Delineation of Reservoir Structure by the Coherence Collapsing Relocation Technique of Microseismicity

Abstract

The authors have investigated a variation of the collapsing method that tries to bridge collapsing and multiplet analysis techniques utilizing the advantages of each of the methods. The collapsing method is a mapping method for relocating microseismicity that involves utilizing information from all the events in the data set. In the version of the collapsing method introduced here the idea of the coherence of the waveforms is also incorporated into the method (coherence collapsing). The new method aims to bridge absolute and relative mapping techniques, because this method has a nature to selectively relocate a group of multiplets to a point. The principle of the coherence collapsing method was developed from the concept of the original collapsing method, and parameters in the analysis are optimized from synthetic studies and from real data. The relocated events in simulation revealed that the coherence collapsing method has the ability to estimate absolute location of multiplets in a seismic cloud. This method was applied to a part of the seismic data set of the Soultz 1993, 2000 and 2003 stimulations and Australian 2003 stimulation in Cooper Basin. The relocation of events with high mutual coherency showed structures consistent with multiplet analysis suggesting the advantage of this method for semi-realtime mapping of the multiplets.