Micro-CT Investigation of Water Influx

Abstract Microscopic Computer Tomography (micro-CT) technology opens new windows into the investigation and visualization of displacement phenomena, and into the structure at the pore level of oil-bearing rocks. The method is non-destructive and as such creates a possibility of observing the processes in a repetitive manner and possibly in real time. The objective of this work is first to verify that desktop micro-CT instruments are capable of picking up interfaces in the pore space of reservoir rocks. Recent literature shows that synchrotron-based micro-CT has the capabilities of detecting pore spaces and also interfaces to the 1 µm resolution. However, when desktop micro-CT systems are tested the results are mixed. When the verification is complete, the second objective of this work is to study imbibition and waterflooding at the microscopic scale. As with conventional tomography contrast enhancement among phases is attempted through the use of high-atomic-number dopants. A considerable effort was directed towards the optimum contrast agent composition for micro-CT work. After the operating conditions were established, we tested the capability of micro-CT by conducting simple water injection tests in rocks of variable pore size distributions and wettability. The effect of small surfactant additives was also investigated Introduction Development of regular Computer Tomography principles(1) brought up an idea of X-ray microtomography(2). Using point source of X-rays, a screen converting X-rays into visible light and CCD array made it possible to obtain 3D images of objects with substantial magnification(2). Because of the high brightness and monochromatic character of X-ray radiation from synchrotron this type of radiation was prevailing in the first stage of development of this technique into different areas of research. Being monochromatic it provides a number of advantages, particularly, the possibility of introduction of X-ray optics and no presence of beam hardening artifacts (1,2). Submicron resolution is also achievable due to the same advantages of synchrotron radiation and nanoscale is already an achievable goal(3). Accordingly, most of the research to date focused around synchrotron facilities. Access to these facilities has to be planned ahead, arranged through third parties and as such is not flexible enough to be used as a routine tool needed in ongoing research(4). Nonetheless, substantial amount of research was performed with the use of this method. Most of this research was taking advantage of high resolution provided by synchrotron facilities and was directed to analysis of the pore structure of porous materials and on verification of different theoretical models of flow in such materials(5–8). It is important to note, that micro-tomography not only provides high resolution and non-destructive analysis of samples, but supplies enough data to obtain 3D images of the studied microstructures(2,9). The desktop version of micro-CT was also developed(10,11), which facilitated research in different areas(11–16). Currently, the quality of images and the resolution of desktop instruments