An On-Site Method For Optimizing Oil Recovery During Drilling Of Deviated And Off-Target Wells At Norman Wells
Authors: Heacock D.W. 
Published: March 2010

The thick oil zone and the close well spacing in the anisotropically fractured Norman Wells reservoir make it important to locate and orient wells properly. Nearly eighty per cent of the wells drilled in Norman Wells wilt be directionally drilled. A method has been developed for the preplanning and on-site optimization of directional drilling in a closely-spaced jive-spot waterflood pattern. This technique was the key to evlaluating the economic benefits of drilling S-bend well profiles which provide a near vertical trajectory through the reservoir. S-bend drilling profiles have been used successfully on wells up to 60 degrees, while higher angle wells (to 75 degrees) have been drilled using the more conventional build-and-hold profiles without serious drilling problems. The technique is used to optimize the wellbore configuration within the reservoir and to justify drilling expense for directional correction runs and plugback /sidetrack operations.

The theory has been incorporated into a hand-held calculator. The program allows an on-site drilling engineer to calculate combined effects off-target drilling and wellbore orientation for both the pre-drill plan and while drilling projected trajectories through the 150 m thick carbonate reef. This enables the driller to weigh the benefits of alternate drilling trajectories against the cost of deviating from the projected wellbore path. As a result, success has been achieved in ensuring better waterflood conformance by providing the quantitative directional evaluation tool required to optimize well location and trajectory.

Introduction

The Norman Wells oil reservoir is currently being developed by Esso Resources Canada. More than half of the planned 162 wells have been drilled to date. Waterflooding of this thick naturally fractured reservoir will utilize an elongated five-spot waterflood pattern with 6.2 ha spacing. Start of the waterflood systems is scheduled for mid-1984 with planned start-up of the production facilities in 1985 following completion and tie-in of the Norman Wells pipeline to the Rainbow-Zama pipeline system some 870 km away. Figure 1 shows the location or Norman Wells on the Mackenzie River and the Norman Wells pipeline to Rainbow Zama. Although Norman Wells was discovered in 1920 and has been producing continuously since the early 1940s(1), the remote location of the field and the difficulty of accessing the 60% of the reservoir under the Mackenzie River have precluded development to this time. Prior to the project, development of the Norman Wells field was limited to three areas; Bear Island, Goose Island and the mainland. Until the mainland waterflood was started up in 1980, depletion of the pool had been by primary depletion. To date, oil production has totalled four million m3, approximately 4% of initial oil-in-place. Under waterflooding it is expected that 42% of initial oil-in-place will be recovered.

Development of the Norman Wells reservoir is planned from the three existing areas plus six artificial islands constructed in the Mackenzie river, or the 162 wells planned for development, 78% will be directional wells.