ULTRASONIC MEASUREMENTS AND ROCK PHYSICS MODELING OF IRATI SHALE FROM BRAZIL
Hu, Xiaofan 1987-
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Unconventional shale reservoirs have gained significant attention in recent years in terms of hydrocarbon reserves and production potential. However, exploration and production from shale reservoirs are still very challenging. One of the problems is that the composition of shale are very complex, and it becomes even more difficult to be understood when shale rocks contain organic matter which we are looking for. Organic matter has a very different behavior compared with other mineral components that are in shales, and that difference might give us a chance to see and model elastic properties of organic matter. To study this, we combined in-situ measurement and rock physics modeling which are important for the interpretation and modeling of seismic response. Our understanding of rock properties is primarily based on laboratory tests and observations. The experiment includes four Irati shale cores from Brazil. First we measured porosity and grain density which are indicators to kerogen contents. It ranges from 1.97 to 2.58 g/cm Then, acoustic P- and S-wave velocities are measured in both dry and saturated conditions with increasing differential pressure. P-wave velocity is from 2247 to 3960 m/s and 2786 to 4010 m/s in dry and saturated conditions respectively. S-wave velocity is from 661 to 2052 m/s and 1163 to 1824 m/s in dry and saturated conditions respectively. The measured data indicate strong transverse isotropy and drive the modeling. In this study, we propose a physically consistent solution based on partitioning the system into organic and non-organic domains with their associated porosities. We assume organic matter and non-organic parts are strongly laminated. By applying an inversion technique based on bound theory, we could compute elastic properties of organic and non-organic parts. Then, they can be used for predicting Thomsen anisotropic parameters by combining Postma's model. This model has been successfully applied on our measured organic shale data and helps us to gain more details on organic shales.