Sweep Efficiency of Miscible Floods in a High-Pressure Quarter Five-Spot Model

2006 ◽  
Author(s):  
Ed Lewis ◽  
Eric Dao ◽  
Kishore Kumar Mohanty
Keyword(s):  
High Pressure ◽  
Sweep Efficiency ◽  
Spot Model

Sweep Efficiency of Miscible Floods in a High-Pressure Quarter-Five-Spot Model

SPE Journal ◽  
2008 ◽  
Vol 13 (04) ◽  
pp. 432-439 ◽  
Author(s):  
Edward J. Lewis ◽  
Eric Dao ◽  
Kishore K. Mohanty
Keyword(s):  
High Pressure ◽  
Oil Recovery ◽  
Oil Reservoirs ◽  
Recovery Efficiency ◽  
Sweep Efficiency ◽  
Viscous Oil ◽  
Spot Model ◽  
Reservoir Conditions ◽  
Wag Injection ◽  
Medium Viscosity

Summary Evaluation and improvement of sweep efficiency are important for miscible displacement of medium-viscosity oils. A high-pressure quarter-five-spot cell was used to conduct multicontact miscible (MCM) water-alternating-gas (WAG) displacements at reservoir conditions. A dead reservoir oil (78 cp) was displaced by ethane. The minimum miscibility pressure (MMP) for ethane with the reservoir oil is approximately 4.14 MPa (600 psi). Gasflood followed by waterflood improves the oil recovery over waterflood alone in the quarter five-spot. As the pressure decreases, the gasflood oil recovery increases slightly in the pressure range of 4.550-9.514 MPa (660-1,380 psi) for this undersaturated viscous oil. WAG improves the sweep efficiency and oil recovery in the quarter five-spot over the continuous gas injection. WAG injection slows down gas breakthrough. A decrease in the solvent amount lowers the oil recovery in WAG floods, but significantly more oil can be recovered with just 0.1 pore volume (PV) solvent (and water) injection than with waterflood alone. Use of a horizontal production well lowers the sweep efficiency over the vertical production well during WAG injection. Sweep efficiency is higher for the nine-spot pattern than for the five-spot pattern during gas injection. Sweep efficiency during WAG injection increases with the WAG ratio in the five-spot model. Introduction As the light-oil reservoirs get depleted, there is increasing interest in producing more-viscous-oil reservoirs. Thermal techniques are appropriate for heavy-oil reservoirs. But gasflooding can play an important role in medium-viscosity-oil (30-300 cp) reservoirs and is the subject of this paper. Roughly 20 billion to 25 billion bbl of medium-weight- to heavy-weight-oil deposits are estimated in the North Slope of Alaska. Approximately 10 billion to 12 billion bbl exist in West Sak/Schrader Bluff formation alone (McGuire et al. 2005). Miscible gasflooding has been proved to be a cost-effective enhanced oil recovery technique. There are approximately 80 gasflooding projects (CO2, flue gas, and hydrocarbon gas) in the US and approximately 300,000 B/D is produced from gasflooding, mostly from light-oil reservoirs (Moritis 2004). The recovery efficiency [10-20% of the original oil in place (OOIP)] and solvent use (3-12 Mcf/bbl) need to be improved. The application of miscible and immiscible gasflooding needs to be extended to medium-viscosity-oil reservoirs. McGuire et al. (2005) have proposed an immiscible WAG flooding process, called viscosity-reduction WAG, for North Slope medium-visocisty oils. Many of these oils are depleted in their light-end hydrocarbons C7-C13. When a mixture of methane and natural gas liquid is injected, the ethane and components condense into the oil and decrease the viscosity of oil, making it easier for the water to displace the oil. From reservoir simulation, this process is estimated to enhance oil recovery compared to waterflood from 19 to 22% of the OOIP, which still leaves nearly 78% of the OOIP. Thus, further research should be directed at improving the recovery efficiency of these processes for viscous-oil reservoirs. Recovery efficiency depends on microscopic displacement efficiency and sweep efficiency. Microscopic displacement efficiency depends on pressure, (Dindoruk et al. 1992; Wang and Peck 2000) composition of the solvent and oil (Stalkup 1983; Zick 1986), and small-core-scale heterogeneity (Campbell and Orr 1985; Mohanty and Johnson 1993). Sweep efficiency of a miscible flood depends on mobility ratio (Habermann 1960; Mahaffey et al. 1966; Cinar et al. 2006), viscous-to-gravity ratio (Craig et al. 1957; Spivak 1974; Withjack and Akervoll 1988), transverse Peclet number (Pozzi and Blackwell 1963), well configuration, and reservoir heterogeneity, (Koval 1963; Fayers et al. 1992) in general. The effect of reservoir heterogeneity is difficult to study at the laboratory scale and is addressed mostly by simulation (Haajizadeh et al. 2000; Jackson et al. 1985). Most of the laboratory sweep-efficiency studies (Habermann 1960; Mahaffey et al. 1966; Jackson et al. 1985; Vives et al. 1999) have been conducted with first-contact fluids or immiscible fluids at ambient pressure/temperature and may not be able to respresent the displacement physics of multicontact fluids at reservoir conditions. In fact, four methods are proposed for sweep improvement in gasflooding: WAG (Lin and Poole 1991), foams (Shan and Rossen 2002), direct thickeners (Xu et al. 2003), and dynamic-profile control in wells (McGuire et al. 1998). To evaluate any sweep-improvement methods, one needs controlled field testing. Field tests generally are expensive and not very controlled; two different tests cannot be performed starting with identical initial states, and, thus, results are often inconclusive. Field-scale modeling of compositionally complex processes can be unreliable because of inadequate representation of heterogeneity and process complexity in existing numerical simulators. There is a need to conduct laboratory sweep-efficiency studies with the MCM fluids at reservoir conditions to evaluate various sweep-improvement techniques. Reservoir-conditions laboratory tests can be used to calibrate numerical simulators and evaluate qualitative changes in sweep efficiency. We have built a high-pressure quarter-five-spot model where reservoir-conditions multicontact WAG floods can be conducted and evaluated (Dao et al. 2005). The goal of this paper is to evaluate various WAG strategies for a model oil/multicontact solvent in this high-pressure laboratory cell. In the next section, we outline our experimental techniques. The results are summarized in the following section.

