ABSTRACT:

We report on a series of compression and tension tests in Berea, Bandera, Lyons, and Tennessee sandstones to investigate the effect of saturating fluids on rock strength. We tested three different samples of each sandstone under dry and liquid (brine, and dodecane) saturated conditions using a multistage triaxial test (Pagoulatos, 2004). In this multistage technique, we define a crack propagation threshold based on the net volumetric strain at the onset of dilatancy as termination criterion between axial loading stages. Each of the multistage experiments allowed us to define a linear failure envelope using a single sample. We measured the tensile strength using a separate suite of samples for Brazilian tensile testing. Our findings suggest a reduction of compressive and tensile rock strength by up to 40% and 45%, respectively in fluid saturated rocks; the magnitude of this strength reduction is fluid type and lithology dependent, greatest reduction happened in more porous rocks while saturated with brine.

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