The Application Of Slant Hole Drilling In Development Of Shallow Heavy Oil Deposits
Authors: Hart K.W. , Jankowski L.V. 
Published: March 2010

This paper discusses the slant hole drilling program carried out by Suncor Inc., as a part of-the expansion of their Fort Kent Thermal Project.

The text of the paper contains three major topics. The first is a general outline of the drilling project. The layout of the wellsite c1listers Is described and the reasons for employing slant hole drilling, as opposed to conventional directional drilling, are explained.

The second topic Is-the slant drilling rig that was developed by North Eastern Drilling and Suncor Inc. To be capable af drilling the wells as planned, there were special requirements in' the rig to be used. These requirements and resulting rig design are discussed.

The third major area of discussion deals with the development of the drilling procedures used and summarizes the performance on the project. As the project progressed a number of improvements were made in both the equipment and drilling operations.

Introduction

In partnership with Canadian Worldwide Energy Co., Suncor Inc. has operated a heavy oil pilot project at Fort Kent, Alberta since 1976. The project is a "huff and puff' scheme with thirty four vertical producing wells on a two hectare spacing. An expansion of the project commenced in 1982 which required one hundred new wells and is expected to boost oil production from 180m3/d to 650 m3/d.

Two drilling methods, were examined in the planning stage of the expansion:The first method was to drill the wells vertically. This would have been the least expensive drilling method and would have required conventional heavy oil production equipment. However, with a well every two hectares and above ground flowlines, a considerable quantity of farmland would have been left useless. Approvals for the project would have been almost impossible to obtain. Based on the above reasoning, the vertical well alternative was discarded.The second method was to drill the wells directionally from pads. This would minimize the amount of farmland used. Also, despite higher drilling costs, there would be an over-all saving on the project cost due to centralized production facilities and reduced pipelining requirements.

Slant Hole Concept

The depth of the oil sand at Fort Kent is approximately 350 m. Using conventional pad drilling techniques, that is spudding vertically and kicking off at 30 m, the maximum expected displacement would be approximately 200 m at target depth. Assuming a 150 m by 150 m pad, 24 ha would be drilled up from a pad. Therefore, three pads would be required on each quarter section and considerable surface area would still be used.

By spudding the wells on a slant, a much larger area would be drilled up from a single pad, thereby reducing the surface area usage and the over-all project costs. Studies indicated that one pad per quarter section was practical from an economic, drilling, and production standpoint.

Figure 1 shows a typical four-hectare drilling pad located in the middle of a quarter section. Based on a two-hectare spacing, thirty-two wells would be drilled from each pad.