Not surprisingly, the best champions for emerging technologies tend to be those folks who have formed companies to commercialize those technologies. Such is the case of Peter Duncan, president of MicroSeismic Inc., a company that offers passive seismic services to the oil and gas industry. Recently Duncan spoke to the Geophysical Society of Houston on “Aggressively passive: Opportunities over an oilfield’s life.” Like a true evangelist, he outlined the case for passive seismic while also maintaining that there is much work to be done. Passive seismic is what its name implies – geophones are placed in a field “in a pastoral way” without live sources, and they listen to the natural sounds of the earth and the mechanical sounds of a producing reservoir. “We’re trying to imply something about how effective our interaction is with the reservoir,” Duncan said. “We record the noise that normal geophysics would throw away.” Duncan formed MicroSeismic Inc. in 2003, and at the time his colleagues’ main response was, “What have you been smoking?” Perhaps it’s not surprising. Eleven years earlier an opinion piece by Peter Edwards appeared in The Leading Edge saying the oil industry was “missing the boat” by not paying more attention to passive seismic techniques. The TLE editorial board went so far as to say he was ignoring the commonly known research and that “board members strongly disagree” with his assessments. With that kind of resounding support, it’s not surprising that passive seismic proponents slunk into their respective corners. But research did continue. While many of the projects were intended to study the correlation between the injection of liquid and the resulting mini-earthquakes that resulted, in 1973 Senturian Science actually received a patent on monitoring hydraulic fracturing operations with seismic. “Thank God for all of us that patent has expired,” Duncan quipped. Shell and Anadarko also experimented with passive seismic techniques over their fields, and Phillips Petroleum used it to measure subsidence at the Ekofisk field in the North Sea. In 1998 a study was done over the Seventy Six field in Kentucky. In this instance there was no injection; the sensors were used just to listen to the field during normal production operations. After six months it was determined that there were faults in the field that were below the resolution of conventional 3-D seismic, and these faults were controlling the production mechanism of the field. Most recently the technique has found a use in monitoring fractures in tight reservoirs such as the Barnett Shale in Texas. This is an obvious application since the standard isotropic “bi-wing” pattern that is assumed in fracture modeling is rarely what actually happens downhole. Passive seismic is also useful in steamfloods to determine where the steam is going. And it has great promise for CO2 sequestration. So while passive seismic is finally being acknowledged as a useful tool in the upstream, Duncan said that challenges remain. These include acquisition challenges such as the need to detect very small signals, noise issues, expense, and site access; processing challenges due to large datasets and needing a real-time solution; and interpretation and analysis challenges based on the need to not only apprehend the data but to comprehend it as well.