In this paper we examine diagnostic tools for hydraulic fracture stimulation (HFS) that can help determine the geometry, reach, and effectiveness of the created fracture(s). In particular we focus on using the combination of micro-seismic and Distributed Acoustic Sensing (DAS) technology to gain a more complete understanding of the resulting stimulation treatment and identify further optimization opportunities.
DAS has many applications, and this paper will consider two particular cases in combination with micro-seismic data acquired by geophones in an observation well:
When DAS is recorded in a treatment well, it can be used to determine and quantify which stages and perforations take fluid. When this is combined with micro-seismic data we can establish a relationship between the micro-seismic events and the fracture fluid itself. This can help determine the overall effectiveness of the fracture design and resulting treatment.
When DAS is recorded in an offset well (developed in the same pad as the treatment well), it can be used to determine when hydraulic fracture fluid (initiated from the neighboring treatment well in the same pad) intersects that well. We can then establish how the micro-seismic events relate to actual fluid placement and interference from neighboring wells. It can also provide an exact location and timing where fractures intercept offset wells and are linking up, and are a direct measurement of a conductive fracture.
In both cases micro-seismic combined with DAS data provides an opportunity for further completion optimization, well spacing optimization, and/or pad design and/or well spacing.
Integrated Hydraulic Fracture Stimulation Diagnostics
To determine the geometry, reach and effectiveness of hydraulically created fractures, micro-seismic data is often recorded at wells or well pads where hydraulic fracture stimulation (HFS) is to take place. Frequently geophones are deployed in a dedicated vertical observation well with the possibility of deploying more geophones in horizontal offset wells to help reduce the uncertainty in location and magnitude of the micro-seismic events.
Distributed Acoustic Sensing (DAS) is an acoustic detection technology that has recently been applied in production (Molenaar et al. 2011) and geophysical settings (Mestayer et. al, 2012).
Downhole DAS is a fiber-optic distributed sensing technology that can provide key diagnostic insights during hydraulic fracturing operations. During the course of 2009 through 2012, a number of DAS and Distributed Temperature Sensing (DTS) deployments have been carried out in North America's tight sand and shale gas fields to monitor (in real-time) hydraulic fracturing operations. Recordings were made in different fields and different reservoir formations for different well configurations and completions.