Sedimentary Rock Compressibility Related to Porosity Under Hydrostatic Loading: New Approach with Uniaxial Corrections

2019 ◽  
Author(s):  
Ricardo de Souza Fasolo ◽  
Roseane Marchezi Misságia ◽  
Marco Antônio Rodrigues de Ceia
Keyword(s):  
Sedimentary Rock ◽  
New Approach ◽  
Hydrostatic Loading ◽  
Rock Compressibility

Influence of Reservoir Stress Path on Deformation and Permeability of Weakly Cemented Sandstone Reservoirs

1999 ◽  
Vol 2 (03) ◽  
pp. 266-272 ◽  
Author(s):  
H. Ruistuen ◽  
L.W. Teufel ◽  
D. Rhett
Keyword(s):  
Pore Pressure ◽  
Stress Path ◽  
Stress Sensitivity ◽  
Uniaxial Strain ◽  
Matrix Permeability ◽  
Hydrostatic Loading ◽  
Stress Changes ◽  
Reservoir Conditions ◽  
Path Dependent ◽  
Rock Compressibility

Summary The influence of production-induced changes in reservoir pore pressure on compressibility and permeability of weakly cemented sandstones has been analyzed. Laboratory experiments simulating reservoir depletion have been conducted over a range of stress paths that a reservoir may follow. The results suggest that compressibility of weakly cemented sandstones is stress path dependent. Compressibility measured under uniaxial strain conditions, or a stress path defined by a lower ratio of the rate at which the effective horizontal to effective vertical stress were increased than the one associated with uniaxial strain, is more than twice the corresponding value found from the hydrostatic loading experiment. In contrast, matrix permeability measured in the maximum stress direction show no significant stress path dependence. Experimental results suggest that a better understanding of the stress-sensitive behavior of weakly cemented sandstones can only be gained by dealing more directly with the microstructure of the rock. The stress-path-dependent nonlinear behavior of weakly cemented sandstones is related to effects of shear-enhanced compaction. Increasing cementation has been experimentally shown to reduce stress sensitivity. The observed nonlinearity is attributed to dilatancy rather than shear-enhanced compaction, also reflected by permeability measurements made in the maximum stress direction. Introduction Reliable data on rock compressibility and matrix permeability are essential in reservoir engineering due to the significant impact these parameters have on reserves and productivity estimations. Laboratory measurements of rock compressibility are applied to production forecasts, reservoir pressure maintenance evaluations, as well as reservoir compaction and subsidence studies,1–4 while matrix permeability heavily influences reservoir productivity and injectivity and is essential in performance forecasting.4 Formation compressibility is defined as the in situ bulk volume strain that results from changes in reservoir pore pressure: c = − 1 V i d V d P . ( 1 ) By adopting this definition, formation compressibility is not related to specific stress conditions. Formation compressibility is simply defined as the bulk response of the reservoir rock to production-induced changes in pore pressure. The stress changes that result from changes in pore pressure are uniquely defined by reservoir characteristics such as boundary conditions, reservoir geometry, and the mechanical properties of the reservoir rocks and bounding formations. A common procedure within the oil industry has been to use the so-called uniaxial correction factor to correct the results obtained from the hydrostatic compressibility test (cb) to "formation compressibility:"5 c = 1 + μ 3 ( 1 − μ ) c b . ( 2 ) An inherent assumption in this expression is that the rock is elastic throughout its production-induced deformation history, which may not be the case for weakly cemented reservoir rocks. The validity of the procedure also relies on the assumption that the uniaxial strain model adequately simulates reservoir conditions during depletion. Recent in situ stress measurements have demonstrated that this assumption is not necessarily valid. Since the early 1950's a number of researchers have investigated the relationships between rock matrix permeability and applied external pressure. Early observations suggested that permeability declines approximately exponentially with increasing confining pressure6 and that a relatively greater permeability reduction should be expected for a lower permeability matrix.7 These results were obtained from tests conducted under hydrostatic loading conditions. More recently, permeability measurements have also been performed under triaxial stress conditions.8–10 Matrix permeability has been related to compressibility and thus to the fabric and mineralogy of rocks. Bruno, Bovberg, and Nakagawa9 have shown that mineralogy may play a significant role in high-porosity rocks. Both increasing clay content and decreasing cementation resulted in a larger reduction in permeability with increasing stress. Holt8 reported experimental results on stress sensitivity of matrix permeability of a Jurassic sandstone. Samples were loaded under both triaxial compression and extension. No major differences in permeability were found between deviatoric and hydrostatic loading prior to yielding. At the yield stress, a sharp decline in permeability was observed. Most of the permeability reduction took place in the range of 60% of 90% of the peak shear stress. Teufel and Rhett3 introduced the term "stress path" to quantify the actual stress changes that take place in the reservoir during pressure depletion. (In this work, stress path is denoted K (not K0) to avoid confusion with uniaxial strain conditions, which is commonly denoted K0 test conditions. Also note that stress path here describes a constant ratio of change in stress state, which implies that different stress paths do not approach a common point in stress space.) The term describes the constant ratio of change in effective minimum (horizontal) stress to effective maximum (vertical) stress from initial reservoir conditions: K = Δ σ m i n Δ σ m a x . ( 3 ) The changes in the reservoir stress state resulting from depletion along stress paths of K=0, 0.5, and 1 are illustrated in Fig. 1. The importance of the reservoir stress path is that the shear stress has a larger increase for a lower stress path.

