Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

Shi, Lu; Zeng, Zhijiao; Fang, Zhiming; Li, Xiaochun

doi:10.1155/2019/1796380

Cited by 9 publications

(5 citation statements)

References 66 publications

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“…In Fig. 13a, the results of the Malm carbonates, averaged for each rock type, show a good agreement between the maxima and minima of the range observed by different authors (Bakhtiari et al 2011;Dautriat et al 2011;Hassanzadegan 2013;Moosavi et al 2014;Teklu et al 2018;Meng et al 2019;Shi et al 2019). Some of the (dolomitic) limestone samples tend to have a high stress sensitivity of permeability and might be controlled by crack-like pores and microcracks (double-porous medium), while others exhibit a well-connected flow network that is more persistent to compressive stress (see Fig.…”

Section: Dependencies Of Different Rock Types Of the Malm Aquifersupporting

confidence: 77%

“…Several authors observed a high variance of the stress sensitivity for different rock types (Fig. 13), even for rocks of similar lithology (Moosavi et al 2014;Blöcher et al 2014;Pei et al 2014;Meng et al 2019;Bakhtiari et al 2011;Hassanzadegan 2013;Shi et al 2019;Ghabezloo et al 2009a;Teklu et al 2018;Dautriat et al 2011). Considering the facies of the individual rock types, a general decrease in sensitivity to well-connected pore networks becomes apparent.…”

Section: Dependencies Of Different Rock Types Of the Malm Aquifermentioning

confidence: 94%

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Stress sensitivity of porosity and permeability under varying hydrostatic stress conditions for different carbonate rock types of the geothermal Malm reservoir in Southern Germany

et al. 2021

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In geothermal reservoir systems, changes in pore pressure due to production (depletion), injection or temperature changes result in a displacement of the effective stresses acting on the rock matrix of the aquifer. To compensate for these intrinsic stress changes, the rock matrix is subjected to poroelastic deformation through changes in rock and pore volume. This in turn may induce changes in the effective pore network and thus in the hydraulic properties of the aquifer. Therefore, for the conception of precise reservoir models and for long-term simulations, stress sensitivity of porosity and permeability is required for parametrization. Stress sensitivity was measured in hydrostatic compression tests on 14 samples of rock cores stemming from two boreholes of the Upper Jurassic Malm aquifer of the Bavarian Molasse Basin. To account for the heterogeneity of this carbonate sequence, typical rock and facies types representing the productive zones within the thermal reservoir were used. Prior to hydrostatic investigations, the hydraulic (effective porosity, permeability) and geomechanical (rock strength, dynamic, and static moduli) parameters as well as the microstructure (pore and pore throat size) of each rock sample were studied for thorough sample characterization. Subsequently, the samples were tested in a triaxial test setup with effective stresses of up to 28 MPa (hydrostatic) to simulate in-situ stress conditions for depths up to 2000 m. It was shown that stress sensitivity of the porosity was comparably low, resulting in a relative reduction of 0.7–2.1% at maximum effective stress. In contrast, relative permeability losses were observed in the range of 17.3–56.7% compared to the initial permeability at low effective stresses. Stress sensitivity coefficients for porosity and permeability were derived for characterization of each sample and the different rock types. For the stress sensitivity of porosity, a negative correlation with rock strength and a positive correlation with initial porosity was observed. The stress sensitivity of permeability is probably controlled by more complex processes than that of porosity, where the latter is mainly controlled by the compressibility of the pore space. It may depend more on the compaction of precedented flow paths and the geometry of pores and pore throats controlling the connectivity within the rock matrix. In general, limestone samples showed a higher stress sensitivity than dolomitic limestone or dolostones, because dolomitization of the rock matrix may lead to an increasing stiffness of the rock. Furthermore, the stress sensitivity is related to the history of burial diagenesis, during which changes in the pore network (dissolution, precipitation, and replacement of minerals and cements) as well as compaction and microcrack formation may occur. This study, in addition to improving the quality of input parameters for hydraulic–mechanical modeling, shows that hydraulic properties in flow zones largely characterized by less stiff, porous limestones can deteriorate significantly with increasing effective stress.

