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Summary of Project Objective

Detecting and quantifying multiphase flow channeling is a critical problem for the management of petroleum reservoirs.  The occurrence of preferential flow paths can cause short circuiting of viable reserves during waterfloods leading to decreases in sweep efficiency and large volumes of residual oil left unrecovered.  Identifying flow channeling in reservoirs is essential for implementing management strategies for enhancing oil recovery.  Low-frequency electromagnetic methods have excellent potential for monitoring reservoir production given the sensitivity of electrical resistivity to oil-water saturation.  Effective interpretation of this data, however, requires a good understanding of how resistivity values are affected by flow processes – including flow channeling.  Since geologic heterogeneity and viscous fingering can cause flow channeling to occur at the pore to the reservoir scale, the impact on resistivity across these scales must also be understood.   

This study is using physical analog models to study how DC electrical responses evolve with flow channeling during a waterflood experiment.  Experiments are being conducted in a thin (approximately 2D) flow cell within which the electrical measurements are performed as the spatial variation of water saturation is mapped in real time using a camera.  A key objective of this study is to observe how changes in apparent resistivity through time are correlated to the spatial distribution of preferential channels in the flow cell and to provide a means to quantify this relationship using percolation theory.  The results of this research are expected to be important for understanding how to interpret and model electrical resistivity measurements at the reservoir scale.

 First Year Progress

A considerable effort has been placed over the past year on constructing and testing the apparatus for performing the multiphase flow experiments.  One major accomplishment on the project has been the design and construction of a custom 45cm x 45cm x 1cm flow tank.  The tank is unusual in that it can be oriented at arbitrary angles to control the balance between gravitational forces versus capillarity and viscosity during flow.  The tank also has a removable 45cm x 45cm faceplate that allows us to change the experimental design easily and inexpensively.  For example, we can perform experiments with different electrode arrangements (e.g., 4 electrode measurements, borehole tomography analogs, and electrode grids) or change the flow regime (e.g., uniform flow versus isolated wells) by simply changing the tank faceplate.  Because the faceplate encloses the broad side of the tank, we can also pack the tank with complex distributions of materials and perform experiments under positive pressure.  We have performed initial multiphase flow experiments in the tank using water with both Soltrol and glycerol and found that we can achieve the required range of flow conditions (stable to viscous fingering) needed for the project.  The experiments have been conducted using homogeneous glass beads with 0.2, 1, and 2 mm diameters.   

The second major accomplishment achieved in this period has been the development of an automated resistivity measurement system to be used in the experiments.  A National Instruments (NI) USB-4065 DMM and PCI-6255 DAQ were used to perform preliminary resistivity measurements on glass beads and synthetic rock samples.  The main purpose of these tests was to establish the measurement capabilities of the NI equipment proposed for this project while learning how to develop LabView programs for automating the resistivity measurements.  As a result of these tests, we have purchased a NI PXI resistivity system that will provide better measurement resolution than the SCXI system initially proposed.  We are currently completing calibration measurements to establish resistivity-saturation relationships for batch systems.  Graduate student Jeolin Liu has joined the project and is preparing to start flow experiments in the tank.

 Career Impacts

This project is enabling new research capabilities for me and my laboratory and is therefore having a significant impact on my career.  As a result of the project I have made significant advances in developing protocols for performing multiphase flow experiments and resistivity measurements.  I am expanding both my core knowledge base and developing technical skills that will be useful in a wide range of future research. 

 Project Impact on Students

To date there have been three undergraduate students (2 during the last reporting period) and one graduate student involved in the project.  The undergraduate students, one geology major and two electrical engineering majors, have worked closely with me in developing and testing the hardware and software for the resistivity measurement system.  The impact on these students is clear by their remarks on how the project has extended their education and viewpoint beyond what is possible in a classroom setting.  For example, as a result of his involvement in the project one of the electrical engineering students is considering pursuing graduate study focused on the use of sensor systems in earth sciences.  The project is the thesis work for the graduate student.