Influence of Horizontal Section Sinuosity and Lateral Accuracy on Heavy Oil Cold Production from Close-Spaced Senlac/Winter Saskatchewan Wells

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHorizontal well drilling for heavy oil cold production in Western Canada was initiated in 1988, and has matured to the extent that over 550 horizontal wells have been drilled into the Cummings/Dina channel trend between Senlac and Winter, Saskatchewan. A significant fraction of the more recent wells have been drilled as infills to enhance reservoir drainage. Reviews of the performance of these wells suggest drilling accuracy in all three dimensions within the horizontal section strongly affects the performance of original wells and the ability to optimize placement of infill horizontal wells between the original wells.Horizontal trajectory control has improved significantly in the last 10 years, the latest improvement being 'inclination at the bit.' Selected wells were analyzed to determine the key factors between horizontal section sinuosity and both production rate and ultimate recovery, and the changes in the effect of these key factors over the last 10 years. Incentive and methodology for development of current flatter wells is discussed, and predictions of improved production are given.Initial spacing in many areas was nominally 75 meters, and several areas are being infill drilled to 37.5 meter spacing to increase reservoir drainage. The heels of the infill wells are placed between the toes of the original wells to avoid expected greater oil depletion and water coning at the heels of the original wells.Several recent infill wells encountered lost circulation and/or magnetic interference from offsetting original wells, indicating the locations of the original wells obtained from MWD data were not accurate. For subsequent infill wells gyros were run in the original wells, and the gyro-based original well locations disagreed with the MWD-based locations. This prompted an examination of existing drilling, MWD, gyro, and magnetic North positioning data and technology.This paper discusses the theoretical and practical aspects of drilling flatter horizontal wells, establishing the locations of existing horizontal wells, and optimum placement of infill horizontal wells between the existing wells in the Senlac/Winter, Saskatchewan pools.