ◽  
Vol 268 (1333) ◽  
pp. 240-256 ◽  
Keyword(s):  
Molecular Weight ◽  
Generating Functions ◽  
Repeat Unit ◽  
Average Molecular Weight ◽  
Stochastic Theory ◽  
Direct Calculation ◽  
Gel Point ◽  
Statistical Parameters ◽  
Cascade Processes ◽  
The Difference

Important statistics of polymerization reactions, whether of the condensation or addition type, can be calculated rather simply and in a standardized way, by an adaptation of Good’s stochastic theory of cascade processes. Examples of such statistics are the various molecular weight averages, the gel point, and the sol fraction. The use of generating functions in the theory greatly reduces the use of probability theory and it allows the direct calculation of the required statistics without the need of explicit expressions for the distributions concerned, or for the summations required in calculating their moments. The generating functions required are mostly combinations of powers of the basic form (1— α) θ 1 + αθ 2 where θ 1 and θ 2 are dummy variables (or unity) and α some parameter measuring the conversion of a functionality. Ordinary (non-vectorial) generating functions suffice when the system contains essentially one type of repeat unit, but for copolymers (in a broad sense) generalization to vectorial generating functions is required. Calculations of the former type, useful in describing the principles involved, include the calculation of new sol-fraction equations for simple polycondensation reactions, and a somewhat more exact sol-fraction equation for the vulcanization of chains initially distributed randomly in length. Copolymerization systems are then exemplified by calculating the weight-average molecular weight and sol fraction for the system glycerol/adipic acid from general formulae derived. Exact allowance is made for the statistical effects due to complete or partial elimination of water and to the difference in rate of esterification of primary and secondary hydroxyls. The gel-point condition for a system involving copolymerization of s different units is generally found by equating to zero a determinant of order s . The mechanism of polycondensation reactions could be elucidated by comparing experimental measurements of the statistical parameters with those calculated from postulated kinetic schemes using the unified and comparatively simple theory here presented.

Application of NMR Technology on Test of Movable Fluid Saturation of Tight Sandstone Gas Reservoir

2015 ◽  
Vol 1092-1093 ◽  
pp. 1361-1365
Author(s):  
Hong Xia Ming ◽  
Wei Sun ◽  
Ping Wu
Keyword(s):  
Pore Structure ◽  
Transverse Relaxation Time ◽  
Single Peak ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Fluid Saturation ◽  
Structure Heterogeneity ◽  
Spectrum Distribution ◽  
The Difference

The difference of movable fluid saturation of tight sandstone gas reservoir is researched, with transverse relaxation time (T2) distribution derived from nuclear magnetic resonance technique (NMR). This article newly calculate T2 cutoff value and elaborate the influence of pore structure on the occurrence characteristics of movable fluid. The study had revealed T2 spectrum distribution includes the following types: (1) wide and flat single peak; (2) left single peak; (3) high left peak with low right peak. Movable fluid saturation is low, with class IV and class V movable fluid mainly. Pore structure control properties and percolation ability of rock reservoir and whether oil could be driven out depends on throat parameters of interconnected pores. Movable fluid saturation is low with bigger pore throat ratio, narrower pore throat distribution and higer pore structure heterogeneity.

Time-lapse seismic signal analysis for enhanced oil recovery at Cranfield CO2 sequestration site, Cranfield field, Mississippi

2013 ◽  
Vol 1 (2) ◽  
pp. T157-T166 ◽  
Author(s):  
Julie Ditkof ◽  
Eva Caspari ◽  
Roman Pevzner ◽  
Milovan Urosevic ◽  
Timothy A. Meckel ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Time Lapse ◽  
Seismic Signal ◽  
Injection Well ◽  
Saturation Curve ◽  
Seismic Surveys ◽  
Seismic Amplitude ◽  
The Difference ◽  
Seismic Volumes ◽  
4D Seismic

