Abstract

Major operators are beginning to realize the vast potential of the non-mineable Athabasca Oil Sands using the SAGD (Steam Assisted Gravity Drainage) Process. Nexen Canada Ltd. and OPTI Canada Inc. together in a 50/50 joint venture, initiated a three-pair slant hole SAGD horizontal pilot project at Long Lake, located approximately 40km. southeast of Fort McMurray, in preparation for a 130-well commercial project to commence in the fall of 2004. SAGD drilling technology has been developed in Canada over the last 12 years; however, this pilot presented several unique drilling challenges associated with larger hole sizes coupled with spudding at an angle. This paper describes these, as well as others including community relations, weather, reservoir geology, pre-planning, well design, execution, optimization and unexpected problems. Lessons learned and recommendations for future operations will be reviewed.

Introduction

The Long Lake SAGD Pilot Drilling Project was the first project for Nexen/OPTI. The objectives of the project were as follows:

  1. Demonstrate the ability to safely and successfully drill, complete and start up SAGD wells;

  2. Gain and build inhouse experience;

  3. Demonstrate commercially viable well performance;

  4. Understand the impact of Long Lake Geology on SAGD performance and evaluate the use of 3D seismic in well placement;

  5. Drill and case three well pairs (2 large diameter; 1 slim diameter) that achieve the desired trajectories in the minimum amount of time and within the approved budget;

  6. Identify areas for improvement and capture lessons learned for possible application to the SAGD commercial phase of the project.

Resource And Geology

Nexen and OPTI are equal partners in the Long Lake property, located 40km. southeast of Fort McMurray (Figure #1). The lease covers about 52,000 acres (81 sections).

The Long Lake Commercial Project will be developed in several phases. The first will encompass 65 well pairs intersecting approximately 20 sections; and its pilot project located almost at the center of the Project Area (Figure #2).

The oil sands in this Long Lake property are contained within the McMurray Formation, the basal unit of the Lower Cretaceous Mannville Group. The McMurray Formation directly overlies the sub-Cretaceous unconformity that is developed on the Paleozoic carbonates of the Beaverhill Lake Group (Figure #3). Directly overlying the McMurray Formation are the Wabiskaw, Clearwater and Grand Rapids formations of the Mannville Group. The Quaternary zone which overlies the Grand Rapids also exists as a deep incising channel which cuts through the McMurray on the eastern side of the lease. A buffer of 150m is to be established between the ends of the horizontal well and the point where the Quaternary Channel intersects the McMurray Formation seismic marker, to minimize the potential for communication between any steam chambers and the Channel.

Over the project area, gross sand in the McMurray Formation ranges from 46m in areas of abandoned channel sequences, to over 120m in areas of channeled sand sequences. Within this thickness, the McMurray net pay can range from several meters to more than 60m.

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