| The effect of fluids on rock strength, Young's Modulus and Poisson's Ratio is complicated and not well understood. However, many applications involving rock-fluid interactions are of considerable interest, and often pose significant physical and economic impact on a given project. Experimental measurements were carried out to assess the role of various fluids on Young's modulus, Poisson's ratio and strength of three rock types---Indiana limestone, Salt Wash South and Berea Buff sandstone. The alteration of mechanical properties as a function of fluid and exposure time was evaluated. Oven-dried, deionized water saturation, salt brine saturation, and odorless mineral spirits (OMS) saturation were assessed using unconfined compression testing. A number of triaxial compression tests at high confining pressures were also conducted. In all cases, drained conditions were maintained.;Results are provided, showing substantial impact from water alone as the saturation fluid and less for the specific hydrocarbon saturants considered. Deionized water-saturated Indiana limestone samples were ∼25% weaker than dry samples. Young's modulus was also reduced by ∼25% with no significant change in Poisson's ratio. Samples that were saturated in deionized water for up to 8 weeks showed the same change in strength and Young's modulus as iv samples that were saturated for less than 24 hours. A 9% potassium chloride solution weakened Salt Wash South samples and reduced Young's modulus by ∼75% while increasing Poisson's ratio by ∼25%. Berea Buff sandstone, when saturated with deionized water, showed ∼20% reduction in strength with no substantial changes in Young's modulus and Poisson's ratio. Hypotheses for chemical interactions that occurred are provided, suggesting why aqueous compounds can substantially alter strength even in clay-poor rocks. |