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Section: Dependencies Of Different Rock Types Of the Malm Aquifersupporting

confidence: 77%

Section: Dependencies Of Different Rock Types Of the Malm Aquifermentioning

confidence: 94%

Stress sensitivity of porosity and permeability under varying hydrostatic stress conditions for different carbonate rock types of the geothermal Malm reservoir in Southern Germany

et al. 2021

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“…The exponential nature of the decrease in volumetric permeability of the Clashach sandstone samples (composed of 90% of quartz and 10% of feldspar) depending on the deformation and effective compressional pressure was revealed in [7]. An exponential dependence of permeability on effective rock pressure was also obtained in other previous experimental works [8][9][10][11][12][13].…”

Section: Introductionsupporting

confidence: 61%

A Model of Reservoir Permeability Evolution during Oil Production

2021

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In this paper, we present a mathematical model to predict the evolution of rock permeability depending on effective pressure during oil production. The model is based on the use of the results of well testing data from wells operating in the oil fields of the Perm–Solikamsk region in the north of the Volgo Ural oil and gas province. Dependences of the change in flow characteristics in the reservoir on the effective pressure were established. We performed a comparative assessment using permeability and effective pressure data that were normalized to dimensionless forms of k/ko and P/Po. The factors and their influence on the nature of the change in permeability from the reservoir pressure were determined. Depending on the type of rock, its composition, initial permeability, and bedding conditions, we determined the limits of variation of the constants in empirical equations describing the change in the permeability of rocks from the effective pressure. The mathematical model we developed enables the prediction of the change in permeability of rocks during oil production from reservoirs on the basis of reservoir properties such as initial permeability, initial reservoir pressure, average bedding depth, net-to-gross ratio, and initial effective rock pressure.

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“…The simplified exponential dependence of the porous media permeability on the effective pressure, established by the experimental studies [34][35][36][37][38][39]68,69], has the following form:…”

Section: Porous Rocksmentioning

confidence: 99%

Effect of Effective Pressure on the Permeability of Rocks Based on Well Testing Results

et al. 2021

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During the development of oil and gas fields, the permeability of the reservoirs decreases due to a decrease in reservoir pressure and an increase in effective pressure, as a result of which significant reserves of oil and gas remain in the reservoir. To predict the rate of decrease in oil production rates during field development and to respond quickly, it is necessary to know the law of permeability decrease with an increase in effective pressure. Existing methods for describing the change in the permeability of rocks were analyzed in the paper. Numerical analysis of the results of core studies from previously published papers and the results of field well testing on the examples of the north Perm region oil fields showed that in both cases, regardless of the type of rock and the type of reservoir, the change in permeability can be described by the same equations (exponential and power-law). Obtained equations can be used to predict changes in the permeability of terrigenous reservoirs of the north Perm region oil fields. At the same time, according to the results of well testing, an intensive decrease in permeability is observed with an increase in effective pressure. Analysis of the nature of permeability changes using the Two-Part Hooke’s Model showed that significant irreversible deformations are currently taking place in the formations of the oil fields under consideration. Predicting the change in permeability from effective pressure can allow to optimize the development of oil deposits.

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Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

Cited by 9 publications

References 66 publications

Stress sensitivity of porosity and permeability under varying hydrostatic stress conditions for different carbonate rock types of the geothermal Malm reservoir in Southern Germany

Stress sensitivity of porosity and permeability under varying hydrostatic stress conditions for different carbonate rock types of the geothermal Malm reservoir in Southern Germany

A Model of Reservoir Permeability Evolution during Oil Production

Effect of Effective Pressure on the Permeability of Rocks Based on Well Testing Results

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