Laboratory Measurement of Low-Permeability Rocks With a New Flow Pump System

1997 ◽  
Vol 506 ◽  
Author(s):  
Ming Zhang ◽  
Manabu Takahashi ◽  
Tetsuro Esaki
Keyword(s):  
Pore Pressure ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Test System ◽  
Low Permeability ◽  
Specific Storage ◽  
Pump System ◽  
The Difference ◽  
Host Rocks ◽  
Flow Pump

ABSTRACTNearly impermeable host rocks have been recognized as favorable media for many kinds of underground utilization such as radioactive nuclear waste disposal, storage of oil and LP gas, and CAES. To properly evaluate the ability of a geologic medium to retard transmission of fluids, it is necessary to accurately measure its hydraulic properties, most notably the permeability and specific storage. This paper presents a new flow pump permeability test system capable of testing low-permeability rocks under high confining and high pore pressure conditions, which simulate ground pressures at large depths. The new system was used to test the Inada Granite from Japan. The results of present study show that: 1) both permeability and specific storage of the rock are dependent not only on the confining pressure but also on the pore pressure. They decrease with the increment of the effective confining pressure, i.e., the difference between confining and pore pressures; 2) the permeability and specific storage of Inada Granite range from 10−11 to 10−12 cm/s and 10−6 to 10−7 1/cm, respectively. The flow pump technique with its rigorous theoretical analysis can be used to effectively obtain such low permeabilities within several tens of hours; 3) the storage capacity of flow pump system itself decreases with the increment of fluid pressure within the permeating system.

Fluid pressure response to undrained compression in saturated sedimentary rock

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 948-956 ◽  
Author(s):  
Douglas H. Green ◽  
Herbert F. Wang
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Wave Attenuation ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Pressure Response ◽  
Additional Parameter ◽  
Seismic Wave Velocity ◽  
Specific Storage ◽  
Order Of Magnitude

The pore pressure response of saturated porous rock subjected to undrained compression at low effective stresses are investigated theoretically and experimentally. This behavior is quantified by the undrained pore pressure buildup coefficient, [Formula: see text] where [Formula: see text] is fluid pressure, [Formula: see text] is confining pressure, and [Formula: see text] is the mass of fluid per unit bulk volume. The measured values for B for three sandstones and a dolomite arc near 1.0 at zero effective stress and decrease with increasing effective stress. In one sandstone, B is 0.62 at 13 MPa effective stress. These results agree with the theories of Gassmann (1951) and Bishop (1966), which assume a locally homogeneous solid framework. The decrease of B with increasing effective stress is probably related to crack closure and to high‐compressibility materials within the rock framework. The more general theories of Biot (1955) and Brown and Korringa (1975) introduce an additional parameter, the unjacketed pore compressibility, which can be determined from induced pore pressure results. Values of B close to 1 imply that under appropriate conditions within the crust, zones of low effective pressure characterized by low seismic wave velocity and high wave attenuation could exist. Also, in confined aquifer‐reservoir systems at very low effective stress states, the calculated specific storage coefficient is an order of magnitude larger than if less overpressured conditions prevailed.

scholarly journals Fluid pressure heterogeneity during fluid flow in rocks: new laboratory measurement device and method

2021 ◽  
Vol 225 (2) ◽  
pp. 968-983
Author(s):  
Nicolas Brantut ◽  
Franciscus M Aben
Keyword(s):  
Pore Pressure ◽  
Transient Flow ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Dead Volume ◽  
Low Permeability ◽  
Pore Fluid Pressure ◽  
Working Pressure ◽  
New Type ◽  
Internal Pore

SUMMARY We present a new type of transducer capable of measuring local pore fluid pressure in jacketed rock samples under elevated confining pressure conditions. The transducers are passive (strain-gauge based), of small size (7 mm in diameter at the contact with the rock and around 10 mm in length), and have minimal dead volume (a few mm3). The transducers measure the differential pressure between the confining fluid and the internal pore pressure. The design is easily adaptable to tune the sensitivity and working pressure range up to several hundred megapascals. An array of four such transducers was tested during hydrostatic pressurization cycles on Darley Dale sandstone and Westerly granite. The prototypes show very good linearity up to 80 MPa with maximum deviations of the order of 0.25 MPa, regardless of the combination of pore and confining pressure. Multiple internal pore pressure measurements allow us to quantify the local decrease in permeability associated with faulting in Darley Dale sandstone, and also prove useful in tracking the development of pore pressure fronts during transient flow in low permeability Westerly granite.