The Cranfield field in southwest Mississippi has been under continuous [Formula: see text] injection by Denbury Onshore LLC since 2008. Two 3D seismic surveys were collected in 2007 and 2010. An initial 4D seismic response was characterized after three years of injection, where more than three million tons of [Formula: see text] remain in the subsurface. This interpretation showed coherent seismic amplitude anomalies in some areas that received large amounts of [Formula: see text] but not in others. To understand these effects better, we performed Gassmann substitution modeling at two wells: the 31F-2 observation well and the 28-1 injection well. We aimed to predict a postinjection saturation curve and acoustic impedance (AI) change through the reservoir. Seismic volumes were cross-equalized, well ties to seismic were performed, and AI inversions were subsequently carried out. Inversion results showed that the change in AI is higher than Gassmann substitution predicted for the 28-1 injection well. The time-lapse AI difference predicted by the inversion is similar in magnitude to the difference inferred from a time delay along a marker horizon below the reservoir.

scholarly journals Detection of Multi-pixel Low Contrast Object on a Real Sea Surface

2021 ◽  
Author(s):  
Victor Golikov ◽  
Oleg Samovarov ◽  
Daria Chernomorets ◽  
Marco Rodriguez-Blanco
Keyword(s):  
Spectral Characteristics ◽  
False Alarm Probability ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Statistical Parameters ◽  
Low Contrast ◽  
Video Images ◽  
Floating Object ◽  
The Difference ◽  
Floating Objects

The video images captured at long range usually have low contrast floating objects of interest on a sea surface. A comparative experimental study of the statistical characteristics of reflections from floating objects and from the agitated sea surface showed the difference in the correlation and spectral characteristics of these reflections. The functioning of the recently proposed modified matched subspace detector (MMSD) is based on the separation of the observed data spectrum on two subspaces: relatively low and relatively high frequencies. In the literature the MMSD performance has been evaluated in generally and moreover using only a sea model (additive Gaussian background clutter). This paper extends the performance evaluating methodology for low contrast object detection and moreover using only the real sea dataset. This methodology assumes an object of low contrast if the mean and variance of the object and the surrounding background are the same. The paper assumes that the energy spectrum of the object and the sea are different. The paper investigates a scenario in which an artificially created model of a floating object with specified statistical parameters is placed on the surface of a real sea image. The paper compares the efficiency of the classical Matched Subspace Detector (MSD) and MMSD for detecting low-contrast objects on the sea surface. The article analyzes the dependence of the detection probability at a fixed false alarm probability on the difference between the statistical means and variances of a floating object and the surrounding sea.

scholarly journals An experimental approach for determining unsaturated hydraulic properties of rock fractures

2004 ◽  
Vol 35 (3) ◽  
pp. 251-260 ◽  
Author(s):  
Hu Yunjin ◽  
Su Baoyu ◽  
Mao Genhai
Keyword(s):  
Hydraulic Conductivity ◽  
Capillary Pressure ◽  
Water Flow ◽  
Hydraulic Properties ◽  
Experimental Approach ◽  
Single Fracture ◽  
Rock Fractures ◽  
Unsaturated Hydraulic Conductivity ◽  
Connected Channels ◽  
Theoretical Saturation

An experimental approach for determining the unsaturated hydraulic properties (the relations between capillary pressure, saturation and unsaturated hydraulic conductivity) of rock fractures is developed and tested. Applying this approach to a single fracture, and with only water flowing, the capillary pressure–saturation and unsaturated hydraulic conductivity–capillary pressure relationships of the fracture during drainage and imbibition can be determined simultaneously. To facilitate the test of the validity of the experimental approach and to elucidate the characteristics of water flow in unsaturated fractures, an analogous fracture with parallel, connected channels of different apertures was fabricated. Experiments of unsaturated water flow in the analogous fracture were carried out. Some characteristics of water flow in unsaturated fractures (hysteresis between drainage and imbibition, etc.) were elucidated. Comparison of measured saturation values and theoretical saturation values corresponding to different apertures at the beginning of drainage and imbibition shows that the experimental approach presented in this paper is valid.

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