Fluid Initiation of Fracture in Dry and Water Saturated Rocks

Smirnov, V.B.; Ponomarev, A.V.; Isaeva, A.V.; Bondarenko, N.B.; Patonin, A.V.; Kaznacheev, P.A.; Stroganova, S.M.; Potanina, M.G.; Chadha, R.K.; Arora, K.

Авторы: Smirnov V.B., Ponomarev A.V., Isaeva A.V., Bondarenko N.B., Patonin A.V., Kaznacheev P.A., Stroganova S.M., Potanina M.G., Chadha R.K., Arora K.
Журнал: Izvestiya. Physics of the Solid Earth
Том: 56
Номер: 6
Год издания: 2020
Издательство: Pleiades Publishing, Inc.
Местоположение издательства: New York, USA
Первая страница: 808
Последняя страница: 826
Оригинальные версии: ФЛЮИДНАЯ ИНИЦИАЦИЯ РАЗРУШЕНИЯ В СУХИХ И ВОДОНАСЫЩЕННЫХ ГОРНЫХ ПОРОДАХ
DOI: 10.1134/S1069351320060099
Аннотация: We present the results of the laboratory studies on fluid initiated fracture in the samples of porousfracturedrocks that have been initially saturated with a pressure-injected fluid and then tested under increasingfluid pressure in saturated rocks. The tests were conducted at the Geophysical observatory “Borok” ofSchmidt Institute of Physics of the Earth of the Russian Academy of Sciences. The laboratory is equippedwith electrohydraulic press INOVA-1000. The experiments were conducted on the rock samples with substantiallydifferent porosity. The tested samples were made of Buffalo sandstones, granites from the welldrilled in a seismically active region and of granites from the well in the Voronezh crystalline massif. The permeabilityof granite samples was varied by their controlled artificial cracking by successive heating and cooling.The experimental procedure was set up in the following way. A preliminarily dried sample was initiallysubjected to uniaxial loading in uniform compression (confining pressure). Loading was performed at a constantstrain rate until the moment when the growth rate of acoustic emission (AE) activity began to acceleratewhich indicated that the stress level approaches ultimate strength. Since that, the loading rate was decreasedby an order of magnitude, and water was infused into a sample from its top face. The bottom end of a samplewas tightly sealed and impermeable to water. After this, the pore pressure in the sample that had got saturatedwith water to that moment was raised in steps whose amplitudes were varied. The obtained results of the laboratorystudies show that the character and intensity of fluid initiation of fracture markedly differ under primaryfluid injection into the porous-fractured samples and under the subsequent increases of the pore pressurein the saturated samples. The time delay of acoustic response relative to fluid initiation and the amplitudeof the response proved to be larger in the case of water injection into dry samples than in the case of raisingthe pore pressure in saturated samples. The AE response to the decrease in the pore pressure was also detectedin the experiments. The theoretical analysis of fluid propagation in a pore space of an air-filled sample in themodel with piston-type air displacement has shown that in the case of water injection into a dry sample, thefluid pressure front propagates more slowly than in the saturated sample.
Добавил в систему: Смирнов Владимир Борисович

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Fluid Initiation of Fracture in Dry and Water Saturated Rocksстатья

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