Experimental and simulation study of the tensile strength of wet carbonate rocks using the Brazilian Test

Abstract Mechanical behavior of rocks would have substantial implications for different operations from fluid injection and hydraulic fracturing in hydrocarbon reservoirs to underground carbon dioxide storage in the crust of the earth. In all of these operations, restricting the undesired seismicity events and preserving the integrity of formations is a crucial subject that enforces engineers to evaluate the mechanical behaviors of constituent rocks and predict the formation response. Tensile strength is an important factor for maintaining caprock and reservoir formation from induced tensile cracking which can be influenced by the pore fluid. This paper focuses on the tensile strength of carbonate rock, as an important reservoir rock, in the presence of seawater, as a common injection fluid candidate for enhanced oil recovery objectives. For this purpose, twelve dolomite samples from the Asmari-Jahrum Formation outcrop in Fars province, Iran, were prepared for performing tensile tests. Also for a thorough comparison, sample properties, fluid contents, digital image correlation measurements, and a finite element simulation have been investigated. The experimental results showed a noticeable reduction in the tensile strength of dolomite samples in the presence of distilled water and seawater. In comparison with a dry sample though, a reduction of 16% tensile strength for a seawater saturated sample was observed for similar samples. Among the various mechanisms, which are reported in the open literature, the hydration force seems to be the main reason for the tensile strength reduction and this conclusion was examined by measuring the mass of vaporized adsorbed water on the powder of the same dolomite sample. In addition by testing flooded samples, the impact of flow on the tensile strength was examined. For both cases of seawater and distilled water flooding, the samples which were placed in the outlet zone during the flooding showed lower tensile strength. Moreover, simulation results confirmed the similarity of the weakening trend and impact of seawater.