Microseismic Response and Geomechanical Principles of Short Interval Re-injection (SIR) Treatments

Kent, Alana (University of Calgary) | Eaton, David W. (University of Calgary) | Maxwell, Shawn (Itasca Microseismic and Geomechanical Evaluation)

OnePetro 

Summary

We present a case study of hydraulic fracturing treatments for two horizontal wells located in the Horn River Basin, B.C. The wells were completed using a technique that we refer to as Short Interval Re-injection (SIR). For each individual treatment stage, this technique makes use of an initial injection interval using conventional hydraulic fracturing pumping procedures, followed by a “soaking" period that may last from a few hours to about one day in duration, during which the well is temporary shut in. This is followed by a subsequent re-injection interval with a pumping schedule similar to the first interval. Several commercial names are in use to describe this type of approach, which has a desired goal of enhancing the overall effectiveness of the treatment. In this study, we observe a significant increase in the rate of microseismic activity that occurs after the initial soaking period. This type of response has been documented previously and, in some cases, has been empirically related to increased production for wells. We postulate that cohesion of pre-existing fractures is reduced by the initial injection and soaking period, facilitating reactivation of fractures during the second injection. A numerical model has been developed using the software 3DEC in which the cohesion parameter for a discrete fracture network (DFN) is set to zero after the first injection stage. Preliminary results produce a satisfactory match with respect to increased events. Future work will include adjustments to the DFN in order to increase the match with the spatial locations.

Introduction

The Horn River Basin (HRB) is an important resource play in northeastern British Columbia, Canada. While conventional oil and gas developments have been underway in the HRB for several decades, since 2005 operators have targeted the large shale resources that are in place.