Publications

The last few years have seen a dramatic growth of shale oil and shale gas production and development, also known as Resource Plays, in the USA and around the globe. Their development relies on hydraulic fracturing to unlock the ultra-low permeability reservoir and enable it to release trapped hydrocarbons. Completion engineers generally design these hydraulic fracture stimulations with the intent that induced frac lengths do not interfere with fracs from adjacent wells and that heights do not grow outside of the reservoir zone. The geophysical technology of passive microseismic monitoring provides the means of measuring these dimensions by recording the seismic energy released as the rock is split. This important information enables the completions engineers to tune the hydraulic fractures to stimulate the optimum rock volume. There are several different types of passive microseismic acquisition geometries. Downhole monitoring uses a few geophones (10-30) placed in a monitoring wellbore close to the events being observed for optimal sensitivity but requires an expensive, dedicated borehole. Surface arrays avoid the need for the dedicated well but monitor events at a long distance from the seismic source. A large number of geophones (>1000) are needed to compensate for the very low signal:noise level. A hybrid method is buried arrays at shallow depths (100m-200m) that eliminate most of the surface noise allowing a reduced number of receivers but still monitor at long distances from the source. This paper evaluates event location accuracy of one downhole microseismic survey. Three contractors were asked to independently process the recorded * ConocoPhillips data. The objective was to determine the robustness of microseismic technology to locate the source of microseismic events. This was intended to be a practical evaluation of technology currently commercially available to the oil and gas industry. A minimum error of 20m (60ft) and a mean error of 60m (200ft) was established for the location of any single microseismic event.