SAGD Development Strategy for Concurrent Production of Two Vertically Stacked Clastic Reservoirs

Abstract

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 geo-mechanical 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.