SAGD Development Strategy for Concurrent Production of Two Vertically Stacked Clastic Reservoirs
- Qi Jiang (Osum Oil Sands Corp) | Daniel Nugent (Osum Oil Sands Corp) | Kelli Meyer
- Document ID
- Society of Petroleum Engineers
- Canadian Unconventional Resources Conference, 15-17 November, Calgary, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 5.1.5 Geologic Modeling, 4.1.5 Processing Equipment, 5.3.4 Integration of geomechanics in models, 5.5 Reservoir Simulation, 5.8.5 Oil Sand, Oil Shale, Bitumen, 4.3.4 Scale, 3.3 Well & Reservoir Surveillance and Monitoring, 1.2.2 Geomechanics, 5.1.7 Seismic Processing and Interpretation, 5.2.1 Phase Behavior and PVT Measurements, 5.5.3 Scaling Methods, 2 Well Completion, 4.1.2 Separation and Treating, 5.3.9 Steam Assisted Gravity Drainage, 1.6 Drilling Operations, 5.4.6 Thermal Methods, 2.4.3 Sand/Solids Control
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The southwest portion of the proposed Taiga project has two vertically stacked bitumen-filled Cretaceous sandstone reservoirs in the Cold Lake area of NW Alberta, Canada. The shallower Lower Grand Rapids Formation is separated from the Clearwater Formation by the transgressive Clearwater. SAGD (steam assisted gravity drainage) is planned for producing both formations simultaneously.
The Lower Grand Rapids Formation differs from the Clearwater Formation in initial reservoir pressure, oil viscosity and fluid distribution. Therefore, this will require individual well placement and operational strategies for each reservoir. The sequence of development for the two reservoirs will not only affect the pad facility design and operation strategy but will also affect the drilling operations. There is a high likelihood of drilling into the areas conductively heated by prior proximal SAGD operations if two formations are developed in a sequential order. This increases drilling risks and costs. Simultaneous SAGD operations within both the Lower Grand Rapids and Clearwater Formations can be used to minimize the complexities associated with well drilling and completions, and to reduce the initial number of surface pads as both formations can be accessed from the wells drilled from the same surface location.
This paper presents the results from both reservoir simulation and geo-mechanical modeling based on geological and reservoir characteristics of these reservoirs. The surface heave due to dual zone thermal operations is also predicted based on the results from geomechanical modeling. These studies have led to an optimal design of pads and operating parameters for concurrent production of the two reservoirs which is technically, environmentally and economically efficient.
In Osum's proposed Taiga project, which is located at the northwest side of Cold Lake, both CSS (Cyclic Steam Stimulation) and SAGD (Steam Assisted Gravity Drainage) are considered forcommercial development scheme. Figure 1 shows the location of Taiga project. The initial development area of the Taiga project contains two stacked reservoirs: the Clearwater and Lower Grand Rapids Formations. Two reservoirs are separated by a thick continuousmudstone layer (see type log in Figure 2), which acts as a caprock for the Clearwater Formation. This allows for the independent operation of SAGD chambers from the two reservoirs. There are several advantages in developing two reservoirs simultaneously including:
(1.) Con-current development of two reservoirs will reduce the overall size of surface pads because the two reservoirs can be accessedby wells drilled from the same surface location.
(2.) Drilling of SAGD wells from two reservoirs at same time will reduce the risks of drilling into future hot zones resulting from heat conduction from SAGD operations in adjacent zones.
(3.) Understanding early performance ofboth reservoirs will provide opportunities for future optimization of development schemes.
(4.) Steam efficiency will be improved for the Lower Grand Rapids Formation due to the conductive heating of bottom water zone from SAGD operations withinthe Clearwater.
The selection of recovery technologies for the Taiga project was reviewed in a previous paper  and commercial applications to the ERCB . All initial phases of the Taiga project will employ SAGD recovery technology to produce bitumen. With the current plan, CSS pads are scheduled for the last phase of development.
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