In this study, we take a preliminary look at microseismic data collected along the length of two Marcellus shale horizontal wells (the 3H and 5H) drilled by Northeast Natural Energy LLC (NNE) in Morgantown, West Virginia. Detailed log data are also available along the length of one of the laterals (the 3H) that provide a wealth of information concerning geomechanical properties, fracture trend and intensity. Logging, processing and interpretation of image logs were provided by Schlumberger. Preliminary interpretation of the microseismic cluster trends reveals orientations on average of about N59°E. Image logs in the vertical pilot well reveal similar average open fracture trend of ~N58°E. The orientation of S estimated from induced fractures observed in the vertical pilot well is ~N57°E, while that from breakouts is about N64°E. The majority of the induced fractures are observed in the Marcellus, while the breakouts are largely observed about 2000 feet above the Marcellus. Image logs collected along approximately 7400’ of lateral provide additional insights into the fracture network within the Marcellus target zone. Over 1600 fractures were interpreted by the Schlumberger analyst. The distribution was unimodal with average fracture trend of N78°E. Along the length of the lateral, average trends of fracture clusters varied from about N64°E to N110°E.
S in the area is approximately 6500 psi with horizontal stress anisotropy varied between 100 to 400psi in agreement with the acoustic scanning platform data. The vertical stress (S) is approximately 8800psi. Asymmetry in the microseismicity associated with the well is interpreted to be associated with a drop in S toward parallel well (the 5H well) located northeast. Hydraulic fracture stimulation of the local fracture network along the 3H well required introduction of a negative horizontal stress gradient in S northeast towards the 5H well that was treated a few days earlier to produce observed asymmetry in the microseismic distribution. Variation in stage-to-stage shut-in pressures did not suggest significant stress shadowing or increase in S stage-to-stage toward the heel (see Nagel et al., 2013a and b) or between wells.
In this initial look at the microseismic data, model fracture stimulation patterns are compared to microseismicity from a single stage along the 3H lateral. Initial uncalibrated MEM and stochastic based DFN models suggest that the observed microseismic event trends require interaction of the local N83°E fracture set observed in the image log along the wellbore in this area with a more regional ~N59°E fracture set. Although the inferred N59°E set is not prominent in the image log interpretations in the target landing zone, it is a prominent open fracture set in the vertical pilot well and its presence appears to control microseismic event trends and natural fracture stimulation at the site. This set appears to provide tensile conduits that channel fluids into and facilitate microseismically audible rupture of east-northeast fractures that are observed in the vicinity of the stage and that fail through shear.
Presentation Date: Tuesday, October 18, 2016
Start Time: 1:00:00 PM
Location: Lobby D/C
Presentation Type: POSTER