Exploratory Drilling: Operations Capability From Labrador to Lancaster Sound

Abstract

Abstract INTRODUCTION Exploratory drilling along the Labrador Shelf dates back to 1971, when Leif L-38 was drilled and abandoned. Since that time, many problems have been encountered, many lessons have been learned and significant technological advances have made it possible to operate seasonally in a safe, efficient and even routine manner. The current operating methods require the most sophisticated drilling equipment in order to work safely in the unique environment of the area. It is north of Davis Strait, in Baffin Bay and Lancaster Sound, that more severe sea-ice and iceberg conditions occur, requiring a further refinement in operating methods. This paper will outline current operating practices and principles, followed by the approach being taken to provide the capability for future exploratory drilling operations. Environment The distinguishing feature of the operating environments of both the Labrador and Baffin Island coasts is the seasonal occurrence of sea ice and icebergs. The open-water or ice-free period is July through November in the region south of Davis Strait, and July through October in northern Baffin Bay. There are many local and seasonal variations to the above generalities, but on the basis of using dynamically positioned drills hips, the gross operating window is in the order of 100 days per year. In the Labrador and Davis Strait areas, severe weather and resulting sea states limit drillship operations during the latter portion of the season; in the north, freeze-up controls the operating end-of-season. The north-to-south drift current, frequently referred to as the Labrador Current, sweeps the sea ice and icebergs to the south. Ablation and decay of the ice occurs throughout this journey and results in a decreasing frequency of iceberg occurrence as well as less severe sea-ice conditions. The degree of severity of the sea-ice and iceberg regimes is the key to the ability to work throughout the region. For Davis Strait and Baffin Bay, a major environmental data gathering and analysis program, known as EAMES (Eastern Arctic Marine Environmental Study), is active. It provides the data necessary to satisfy various regulatory processes, environmental clearances and exploratory operations. In addition, large programs directed to gathering engineering-quality data are conducted. Major feasibility and technology development studies have resulted from these field programs and form the basis for developing future operating capabilities in the region. Table 1 (Approximate Environmental Comparison) contrasts the environment of the Labrador and northern Baffin Bay/Lancaster Sound regions. Drilling Operations All drilling activity in Canadian waters has occurred south of the 63rd parallel to date. As stated above, the average duration of a drilling season is approximately l00 days. A total of 26 wells have been drilled in Canadian waters, between 1971 and 1981. In addition, two more wells were spudded and suspended to be re-entered at a later date. With the exception of Aquitaine et at. Hekja 0-71 and Esso"s Gjoa 0-37, all wells were drilled on what is popularly known as the Labrador Shelf.