The Emerging Roles of Rock Physics: From 4D-Seismic To Pore Scale Imaging

摘要

The need for rock physics information is exploding as we aspire to improve geo-steering; recovery; wellbore management; and reservoir simulation. The most reliable source of this information is experimentation. However, physical measurements on rock fragments are slow and cumbersome, and often impossible to conduct or conduct well. Even when available, such data are sparse -- required are properties not for tens but for thousands or tens of thousands of samples. The only way to obtain such massive data is through the emerging computational rock physics. This methodology includes 2D and 3D high resolution (below micron and even down to nanometers) and fast (minutes) imaging of the pore spaces of cores, plugs, or cuttings. These images are used to (a) accurately and fast (minutes) compute bulk properties of rock and (b) simulate pore scale processes also very fast (tens of minutes). Ingrain was founded in 2007 to develop and implement this technology as a reliable large-scale service. We have implemented cutting edge codes to deliver porosity (including micro porosity in carbonates); absolute and relative permeability, the latter accounting for interfacial tension, wettability, and viscosity contrasts; electrical; and elastic properties. Soon to come are capillary pressure and formation damage simulations. Accurate hydrodynamic characterization of porous media is paramount to understating many large-scale fluid flow phenomena that govern the overall performance of a reservoir system. The ultimate hydrodynamic behavior is completely dominated by the pore level flow phenomena at work. The characterization of this pore scale behavior has traditionally been done with specific, and limited, resource and/or time consuming laboratory measurement processes. The primary measurement vehicle has been core sample analysis; whereby an extracted core is prepared and subjected to laboratory measurements that, in the best light, yield important parameters for the core (and therefore the site under examination). Common parameters such as porosity (the total volume of pore space in a given sample) and permeability (how fluids migrate in the given sample) are two important properties produced in the laboratory. An item missing in all these measurement processes is a complete picture of the overall structure of the pore-space. An accurate representation of the pore-space can lead to detailed simulation and analysis of the processes in rock. Furthermore, if we understand the physical laws at work at the microscopic level, simulations of fluids moving through such pore space representation can be accurately performed. Until now, the total end-to-end process of acquiring an accurate pore scale representation and fluid dynamic modeling in it has not been possible or practical to implement and provide as a service. We have recently finished designing and implementing just such a procedure and we are now in the process of perfecting its application to real rock. This ambitious task is especially relevant to carbonates, whose pore structure is notoriously complex and prone to rapid diagenetic alterations. Figure 1 shows an outcome of such computational experiment simulating two-phase flow of water and oil through a carbonate sample from the Middle East.