The Optimization of Slant-Well Drilling in the Lindbergh Field

Summary Since 1985, Dome Petroleum Ltd. has developed slant-well drilling in the Lindbergh heavy-oil field in east-central Alberta. The oil-bearing sands occur in the lower Mannville formations of the Cretaceous period. To date, four pads, each consisting of 15 or 16 wells, have been completed. The experience gained in completing these projects has allowed us to make optimum use of slant-well technology in multiwell pad applications. The heavy-oil reservoirs in the Lindbergh field contain oil with a gravity of 0.98 g/cm3 [12.5° API]. The reservoir is at a vertical depth of 600 m [1,970 ft]. The wells are drilled on 4-ha [10-acre] spacing and placed on primary production for 2 years, after which steam stimulation is used for EOR. This primary production of cold oil has significant economic impact on the development of this field because capital recovery is achieved for drilling and completion before the massive investment into steam generation and distribution facilities. Maximizing this primary recovery requires that low-dogleg-severity (DLS), "straight" holes be drilled. The Lindbergh area is characterized by high agricultural land use. With slant-well technology, the required spacing unit is achieved with minimum surface land usage, optimum hole quality, and minimum environmental impact. In this application, slant-well drilling provides an attractive alternative to conventional directional multiwell pad projects. In the initial stages of slant-well development, drilling times of 5.5 days/well and costs** of $315/m [$81/ft] were experienced. Through an optimization process involving pad design, drilling equipment, casing design, bits and hydraulics, and directional/survey assemblies, significant savings in drilling time and cost were realized. To date, 71 slant wells have been drilled. In the latest project, drilling time averaged approximately 2 days/well and costs were reduced to $177/m [$45/ft]. These savings were achieved with an improvement in directional control and overall hole quality. This paper describes the optimization process and the techniques used to realize these savings.