Deformation of Chalk Under Confining Pressure and Pore Pressure

1981 ◽  
Vol 21 (01) ◽  
pp. 43-50 ◽  
Author(s):  
Thomas Lindsay Blanton
Keyword(s):  
Mechanical Behavior ◽  
Pore Pressure ◽  
Hydrostatic Stress ◽  
Confining Pressure ◽  
Low Permeability ◽  
High Porosity ◽  
Pore Collapse ◽  
Soft Matrix ◽  
Pore Pressures ◽  
Ductile Behavior

Abstract Compression tests with and without pore pressure have been run on Danian and Austin chalks. The rocks yielded under increasing hydrostatic stress by pore collapse. The same effect was produced by holding a constant hydrostatic stress and reducing the pore pressure. This pore collapse reduced the permeability. The ultimate strength of the chalks increased with increasing confining pressure. The yield strength increased initially, but at higher confining pressures it decreased until it yielded under hydrostatic stress. Relatively high pore-pressure gradients developed when the chalks. were compressed. In these situations, the mechanical behavior tended to be a function of the average effective stresses. Introduction Hydrocarbons have been found in chalks in the North Sea, the Middle East, the Gulf Coast and midcontinent regions of the U.S., and the Scotian Shelf of Canada1; however, problems have been encountered in developing these reservoirs efficiently because of the unusual mechanical behavior of chalk. Chalks have three characteristics that interact to differentiate their behavior from most reservoir rocks. High Porosity. Porosities may be as high as 80070.1,2 Effects of burial and pore-water chemistry can reduce this porosity to less than 1%, but notable exceptions occur in areas of early oil placement and overpressuring where porosities in excess of 40% have been reported.2,3 Low Permeability Regardless of porosity, chalks have low permeabilities, usually around 1 to 10 md. Soft Matrix. Chalks are predominantly calcite, which has a hardness of 3 on Mohr's scale. These properties create problems in the following areas of reservoir development. Drilling. High porosity combined with a soft matrix material makes for a relatively weak and ductile rock. Efficient drilling involves chipping the rock and ductile behavior inhibits this process. Stimulation. The combination of high porosity and low permeability makes chalks prime candidates for stimulation by hydraulic fracturing or acid fracturing. The best production often is associated with natural fractures.2,3 Man-made fractures could open up new areas to production, but again ductile behavior inhibits the fracturing process. Production. In many cases permeabilities are low enough to trap pore fluids and cause abnormally high pore pressures.2 These high pore pressures help maintain the high porosities at depth by supporting some of the weight of the overburden. As the field is produced and the pore pressure lowered, some of the weight will shift to the soft matrix. The result may be pore collapse and reduction of an already low permeability. These problems indicate a need for basic information on the mechanical behavior of chalks. Determining methods of enhancing brittle behavior could lead to improved drilling and stimulation techniques. The ability to predict and prevent pore collapse could increase ultimate recovery. The approach taken in this study was experimental. Specimens of chalk were subjected to different combinations of stress and pore pressure in the laboratory, and the resulting deformations were measured.

