Future of Microseismic

Recently I was asked about the future of microseismic? This proved to be a surprisingly difficult question to answer. Would automation take over? Will surface deployed arrays replace the downhole? Will other techniques supplant both?

The best way to address this would be to explore first the drawback and advantages of each of the current techniques and some emerging ones.

DAS/Fiber Optics:

This method is deployed during the well design and is a permanent emplacement designed to record for the duration of the life of the well. This method unfortunately, is limited to a single sensor orientation along the well path which can only be used to locate an event in a single direction within a 3D space. With the deployment of a second fiber optic line down a nearby well, a second dimension can be added to improve the location. This method is the most expensive.

Surface/Downhole Arrays

These methods are the most mature and can accurately locate events in 3D space. A single downhole system can record events approximately an order of magnitude weaker than that detected by the surface array. Surface arrays eliminate the wellbore bias which may be present in some downhole projects where the geometry is less than ideal. Downhole surveys are typically 1/10th of the cost of the surface array and can record weaker magnitude events undetected by the surface array due to signal attenuation.

Early reporting included SRV (stimulated rock volume) which tended to overestimate the stimulated zone. DFN (discrete fracture network) involved the use of the event properties to define a fracture network to approximate the stimulation success, however there remains a gap between this method and real production data. Additional incorporation of geomechanics and seismology observations may help improve DFNs and bridge the connection between events and production.

New Techniques:

K-waves are a new method that is used to explore the connection from the frac to the wellbore. This method has been in the realm of academia for several years and is positioned to be released soon. This method is projected to be the lowest cost and holds considerable promise in locating and describing the attributes of the fractures connected to the well.

Another new method uses FWI surface based approach, is more expensive than a downhole microseismic survey and on par with that of a surface based microseismic survey. This method focuses more on the deformation and shows some promise in identifying the propped fractures from the unpropped. This is a potential game changer and much like the K-wave method, more data needs to be presented.