Pierre Berest

• PhD, graduated from Ecole Polytechnique and Ecole des Mines de Paris
• École Polytechnique

In 2014–2016, creep tests were performed in a dead-end drift of the Altaussee mine, where temperature and relative humidity experience very small fluctuations. These tests, which were several months long, proved that the creep rate of a natural salt sample is much faster in the 0.2–1 MPa deviatoric stress range than the creep rate extrapolated from...

To prevent climate change, Europe and the world must shift to low-carbon and renewable energies. Hydrogen, as an energy vector, provides viable solutions for replacing polluting and carbon-emitting fossil fuels. Gaseous hydrogen can be stored underground and coupled with existing natural gas pipe networks. Salt cavern storage is the best suited tec...

From 1996 to 2021, uniaxial creep tests were performed on salt samples in dead-end drifts of the Varangéville (France) and Altaussee (Austria) mines to take advantage of constant temperature and hygrometry. The applied loads were from 0.05 MPa (relative) to 4.5 MPa, i.e., much smaller than the loads currently applied during standard creep tests per...

The KEM-17 project of the Dutch State Supervision of Mines presented a critical review of concepts of cavern abandonment and related science. It recommended that analyses of cavern abandonment are done as an integrated project, addressing (i) micro-scale physical processes, (ii) cavern scale models based on field scale experiments and numerical mod...

On présente un ensemble de mesures d’oscillations de la pression effectuées en tête de puits de cavités salines. Ces cavités sont caractérisées par un grand volume (V = 10 ⁴ à 10 ⁶ m ³ ), une profondeur kilométrique (h = 250 m à 2000 m) et un petit diamètre (quelques décimètres) du puits métallique cimenté aux terrains qui en permet l’accès. Ce der...

Ambitious targets for renewable penetration in the electricity production mix go with the emergence of new challenges, such as the integration of intermittent electricity into the transmission and distribution grid and the need for storage or power production backups. Different technologies exist and are simultaneously competing and complementary t...

Tightness is a fundamental prerequisite to any underground storage. In storage salt caverns, a safe maximum admissible pressure must be selected to avoid product loss. The tensile strength of salt is small, and cavern pressure must be kept lower than geostatic pressure or, more precisely, lower than the least compressive stress at the cavern wall....

A creep test performed on a Landes salt sample during one year and a half is described. During the first year, a 0.6 MPa axial load is applied to the sample. At the end of this one-year phase, strain rate (9×10−12s-1) is much faster than the strain rate extrapolated from high-stress tests. Steady state strain rate is not reached. In an attempt to r...

New evidence supporting views previously expressed in a paper dedicated to the thermodynamic behavior of gas storage caverns (Bérest, 2019, Heat transfer in salt caverns, Int. J. Rock Mech. Rock Eng. Sci. 120 , 82 – 95 . https://doi.org/10.1016/j.ijrmms.2019.06.009 ) is provided. In a fluid-filled cavern, conditions for the onset of natural convect...

In wells producing water, oil, gas or geothermal energy, or in access wells to hydrocarbon storages, it is critical to evaluate the permeability of the formation as a function of depth. Continuous permeability logs in these wells are typically derived using tools that measure electrical, nuclear, magnetic or acoustic signals, using empirical relati...

The objective of this paper is to assess the creep law of natural salt in a small deviatoric stress range. In this range, creep is suspected to be much faster than what is predicted by most constitutive laws used in the cavern and mining industries. Five 2-year, multistage creep tests were performed with creep-testing devices set in a gallery of th...

Several aspects of the thermodynamic behavior of salt caverns containing brine, oil, natural gas, air or hydrogen are discussed. It is shown that natural convection always appears in a liquid-filled cavern. This is not true in the case of gas caverns. Gas type, brine temperature at the cavern bottom and water vapor content are influential. Equation...

Twelve incidents involving well casing and/or cement leaks in the salt caverns storage industry are described. These incidents occurred at the following storage sites: Eminence salt dome, Mississippi; Elk City, Oklahoma; Conway, Kansas; Yoder, Kansas; Mont Belvieu, Texas; Teutschenthal/Bad Lauchstädt, Germany; Clute, Texas; Mineola, Texas; Hutchins...

The formation of a brine geyser erupting from the wellhead of a large underground salt cavern is described. In most cases, the brine outflow from an opened cavern is slow; it results from the cavern creep closure and the thermal expansion of the cavern brine. These two processes are smooth; however, the brine outflow often is bumpy, as it is modula...

Based on the description of a dozen of cases, this paper suggests a categorization of craters formed above brine-production caverns for “piston” and “hourglass” types. The deliberate creation of three craters in Lorraine (France) above the Keuper salt formation is described first. After the cavern roof reaches the top of the salt formation, stoping...

Cet ouvrage s’inscrit dans la série des Manuels de Mécanique des Roches coordonnés par Pierre Duffaut sous le patronage du Comité français de mécanique des roches. Il renouvelle une publication maintenant épuisée, La Thermomécanique des Roches, parue en 1988. Cet ouvrage se propose de présenter de manière aussi complète que possible les connaissanc...

