Long-term monitoring of microseismic emissions: Earth tides, fracture distribution, and fluid content

Abstract

Monitoring of microseismic emissions for periods of 10–30 days has established a clear relationship between solid earth tides and microseismic activity. In addition, an event magnitude versus recurrence relationship has been established that can be used to predict oil, gas, or water content of open fractures in imaged rock volumes. Originally developed to explore for oil and gas, the detection technology used has been applied in Eurasia, the Middle East, and Texas. When visualized in three dimensions at scales of several kilometers on a side, including depth, the observations shows systems of subvertical fracture volumes distributed as clusters in the subsurface. When visualized in sequential time windows, microseismic activity can be seen to respond in detail to lunar-solar gravitational changes. The seismic imaging technology used to detect the location and temporal changes within these fracture systems is based on deploying geophone receiver arrays using array patterns and processing algorithms similar to those used in phased array radar in the electromagnetic spectrum. This passive listening technology has been termed seismic location of emission centers (SLEC). Examples of applied SLEC monitoring are presented for surveys performed in Russia and Texas.