Buffalo Field High-Pressure Air Injection Projects 1977 to 2007: Technical Performance and Operational Challenges

2009 ◽  
Vol 12 (04) ◽  
pp. 542-550 ◽  
Author(s):  
Dubert Gutiérrez ◽  
Ronald J. Miller ◽  
Archie R. Taylor ◽  
Pete Thies ◽  
Vinodh Kumar
Keyword(s):  
High Pressure ◽  
Oil Recovery ◽  
Management Practices ◽  
Air Injection ◽  
Vertical Wells ◽  
Sweep Efficiency ◽  
Injection Wells ◽  
Technical Performance ◽  
Well Completion ◽  
Incremental Oil Recovery

Summary The Buffalo field air-injection units, located in northwest South Dakota, are the oldest high-pressure-air-injection (HPAI) projects currently in operation. Air injection began in January 1979, and as of December 2007, approximately 240 Bscf of air has been injected into the field. A total of 17.2 million bbl of incremental oil has been produced by the HPAI process, which is equivalent to 9.4% of the original oil in place (OOIP). The cumulative air/oil ratio (AOR) after 29 years of air injection is approximately 14 Mscf of air/bbl of incremental oil. This paper summarizes the performance of the projects and the overall experience gained by the operators after nearly 30 years of air injection. It covers almost every aspect of the entire operation since its inception; it discusses general management practices, technical and operational challenges encountered, injection and production facilities, and drilling and well-completion practices. It also includes estimates of incremental oil recovery caused by air injection and discusses how the air use has changed over time To date, the three HPAI projects in the Buffalo field continue to be a commercial success. In the last 3 years, horizontal laterals have been drilled out of more than 40 old vertical wells to enhance production, to take advantage of accumulated reservoir energy, and to improve sweep efficiency. Drilling injection wells out of old vertical wells was not possible because the openhole laterals cross a porosity zone that would have taken away some of the injection into nonproductive reservoir.

High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

1991 ◽  
Vol 49 ◽  
pp. 64-65
Author(s):  
Marek Malecki ◽  
James Pawley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Low Voltage ◽  
Culture Media ◽  
Cell Structure ◽  
Freeze Substitution ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Culture Media ◽  
Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

Prolonged Fixation Studies For Spaceflight

1973 ◽  
Vol 31 ◽  
pp. 332-333
Author(s):  
Robert Corbett ◽  
Delbert E. Philpott ◽  
Sam Black
Keyword(s):  
High Pressure ◽  
Living Systems ◽  
Prolonged Storage ◽  
Time Intervals ◽  
Early Signs ◽  
Large Numbers

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).

