AmericanChemicalSociety.com

Geoffrey R. Tick (PI) and Jaydeep Ghosh (PhD Student)

Introduction

Crude oil mobility and the trapping mechanism in a reservoir are controlled by pore geometry, grain size, sorting, viscosity, capillary action, and interfacial tension existing between the oil-water and solid media. The use of surfactant to lower interfacial tension will increase the mobility of oil thereby enhancing the recovery potential from the reservoir. Morphology of oil blobs and pattern of distributions will impact the resulting available oil-water-solid surface contact area thus controlling the interfacial processes for oil mobilization and recovery. The purpose of this research is to analyze three dimensional (3D) distributions of crude oil particles and understand the interfacial phenomena controlling oil mobilization at the pore scale in order to optimize innovative techniques for tertiary extraction of oil.

Several columns were packed with homogeneous, mildly heterogeneous, and heterogeneous mixed porous media, respectively (uniformity coefficients of 1, 5.7, and 10.8) and saturated with water to simulate a water-wetting-reservoir, and then separately flooded with light (41˚API), medium (29.6˚ API) and heavy (14˚API) crude oil. The columns were flushed with an anionic surfactant in two different episodes. Synchrotron X-Ray microtomography (SXM) at Argonne National Laboratory was used to capture high-resolution (9.9-10.3 µm) 3D images of the oil distribution within the columns before and after the surfactant flooding events.

Results and Discussion

Selected results show complete recovery (100%) attained for both light and medium oil fractions present within the homogeneous medium after 5 pore-volumes (PV) of surfactant flooding event. The other two reservoir systems exhibited a 20-40% recovery. Light oil shows 21% and 44% net recovery from heterogeneous and highly heterogeneous medium after 5PV surfactant flooding event. Medium oil shows net recovery of 8% and 16% from heterogeneous and highly heterogeneous media, respectively. Blob size distribution in various crude oil-media systems were characterized and compared as lognormal distribution. Both light and medium oil residual saturation within homogenous and highly heterogeneous media show relatively homogeneous distribution (uniformity coefficient, Cu, and coefficient of variation, Cv, ranges from 2-3), however, both oil fractions show relatively heterogeneous distribution (Cu and Cv ranges from 3-14) in medium heterogeneity porous media. For both oil fractions, the number of blobs increased after each surfactant flooding event by segregating into smaller particles and blob morphology deviated greater from spherical shape, thereby increasing the blob contact surface area with flushing time. These results reveal that oil distribution pattern and trapping mechanisms are controlled by the heterogeneity of the media, whereas the extraction potential for a particular reservoir is highly dependent upon the available surface area and the flow dynamics of the oil blobs controlled by the surfactant flooding event.

Impact of Research

The impact of this research has produced outstanding contributions to understanding how variation of porous media (reservoir) permeability controls crude oil fraction distribution, morphology, and resulting recovery after sequential surfactant flooding events. This is the first known study at this level of detail, implementing cutting-edge techniques, to investigate processes influencing oil distribution and recovery at the pore scale. This research has led to several peer-reviewed published abstracts and presentations including two first-place Ph.D. student presentations at AAPG/SEG Meetings. It is expected that the findings from this work will lead to new conceptual models for reservoir types that may be most amenable to tertiary recovery processes.

            This research has expanded my research program into new directions further enhancing national recognition, initiating new collaborations and interests, providing unique opportunities to utilize cutting-edge pore-scale characterization technologies (i.e. SXM), expanding potential funding sources, and initiating new research questions and ideas to further pursue. This research will produce several published articles in high-level peer-reviewed journals.

            This research project has significantly contributed to my student's career by advancing my Ph.D. student into a strong and independent researcher. This research project has provided the outstanding opportunity for my student to collaborate with high caliber researchers and conduct experiments at cutting-edge facilities. This project has expanded my student's experience and knowledge by presenting research at various national conferences, interacting in colleague discussions, and exchanging scientific information with a broad diversity of researchers within and outside of his field.  Lastly, the contributions and exposure of this research have led to several potential career opportunities within the petroleum industry, the career path he is most excited and interested in pursuing.

Acknowledgements

Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for support (or partial support) of this research.

Table 1. Light oil in homogeneous media

Table 2. Light oil in mildly heterogeneous media

Table 3. Light oil in heterogeneous media

Table 4. Medium oil in homogeneous media

Table 5. Medium oil in mildly heterogeneous media

Table 6. Medium oil in heterogeneous media