scholarly journals Study on Reasonable Energy Supplement Time of Tight Sandstone Oil Reservoirs with Rock Compressibility Stress Sensitivity

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Tian Xiaofeng ◽  
Tan Xianhong ◽  
Tian Ji ◽  
Li Nan ◽  
Yuan Zhongchao ◽  
...  
Keyword(s):  
Stress Sensitivity ◽  
Oil Well ◽  
Formation Pressure ◽  
Tight Sandstone ◽  
Threshold Pressure Gradient ◽  
New Approach ◽  
Energy Supplement ◽  
Original Rock ◽  
Rock Compressibility ◽  
Reasonable Energy

A-HBR field is a tight sandstone oil reservoir with a threshold pressure gradient and a rock compressibility stress sensitivity. However, no existing approach could predict reasonable energy supplement time considering both of them. Therefore, in this paper, rock compressibility stress sensitivity experiments are conducted. Then, a new approach is presented. This approach considers the correlation of rock compressibility and formation pressure. And the formation pressure is different from the development time and distance to oil well. The study suggests that the energy supplement time is later when the original rock compressibility is larger. The energy supplement time is earlier when the rock compressibility is more severe. A-HBR field’s reasonable energy supplement time is 83 days when considering the effect of rock compressibility stress sensitivity. It is much earlier than that when not considering the effect of rock compressibility stress sensitivity.

The O–C diagrams of minor planets − a new approach to modelling the rotation

1999 ◽  
Vol 173 ◽  
pp. 185-188
Author(s):  
Gy. Szabó ◽  
K. Sárneczky ◽  
L.L. Kiss
Keyword(s):  
Error Analysis ◽  
Time Dependence ◽  
Theoretical Work ◽  
Minor Planet ◽  
Minor Planets ◽  
New Approach ◽  
Preliminary Results ◽  
Ccd Observations

AbstractA widely used tool in studying quasi-monoperiodic processes is the O–C diagram. This paper deals with the application of this diagram in minor planet studies. The main difference between our approach and the classical O–C diagram is that we transform the epoch (=time) dependence into the geocentric longitude domain. We outline a rotation modelling using this modified O–C and illustrate the abilities with detailed error analysis. The primary assumption, that the monotonity and the shape of this diagram is (almost) independent of the geometry of the asteroids is discussed and tested. The monotonity enables an unambiguous distinction between the prograde and retrograde rotation, thus the four-fold (or in some cases the two-fold) ambiguities can be avoided. This turned out to be the main advantage of the O–C examination. As an extension to the theoretical work, we present some preliminary results on 1727 Mette based on new CCD observations.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Processing Immunoperoxidase Labeled Cell Monolayers and Cryostat Sesctions For Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 714-715
Author(s):  
K. Chien ◽  
R. Van de Velde ◽  
I.P. Shintaku ◽  
A.F. Sassoon
Keyword(s):  
Cell Monolayer ◽  
Cell Types ◽  
Surface Antigens ◽  
Immunoperoxidase Method ◽  
Reaction Step ◽  
Hot Plate ◽  
Air Drying ◽  
New Approach ◽  
Cell Monolayers ◽  
Glass Slides

