Completing the World's Deepest Directionally Drilled Pipeline Shore Approach

Abstract

ABSTRACT The Vancouver Island Natural Gas Pipeline Project is an ambitious project to install a 10.75 inch diameter, 2160 psi pipeline from the British Columbia mainland to Vancouver Island on Canada's west coast. The project entails many engineering and construction challenges including pipeline installation in 1450 feet water depth, marking this one of the deepest marine pipelines in the world. One of the shore approaches along the pipeline route also presented a unique challenge. At the southeast shore of Texada Island, an intermediate island along the pipeline route, the steeply sloped, rind rocky seabed required the utilization of directional drilling technology to provide the pipeline shore approach at this location, since conventional methods such as trenching and/or blasting were uneconomic and might have had an unacceptable impact upon the marine environment in the area. This drilled shore approach entailed a hole entry location on a level plateau on Texada Island approximately 650 feet from the shoreline. An oilfield slant drilling rig was utilized to establish a drill entry angle of 45°. From this entry angle, the drilling was directionally deviated along the borehole length of 2200 feet to exit at an angle of approximately 80°, 1275 feet offshore at a water depth of 725 feet. The exit location was a near vertical rock face of very limited height along the seabed. The limited height of this face required drilling accuracy with very little tolerance for deviation from target location. This presentation describes the preparations and the operations associated with completing this directionally drilled pipeline shore approach. INTRODUCTION For almost 30 years, the prospect of installing a natural gas pipeline from the British Columbia mainland to Vancouver Island on Canada's west coast has been considered. In late 1989, Pacific Coast Energy Corporation (PCEC), a joint venture of Westcoast Energy Inc. and Alberta Energy Company Ltd., received the necessary approvals to commence construction of a pipeline to provide natural gas service to Vancouver Island. Westcoast Energy Inc. was to provide engineering and construction management of the pipeline while PCEC was to operate the pipeline upon completion. The construction of the Vancouver Island Natural Gas Pipeline entails installation of 366 miles of pipe: 102 miles on the British Columbia mainland, 32 miles on Texada Island (an intermediate island along the pipeline route), 175 miles on Vancouver Island and 57 miles of marine line laid upon the seabeds of the Strait of Georgia and the Malaspina Strait. Figure 1 depicts the routing of this pipeline. The Vancouver Island Pipeline commences near the Canada/United States border and proceeds through the Coquitlam watershed, around Howe Sound to the Community of Sechelt on the British Columbia mainland. Just north of Sechelt, the pipeline leaves the mainland and proceeds west across the southern portion of Malaspina Strait to the southeast comer of Texada Island. The routing comes ashore at this location and proceeds north the length of the island.