An in-situ test performed in a brine-filled cavern proves that, when brine pressure decreases rapidly, the creep closure rate increases drastically. Conversely, a rapid pressure increase leads to “reverse” creep closure: cavern volume increases, even when, at cavern depth, fluid pressure is lower than geostatic pressure. It is tempting to explain t...

Be it electrical signals in resistivity logs, radioactivity in gamma ray logs or magnetic moments of hydrogen protons in NMR logs, most logging techniques use an indirect approach to estimate permeability, which, in simple terms, is the measure of the ease with which a fluid of given viscosity can flow through porous media. These logging techniques...

The applied deviatoric stress during most creep tests performed on salt samples is in the 3.5–20 MPa range. However, the stresses actually experienced in the vicinity of a salt cavern are much smaller. Any extrapolation is difficult to vindicate, as the dominant micro-mechanisms are strongly suspected to be very different in the low-stress and medi...

In some laboratory tests, it was observed that after a rapid stress drop, the sign of the strain rate changed. A simple constitutive model is proposed that accounts for this phenomenon, which is called “rheological reverse creep”. Reverse creep also is observed following a rapid pressure increase in a salt cavern: in this environment, cavern volume...

Creep closure and structural stability of a cylindrical elongated cavern leached out from a salt formation are discussed. The Norton-Hoff creep law, or ‘‘power law’’, is used to capture the main features of salt rheological behavior. Two failure criteria are considered: (1) shear stresses must not be larger than a certain fraction of the mean stres...

Creep closure and structural stability of a cylindrical elongated cavern leached out from a salt formation are discussed. The Norton-Hoff creep law, or “power law”, is used to capture the main features of salt rheological behavior. Two failure criteria are considered: (1) shear stresses must not be larger than a certain fraction of the mean stress...

A small number of blowouts from gas storage caverns has been described in the literature. Gas flow lasted several days before the caverns were emptied. In this paper, we suggest simplified methods that allow for computing blowout duration, and evolution of gas temperature and pressure in the cavern and in the well. This method is used to compute ai...

In this paper, the nucleation and the propagation of thermal cracks following a severe thermal shock in gas storage caverns leached out from a salt formation are studied. This shock is induced by a quick release of the gas stored in the cavern following a rapid gas withdrawal from the cavern. A first model takes into account pressure and temperatur...

Rapid gas depressurization leads to gas cooling followed by slow gas warming when the cavern is kept idle. Gas temperature drop depends upon withdrawal rate and cavern size. Thermal tensile stresses, resulting from gas cooling, may generate fractures at the wall and roof of a salt cavern. However, in most cases, the depth of penetration of these fr...

Four in-situ tests performed in salt caverns in France and Germany are described. The main objective of these tests was to increase our understanding of the long-term behavior of abandoned caverns. It is proven that, in the long term, when cavern brine has reached thermal equilibrium with the rock mass, pressure evolution is governed by cavern cree...

A well passing through a geological formation is fitted with a tube, open at its bottom end, that is filled with a fluid. Another fluid is in the annular space between the tube and the wall of the well, the two fluids exhibiting an interface situated in the annular space. A hydraulic balance of the fluids of the well is disturbed and the trend of c...

Rapid gas depressurization leads to gas cooling followed by slow gas warming when the cavern is kept idle. Gas temperature drop depends upon withdrawal rate and cavern size. Thermal tensile stresses, resulting from gas cooling, may generate frac-tures at the wall and roof of a salt cavern. These fractures are perpendicular to the cavern wall; in mo...

A small number of blow-outs from gas storage caverns (for example, in Moss Bluff, Texas and Fort Saskatchewan, Canada) have been described in the literature. Gas flow lasted several days before the caverns were empty. In this paper, we suggest simplified methods that allow for computing blow-out duration and evolution of gas temperature and pressur...

Storage of natural gas in salt caverns had been developed mainly for seasonal storage, resulting in a small number of yearly pressure cycles and moderate gas-production rates. The needs of energy traders are changing towards more aggressive operational modes. The "high-frequency cycling" operation of salt caverns raises questions concerning the eff...

The "no-tensile effective stress" criterion is discussed. It is proven that effective tensile stresses can be generated at a cavern wall after a rapid increase or decrease in pressure. The Etzel K-102 test, performed in Germany more than 20 years ago, is revisited using the notion of effective tensile stresses.

Water hammers commonly are observed at wellheads and often are considered a potential hazard that should be avoided. Nevertheless, there are a few situations in which water hammers provide very valuable information about a well. A comprehensive data-acquisition and analysis system has been developed by Brouard Consulting and Ecole Polytechnique. On...

Rapid gas depressurization leads to gas cooling that is followed by slow gas warming when the cavern is kept idle. The decrease in the temperature of gas depends upon the relative withdrawal rate (in %/day), and cavern size and shape. Gas cooling may result in the onset of tensile stresses at cavern walls and roofs that may generate fractures or cr...

