A high-efficiency development mode of shale gas reservoirs in mountainous areas based on large cluster horizontal well engineering

With the basic characteristics of conventional horizontal wells, the so-called complex wells including horizontal extended-reach wells, multi-lateral horizontal wells, U-shaped wells, cluster horizontal wells, etc., are advanced well types for the efficient development of low-permeability, unconventional, deep-water, and deep oil and gas reservoirs, which have been highly concerned all over the world. Significant progress at home and abroad has been made in relevant researches and practices and is expected to play an important role in the efficient development of shale oil and gas. To meet the basic needs of environment & safety, land conservation, cost reducing and efficiency improving, it is urgent to create a unique and efficient mode for developing shale gas. Therefore, an efficient shale gas development mode for mountainous areas and an engineering and technical support system are presented based on large cluster horizontal-well engineering. An equation is thus obtained for calculating the maximum number of horizontal wells arranged allowably in “Well Factory” on a single platform. The general research and development of large extended-reach well technology are analyzed by expounding the basic concept of an extended-reach well and its drilling extension limit. And a calculation method is thus established to predict the maximum measured depth of open hole in extended-reach drilling. Moreover, some relevant research results and their significance for downhole tubular mechanics & mechanical extension limits in extended-reach drilling are also briefly introduced in this paper. The conclusions are drawn that, by following the idea of “integration of geology and engineering” in oil and gas development, these research results have a foreseeable application prospect in shale gas development in the mountainous areas in the future, and will contribute to new progress in China's “Shale Revolution”. Keywords: China, Mountainous areas, Shale gas, Efficient development mode, Large cluster horizontal wells, Integration of geology and engineering, Extended-reach drilling, Design and contro