Unconventional Tight Light Oil Play Types — Western Canada Sedimentary Basin
Unconventional low-permeability (tight) light oil
reservoirs, being targeted by hydraulically-fractured horizontal wells, have
emerged as very attractive plays in North America. These low-permeability oil
plays exhibit a wide variety of reservoir and production characteristics,
requiring different drilling and completion strategies to exploit them. We
propose for unconventional light oil reservoirs a play type categorization
analogous to that used for unconventional gas reservoirs, i.e. based on
reservoir/fluid properties and completion/stimulation styles. We use the term
“Unconventional Light Oil” (ULO) to capture the spectrum of play
types and to distinguish them from unconventional heavy (high viscosity) oil
plays. We further propose the following categories of ULO:
1. “Halo Oil” - light oil plays where the source ≠ the reservoir, and matrix permeability is relatively high (> 0.1 md) compared to the other play type categories. Halo Oil plays represent portions of conventional light oil pools that do not meet traditional petrophysical cutoffs and pay criteria, and may be clastics or carbonates e.g. Cardium, Viking, etc.
2. “Tight Oil” - light oil plays where the source ≠ the reservoir, and matrix permeability is low (< 0.1 md). These plays are analogous to tight gas plays and may be clastics or carbonates e.g. Bakken (Viewfield), Montney, etc.
3. “Shale Oil” - light oil plays where the
source = the reservoir, matrix permeability is very low, and organic matter
content may be high. These plays are analogous to shale gas plays e.g. 2nd
White Speckled Shale, Duvernay, Muskwa, etc.
We will present examples of all three ULO play types
from the Western Canada Sedimentary Basin using core, well logs and production
data to infer the primary controls on production performance in each play type.
The above listed examples of tight oil sandstone and carbonate reservoirs
encompass a wide age span and range of depositional settings and thereby very
different reservoir geometries and lateral extent. Establishment of an
Unconventional Light Oil play classification scheme facilitates categorization
of a broad range of light oil plays and better use of analogs for new light oil
plays. We note that the same stratigraphic unit might in different parts of a
basin fall into different categories depending on geologic setting, reservoir
type, fluids and pressure.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California