Research Interests:

Seismic Monitoring of Fluid Flow

I believe one of the next major breakthroughs in Geophysics will be in the research area of "4-D seismic monitoring of subsurface fluid flow."

Seismic monitoring defined

4-D seismic monitoring consists of time-lapse 3-D seismic surveys conducted over time intervals in which interesting subsurface fluid movement can take place. Integrated with rock physics and fluid-flow simulation, estimates of fluid-flow geometry, permeabilities and fluid phase-front movement in the Earth may be inferred from the time-lapse seismic data. Seismic monitoring offers us the possibility of finally being able to estimate where and how fluids are flowing in the Earth.

Why is monitoring fluid flow important?

Seismic monitoring of subsurface fluid flow has the potential for immense impact in: oil and gas energy resources, groundwater and environmental studies, global warming issues related to massive methane hydrate deposits, and earthquake prediction related to pore-fluid pressurization before fault failure.

Oil and gas energy resources

Hydrocarbons fuel the world's economy, including transportation, power generation, and manufactured goods that we depend on. Most of the Earth's potential oil and gas reserves have already been found and are currently being rapidly depleted. Because we do not understand the complexity of flowpaths and flow barriers in oil reservoirs, we leave behind at least as much oil as we produce in each reservoir due to inefficient production strategies. I believe seismic monitoring will become an interactive tool for understanding reservoir fluid flow, and help us double the amount of oil and gas reserves we currently produce.

Groundwater and environmental issues

Groundwater is becoming a precious resource. High-resolution shallow seismic surveys might be useful in monitoring water table fluctuations with time over large surface areas to better understand aquifer depletion and recharge. Also, it is becoming increasingly important to monitor contaminant plumes at hazardous spill sites to make sure clean water is not polluted. While seismic data cannot "see" most contaminants in water, the closely related electromagnetic surveying technique called Ground Penetrating Radar can image contaminant plumes by electrical conductivity differences.

Methane hydrates and global warming

Methane hydrates are ice-like deposits which contain huge amounts of trapped methane gas. Methane hydrate deposits have been found at continental margins on a world-wide basis. It is estimated that the amount of methane gas trapped in the ice is at least as large as all the conventional oil and gas reserves found to date. This means that methane hydrates may be a future energy resource when they are understood better. Methane is also a greenhouse gas, and plays an important role in global warming. Monitoring the rate at which these deposits accumulate or dissolve could provide very useful information to climate models, and help understand the buffering role of methane hydrates. Finally, many methane hydrate deposits have been found near offshore plate subduction zones. I believe there may be a link between the location of these deposits and the fluids that are being heated, pressurized and driven out of the saturated downgoing slab. Monitoring subduction-zone hydrates might give a clue to the fluid flow system in a subducting plate, and how that is related to subduction rates, depth and magnitude of earthquakes, and chemistry of upwelling magma at subduction volcanic chains.

Earthquake mechanisms and prediction

Earthquake seismologists believe that fluid flow has an important role in how frequent and how strong earthquakes occur. Fluids can lubricate fault surfaces making it easier for an earthquake to occur. Highly pressurized pore-fluid in a fault region might indicate that an earthquake is about to occur. Pore pressure increases cause seismic velocity decreases which might be monitorable over time. I can imagine a seismic monitoring experiment consisting of a small array of geophones on one side of the San Andreas, and a shot location on the other. Repeated shots could be fired at reasonable time intervals (1 week?) and the seismic arrivals at the geophone array could be analyzed to see if the velocity (pore pressure) in the fault zone is decreasing (increasing). This type of seismic monitoring might help to better understand the earthquake mechanism along a fault, and perhaps be useful as a tool to predict when an earthquake is about to occur.

For more information...

You can view a selection of my research movies and award-winning papers on seismic monitoring and other subjects.

I would be pleased to interact with other researchers who have an interest in any of these topics. Please feel free to contact me.

Copyright © 1994 by David E. Lumley; david@sep.stanford.edu

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