An experimental study on the cryogenic face seal at different inlet pressures

2019 ◽  
Vol 234 (9) ◽  
pp. 1470-1481
Author(s):  
Guoyuan Zhang ◽  
Yangyang Zhao ◽  
Weigang Zhao ◽  
Xiutian Yan ◽  
Maotan Liang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
High Speed ◽  
Fluid Pressure ◽  
Stable State ◽  
Test System ◽  
Leakage Rate ◽  
Mechanical Seals ◽  
Closing Force ◽  
The Difference

An experimental test system for cryogenic high-speed hydrodynamic non-contact mechanical seals is developed. Based on this system, the performances of seals under different working conditions are studied in detail in this paper. With the experimental results, the main performances of the seals (such as inlet and outlet temperatures, separated speed, face temperature, friction force, friction coefficient, leakage rate) are obtained, and the relationships of the performances with the inlet fluid pressure, the closing force and the rotational speed are discussed. The results show that the difference between the outlet and inlet temperatures decreases with increasing inlet fluid pressure. As the speed increases, the friction force varies little and remains at a constant value. The friction coefficient of the seal is approximately 0.12 and basically does not change with the speed. The leakage rate is also maintained at approximately 190 g/s. With the increase in the closing force, the friction at the seal’s face does not change greatly, which indicates that the friction at the face is always in a stable state with the seal’s closing force.

Experimental Study and Numerical Simulation of Rock Mass Seepage Characteristics of Tunnel Engineering

2011 ◽  
Vol 243-249 ◽  
pp. 3538-3545
Author(s):  
Yong Dong Jiang ◽  
Ling Xiong ◽  
Xing Yang Yang ◽  
Quan Zhen ◽  
Zong Ling Yan
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Pore Pressure ◽  
Confining Pressure ◽  
Test System ◽  
Surrounding Rock ◽  
Simultaneous Action ◽  
Seepage Field ◽  
Variation Characteristics ◽  
Seepage Characteristics

In this research, the MTS815 rock mechanics test system , produced by American MTS co., has been conducted with transient method to study the seepage characteristics of rock under different confining pressure. Experiments have obtained the following results: with the confining pressure increased, penetration ability of water in rock decreased, but the start-up pressure gradient increased; permeability of rock decreased with the increase of effective confining pressure, which had negative exponent functional relationship between them. Based on previous researches, the study has established filtration equation which couples with stress field, temperature field and seepage field. Combined with the practical tunnel project, numerical simulated the variation characteristics of deformation of tunnel surrounding rock, pore pressure and seepage field under three fields non-coupling and coupling, numerical simulation obtained: the difference among deformation of surrounding rock, pore pressure and seepage field distribution under the coupling and non-coupling is remarkable, so it must consider the simultaneous action of fluid - solid - heat when we need to research the working of seepage law of groundwater in tunnel rock mass, and the research results enjoy important theoretical significance and practical application value.

Biot coefficient is distinct from effective pressure coefficient

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. L27-L33 ◽  
Author(s):  
Tobias M. Müller ◽  
Pratap N. Sahay
Keyword(s):  
Pressure Coefficient ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Effective Pressure ◽  
Pore Scale ◽  
Biot Coefficient ◽  
Saturated Rock ◽  
Bulk Volume ◽  
The Difference ◽  
Pressure Changes

Within the Biot poroelasticity theory, the effective pressure coefficient for the bulk volume of a fluid-saturated rock and the Biot coefficient are one and the same quantity. The effective pressure coefficient for the bulk volume is the change of confining pressure with respect to fluid-pressure changes when the bulk volume is held constant. The Biot coefficient is the fluid volume change induced by bulk volume changes in the drained condition. However, there is experimental evidence showing a difference between these two coefficients, arguably caused by microinhomogeneities, such as microcracks and other compliant pore-scale features. In these circumstances, we advocate using the generalized constitutive pressure equations recently developed by Sahay wherein the effective pressure coefficient and the Biot coefficient enter as distinct quantities. Therein, the difference is attributed to the porosity effective pressure coefficient that serves as a measure for the deviation from the Biot prediction and accounts for microinhomogeneities. We have concluded that these generalized constitutive pressure equations offer a meaningful alternative to model observed rock behavior.