On 31st October 1873 the flatly bedded mining field Saint-Maximilien of Varangeville (France) suddenly collapsed. The tremor were felt up to 10 km away, in Nancy. The back-calculation of this mining field collapse in Varangeville is the first attempt to understand and to reproduce the dynamic process of the failure of a rock salt room-and-pillar mi...

Twelve years ago, creep tests at very low deviatoric stress were performed on an Etrez salt sample in the Varangeville Mine. Recently, a new testing campaign was performed on various salt samples to gain further insight on salt behavior. Creep tests are performed under a 0.1 MPa uniaxial loading on rock-salt samples from the Varangeville and Avery...

Storage of natural gas in salt caverns had been developed mainly for seasonal storage, resulting in a small number of yearly pressure cycles and moderate gas-production rates. The needs of energy traders are changing toward more aggressive operational modes. Gas temperature changes and additional stresses generated by high-frequency cycling in a st...

Cavern creep closure rate was recorded in the SG13-SG14 salt cavern of the Gellenoncourt brine field operated by CSME at Gellenoncourt in Lorraine, France. Cavern compressibility and the evolution of cavern brine temperature first were measured. In this shallow cavern (250-m deep), which had been kept idle for 30 years, cavern-brine thermal expansi...

Twelve years ago, creep tests at very low deviatoric stress were performed on an Etrez salt sample in the Varangeville Mine. Recently, a new testing campaign was performed on various salt samples to gain further insight on salt behavior. Creep tests are performed under a 0.1 MPa uniaxial loading on rock-salt samples from the Varangeville and Avery...

Storage of natural gas in salt caverns had been developed mainly for seasonal storage, resulting in a small number of yearly pressure cycles and moderate gas-production rates. The needs of energy traders are changing toward more aggressive operational modes. Gas temperature changes and additional stresses generated by high-frequency cycling in a st...

This collection of papers on research into and management of underground structures in salt formations represents the state-of-the-art on applications of salt mechanics in mines and storage caverns for gas/hydrocarbon, radioactive waste and toxic waste disposal. The contributions cover laboratory experiments, constitutive numerical modeling and fie...

Contrôle, la Revue de l'autorité de Sûreté Nucléaire, n°190, février 2011

Obtaining formation characteristics in a tight-gas environment is highly challenging: formation tester tools run during open-hole logging are often unsuccessful, and conventional well tests are not appropriate as no gas flow is commonly observed before hydraulic fracturing. This paper presents a new well testing methodology adapted from techniques...

Long-term creep tests have been performed on rock-salt and argillite samples under very small uniaxial loadings (σ = 0.02 to 0.1 MPa) . To minimize the effects of temperature variations, testing devices were set in a mine where temperature fluctuations are of the order of one-hundredth of a degree Celsius. The mechanical loading was provided by dea...

In 1997-1998, an abandonment test was performed in a 950-m deep, 8000-m3 salt cavern operated by GDF SUEZ at Etrez, France. In this relatively small brine-filled cavern, which had been kept idle for 15 years before the test, thermal equilibrium was reached. A special system was designed to monitor leaks, which proved to be exceedingly small. In the...

Flash X, la lettre scientifique de l'Ecole Polytechnique, janvier 2009, n°10, p.9-13.

The 1873 panel collapse at the Varangéville salt mine (Lorraine, France) is described. Post-accident reports, as well as the experience drawn from neighbouring panels and mines, proved that pillars punched the marly layers on which they rested—a unique failure mechanism in the history of salt mines. The database on rock mechanical behaviour is rela...

Tightness tests performed in underground salt caverns used for storing oil and gas are described and assessed. It is proved that, together with an actual leak, various factors may influence the results of such test, possibly leading to severe misinterpretation. These factors include thermal disequilibrium, brine permeation through cavern walls, add...

The French authorities commissioned a group of experts to discuss trends in salt mining techniques (solution mining and dry mine) and abandonment methods. Safety margins in the stable caverns methods, methods in which caverns may become instable, methods including deliberate collapse were discussed; recommendations were provided on such topics as p...

Long-term creep tests have been performed under very small uniaxial loadings (σ=0.02 to 0.1 MPa). Testing devices were set in an underground gallery, where temperature fluctuations are in the order of one hundredth of a Celsius degree. The mechanical loading was provided by dead weights. The displacements were measured through special sensors whose...

Clayey rock may be the host medium for a French long-term nuclear-waste storage facility. To gain better understanding of the delayed behavior of this potential host rock, we conducted a testing program that focused on creep tests. Fourteen tests were conducted: short-term multi-step creep tests (six at ambient temperature, four at T=80 °C and four...

We discuss the positiveness of the second variation of a Lagrangian Action subjected to an integral constraint when the end-points of the range of integration of the integrals can be displaced along prescribed curves. The Lagrangian does not depend explicitly on the variable of integration. The results are illustrated by the problem of a liquid dro...