Immunoelectron microscopy of neoplastic lymphoma cells is valuable for precise localization of surface antigens and identification of cell types. We have developed a new approach in which the immunohistochemical staining can be evaluated prior to embedding for EM and desired area subsequently selected for ultrathin sectioning.A freshly prepared lymphoma cell suspension is spun onto polylysine hydrobromide- coated glass slides by cytocentrifugation and immediately fixed without air drying in polylysine paraformaldehyde (PLP) fixative. After rinsing in PBS, slides are stained by a 3-step immunoperoxidase method. Cell monolayer is then fixed in buffered 3% glutaraldehyde prior to DAB reaction. After the DAB reaction step, wet monolayers can be examined under LM for presence of brown reaction product and selected monolayers then processed by routine methods for EM and embedded with the Chien Re-embedding Mold. After the polymerization, the epoxy blocks are easily separated from the glass slides by heatingon a 100°C hot plate for 20 seconds.

TEM study of a biofilm on copper corrosion

1996 ◽  
Vol 54 ◽  
pp. 220-221
Author(s):  
W. A. Chiou ◽  
N. Kohyama ◽  
B. Little ◽  
P. Wagner ◽  
M. Meshii
Keyword(s):  
Marine Bacterium ◽  
Culture Medium ◽  
Copper Alloys ◽  
Pure Copper ◽  
Localized Corrosion ◽  
Natural Seawater ◽  
Copper Corrosion ◽  
New Approach ◽  
The Past ◽  
Copper Tolerant

The corrosion of copper and copper alloys in a marine environment is of great concern because of their widespread use in heat exchangers and steam condensers in which natural seawater is the coolant. It has become increasingly evident that microorganisms play an important role in the corrosion of a number of metals and alloys under a variety of environments. For the past 15 years the use of SEM has proven to be useful in studying biofilms and spatial relationships between bacteria and localized corrosion of metals. Little information, however, has been obtained using TEM capitalizing on its higher spacial resolution and the transmission observation of interfaces. The research presented herein is the first step of this new approach in studying the corrosion with biological influence in pure copper.Commercially produced copper (Cu, 99%) foils of approximately 120 μm thick exposed to a copper-tolerant marine bacterium, Oceanospirillum, and an abiotic culture medium were subsampled (1 cm × 1 cm) for this study along with unexposed control samples.

High resolution at low voltage: A new approach

1989 ◽  
Vol 47 ◽  
pp. 76-77
Author(s):  
Arthur V. Jones
Keyword(s):  
Low Voltage ◽  
Emission Sources ◽  
New Approach ◽  
Design Concepts ◽  
Probe Diameter ◽  
Low Voltage Operation ◽  
Sufficient Intensity ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Immersion Type

With the introduction of field-emission sources and “immersion-type” objective lenses, the resolution obtainable with modern scanning electron microscopes is approaching that obtainable in STEM and TEM-but only with specific types of specimens. Bulk specimens still suffer from the restrictions imposed by internal scattering and the need to be conducting. Advances in coating techniques have largely overcome these problems but for a sizeable body of specimens, the restrictions imposed by coating are unacceptable.For such specimens, low voltage operation, with its low beam penetration and freedom from charging artifacts, is the method of choice.Unfortunately the technical dificulties in producing an electron beam sufficiently small and of sufficient intensity are considerably greater at low beam energies — so much so that a radical reevaluation of convential design concepts is needed.The probe diameter is usually given by

New approach to drawing in dental anatomy

1968 ◽  
Vol 32 (3) ◽  
pp. 279-282
Author(s):  
JI Mock ◽  
JW Grenfell ◽  
WA Richter
Keyword(s):  
New Approach ◽  
Dental Anatomy

Errata

1969 ◽  
Vol 34 (2) ◽  
pp. 176-176
Keyword(s):  
Speech Audiometry ◽  
New Approach ◽  
Sentence Reading

In the November 1968 issue of this journal, Margaret M. Martyn’s name was misspelled Martin on page 315. In the same issue, page 325, column 2 (Jerger, Speaks, and Trammell, “A New Approach to Speech Audiometry”), the sentence reading “Whenever the loss is sloping, however, the PB area underestimates and the SSI area overestimates the amount of handicap” should read as follows: “Whenever the loss is sloping, however, the PB area overestimates and the SSI area underestimates the amount of the handicap.”

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