Microseismic case study: Investigating the natural fractures and faults of the Muskwa and Evie shale play in northeastern British Columbia

Abstract

In this case study the natural fracture and faulting characteristics of the Muskwa and Evie shale play in Northeastern British Columbia are discussed. The Muskwa is an ideal formation for studying the acoustic effects of hydraulic fracture stimulation as these shales are known to be generally very brittle, producing lengthy linear fractures. The Evie shales have a different characteristic than the Muskwa shales, consisting of variably calcareous siliceous shales (McPhail, 2008). Both of these shales were studied during microseismic monitoring while hydraulic fracture treatments were performed. The recording geometry for this study was a near-surface array operated during hydraulic fracturing for nine horizontal wells, eight of them within the Muskwa Formation and the ninth in the Evie Formation. Two different completion techniques were used, affecting how the rock fractured: perforation and plug and ball and sliding sleeve. The pointset has a dominant 70° fracture azimuth. The focal mechanisms and b-values support this trend result. The Muskwa stimulations differ from the Evie stimulations in that the Evie produces shorter, complex fractures with lower b-values and lower stimulated rock volume (SRV). The b-value calculated for the H well is 2.97 while it is less than 1 for the A well. This indicates that the fractures in the Muskwa are hydraulically induced while the fractures in the Evie are due to fault reactivation. The SRV calculated for the H well in the Muskwa was 5.5 times more than the SRV for the A well located in the Evie.