The electric or e-field has been discussed at length in literature, in terms of the methodology of continuously remotely monitoring oil field production over a long term using vertical and horizontal wells, and transmitting data back to a monitoring centre. Conventional vertical well monitoring methods is adequate to monitor at points around an oil field but continuously monitoring where fluids are moving requires monitoring over an area using horizontal wells.
Recent research has shown that seismic methods can show subtle changes in pore fluid phase which enhances the potential for long term monitoring where pore pressure is reducing, where injected water or CO2 flood options have been chosen, and areas where gas is being replaced by water. If we can marry the use of slim-hole horizontal sensor cables with this recent demonstration of the detection of phase changes, then we have the tools for the first applied e-field scenario.
During 2007, laboratory tests injecting different amounts of CO2 into pore water showed that by monitoring the seismic transmission through a simulated rock, there was a change in seismic frequency response and transmission amplitude. Physical modeling has shown that a horizontal slim-hole well drilled to test the ability to put sensors in a horizontal well, can then be used for remote reservoir surveillance. A seismic source which walks around at the surface, produces data which is then processed to produce an indication that this method can be used as a first step for determining pore fluid properties over an area.
This paper presents the results of the experiments on pore fluid phase and discusses how the use of horizontal wells allows the ability to develop the e-field concept towards reality.