An extensive series of laboratory tests on going since January 1997 demonstrate unequivocally that largeamplitude periodic excitation of porous media experiencing flow leads to large flow enhancements. These are not small improvements in rate, but are as large as a factor of 2 to 4. Based on these results, a new technical approach to enhancing fluid flow in reservoirs was formulated, and a full-scale field experiment in Alberta was initiated in December 1998.
The field trial successfully showed that periodic application of large amplitude excitation to a porous medium experiencing pressure gradient-driven fluid flow increased oil production rates, decreased produced fluid water content, and increased the percentage of sand produced.
The scope of potential applications to the extraction of conventional and heavy oils using primary and enhanced recovery methods is substantial. As well, PE-TECH's novel technology will stabilize viscosity-graded liquid floods, provide longer production times during cold flow production of heavy oils, and so on.
The laboratory and field results obtained from our research and development over the past two years were predicted by the physical theory. Using volume averaging in conjunction with basic physical arguments, we have constructed a complete system of equations for lowfrequency wave propagation. This system of equations has been shown to be consistent with the laws of thermodynamics in the component phases at the pore scale. They also yield large-scale thermodynamic relationships in which porosity is found to play a fundamental role, similar to that of temperature in single component systems. In other words, it has been proven that porosity is a basic thermodynamic variable, and that induced variations in porosity are responsible for the flow rate enhancement effect. The physical theory dictates the experiments required determining the parameters that arise in the equations.
What are the potential consequences of this process for oil production? Properly executed in appropriate reservoir conditions, more oil can be induced to flow more rapidly to oil wells. Also, in the case of cold flow with sand production in heavy oils, fewer blockages and higher fluid rates can be expected.
During the 1970's, in Russia, earthquakes were observed to have affected the fluid levels in petroleum reservoirs1. In most cases, the fluid levels were reported to have increased, leading to enhanced flow from the reservoir. It has also been observed that the water/oil ratio during an earthquake swarm may change1. Wells with initially large water/oil ratios were observed to have lower post-earthquake-swarm water/oil ratios and vice-versa in wells with initially low water/oil ratios. Earthquakes and explosions have also been known to affect underground fluid levels (water table and oil reservoir levels) in some areas2. These observations led to the concept of seismic excitation enhancing the flow of (underground) fluids in porous media.
The concept of seismic excitation involves applying small strain excitation, of magnitude 10−10 to 10−6, either at the surface above the reservoir, or underground within the reservoir.
