Design of a Commercial SAGD Heavy Oil Project

Paper Number: 30277-MS

Authors: Edmunds, N.R., Suggett, J.C., CS Resources Limited

Source: SPE International Heavy Oil Symposium, 19-21 June, Calgary, Alberta, Canada

Copyright: Copyright 1995, Society of Petroleum Engineers, Inc.

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CS Resources is currently undertaking the construction of an 800 m3/day (5,000 bpd) thermal project near Senlac, Saskatchewan. The Senlac Thermal Project will use a steam assisted gravity drainage (SAGD) process to recover as much as 3.2 e6 m3 (20 mmbbl) of 13 API oil from a Dina channel sand.

This paper discusses some of the production and facility engineering issues arising in this full scale SAGD scheme. Compared to primary or conventional thermal operations, some of the unusual aspects are: very high injection and production rates from individual wells; the need to manage the large amount of heat in the production stream; and a pronounced interdependence between the various project components. Reservoir description, production forecasting, and facility optimization are briefly discussed.

Introduction
CS Resources Limited is planning to construct and operate a steam assisted gravity drainage (SAGD) project near Senlac, Saskatchewan during 1995. The Senlac Thermal Project will employ dual horizontal wells for steam injection and production recovery. A plant site, wells, and oil, gas and water pipelines will be constructed as part of the project, which is located in an area of rolling hills approximately 100 km south of Lloydminster, Saskatchewan.

The resource is located on sections 11, 12 & 13-40-26W3M and sections 7 & 18-40-25W3M. CS Resources has a 100% working interest in the area. The pool has been delineated with 12 vertical wells, 3 horizontal wells and a 3-D seismic survey. Currently, CS Resources has two horizontal wells on primary production at this location (a third one is shut in); these produced an average of 27 m3/day during October 1994.

Initially, thermal development will consist of three pairs of 500 m horizontal wells. A total of from 8 to 21 well pairs are planned over a project life of 7 to 15 years, depending on future oil prices and technology developments. The facility design oil production rate is 800 m3/day (5,000 bpd). Field construction is expected to begin as early as June 1995 with facilities start-up in November 1995. Lifetime capital costs for the project are estimated at $30 mm to $50 mm, depending on the number of well pairs ultimately developed.

Some of the major aspects of the design of a SAGD project are discussed in this paper.

Geological And Reservoir Description

Detailed geological mapping of the East Senlac Dina pool was conducted using a combination of existing vertical and horizontal well control and an inversion-processed 3-D seismic study. An isopach of the oil pay is shown in Figure 1. Figure 2 is a typical well log in the Senlac pool identifying key geological horizons.

The primary zone for heavy oil accumulations in the Senlac area is the Lower Cretaceous Dina/Cummings interval. The Dina/Cummings reservoir developed as a basal Mannville valley fill channel sequence, which unconformably overlies the Palaeozoic Duperow formation and is laterally offset by regional interbedded argillaceous sands and shales. The Channel sequence is directly overlain by the Cummings Coal followed by the Lloydminster shale (Figure 2).

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