scholarly journals Effect of pore pressure on the elastic moduli, porosity and permeability of Berea sandstone and Leuders limestone

1983 ◽  
Author(s):  
T.W. Thompson ◽  
S.M. Kelkar ◽  
K.E. Gray
Keyword(s):  
Pore Pressure ◽  
Elastic Moduli ◽  
Berea Sandstone ◽  
Porosity And Permeability

On: “The influence of pore pressure and confining pressure on dynamic elastic properties of Berea sandstone,” by N. I. Christensen and H. F. Wang (GEOPHYSICS, 50, 207–213, February 1985).

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 1016-1016
Author(s):  
G. H. F. Gardner
Keyword(s):  
Pore Pressure ◽  
Confining Pressure ◽  
Hysteresis Curve ◽  
Hysteresis Cycle ◽  
Berea Sandstone ◽  
Experimental Accuracy ◽  
Confining Pressures ◽  
History Of ◽  
Pressure Changes ◽  
Dynamic Elastic Properties

The authors present their results as if Berea sandstone were an elastic material; that is, velocities are given as functions of confining and pore pressure. In fact, most rocks are inelastic and velocities depend on the history of the confining and pore pressure, and not just on the present values. Some measurements of hysteresis were reported by Gardner et al. (1965). The confining pressure was cycled between two pressures [Formula: see text] and [Formula: see text] for a fixed pore pressure [Formula: see text], following a fixed schedule of pressure changes, until repeatable values of velocity were obtained. (At any intermediate pressure the velocity measured for increasing pressure was different from the value for decreasing pressure, giving rise to a hysteresis cycle). When the same schedule of pressure changes for the differential pressure [Formula: see text] was followed by holding [Formula: see text] fixed and varying [Formula: see text], the measured velocities followed the same hysteresis curve within the limits of experimental accuracy. In brief, when hysteresis was taken into account, changes in pore and confining pressures were equally effective in changing velocity. In their article, Christensen and Wang do not refer to hysteresis; perhaps they would like to comment on its relevance.

Pore-Pressure-Coefficient Anisotropy Measurements for Intrinsic and Induced Anisotropy in Sandstone

2010 ◽  
Vol 13 (02) ◽  
pp. 265-274 ◽  
Author(s):  
Ashraf Al-Tahini ◽  
Younane Abousleiman
Keyword(s):  
Pore Pressure ◽  
Elastic Moduli ◽  
Pressure Coefficient ◽  
Induced Anisotropy ◽  
Transverse Anisotropy ◽  
Significant Control ◽  
Bedding Planes ◽  
Rock Structure ◽  
Stress Induced Anisotropy ◽  
The Difference

Summary In this study, we determine experimentally the effect of inherent and stress-induced anisotropy on stiffness components, elastic moduli, and Biot's pore-pressure coefficients (PPCs) for Lyons outcrop Colorado sandstone, which exhibits a clear transverse isotropic rock structure. Both dynamic and quasistatic methods were used under a nonhydrostatic state of stress to perform the measurements on dry core samples. Our assumption of apparent transverse anisotropy was confirmed initially with acoustic velocity measurements and at a later stage in the loading with experimental transverse anisotropic failure analysis. The objective of this study is to identify and isolate the effect of stress-induced anisotropy from the inherent transverse anisotropy on the measured stiffness components, elastic moduli, and Biot's PPCs. The effect of stress-induced anisotropy appears to have significant control on measured stiffness components, elastic moduli, and Biot's PPCs in comparison to the inherent-transverse-anisotropy effect. Our work shows that the stiffness components, Mij and thus the computed elastic moduli, are highly influenced by the stress-induced anisotropy, especially the off-diagonal stiffness components, M12 and M13, where the increase in their magnitudes from the dynamic measurements before failure is determined to be 100 and 81%, respectively. The difference in the magnitude between the axial and lateral Biot's PPCs in line with bedding planes and perpendicular to them is measured to be 24 and 16% from the quasistatic and dynamic methods, respectively; whereas, the effect of stress-induced anisotropy reduced the dynamic average magnitude of the Biot's PPCs along the bedding planes and transverse to these planes by 63% across a stress range of 145 MPa.