A review of specific storage values from pore pressure response to passive in situ stresses: Implications for sustainable groundwater management

2020 ◽  
Author(s):  
Wendy A Timms ◽  
M Faysal Chowdhury ◽  
Gabriel C Rau
Keyword(s):  
Groundwater Management ◽  
Pore Pressure ◽  
Pressure Response ◽  
Earth Tides ◽  
Low Permeability ◽  
Specific Storage ◽  
Sustainable Groundwater Management ◽  
In Situ Stresses ◽  
Pore Pressure Response

<p>Specific storage (S<sub>s</sub>) values are important for analyzing the quantity of stored groundwater and for predicting drawdown to ensure sustainable pumping. This research compiled S<sub>s</sub> values from multiple available studies based on pore pressure responses to passive stresses, for comparison and discussion with relevant poroelastic theory and groundwater applications. We find that S<sub>s</sub> values from pore pressure responses to passive in situ stresses ranged from 1.3x10<sup>-7</sup> to 3.7x10<sup>-5</sup> m<sup>-1</sup> (geomean 2.0x10<sup>-6</sup> m-1, n=64 from 24 studies). This large S<sub>s</sub> dataset for confined aquifers included both consolidated and unconsolidated strata by extending two recent literature reviews. The dataset included several passive methods: Individual strains from Earth tides and atmospheric loading, their combined effect, and values derived from soil moisture loading due to rainfall events. The range of S<sub>s</sub> values spans approx. 2 orders of magnitude, far less than for hydraulic conductivity, a finding that has important implications for sustainable groundwater management. Both the range of values and maximum S<sub>s</sub> values in this large dataset were significantly smaller than S<sub>s</sub> values commonly applied including laboratory testing of cores, aquifer pump testing and numerical groundwater modelling. </p><p>Results confirm that S<sub>s</sub> is overestimated by assuming incompressible grains, particularly for consolidated rocks. It was also evident that Ss that commonly assumes uniaxial conditions underestimate S<sub>s</sub> that accounts for areal or volumetric conditions.  Further research is required to ensure that S<sub>s</sub> is not underestimated by assuming instantaneous pore pressure response to strains, particularly in low permeability strata. However, in low permeability strata S<sub>s</sub> could also be overestimated if based on total porosity (or moisture content) rather than a smaller free water content, due to water adsorbed by clay minerals. Further evaluation is also required for influences on S<sub>s</sub> from monitoring bore construction (ie. screen and casing or grouting), and S<sub>s</sub> derived from tidal stresses (undrained or constant mass conditions) that could underestimate S<sub>s</sub> applicable to groundwater pumping (drained or changing mass conditions). In summary, poroelastic effects that are often neglected in groundwater studies are clearly important for quantifying water flow and storage in strata with changing hydraulic stress and loading conditions. </p>

Effects of Confining Pressure on Gas and Water Permeabilities of Rocks

2000 ◽  
Vol 663 ◽  
Author(s):  
M. Zhang ◽  
M. Takeda ◽  
T. Esaki ◽  
M. Takahashi ◽  
H. Endo
Keyword(s):  
Rock Specimen ◽  
Pulse Method ◽  
Confining Pressure ◽  
Great Depth ◽  
Test System ◽  
Saturated Rock ◽  
Underground Disposal ◽  
High Confining Pressure ◽  
Confining Pressures ◽  
The Difference

ABSTRACTKnowledge of the permeability of hydraulically-tight rock at great depth is crucially important for the design and/or assessment of facilities associated with underground disposal of radioactive nuclear wastes. This paper presents a recently developed laboratory permeability test system capable of testing low permeability rocks either by using air as a permeant or by the transient-pulse method under high confining pressure conditions that simulate ground pressures at depths. The new system was used to test Shirahama sandstone and Inada granite, which are two types of rock widely available in Japan. To investigate the effects of heterogeneity on rock permeability, specimens cored parallel to and perpendicular to bedding for sandstone, and specimens cored in the direction perpendicular to Rift Plane, Grain Plane and Hardway Plane for granite, were used. The results of this study showed that: 1) gas permeabilities of a dried rock specimen tested by air permeation are almost the same values as water permeabilities of the same saturated rock specimen tested by the transient-pulse method; 2) the intrinsic permeabilities of Shirahama sandstone and Inada granite range from about 8.33E-16 to 7.38E-17 m2 and from 1.86E-17 to 6.94E-20 m2, respectively. They decrease monotonously with increase in effective confining pressure (defined as the difference between the confining and pore pressures), while the rate of decrease diminishes at higher confining pressures. The reduction in permeabilities is due to the closure of microcracks that control fluid flow at low confining pressures; and 3) Inada granite is a heterogeneous and isotropic material. Its hydraulic heterogeneity is more significant in Rift Plane than in Hardway and Grain Planes.

