Girouxville East Montney Waterflood

Abstract This paper presents the design, current status and future expansion plan of the waterflood scheme in the Girouxville East Lower Triassic Montney reservoir, which is located about 350km north-west of the city of Edmonton, Alberta, Canada (Figure 1). The Girouxville East Montney reservoir is a structural trap and is composed of predominantly marine interbedded shales, siltstones and dolomitic sandstones. The reservoir produces 30 – 32 °API crude oil and is a saturated hydrocarbon system with an up-dip gas cap and a down-dip water zone with unusually long oil-water and gas-oil transition zones. The reservoir was initially developed in the early 1990's with vertical wells targeting the up-dip gas cap. Over the last 4 years the down dip oil leg has been targeted and developed exclusively with horizontal drilling technology coupled with multi-stage hydraulic fracturing. This technology has been instrumental to improve well productivity and oil reserves. However, oil recovery under primary depletion still has been low, often less than 5% of original oil-in-place (OOIP), due in large part to local pressure depletion caused by large reservoir withdrawals including formation water and gas. This sets the stage for improved oil recovery via waterflood. A small water injection pilot was initiated in October 2013 with a single water injector to alleviate reservoir pressure depletion in the local area. The results were encouraging, and the project has been expanded to a larger scale waterflood scheme in 2015, which currently consists of 6 horizontal producers and 4 horizontal water injectors. A 388 ha (1½ sections) waterflood expansion was designed based on comprehensive geological and engineering evaluations. A detailed geomodel was created with available core data, well petrophysical analyses, horizontal well geologic descriptions and seismic data in the area; the Montney formation was subdivided into 4 coarsening-upward cycles, with 6 facies identified within. Dynamic reservoir simulation was initiated by importing data from the geomodel. Reservoir and well properties were fine-tuned with a high-quality history. Multiple forecast scenarios were run to determine an optimal waterflood recovery scheme. Within half a year most offsetting oil producers have shown positive response to water injection with an increase in total fluid and gradual decrease in the producing gas-oil ratio (GOR). The oil rate decline has slowed down significantly with anticipated incremental oil recovery of 5 – 7% OOIP over the primary depletion. Further expansion has been identified in the oil-leg of the surrounding sections. The waterflood design will focus on down-dip injection to maintain more gravity stable injection water fronts along the field oil-water contacts for optimum pressure support and oil displacement.