Pressure Pulsing: The Ups And Downs of Starting a New Technology

Abstract

Abstract When technology based on new science is started, there can be a lot of skepticism, which is a healthy reaction. The skepticism encountered by PE-TECH as pressure pulsing is gradually introduced has been partly overcome, but only in the Canadian heavy oil industry. Here are some typical remarks we have encountered over the last three years, accompanied by our responses. "This is not predicted by Darcy's Law." This is quite correct since Darcy's Law is a static law and cannot handle inertial effects. For example, look at how Darcy's Law is fudged to handle turbulent flow. "Well, it works in heavy oil, but it won't in light oil." Or, "Our reservoirs are different." Physics is physics; it will work in all liquid-saturated systems, but will have to be optimized in individual cases. "We don't need this because we use horizontal wells." It can be used in many different configurations, and can help horizontal wells just as it does vertical and inclined wells. "It's not the pulsing, it's a relative permeability effect (or permeability increase or viscosity decrease, etc.)." Nope, we've proven otherwise, although in the case of highly viscous oils of large molecular weight, there may be an additive effect of viscosity reduction. "It won't work in consolidated rocks." We're confident of field success; limited laboratory tests indicate that it does indeed work, but we have a lot more testing to do. "Sounds like Cold Fusion to me." Frankly, we were pretty startled ourselves at how large the effect is, but you can do the experiments yourself. "Come back when you have some real field data." We have. We're here. History Pressure pulsing is an emerging technology. Its roots go back several decades; as a rigorous theory, it goes back about 15 years. Russian engineers noticed decades ago that large earthquakes often caused changes in oil well behaviour, usually a short-term rate increase. This was variously ascribed to compaction, shaking loose of particles blocking pore throats, or changes in permeability, viscosity, and capillary entry pressure. However, attempts to use seismic excitation have, to our knowledge, met with failure in China, Canada, and the United States. Senior engineers from western oil companies have examined claims that mechanical vibrations are being used successfully, they appear unconvinced, even after site visits. Also, the numerous articles in the Russian literature, mainly by geophysicists, tend to be mathematicallyopaque, unfathomable in terms of physical processes, based on debatable premises, or without sufficient clear and unequivocal information to allow evaluation. Nevertheless, published Russian data appear convincing, and R&D programs are active in Alberta, USA, and other areas, albeit without much apparent success. We believe we know why: seismic excitation is the wrong type of impulse, of insufficient amplitude, and applied at the wrong place. Pressure pulsing experiments in the laboratory started only in January 1997; in the field, it was first tried in June 1998. PETECH conducted the first commercial applications in workover mode in September 1998, and in full field-wide rate enhancement mode in June 1999.