scholarly journals Fluid pressurisation and earthquake propagation in the Hikurangi subduction zone

2021 ◽  
Author(s):  
Stefano Aretusini ◽  
Francesca Meneghini ◽  
Elena Spagnuolo ◽  
Christopher Harbord ◽  
Giulio Di Toro
Keyword(s):  
Shear Strength ◽  
Pore Pressure ◽  
Subduction Zone ◽  
Subduction Zones ◽  
Fluid Pressure ◽  
Low Permeability ◽  
Earthquake Rupture ◽  
Fault Rocks ◽  
Seismic Slip ◽  
Saturated Clay

<p>In subduction zones, seismic slip at shallow crustal depths can lead to the generation of tsunamis. Large slip displacements during tsunamogenic earthquakes are attributed to the low coseismic shear strength of the fluid-saturated and non-lithified clay-rich fault rocks. However, because of experimental challenges in confining these materials, the physical processes responsible of the coseismic reduction in fault shear strength are poorly understood. Using a novel experimental setup, we measured pore fluid pressure during simulated seismic slip in clay-rich materials sampled from the deep oceanic drilling of the Pāpaku thrust (Hikurangi subduction zone, New Zealand). Here we show that seismic slip is characterized by an initial decrease followed by an increase of pore pressure. The initial pore pressure decrease is indicative of dilatant behavior. The following pore pressure increase, enhanced by the low permeability of the fault, reduces the energy required to propagate earthquake rupture. We suggest that thermal and mechanical pressurisation of fluids facilitates seismic slip in the Hikurangi subduction zone, which was tsunamigenic about 70 years ago. Fluid-saturated clay-rich sediments, occurring at shallow depth in subduction zones, can promote earthquake rupture propagation and slip because of their low permeability and tendency to pressurise when sheared at seismic slip velocities.</p>

scholarly journals Sealing Performance of New Solidified Materials: Mechanical Properties and Stress Sensitivity Characterization of Pores

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Chao Zhang ◽  
Gaohan Jin ◽  
Chao Liu ◽  
Shugang Li ◽  
Junhua Xue ◽  
...  
Keyword(s):  
Coal Sample ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Peak Stress ◽  
Confining Pressure ◽  
Stress Sensitivity ◽  
Test System ◽  
Sample Material ◽  
Sealing Material ◽  
The Difference

Borehole-sealing solidified material plays a significant role in improving sealing quality and enhancing gas drainage performance. In this study, the MTS815 electro-hydraulic triaxial servo test system and MR-60 NMR test system were adopted to conduct triaxial compression control experiment on the coal sample material, concrete material, and new solidified sealing material, respectively. This paper aims to analyze the difference of support effects, porosity, and stress sensitivity between those materials. Experimental results show that under the same stress condition, the stiffness of traditional concrete solidified material is the largest, while the new solidified material is the second, and the coal sample material is the smallest. Compared with the traditional concrete solidified material, the new solidified sealing material has better strain-bearing capacity and volumetric expansion capacity under each confining pressure in the experiment. The axial strain and volume increment of new solidified material is higher than those of the traditional concrete solidified material at the peak stress. Meanwhile, the confining pressure has a certain hysteresis effect on the postpeak stress attenuation. Fracture has the strongest stress sensitivity in three pore types, and its T2 map relaxation area has a larger compression than adsorption pore and seepage pore under the same pressure. The relative content of seepage pore and fracture in the new solidified material is less than that of coal and concrete samples, and the stress sensitivity of the new solidified materials is weaker than that of coal and concrete materials, thence, new solidified material will have better performance in borehole sealing. Outcomes of this study could provide guidance on the selection of the most effective sealing materials for sealing-quality improvement.

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