Permeability variation with porosity, pore space geometry, and cement type: A case history from the Snøhvit field, the Barents Sea

Geophysics ◽  
2015 ◽  
Vol 80 (1) ◽  
pp. D43-D49 ◽  
Author(s):  
Sissel Grude ◽  
Jack Dvorkin ◽  
Martin Landrø
Keyword(s):  
Grain Size ◽  
Elastic Moduli ◽  
Barents Sea ◽  
Pore Space ◽  
Rock Physics ◽  
Additional Information ◽  
Order Of Magnitude ◽  
Porosity And Permeability ◽  
Lower Permeability ◽  
Permeability Variation

Laboratory permeability data from the brine-filled Tubåen Formation in the Snøhvit field show an order of magnitude permeability variation for approximately the same porosity. This variation in permeability is explained by a modified Kozeny-Carman equation that exploits the relationships among permeability, porosity, cementation, and pore geometry. The expression correlates the slope in a logarithmic plot of porosity versus permeability with the amount of contact cement and sorting, and the intercept with the grain size. Additional information about sorting and/or cementation can be used to better constrain the slope of the plot. Based on this equation, we found that the grain size and the amount of contact cement increased with depth in the lowermost Tubåen 1–3 sandstone units, this led to an increasing permeability with depth, in the same porosity range. The permeability variation in the shallowest Tubåen 4 sandstone unit was affected by sorting to a larger degree than the remaining Tubåen intervals, which influenced the cementation factor, porosity, and permeability simultaneously. These findings were supported by the depositional environment of the formation, a petrology study of grain size and sorting and a rock-physics study. The rock-physics study indicated that the samples with higher permeability had higher elastic moduli compared with the samples with lower permeability. This correlation between permeability and elastic moduli can be explained by the increasing amount of contact cement for the stiffer, high-permeability samples.

scholarly journals Disequilibrium Compaction, Fluid expansion and unloading effects: Analysis from well log and its pore pressure implication in Jay Field, Niger Delta

2020 ◽  
pp. 389-400 ◽  
Author(s):  
Chukwuemeka Patrick Abbey ◽  
Meludu Chukwudi Osita ◽  
Oniku Adetola Sunday ◽  
Mamman Yusuf Dabari
Keyword(s):  
Acoustic Wave ◽  
Pore Pressure ◽  
Niger Delta ◽  
Sedimentary Basins ◽  
Burial Depth ◽  
Well Log ◽  
Major Mechanism ◽  
Porosity And Permeability ◽  
Well Log Analysis ◽  
Pressure Regime

     Disequilibrium compaction, sometimes referred to as under compaction, has been identified as a major mechanism of abnormal pore pressure buildup in sedimentary basins. This is attributed to the interplay between the rate at which sediments are deposited and the rate at which fluids associated with the sediments are expelled with respect to burial depth. The purpose of this research is to analyze the mechanisms associated with abnormal pore pressure regime in the sedimentary formation. The study area “Jay field” is an offshore Niger Delta susceptible to abnormal pore pressure regime in the Agbada –Akata formations of the basin. Well log analysis and cross plots were applied to determine the under compacted zone in the formation since compaction increases with burial depth. It was observed that porosity and permeability of the deeper depth (3700 m to end of Well) are higher than those of the shallow part (3000 – 3700 m). This is against what is expected from normal compacted sediment, demonstrating disequilibrium compaction in deposition. Furthermore, it reveals that sedimentation rate was high, making it unable for the sediments to expunge its fluid as expected. Density and acoustic wave increase with depth in normal compaction trend. However, the reverse that was identified in the mapped interval is attributed to disequilibrium compaction, unloading, clay diagenesis, and fluid expansion. The cross plot divulges sediments at the deeper depth had lower density and acoustic wave value with increased porosity when compared to those at shallow depth. This forms the basis that the sediments from this mapped interval experienced disequilibrium and unloading traceable to clay diagenesis during and after deposition, respectively.

