Temperature-Dependent Elasticity of Common Reservoir Rocks

Davis, E. S. (Los Alamos National Laboratory) | Sinha, D. N. (Los Alamos National Laboratory) | Pantea, C. (Los Alamos National Laboratory)

OnePetro 

ABSTRACT ABSTRACT: Many sandstones and limestones are key oil and gas reservoirs and thus understanding their elastic properties at temperatures commonly found at drilling depths is important for the oil and gas industry. In particular, it is important to study the elastic behavior of these materials when subjected to thermal shock, possibly caused by introduction of fracking fluids or drilling, as the response may be unexpected. Any such unexpected behavior can cause problems with hydraulic fracturing calculations that depend on the mechanical properties of the reservoir materials. In this study, the qualitative mechanical properties of selected limestones and sandstones were measured over a wide temperature range via a mechanical resonance shifting technique to explore the temperature effects on elastic properties. It was found that although several reservoir materials react in predictable ways, others display anomalous elastic behavior with temperature changes. Two Berea Sandstone varieties from two separate quarries (Cleveland and Kipton Quarries) were found to soften with cooling in certain temperature ranges, causing a significant deviation in their expected elastic properties. INTRODUCTION With the quick rise of hydraulic fracturing and the domestic oil and gas industry in the United States, the demand for detailed knowledge of the mechanical properties of reservoir materials at depth has increased. Mechanical properties of different reservoir materials can vary significantly, but all share the common feature of possessing large empty spaces to store oil and gas. The amount of interconnected spaces vary widely among reservoir materials and even the same material can have drastically different permeability values (e.g., Berea sandstone can range from <50 mD to >1,000 mD). Previous work has been performed to characterize different reservoir materials and will be briefly described here. Al-Ameri et al. studied the effects of CO2 sequestration on the mechanical properties of Indiana Limestone using ultrasonic velocity measurements and found that Indiana Limestone is an excellent material for CO2 sequestration as it does not undergo pore collapse or other major changes like more porous carbonates when injected with supercritical CO2 (Al-Ameri et al., 2016). Ojala found that the tensile strength of Austin Chalk does not significantly depend on CO2 saturation and instead is much more correlated with porosity and p-wave velocity of the specific sample (Ojala, 2011). Pimienta et al. studied the role of porosity, pressure, and mineral content on the elastic dispersion of saturated Berea, Wilkenson, and Bentheim sandstone (Pimienta et al., 2017). Peng et al. studied the effects of chosen resolution in X-ray microcomputed tomography on the calculated permeability in Berea Sandstone and found that although resolving smaller pores increases the calculated porosity, the permeability is relatively unchanged (Peng et al., 2013). Hart and Wang measured the poroelastic moduli of both water saturated Berea Sandstone and Indiana Limestone as a function of confining pressure and pore pressure (Hart and Wang, 1995). Ultimately, though, little work has been performed to investigate the behavior of elastic properties of different reservoir materials with temperature, for temperatures typically encountered in real life applications, e.g., when disturbed by extraction activities such as drilling or the introduction of fracking fluids.

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