Cryosectioning plant roots prepared by high-pressure freezing

1987 ◽  
Vol 45 ◽  
pp. 662-663
Author(s):  
R.E. Crang ◽  
M. Mueller ◽  
K. Zierold
Keyword(s):  
High Pressure ◽  
Cell Walls ◽  
Plant Tissues ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Vitreous State ◽  
Radial Depth ◽  
Irregular Topography ◽  
Considerable Depth ◽  
Conventional Freezing

Obtaining frozen-hydrated sections of plant tissues for electron microscopy and microanalysis has been considered difficult, if not impossible, due primarily to the considerable depth of effective freezing in the tissues which would be required. The greatest depth of vitreous freezing is generally considered to be only 15-20 μm in animal specimens. Plant cells are often much larger in diameter and, if several cells are required to be intact, ice crystal damage can be expected to be so severe as to prevent successful cryoultramicrotomy. The very nature of cell walls, intercellular air spaces, irregular topography, and large vacuoles often make it impractical to use immersion, metal-mirror, or jet freezing techniques for botanical material.However, it has been proposed that high-pressure freezing (HPF) may offer an alternative to the more conventional freezing techniques, inasmuch as non-cryoprotected specimens may be frozen in a vitreous, or near-vitreous state, to a radial depth of at least 0.5 mm.

High-pressure freezing and freeze substitution of plant tissue

1992 ◽  
Vol 50 (1) ◽  
pp. 748-749
Author(s):  
William P. Sharp ◽  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Cell Structure ◽  
Leaf Tissue ◽  
Freeze Substitution ◽  
Crystal Formation ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Components ◽  
Cold Metal ◽  
Brome Grass

The aim of ultrastructural investigation is to analyze cell architecture and relate a functional role(s) to cell components. It is known that aqueous chemical fixation requires seconds to minutes to penetrate and stabilize cell structure which may result in structural artifacts. The use of ultralow temperatures to fix and prepare specimens, however, leads to a much improved preservation of the cell’s living state. A critical limitation of conventional cryofixation methods (i.e., propane-jet freezing, cold-metal slamming, plunge-freezing) is that only a 10 to 40 μm thick surface layer of cells can be frozen without distorting ice crystal formation. This problem can be allayed by freezing samples under about 2100 bar of hydrostatic pressure which suppresses the formation of ice nuclei and their rate of growth. Thus, 0.6 mm thick samples with a total volume of 1 mm3 can be frozen without ice crystal damage. The purpose of this study is to describe the cellular details and identify potential artifacts in root tissue of barley (Hordeum vulgari L.) and leaf tissue of brome grass (Bromus mollis L.) fixed and prepared by high-pressure freezing (HPF) and freeze substitution (FS) techniques.

Microstructural Study of Diamond Deformed Under High Pressure and Temperature

1985 ◽  
Vol 43 ◽  
pp. 230-231
Author(s):  
E. F. Koch
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Lattice Structure ◽  
Diamond Particle ◽  
Polycrystalline Diamond ◽  
Sintering Process ◽  
Ion Milling ◽  
Sintered Compact ◽  
Transmission Electron ◽  
High Pressure Sintering

Because of the extremely rigid lattice structure of diamond, generating new dislocations or moving existing dislocations in diamond by applying mechanical stress at ambient temperature is very difficult. Analysis of portions of diamonds deformed under bending stress at elevated temperature has shown that diamond deforms plastically under suitable conditions and that its primary slip systems are on the ﹛111﹜ planes. Plastic deformation in diamond is more commonly observed during the high temperature - high pressure sintering process used to make diamond compacts. The pressure and temperature conditions in the sintering presses are sufficiently high that many diamond grains in the sintered compact show deformed microtructures.In this report commercially available polycrystalline diamond discs for rock cutting applications were analyzed to study the deformation substructures in the diamond grains using transmission electron microscopy. An individual diamond particle can be plastically deformed in a high pressure apparatus at high temperature, but it is nearly impossible to prepare such a particle for TEM observation, since any medium in which the diamond is mounted wears away faster than the diamond during ion milling and the diamond is lost.

