Abstract

Petroleum geomechanics is a multidisciplinary branch of petroleum sciences which aims to understand, model, and control the mechanical response of subsurface geo-materials, such as reservoir rocks and cap rocks. Major geomechanical properties are usually obtained from destructive tests using standardized laboratory procedures and, for practical reasons, the mechanical characteristics of reservoir rocks should be measured at the reservoir conditions. In this study six geomechanical units (GMUs) in a carbonate reservoir in an Iranian gas field (T ~ 90°C) were defined and then 24 plugs were taken from the cored intervals. Afterward, uniaxial compression tests were performed at 20°C and 90°C. Various geomechanical properties including unconfined compressive strength (UCS), Young’s modulus (E) and Poisson’s ratio (?) were determined and compared with each other. Results show that temperature may have some impact on the UCS of specimens but different GMUs show different kind of impacts and most were unaffected in this temperature range. Although E values vary from one GMU to another, temperature has almost no effect on this parameter for each GMU. Moreover, experimental results show that not only is there no significant difference among values of ? for each GMU, this parameter is also not sensitive to temperature changes. We conclude that, given normal dispersion of results and heterogeneity of rocks, for this class of rocks at these conditions, it is sufficient to execute tests at room temperature for engineering design purposes.

1. INTRODUCTION

The branch of petroleum engineering called petroleum geomechanics aims to understand and predict the mechanical behavior of reservoirs and adjacent formations through the full process of exploration to exploitation to abandonment [1, 2]. Generally, basic geomechanical characteristics of rock material are obtained from experimental tests on core samples at ambient conditions. To define these characteristics under in-situ conditions at depth (temperature, confining stress, pore pressure, saturation etc.), may require extensive laboratory experiments [3, 4, 5, 6, 7, 8] at more challenging and expensive conditions.

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