Inversion of seabed porosity and permeability using pore pressure probe data

1998 ◽  
Vol 104 (3) ◽  
pp. 1788-1788
Author(s):  
Yongke Mu ◽  
Mohsen Badiey ◽  
Alexander H.‐D. Cheng ◽  
Zhong Liu ◽  
Richard H. Bennett
Keyword(s):  
Pore Pressure ◽  
Pressure Probe ◽  
Porosity And Permeability

Measurements of seismic-wave attenuation and dynamic pore pressure in Berea sandstone

2018 ◽  
Author(s):  
Nicola Tisato ◽  
Luca Duranti ◽  
Claudio Madonna
Keyword(s):  
Pore Pressure ◽  
Seismic Wave ◽  
Wave Attenuation ◽  
Berea Sandstone ◽  
Seismic Wave Attenuation

Analysis of Effective Porosity and Effective Permeability in Shale-Gas Reservoirs With Consideration of Gas Adsorption and Stress Effects

SPE Journal ◽  
2017 ◽  
Vol 22 (06) ◽  
pp. 1739-1759 ◽  
Author(s):  
Y.. Pang ◽  
M. Y. Soliman ◽  
H.. Deng ◽  
Hossein Emadi
Keyword(s):  
Pore Pressure ◽  
Shale Gas ◽  
Gas Adsorption ◽  
Effective Porosity ◽  
Gas Production ◽  
Gas Reservoirs ◽  
Adsorption Effect ◽  
Shale Gas Reservoirs ◽  
Porosity And Permeability ◽  
Stress Dependent

Summary Nanoscale porosity and permeability play important roles in the characterization of shale-gas reservoirs and predicting shale-gas-production behavior. The gas adsorption and stress effects are two crucial parameters that should be considered in shale rocks. Although stress-dependent porosity and permeability models have been introduced and applied to calculate effective porosity and permeability, the adsorption effect specified as pore volume (PV) occupied by adsorbate is not properly accounted. Generally, gas adsorption results in significant reduction of nanoscale porosity and permeability in shale-gas reservoirs because the PV is occupied by layers of adsorbed-gas molecules. In this paper, correlations of effective porosity and permeability with the consideration of combining effects of gas adsorption and stress are developed for shale. For the adsorption effect, methane-adsorption capacity of shale rocks is measured on five shale-core samples in the laboratory by use of the gravimetric method. Methane-adsorption capacity is evaluated through performing regression analysis on Gibbs adsorption data from experimental measurements by use of the modified Dubinin-Astakhov (D-A) equation (Sakurovs et al. 2007) under the supercritical condition, from which the density of adsorbate is found. In addition, the Gibbs adsorption data are converted to absolute adsorption data to determine the volume of adsorbate. Furthermore, the stress-dependent porosity and permeability are calculated by use of McKee correlations (McKee et al. 1988) with the experimentally measured constant pore compressibility by use of the nonadsorptive-gas-expansion method. The developed correlations illustrating the changes in porosity and permeability with pore pressure in shale are similar to those produced by the Shi and Durucan model (2005), which represents the decline of porosity and permeability with the increase of pore pressure in the coalbed. The tendency of porosity and permeability change is the inverse of the common stress-dependent regulation that porosity and permeability increase with the increase of pore pressure. Here, the gas-adsorption effect has a larger influence on PV than stress effect does, which is because more gas is attempting to adsorb on the surface of the matrix as pore pressure increases. Furthermore, the developed correlations are added into a numerical-simulation model at field scale, which successfully matches production data from a horizontal well with multistage hydraulic fractures in the Barnett Shale reservoir. The simulation results note that without considering the effect of PV occupied by adsorbed gas, characterization of reservoir properties and prediction of gas production by history matching cannot be performed reliably. The purpose of this study is to introduce a model to calculate the volume of the adsorbed phase through the adsorption isotherm and propose correlations of effective porosity and permeability in shale rocks, including the consideration of the effects of both gas adsorption and stress. In addition, practical application of the developed correlations to reservoir-simulation work might achieve an appropriate evaluation of effective porosity and permeability and provide an accurate estimation of gas production in shale-gas reservoirs.

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