Formation of defects in implanted hipox-structures

1992 ◽  
Vol 50 (2) ◽  
pp. 1406-1407
Author(s):  
Peter Pegler ◽  
N. David Theodore ◽  
Ming Pan
Keyword(s):  
High Pressure ◽  
Cross Section ◽  
Semiconductor Devices ◽  
Silicon Substrates ◽  
Processing Conditions ◽  
Pressure Oxidation ◽  
Deep Trench ◽  
Local Oxidation ◽  
Trench Isolation ◽  
And Behavior

High-pressure oxidation of silicon (HIPOX) is one of various techniques used for electrical-isolation of semiconductor-devices on silicon substrates. Other techniques have included local-oxidation of silicon (LOCOS), poly-buffered LOCOS, deep-trench isolation and separation of silicon by implanted oxygen (SIMOX). Reliable use of HIPOX for device-isolation requires an understanding of the behavior of the materials and structures being used and their interactions under different processing conditions. The effect of HIPOX-related stresses in the structures is of interest because structuraldefects, if formed, could electrically degrade devices.This investigation was performed to study the origin and behavior of defects in recessed HIPOX (RHIPOX) structures. The structures were exposed to a boron implant. Samples consisted of (i) RHlPOX'ed strip exposed to a boron implant, (ii) recessed strip prior to HIPOX, but exposed to a boron implant, (iii) test-pad prior to HIPOX, (iv) HIPOX'ed region away from R-HIPOX edge. Cross-section TEM specimens were prepared in the <110> substrate-geometry.

High-pressure freezing and freeze substitution of teliospores of the rust fungus Gymnosporangium clavipes

1990 ◽  
Vol 48 (3) ◽  
pp. 692-693
Author(s):  
Robert W. Roberson
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Pathogenic Fungus ◽  
Rust Fungus ◽  
Freeze Substitution ◽  
Ice Crystals ◽  
High Pressure Freezing ◽  
Thin Walled Structures ◽  
Cytological Changes ◽  
Dextran Solution

The use of cryo-techniques for the preparation of biological specimens in electron microscopy has led to superior preservation of ultrastructural detail. Although these techniques have obvious advantages, a critical limitation is that only 10-40 μm thick cells and tissue layers can be frozen without the formation of distorting ice crystals. However, thicker samples (600 μm) may be frozen well by rapid freezing under high-pressure (2,100 bar). To date, most work using cryo-techniques on fungi have been confined to examining small, thin-walled structures. High-pressure freezing and freeze substitution are used here to analysis pre-germination stages of specialized, sexual spores (teliospores) of the plant pathogenic fungus Gymnosporangium clavipes C & P.Dormant teliospores were incubated in drops of water at room temperature (25°C) to break dormancy and stimulate germination. Spores were collected at approximately 30 min intervals after hydration so that early cytological changes associated with spore germination could be monitored. Prior to high-pressure freezing, the samples were incubated for 5-10 min in a 20% dextran solution for added cryoprotection during freezing. Forty to 50 spores were placed in specimen cups and holders and immediately frozen at high pressure using the Balzers HPM 010 apparatus.

A photoelectron microscope study of surfaces

1989 ◽  
Vol 47 ◽  
pp. 10-11
Author(s):  
W. Engel ◽  
M. Kordesch ◽  
A. M. Bradshaw ◽  
E. Zeitler
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Field Strength ◽  
Uv Light ◽  
Physical Property ◽  
Photon Flux ◽  
Mercury Lamp ◽  
Object Surface ◽  
The Sixties ◽  
Physical Features

Photoelectron microscopy is as old as electron microscopy itself. Electrons liberated from the object surface by photons are utilized to form an image that is a map of the object's emissivity. This physical property is a function of many parameters, some depending on the physical features of the objects and others on the conditions of the instrument rendering the image.The electron-optical situation is tricky, since the lateral resolution increases with the electric field strength at the object's surface. This, in turn, leads to small distances between the electrodes, restricting the photon flux that should be high for the sake of resolution.The electron-optical development came to fruition in the sixties. Figure 1a shows a typical photoelectron image of a polycrystalline tantalum sample irradiated by the UV light of a high-pressure mercury lamp.

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